JPS5832686B2 - High variable power zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high variable power zoom lens with a zoom ratio of 12 times.

An object of the present invention is to provide a bright and compact zoom lens with a zoom ratio of 12 times from f-16 to f-192.

The zoom lens of the present invention is a focusing lens system, a variator lens system, a compensator lens system, etc., in which the variator and compensator do not separate during zooming so that the overall length does not become long and the diameter of the front lens does not become large. We adopted types in which the power of the system is positive, negative, negative, and positive, respectively.

Then, the focal length of each lens is set to 1.
18 to 127, variator lens system 18 to -21, compensator lens system cuff 6 to -82, erector lens system 47 to 52, and master lens system 47 to 49.

The lens configuration of each system is that the focusing lens system has three positive lenses and one negative lens, the variator lens system has three negative lenses, either a cemented or single lens, and the compensator lens system has three negative lenses, either a cemented or single lens. With a cemented negative lens,
The erector lens system is composed of two positive lenses, and the master lens system is composed of a first group having a positive refractive power, a second group having a negative refractive power, and a third group and a fourth group of positive lenses. It has become.

Furthermore, the refractive index of the three convex lenses in the focusing lens system is Na (however, the refractive index of the three convex lenses is not necessarily equal), and the two lenses on the object side in the variator lens system (these lens groups are cemented In this case, the refractive index of the negative lens is Nb (the two lenses do not need to have the same refractive index), the surface closest to the image side of the variator lens system is Ra, and the first group of the master lens system is The thickness of the inner thick lens is Da, and the sum of the lens distances between the first and second groups of the master lens and between the second and third groups is Db + Dc1 Variator lens system and This zoom lens satisfies the following conditions, where the focal lengths of the Himast lens system are fv and fM, respectively.

The basic configuration of the present invention is as described above, and therefore the focusing lens system is composed of three convex lenses and one concave lens. sequential positive lens,
When it is composed of a negative lens, a positive lens, and a positive lens, or when it is composed of a positive lens, a positive lens, a negative lens, and a positive lens sequentially from the object side, the negative lens is placed first and the negative lens is sequentially arranged from the object side. By making sure that condition (1) is satisfied in any of the lens configurations,
Together with other variator lens systems and the like, it is possible to form a zoom lens capable of achieving the objectives of the present invention.

Next, the contents of each of the above conditions will be explained in detail.

First, condition (1) regulates the refractive index of the focusing lens system.

In general, these convex lenses have a high refractive index and are advantageous for correcting spherical aberration and chromatic aberration if they are made of a material with high dispersion, but zoom lenses use a variator lens system, which is a lens system that moves for zooming. Since a negative lens with a strong power is arranged in the compensator lens system, the negative power becomes strong as a whole, the Petzval sum becomes a negative value, and a large curvature of field occurs.

Furthermore, if the refractive index of the positive lens of the focusing lens system is increased, the Petzval value becomes even more negative, which makes it difficult to correct it with other lenses.

For this reason, an upper limit is set for the refractive index of the positive lens of the focusing lens system of the present invention as shown in condition (1).

Lowering the refractive index of these lenses is advantageous for the Petzval sum, but it becomes difficult to correct spherical aberrations, and the radius of curvature of each lens must also be made small, which increases the likelihood of off-axis aberrations. Too many, which is not desirable.

The lower limit of the above conditions was established for this purpose.

Next, condition (2) relates to aberration correction of the variator lens system, and is for correcting spherical aberration that cannot be completely corrected by the focusing lens system.

2 located on the object side of this variator lens system
If the refractive index of the two negative lenses (or one of the negative lenses if these lenses are cemented lenses) exceeds the lower limit of condition (2), it will not be possible to correct spherical aberration, and if it exceeds the upper limit, the Petzval will become negative. The field curvature worsens and cannot be corrected with other lenses.

Condition (3) is to regulate the exit angle of the oblique rays emerging from the variator lens system, to prevent off-axis aberrations occurring in this variator lens system, and to prevent this aberration from occurring in each subsequent lens as much as possible. The above-mentioned correction effect becomes effective by keeping the radius of curvature of the last surface of the variator lens system within the range of condition (3).

