JPH0772387A - Variable power lens - Google Patents

Abstract

PURPOSE:To obtain the new variable power lens which can make a camera effectively compact without requiring any complicated mechanism for power variation while the field angle of a master lens system exceeds 30 deg.. CONSTITUTION:This lens consists of the master lens system and a converter lens system, and the master lens system is constituted by arraying a positive meniscus lens which is convex to the object side as a 1st lens 1, a negative lens as a 2nd lens, a positive lens as a 3rd lens 3, and a negative meniscus lens which is concave to the object side as a 4th lens in order from the object side to the image side and arranging a stop between the 3rd and 4th lenses, and the converter lens system is attachable and detachable between the 3rd and 4th lenses of the master lens system. The converter lens system is inserted into the master lens system without varying the relative position relation among the respective lenses of the master lens system and focal length which is shorter than the focal length of the master lens system itself is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable power lens.
This variable power lens can be used as a photographing lens of a lens shutter camera or a video camera.

[0002]

2. Description of the Related Art As a variable power lens for changing a focal length by adding a converter lens to a master lens system, there are known ones disclosed in JP-A-60-176013 and US Pat. No. 4,708,442. Has been. However, in both cases, the angle of view of the master lens system is narrow, and it is difficult to meet the demand for a compact camera. Further, since the front group of the master lens system is moved to the image side when the converter lens system is inserted, there is a problem that the mechanism associated with zooming becomes complicated.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the angle of view of the master lens system exceeds 30 degrees, so that a complicated mechanism for zooming is not required, and therefore a camera is used. The objective of the present invention is to provide a new variable magnification lens that enables effective size reduction.

[0004]

The variable power lens of the present invention has a master lens system and a converter lens system. As shown in FIG. 1A, the “master lens system” has first to fourth lenses arranged in order from the object side to the image side, and has a diaphragm S between the third and fourth lenses. Become. First lens 1
Is a positive meniscus lens having a convex surface facing the object side, the second lens 2 is a negative lens, the third lens 3 is a positive lens, and the fourth lens 4 is a negative meniscus lens having a concave surface facing the object side.
The “converter lens system” is attachable / detachable between the third lens 3 and the fourth lens 4 of the master lens system. The converter lens system is inserted into the master lens system without changing the relative positional relationship of each lens in the master lens system, and realizes a focal length shorter than the focal length when only the master lens system is used (claim 1). .

The converter lens system is inserted into the master lens system without changing the relative positional relationship between the lenses in the master lens system and the "relative positional relationship between the master lens system and the converter lens system in the optical axis direction". Therefore, a focal length shorter than the focal length when only the master lens system is used may be realized (claim 2).

Although the diaphragm S is provided between the third and fourth lenses of the master lens system, the insertion position of the converter lens system can be "between the diaphragm S and the fourth lens 4" ( Claim 3).

When the converter lens system is inserted, "the maximum aperture diameter of the aperture S of the master lens system can be reduced" (Claim 4), or the converter lens system is provided with "aperture" on its object side. It is possible to have a fixed diaphragm s "whose diameter is smaller than the maximum diaphragm diameter of the master lens system (claim 5).

In the variable power lens according to claim 1, 2 or 3 or 4 or 5, "the entire master lens system" is used when the converter lens system is not inserted, and "master lens system and converter" is used when the converter lens is inserted. Focusing can be performed by displacing the "variable lens as a whole by the lens system" in the optical axis direction (claim 6).

Further, the "part outside the effective image forming range (shown by the chain line) of the fourth lens 4" of the master lens system shown in FIG. 13B is shown in FIG. Cross section)
The notch can be formed as a part of the space for attaching and detaching the converter lens system as shown in (Claim 7). The converter lens system can be configured by "arranging the positive lens 10 and the negative lens 20 in order from the object side" as shown in FIG. 1 (b) (claim 8). The above lens surfaces can be made aspherical "(claim 9).

Further, at least the object side surface of the fourth lens 4 of the master lens system can be made "aspherical" (claim 10).

The variable power lens according to the eleventh and twelfth aspects is a variable power lens according to the first aspect, that is, "first to fourth lenses are arranged in order from the object side to the image side, and the third, fourth An aperture is provided between the lenses, the first lens is a positive meniscus lens having a convex surface facing the object side, the second lens is a negative lens, and the third lens is a third lens.
The lens is a positive lens, and the fourth lens is composed of a master lens system which is a negative meniscus lens with a concave surface facing the object side, and a converter lens system detachable between the third and fourth lenses of the master lens system. The converter lens system is inserted into the master lens system without changing the relative positional relationship of each lens in the lens system to realize a focal length shorter than the focal length of the master lens system alone. " It

According to the variable power lens of the eleventh aspect, in such a structure, "the object side surface of the fourth lens of the master lens system is an aspherical surface having a curvature increasing with distance from the optical axis, and a reference spherical surface in the periphery. shift amount from: [delta] ₄ is, to satisfy the condition _{(1) 0.05 <δ 4 <} 0.4 "be characterized. In this specification, the “reference spherical surface” refers to a “spherical surface having a radius of curvature on the optical axis” in the surface where the aspherical surface is adopted.

In the variable power lens according to the twelfth aspect of the present invention, in the above-mentioned configuration, "the object side surface of the fourth lens of the master lens system is an aspherical surface whose curvature becomes gentler as it goes away from the optical axis, and the peripheral surface is closer to the reference spherical surface. The amount of deviation: δ ₄ ′ satisfies the condition (2) 0.05 <δ ₄ ′ <0.3 ”.

In the variable power lens according to the eleventh or twelfth aspect, "the most image-side surface in the converter lens system" is an aspherical surface, and the aspherical surface "has a strong curvature as the distance from the optical axis increases. After that, when the curvature becomes weaker and exceeds the midpoint, it intersects with the reference spherical surface, and the deviation amount from the reference spherical surface in the periphery: δ _c satisfies the condition (3) 0.001 <δ _c <0.005. It is possible to do so (claim 13).

Each of the variable power lenses described in claims 11 to 13 can be provided with the features of the invention described in claims 2 to 10.

[0016]

As described above, the "master lens system" in the variable power lens of the present invention has four lenses arranged positively, negatively, positively and negatively, and the diaphragm is arranged between the third and fourth lenses. It is a telephoto type and it is possible to shorten the total length, that is, the distance from the front surface of the lens to the image plane. In addition, the first lens is a positive meniscus lens having a convex surface facing the object side, the second lens is a negative lens, the third lens is a positive lens, and the fourth lens is a negative meniscus lens having a concave surface facing the object side. The angle of view of the lens system can exceed 30 degrees.

Further, the converter lens system is inserted without changing the relative positional relationship of the first to fourth lenses in the master lens system (claim 1). Therefore, it is not necessary to change the lens arrangement of the master lens system when inserting the converter lens system.

In the variable power lens of the second aspect, when the converter lens system is inserted, the first lens in the master lens system is inserted.
~ The relative positional relationship of the fourth lens is kept unchanged, and the "relative positional relationship of the master lens system and the converter lens system in the optical axis direction" is kept unchanged. The insertion position of the converter lens system can be set between the diaphragm and the fourth lens by widening the minimum distance between the diaphragm and the fourth lens (Claim 3). If the "relative positional relationship between the master lens system and the converter lens system in the optical axis direction" remains unchanged during insertion of the converter lens system, the converter lens system should be attached / detached at the "iris and 4 fixed position between the lens,
The converter lens system can be attached to and detached from the master lens system by displacing the converter lens system only in the direction orthogonal to the optical axis relative to the master lens system.

According to the fourth aspect of the invention, the maximum aperture diameter of the aperture of the master lens system is reduced when the converter lens system is inserted. According to the invention of claim 5, the converter lens system has a fixed diaphragm on the object side, but the diaphragm diameter of this fixed diaphragm is smaller than the maximum diaphragm diameter of the master lens system.

As described above, in the variable power lens of the present invention, the focal length of the master lens system is shortened and the angle of view is set wide. Therefore, the amount of movement is small even if focusing is performed by the master lens system itself, and the total length can be kept short even when focusing on a close range. In the variable power lens according to claim 6, when the converter lens system is inserted, focusing is performed by displacing the entire variable power lens by the master lens system and the converter lens system in the optical axis direction.
Focusing only for the master lens system and focusing when the converter lens system is inserted can be performed by the same lens displacement mechanism.