In this condition (3), if the radius of curvature Ra of the last surface of the variator lens system exceeds the upper limit, this surface becomes concave, so the light rays exiting from this surface pass around the lens in the next system. As a result, aberrations worsen and it becomes difficult to correct them in subsequent lens systems.If the lower limit is exceeded, the radius of curvature of this surface becomes small, and a difference of 1 occurs on this surface. The larger the number, the more difficult it becomes to correct.

Generally, the zooming portion of a zoom lens has a strong concave effect, resulting in a state where spherical aberration is largely undercorrected.

The fixed part (master lens system) corrects this undercorrected spherical aberration.
IfCf needs to be over-corrected to balance the spherical aberration as a whole.

Condition (4) is a condition established to overcorrect the spherical aberration of this master lens system, and this is achieved by placing a thick convex lens in the first group in the master lens system. It is.

However, if a lens is too thick, although it is advantageous for correcting spherical aberration, it is not preferable because off-axis aberrations occur.

Therefore, it is necessary that the thickness Da of the thick lens in the first group does not exceed the upper limit of condition (4).

Furthermore, if Da exceeds the lower limit, spherical aberration will be insufficiently corrected, and the overall balance will not be maintained.

As mentioned above, if the spherical aberration becomes under-corrected due to the strong negative power of the zooming section, the Petzval sum also becomes a large negative value, resulting in an under-corrected state.

Therefore, it is necessary to similarly perform correction so that a large positive Petzval sum is generated at the fixed portion.

For this purpose, a Petzval type lens system with a large air gap was arranged as a master lens system.

For this reason, the sum Db+Dc of the lens distance Db between the first and second groups of the master lens system and the lens distance Dc between the third and fourth groups is preferably equal to In view of this relationship and keeping other aberrations, particularly coma aberration, in good condition, it is necessary to ensure that the upper limit of condition (5) is not exceeded.

Furthermore, if Db + Dc exceeds the lower limit of condition (5), as described above, the Petzval sum cannot be achieved satisfactorily in other parts, and the curvature of field deteriorates.

As explained above, a zoom lens having the above-mentioned lens configuration that satisfies each of the above conditions can achieve the object of the present invention. If this is done, an even more excellent lens system can be constructed.

For concave lenses in a focusing lens system, it is not preferable to increase the curvature of the surface in order to minimize the positive Petzval sum and to make the whole lens compact.

Therefore, the higher the refractive index of this lens, the better.
The above is desirable.

Further, since the variator lens system has a large amount of movement during zooming, aberrations are likely to occur particularly with respect to off-axis rays.

Therefore, it is desirable to make the radius of curvature of each surface of each lens constituting this variator as narrow as possible so that each surface of the variator lens system does not have a large refraction angle for oblique rays.

Furthermore, if the radius of curvature of each surface is dog-shaped, the distance between the lenses can be made small, which makes it possible to make the whole lens compact, which is also preferable.

Therefore, it is better to use a material with a high refractive index for each lens, and when a cemented lens is used in each lens group of a variator lens system, it is desirable that the refractive index of the positive lens be set to 1. , it is more desirable to set the value to 75 or more.

Furthermore, in the focusing lens system of the zoom lens of the present invention, a material with a large dispersion is used for the positive lens, and a material with a small dispersion is used for the negative lens, thereby preventing the occurrence of chromatic aberration.

In particular, the occurrence of chromatic aberration in the telephoto state is reduced.

Considering the need to improve the chromatic aberration of magnification, the correction of chromatic aberration and the balance in the next variator lens system, the Atsube number νa of the positive lens in this focusing lens system is determined by the following condition (6). It is desirable to keep it within the range indicated by FC.

If the upper limit of this condition (6) is exceeded, it is good for Hosochi chromatic aberration, but chromatic aberration of magnification often occurs especially in telephoto conditions, and if the lower limit is exceeded, Hosochi chromatic aberration cannot be corrected.