Between the diaphragm of the master lens system and the fourth lens unit,
When the sufficient distance cannot be obtained, the “part outside the effective image forming range” of the fourth lens of the master lens system is cut out as in the invention of claim 7, and this part is attached / detached to / from the converter lens system. Configure as part of the space for use.

Since the converter lens system is inserted into the master lens system to realize "a focal length shorter than the focal length of the master lens system itself", the converter lens system itself has a "positive refractive power". In this case, in order to achieve both the aberration correction and the thinning of the converter lens system itself, as in the invention according to claim 8, the converter lens system has a "configuration in which a positive lens and a negative lens are arranged in order from the object side". Good to do. Furthermore, in order to maintain good performance when the converter lens system is inserted, it is effective to "make one or more lens surfaces aspherical" in the converter lens system as in the invention of claim 9.

In the method of attaching and detaching the converter lens system as in the variable power lens of the present invention, it is preferable to employ an "aspherical surface" on the object side surface of the fourth lens. This way,
The amount of aberration generated on this surface can be effectively reduced.

That is, when the "object side surface of the fourth lens of the master lens system" is an "aspherical surface having a curvature increasing with distance from the optical axis" as in the variable power lens according to claim 11, By satisfying the condition (1), it is possible to effectively correct the “tilt of the image plane”. That is, when the upper limit of the condition (1) is exceeded, the tilt of the peripheral image plane is overcorrected and the balance with the axial image plane is lost. If the lower limit is exceeded, the correction effect due to the aspherical surface will not be exhibited.

Further, as in the variable power lens according to claim 12, the "object side surface of the fourth lens of the master lens system" is
When the aspherical surface has a curvature that becomes gentler as it goes away from the optical axis, it is possible to secure a wide space for inserting the converter lens system by satisfying the condition (2). That is, when the upper limit of the condition (2) is exceeded, the tilt of the peripheral image plane becomes large, and when the lower limit is exceeded, it becomes disadvantageous in securing a space for inserting the converter lens system.

In order to employ an aspherical surface for the converter lens system in the variable power lens according to the eleventh or twelfth aspect, it is most desirable in terms of performance to set the "surface closest to the image side in the converter lens system" to be an aspherical surface. It is effective. At this time, when the aspherical shape has a shape in which the curvature first becomes stronger as the distance from the optical axis increases, and then the curvature becomes weaker and intersects with the reference spherical surface when the intermediate point is exceeded, the condition (3 )
Good performance can be realized within the range that satisfies
That is, even if the upper limit or the lower limit of the condition (3) is exceeded,
The top ray coma gets worse.

When the variable power lens of the present invention is used as a taking lens of a lens shutter camera, it is preferable to shield the exposure range of the film surface from light on both sides in the "screen lateral direction" when the converter lens system is inserted. Panorama shooting is possible.

[0028]

[Examples] Four specific examples will be given below. Throughout all the examples, as for the master lens system, as shown in FIG. 1A, the radius of curvature of the i-th surface (including the diaphragm surface) counted from the object side is R _i (i = 1 to 9). , The i-th surface and the (i + 1) th surface are separated by D _i (i = 1 to 1) on the optical axis.
It is represented by 8). Further, the refractive index and Abbe number of the material of the j-th lens (j = 1 to 4) are represented by N _j and ν _j .

Similarly, in all the embodiments, as for the converter lens system, as shown in FIG. 1B, the m-th surface (fixed diaphragm s) counted from the object side (the diaphragm S side of the master lens system). The radius of curvature of r _m (including the diaphragm surface of r ₎ (m = 1 to 1
5), the surface spacing on the optical axis between the m-th surface and the (m + 1) -th surface is represented by d _m (m = 1 to 4). Further, the refractive index and the Abbe number of the material of the l-th lens counted from the object side are represented by n _l and ν _l (l = 1 to 2). Further, the distance on the optical axis between the stop S of the master lens system and the fixed stop s of the converter lens system is d ₀ , and the final surface of the converter lens system and the object side surface of the fourth lens 4 of the master lens system are on the optical axis. Is represented by d ₅ .

F is the focal length of the entire system, F / No is the brightness,
ω represents a half angle of view (unit: degree). These focal lengths, F /
No and ω are values related to the master lens system when the converter lens system is not inserted, and values related to the combined system of the master lens system and the converter lens system when the converter lens system is inserted.

Aspherical surfaces are used for the master lens system and the converter lens system. As is well known, when the aspherical surface is aligned with the optical axis to take the X coordinate and is orthogonal to the optical axis to set the H coordinate, the curvature on the optical axis (the reciprocal of the radius of curvature) is c, the conic constant is K, A, B, C, D for high-order aspherical coefficients
Then, X = cH ² / {1 + √ [1- (1 + K) c ² H ² ]} + A
A curved surface obtained by rotating a curve represented by H ⁴ + B · H ⁶ + C · H ⁸ + D · H ¹⁰ around the optical axis, and the shape is specified by giving a conic constant and an aspherical surface coefficient. In addition, in the display of the aspherical surface coefficient, E and the number following it indicate a power. That is, for example, "E-9" means 1/10 ⁹ and this number is multiplied by the preceding number.

Further, regarding the aspherical surface adopted as the object side surface of the fourth lens of the master lens system, the above: δ ₄ , δ ₄ ′,
For the aspherical surface adopted as the most image-side surface of the converter lens system, the above-mentioned: δ _c will be mentioned.

Example 1 Master lens system F = 29.1, F / No = 3.6, ω = 35.9 i R _i D _i j N _j ν _j 1 9.033 1.976 1 1.73400 51 .05 2 16.448 0.966 3 -21.610 0.800 2 1.846666 23.78 4 90.550 1.272 5 28.794 1.690 3 1.80450 39.64 6 -23.782 0.500 7 ∞ (aperture S) 6.643 8 -6.208 2.000 4 1.49154 57.82 9 -10.925.

Aspheric surface Eighth surface K = 0.28660, A = -3.741E-4, B =
1.574E-5, C = -3.192E-7, D =-
9.250E-9 9th surface K = -0.11690, A = -2.243E-4, B =
3.084E-6, C = -7.350E-8, D =-
1.943E-10, delta ₄ = -0.3381.

Draw-out amount relative to shooting distance Shooting distance: 0.35 m Extending amount: 2.986
.

Converter lens system mr _m d _m l n _l ν _l 0 0.500 1 ∞ (fixed diaphragm s) 0.727 2 −29.014 1.225 1 1.88300 40.80 3 −8.468 0.100 4 -9.466 0.800 2 1.58500 29.30 5 251.752 3.291.

Aspherical surface Fifth surface K = 8393.000, A = 1.893E-4, B =
-2.092E-4, C = 4.119E-5, D =
-2.961E-6, [delta] _c = -0.0039.

Draw-out amount with respect to shooting distance Shooting distance: 0.35 m Draw-out amount: 2.071
.

FIG. 1A shows the lens arrangement of the master lens system relating to Example 1 with respect to the shooting distance: ∞. FIG. 1B shows the lens arrangement when the converter lens system of Example 1 is inserted into the master lens system with respect to the shooting distance: ∞.

Example 2 Master Lens System F = 30.0, F / No = 3.6, ω = 35.2 i R _i D _i j N _j ν _j 1 9.126 1.616 1 1.73400 51 .05 2 16.489 1.040 3 -21.617 0.815 2 1.846666 23.78 4 95.464 1.489 5 28.794 1.690 3 1.80450 39.64 6-23.816 0.500 7 ∞ (aperture S) 6.798 8 −5.723 1.678 4 1.49154 57.822 9 −9.546.

Aspheric surface Eighth surface K = -0.20650, A = -1.214E-4, B =
-1.374E-5, C = 7.152E-7, D =
-2.525E-8, [delta] ₄ = -0.0074.

Draw-out amount relative to shooting distance Shooting distance: 0.35 m Extending amount: 3.187
.

The converter lens system _{m r m d m l n l} ν l 0 0.500 1 ∞ ( fixed throttle s) 0.928 2 -34.150 1.258 1 1.88300 40.80 3 -8.641 0.100 4 -9.511 0.800 2 1.58500 29.30 5 138.527 3.212.

Aspheric surface Fifth surface K = 2178.000, A = 1.738E-4, B =
-1.580E-4, C = 2.535E-5, D =
-1.619E-6, [delta] _c = -0.0028.

Draw-out amount with respect to shooting distance Shooting distance: 0.35 m Draw-out amount: 2.07
.