Regarding the correction of chromatic aberration in the variator lens system,
Based on the correction status of Hosso chromatic aberration and lateral chromatic aberration in a focusing lens system, the Atsube number νb of the two concave lenses on the object side (or one of the concave lenses in the case of a cemented lens) on the object side of this variator lens system is determined by the following condition ( 7) is desirable.

If this Abbe number νb becomes a value outside of condition (7), the balance between Hosochi chromatic aberration and chromatic aberration of magnification cannot be maintained.

The last lens in the variator lens system is designed to prevent aberrations from occurring when the variator lens system moves for zooming, and to avoid placing any burden on subsequent lens systems. It is better not to have strong power.

In this sense, it is desirable that the focal length tlIfa of the last lens of this variator lens system satisfies the following condition (8).

In addition, in general, in a zoom lens, the degree of freedom is taken away due to the correction of aberrations other than distortion, so it is difficult to correct distortion aberration.

In the zoom lens of the present invention, distortion is corrected by the positive lens located closest to the object side of the focusing lens system and/or by the positive lens next to the negative lens.

The image side surfaces of these positive lenses are concave with respect to the object,
The stronger the curvature of this surface, the more the distortion will be corrected, but even if this surface becomes convex to the object, as long as the curvature is reduced, it is possible to correct it with another surface, which is practical. There is no problem.

Further, when this surface is convex toward the object side, the lens does not need to be relatively thick and the diameter of the front lens can be small, which has the advantage that the entire lens can be kept compact.

From the above, it is desirable that the image-side surface Ra of the convex lens located closest to the object side of the focusing lens system and/or the convex lens located next to the concave lens satisfy the following condition (9). .

If the upper limit of condition (9) is exceeded, this surface will be convex toward the object side and its curvature will be strong, making it impossible to correct distortion.

If the lower limit is exceeded, this surface is concave toward the object side and has a strong curvature, which is advantageous for correcting distortion, but other aberrations occur, making it impossible to correct various aberrations in a well-balanced manner.

Additionally, when the distance is close, aberrations generally deteriorate due to the nature of the lens.

Due to the nature of zoom lenses, focusing is performed by moving the focusing lens forward in response to changes in the distance of the photographed object, but especially with telephoto lenses, the amount of movement required for focusing becomes longer. Significant deterioration of aberrations.

Mainly, astigmatism becomes overcorrected, and the image plane on the axis does not match.

For this reason, in the lens system of the present invention, the lens spacing (d2 ? d4, do) in the part where the axial rays are parallel to the optical axis and the off-axis rays have a large angle with the optical axis is adjusted according to the distance of the object to be photographed. The above-mentioned deterioration of aberrations is corrected by changing the aberration.

In this case, the axial aberration is hardly affected by this change because the axial rays are parallel to the optical axis, and the off-axis astigmatism, on the other hand, changes greatly as the spacing changes. , it is possible to balance astigmatism.

Next, examples of the present invention will be shown.

However, rJ j r2 F... is the radius of curvature of each lens surface, d, , d2. . . . is the thickness of each lens and the distance between the lenses, nl j n21 . . . is the refractive index of each lens, and 4. C2゜... is the Atsube number, fF, fV, fc of each lens.

fE, fM, and f are the focal lengths of the focusing lens system, variator lens system, compensator lens system, erector lens system, master lens system, and total system, respectively.

In each of the above embodiments, Examples 1 to 4 are zoom lenses shown in FIG. 1, and the focusing lens system has a lens configuration of a positive lens, a negative lens, a positive lens, and a positive lens.

Therefore, Na shown in condition (1) is J y n31 n
4 corresponds to this.

Further, the variator lens system consists of two cemented negative lenses and a negative lens, so Nb is n61 n3 and Ra is rJ6.

The compensator lens system consists of a cemented negative lens, and the erector lens system consists of two positive lenses.

In the master lens system, the first group is a positive lens and a thick cemented positive lens, the second group is a negative lens, and the third and fourth groups are each positive lenses.