FIGS. 2A and 2B show the lens arrangement of the master lens system according to the second embodiment and the lens arrangement when the converter lens system is inserted in the master lens system with respect to the photographing distance: ∞, respectively. Show.

Example 3 Master Lens System F = 29.9, F / No = 3.6, ω = 35.3 i R _i D _i j N _j ν _j 1 9.584 1.431 1 1.88066 40 .94 2 15.326 0.980 3 −25.645 2.448 2 1.84700 23.90 4 30.168 0.776 5 23.579 1.307 3 1.88299 40.80 6 −26.046 0.500 7 ∞ (diaphragm S) 6.834 8 -6.098 2.000 4 1.49154 57.82 9 -8.962.

Aspheric surface Eighth surface K = -0.04241, A = -1.003E-5, B =
-1.469E-5, C = 6.892E-7, D =
-2.017E-8, [delta] ₄ = -0.0828.

Draw-out amount with respect to shooting distance Shooting distance: 0.35 m Draw-out amount: 3.59
.

The converter lens system _{m r m d m l n l} ν l 0 0.500 1 ∞ ( fixed throttle s) 1.037 2 -32.122 1.259 1 1.88033 38.84 3 -8.697 0.100 4 -9.551 0.800 2 1.58500 29.30 5 237.836 3.138.

Aspheric surface Fifth surface K = 671.83.6, A = 3.329E-4, B =
-2.179E-4, C = 3.777E-5, D =
-2.389E-6, [delta] _c = -0.0011.

Draw-out amount with respect to shooting distance Shooting distance: 0.35 m Extending amount: 2.065
.

FIGS. 3A and 3B show the lens arrangement of the master lens system according to the third embodiment and the lens arrangement when the converter lens system is inserted in the master lens system with respect to the photographing distance: ∞, respectively. Show.

Example 4 Master Lens System F = 29.2, F / No = 3.6, ω = 35.8 i R _i D _i j N _j ν _j 1 9.290 2.07 1 1.73400 51 .05 2 19.704 0.85 3 -24.949 0.80 2 1.846666 23.78 4 38.500 1.54 5 28.794 1.69 3 1.80450 39.64 6 -24.031 0.50 7 ∞ (diaphragm S) 7.25 8 −5.356 0.80 4 1.49154 57.82 9 −8.271.

Aspheric surface Eighth surface K = -0.12690, A = 4.823E-6, B =
-7.972E-6, C = 4.476E-7, D =
-9.964E-9, [delta] ₄ '= 0.2571.

Ninth surface K = -0.00632, A = 4.928E-6, B =
6.883E-8, C = 1.205E-10, D =
-4.261E-11.

Draw-out amount relative to shooting distance Shooting distance: 0.35 m Extending amount: 3.019
.

Converter lens system mr _m d _m l n _l ν _l 0 0.50 1 ∞ (fixed diaphragm s) 0.61 2 −25.561 1.21 1 1.88300 40.80 3 −8.361 0.10 4 -9.851 0.80 2 1.58500 29.30 5 239.975 4.05.

Aspheric surface Fifth surface K = 7982.000, A = 5.551E-4, B =
-3.602E-4, C = 6.661E-5, D =
-4.622E-6, [delta] _c = -0.0031.

Draw-out amount with respect to shooting distance Shooting distance: 0.35 m Draw-out amount: 2.075
.

FIGS. 4A and 4B show the lens arrangement of the master lens system according to the fourth embodiment and the lens arrangement when the converter lens system is inserted in the master lens system with respect to the photographing distance: ∞, respectively. Show.

Needless to say, in the above-mentioned first to fourth embodiments, the extension amount is 0 at the photographing distance: ∞.

FIG. 5A is an aberration diagram at the shooting distance of the master lens system in the first embodiment: ∞, and FIG. 5B is at the shooting distance of the master lens system in the first embodiment: 0.35 m. The aberration diagram is shown.

FIG. 6 is an aberration diagram ((A) in the same figure) at a shooting distance of ∞ with the converter lens system inserted in the master lens system in the first embodiment and a shooting distance of 0.
The aberration figure in 35 m (the same figure (B)) is shown.

FIG. 7A is an aberration diagram at the shooting distance of the master lens system: ∞ in the second embodiment, and FIG. 7B is at the shooting distance of the master lens system: 0.35 m in the second embodiment. The aberration diagram is shown.