The thickness d26 of the first group thick lens (the object side lens of the cemented positive lens) in this master lens corresponds to Da, and d28+d3o corresponds to D b +D c.

Next, Examples 5 and 7 are lens systems shown in FIG.

The focusing lens system of these embodiments has a lens configuration of a positive lens, a positive lens, a negative lens, and a positive lens, and the value corresponding to Na is n1. n2°n4.

The variator lens system consists of two negative lenses and a cemented lens, and Nb corresponds to n5 and n6, and Ra corresponds to r15.

The other system configurations are substantially the same as in FIG.

Therefore, Da is d25, Db + Dc is d2 □ + d2
．． are the corresponding values.

Examples 6 and 8 are lens systems shown in FIG.

This lens system is a variator lens system, a cemented negative lens,
The lens configuration includes a negative lens and a cemented negative lens, but the other components are substantially the same as in FIG. 2.

Therefore, Nb is n6 and n7, Ra is r16, Da is d26, and Db+Dc is d28+d3o.

Embodiment 9 is a lens system shown in FIG. 4, in which a focusing lens system has a negative lens placed at the beginning, and has a lens configuration of a negative lens, a positive lens, a positive lens, and a positive lens.

Therefore, Na is n22 n32 n4.

The variator lens system consists of a negative lens, a negative lens, and a cemented negative lens, and Nb is f151 n6, and Ra is r
It is 15.

The master lens system of this example is the first lens of the cemented positive lens.
a second group of cemented negative lenses, and a third and fourth group of positive lenses.

The thickness d23 of the thick lens on the object side of the first group corresponds to Da, and d25+d28 corresponds to D b +D c.

Finally, Example 10 is a lens system shown in FIG.

In this embodiment, the variator lens system includes a cemented negative lens, a negative lens, and a cemented negative lens, and the other components are substantially the same as those of the ninth embodiment.

And n27 n31 n4 corresponds to Na, n62
n7 is Nb, r16 is Ra, d24 is D a, d
26 +d2g corresponds to Db + Dc, respectively.

Example 9 and Example 1o among the above examples are based on the condition (5
), and at the same time select the interval Dc (d28 in Example 9, d in Example 10).
2. ) to the dog.

With this, it is possible to correct the lack of Petzval sum as a whole due to the strong concave effect in the zoom section.

That is, as mentioned above, the Petzval sum is corrected under condition (1), but in order to further improve the master lens system, it is desirable to set VCo, 3f<Dc.

Aberration situations in each of the embodiments described above are shown in FIGS. 6 to 15.

In these figures, A is f-16 and B is f=55.4
3. C is each aberration when f=192.

As mentioned above, the zoom lens of the present invention can correct the deterioration of aberrations when photographing a close object by changing the distance between a part of the focusing lens system, and a few specific examples will be explained. do.

In the first embodiment described above, correction can be made by moving the first two lenses toward the object side and changing the distance d4 in a direction to widen it, and when the object distance is 2000 mm, it is sufficient to increase d4 by 1.

The aberration correction situation in this case is as shown in FIG. 16, where A is before correction and B is after correction.

Similarly, in Embodiment 8, by widening and changing the interval d2, it is possible to correct the convergence during close-up photography, and it is possible to
It is sufficient to increase d2 by 1 when m.

The correction situation in this case is as shown in FIG.

In addition, in Example 10, d4 was changed to 2000 m7
When M, the aberration distortion can be corrected by increasing d4 by 1, and the correction situation is shown in FIG.

[Brief explanation of drawings]

Figures 1 to 5 are cross-sectional views of each embodiment of the present invention, Figures 6 to 15 are aberration curve diagrams of each embodiment, and Figures 16 to 18 are graphs of aberration distortion during close-up photography. It is a figure which shows the correction situation.

Claims (1)

[Claims] 1. A focusing lens system consisting of three positive lenses and one negative lens, a variator lens system consisting of three cemented or single negative lenses, and a compensator consisting of a negative cemented lens. A sweater lens system, an erector lens system consisting of two positive lenses, a first group having positive refractive power, a second group of cemented or single negative lenses, a third group of positive lenses, and a positive lens. A high variable power zoom lens comprising a master lens system consisting of a fourth group and a master lens system, and satisfying the following conditions. However, Na is the refractive index of the positive lens in the focusing lens system, Nb is the refractive index of the two lenses on the object side of the variator lens system (if these lenses are a cemented lens, the negative lens among them), Ra is a variator
Da is the layer thickness radius of the last surface of the lens system, Da is the thickness of the thick lens in the first group of the master lens system, Db and Dc are the first group, the second group, and the second group of the master lens, respectively. The air spacing, fV, fM, and fa between the third group are the variator lens system, master lens system, and variator lens system, respectively.
It is the focal length of the last lens in the lens system. 2. A focusing lens system consisting of a positive lens, a negative lens, a positive lens, and a positive lens with their convex surfaces sequentially facing the object side, a variator lens system consisting of three cemented or single negative lenses, and a negative A compensator lens system of a cemented lens, an erector lens system consisting of two positive lenses, a first group having positive refractive power, a second group of cemented or single negative lenses, and a third group of positive lenses. 4th positive lens
A high variable power zoom lens that is comprised of a master lens system consisting of a lens group and a master lens system that satisfies the following conditions. However, Na is the refractive index of the positive lens in the focusing lens system, Nb is the refractive index of the two lenses on the object side of the variator lens system (if they are cemented lenses, the negative lens among them), and Ra is the refractive index of the positive lens in the focusing lens system. The radius of curvature of the last surface of the variator lens system, Da is the thickness of the thick lens in the first group in the master lens system, and Db and DC are the thicknesses of the first and second groups of the master lens system, respectively. The air spacing between the group and the third group, fv, fM, fa, is the focal length of the variator lens system, the master lens system and the last lens in the variator lens system, respectively. 3. A focusing lens system consisting of a positive lens, a positive lens, a negative lens, and a positive lens in order from the object side, a variator lens system consisting of three cemented or single negative lenses, and a compensator lens consisting of a negative cemented lens. an erector lens system consisting of two positive lenses, a first group having positive refractive power, and a second group consisting of a cemented or single negative lens.
1. A high variable power zoom lens comprising a master lens system consisting of a lens group, a third group of positive lenses, and a fourth group of positive lenses, and characterized in that it satisfies the following conditions. However, Na is the refractive index of the positive lens in the focusing lens system, Nb is the refractive index of the two lenses on the object side of the variator lens system (if it is a cemented lens, the negative lens among them), and Ra is the refractive index of the variator lens. - The radius of curvature of the last surface of the lens system, Da is the thickness of the thick lens in the first group of the master lens system, Db and Dc are the thickness of the first group, the second group, and the second group of the master lens system, respectively. The air spacing between the third group, fV, fM, fa are the focal lengths of the variator lens system, the master lens system and the last lens in the variator lens system, respectively. 4 A focusing lens system consisting of a negative lens, a positive lens, a positive lens, and a positive lens in order from the object side, a variator lens system consisting of a cemented or single negative lens, a compensator lens system consisting of a negative cemented lens, and two lenses. A master lens system consisting of an erector lens system consisting of a positive lens, a first group having positive refractive power, a second group of cemented or single negative lenses, a third group of positive lenses, and a fourth group of positive lenses. A high variable power zoom lens that satisfies each of the following conditions. However, Na is the refractive index of the positive lens in the focusing lens system, Nb is the refractive index of the two lenses on the object side of the variator lens system (if it is a cemented lens, the negative lens among them), and Ra is the refractive index of the variator lens. - The radius of curvature of the last surface of the lens system, Da is the thickness of the thick lens in the first group of the master lens system, Db and Dc are the thickness of the first group, the second group, and the second group of the master lens system, respectively. The air spacing between the third group, fV, fM, fa, is the focal length of the variator lens system, the master lens system and the last lens in the variator lens system, respectively.