FIG. 8 is an aberration diagram ((A) in the same figure) at a shooting distance of ∞ when the converter lens system is inserted in the master lens system in the second embodiment and the shooting distance: 0.
The aberration figure in 35 m (the same figure (B)) is shown.

FIG. 9A is an aberration diagram at the shooting distance of the master lens system in the third embodiment: ∞, and FIG. 9B is at the shooting distance of the master lens system in the third embodiment: 0.35 m. The aberration diagram is shown.

FIG. 10 is an aberration diagram ((A) in the same figure) at a shooting distance of ∞ with the converter lens system inserted in the master lens system in Embodiment 3, and the shooting distance:
An aberration diagram at 0.35 m (the same figure (B)) is shown.

FIG. 11A is an aberration diagram at the shooting distance of the master lens system: ∞ in Example 4, and FIG. 11B is at the shooting distance of the master lens system: 0.35 m in Example 4. The aberration diagram is shown.

FIG. 12 is an aberration diagram ((A) in the same figure) at a shooting distance of ∞ with the converter lens system inserted in the master lens system in Embodiment 4, and the shooting distance:
An aberration diagram at 0.35 m (the same figure (B)) is shown.

In the above aberration diagrams, d-SA and g-SA in the spherical aberration diagram represent spherical aberrations associated with the d line and the g line, d-SC represents the sine condition associated with the d line, and astigmatism diagrams. In, solid line: S is a sagittal image plane, and broken line: M is a meridional image plane. Further, Y represents the image height.

In each of the specific examples, the aberrations are corrected well and the performance is good even in the "master lens system alone" and the "state in which the converter lens is inserted in the master lens system" in the case of shooting distance: ∞ and short-distance shooting. Is.

Further, in each of the embodiments, when the converter lens is inserted, the photographing screen is a panoramic screen which shields both ends in the lateral direction of the film surface.
You can perform extremely powerful panoramic shooting. FIG. 14B shows an example of a panoramic screen image capturing state in which the converter lens system is inserted, in the case of the first embodiment. Reference numeral 30 indicates a light shielding plate that shields both ends in the lateral direction (vertical direction in the drawing) of the film surface (image surface). As illustrated in FIG. 14A in the case of the first embodiment, it is possible to obtain a panoramic screen using the light shielding plate 30 even in the case of only the master lens system.

[0074]

As described above, according to the present invention, a novel variable power lens can be provided. Since the present invention is configured as described above, it is possible to realize a compact variable magnification lens that has an angle of view exceeding 30 degrees and that does not require changing the lens arrangement of the master lens system when attaching or detaching the converter lens. The camera equipped with the same can be effectively made compact (claims 1 and 2).

In the third aspect of the invention, since the converter lens system is inserted on the image side of the aperture of the master lens system,
The front lens diameter of the master lens system can be made small, and in the invention of claim 4, the maximum aperture diameter of the master lens system is narrowed when the converter lens system is inserted, so that the outer diameter of the converter lens system can be kept small and The image performance can be kept good.

According to the invention of claim 5, since the converter lens system has a fixed diaphragm, the same effect as that of the invention of claim 4 can be obtained only by inserting the converter lens system and without narrowing the diaphragm of the master lens system. Therefore, the diaphragm mechanism can be simplified.

In the sixth aspect of the invention, when the converter lens system is not inserted, the entire master lens system is displaced in the optical axis direction for focusing, and when the converter lens system is inserted, the master lens system and the converter lens system are integrated. As a result, the focusing is performed by displacing in the optical axis direction, so that it is possible to prevent performance deterioration when focusing at a short distance and to simplify the mechanism for focusing.

According to the seventh aspect of the present invention, even when the sufficient distance cannot be provided between the aperture of the master lens system and the fourth lens, the converter lens system is allowed to move to the optical axis without being obstructed by the fourth lens. It can be attached to and detached from the master lens system with a simple displacement in the direction orthogonal to.

According to the invention described in claim 8, since the converter lens system is formed by arranging the positive lens on the object side and the negative lens on the image side, it is possible to maintain good performance when the converter lens is inserted. As in the invention of Item 9, by adopting one or more aspherical surfaces in the converter lens system, it is possible to more effectively correct the performance deterioration due to the insertion of the converter lens.

In the tenth aspect of the present invention, by adopting an aspherical surface on the object side surface of the fourth lens of the master lens system, good performance can be maintained or a large space for inserting the converter lens system can be secured.

According to the eleventh aspect of the invention, by adopting the aspherical surface on the object side surface of the fourth lens of the master lens system and satisfying the condition (1), the tilt of the image plane is effectively and effectively corrected. According to the invention of claim 12, the aspherical surface is adopted as the object side surface of the fourth lens of the master lens system,
By satisfying the condition (2), a large space for inserting the converter lens system can be secured.

According to the thirteenth aspect of the invention, the aspherical surface is adopted as the most image side surface of the converter lens system, and the condition (3) is satisfied.
By satisfying the above, good performance can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration of a variable power lens of Example 1, where (a) shows a master lens alone and (b) shows a lens arrangement when a converter lens is inserted.

2A and 2B are diagrams showing a lens configuration of a variable power lens of Example 2, wherein FIG. 2A shows a master lens alone, and FIG. 2B shows a lens arrangement when a converter lens is inserted.

3A and 3B are diagrams showing a lens configuration of a variable power lens of Example 3, wherein FIG. 3A shows a master lens alone, and FIG. 3B shows a lens arrangement when a converter lens is inserted.

4A and 4B are diagrams showing a lens configuration of a variable power lens of Example 4, wherein FIG. 4A shows a master lens alone, and FIG. 4B shows a lens arrangement when a converter lens is inserted.

5 is an aberration diagram related to the master lens system of Example 1, FIG.
(A) shooting distance: ∞, (B) shooting distance: 0.35m
Aberration diagrams in are respectively shown.

6A and 6B are aberration diagrams related to a state where a converter lens system is inserted in the master lens system of Example 1, where FIG. 6A is an aberration diagram at a shooting distance of ∞ and FIG. 6B is an aberration diagram at a shooting distance of 0.35 m.

7 is an aberration diagram related to the master lens system of Example 2, FIG.
(A) shooting distance: ∞, (B) shooting distance: 0.35m
Aberration diagrams in are respectively shown.

8A and 8B are aberration diagrams relating to a state where a converter lens system is inserted in the master lens system of Example 2, where FIG. 8A is an aberration diagram at a shooting distance of ∞, and FIG. 8B is an aberration diagram at a shooting distance of 0.35 m.

9 is an aberration diagram related to the master lens system of Example 3, FIG.
(A) shooting distance: ∞, (B) shooting distance: 0.35m
Aberration diagrams in are respectively shown.

FIG. 10 is an aberration diagram regarding a state in which a converter lens system is inserted in the master lens system of Example 3, (A) shows an aberration diagram at a shooting distance: ∞, and (B) shows an aberration diagram at a shooting distance: 0.35 m.

11A and 11B are aberration diagrams related to the master lens system of Example 4, where (A) is a shooting distance: ∞ and (B) is a shooting distance: 0.3.
The aberration diagrams at 5 m are shown respectively.

12A and 12B are aberration diagrams related to a state where a converter lens system is inserted in the master lens system of Example 4, where FIG. 12A is an aberration diagram at a shooting distance of ∞, and FIG. 12B is an aberration diagram at a shooting distance of 0.35 m.

FIG. 13 is a diagram for explaining the invention described in claim 7;

FIG. 14 is a diagram showing a state in which a panoramic screen is realized by a light shielding plate in the case of the first embodiment.

[Explanation of symbols]

 1 First lens of master lens system 2 Second lens of master lens system 3 Third lens of master lens system 4 Fourth lens of master lens system S Aperture of master lens system s Fixed aperture of converter lens system

Claims (13)

[Claims] 1. The first to fourth lenses are arranged in order from the object side to the image side, and a diaphragm is provided between the third and fourth lenses, and the first lens has a convex surface directed toward the object side. A positive meniscus lens, a second lens is a negative lens, a third lens is a positive lens, and a fourth lens is a negative meniscus lens with a concave surface facing the object side. It is composed of a converter lens system detachable between four lenses, and the converter lens system is inserted into the master lens system without changing the relative positional relationship of each lens in the master lens system. A variable power lens characterized in that it is configured to realize a focal length shorter than the focal length at the time. 2. The first to fourth lenses are arranged in order from the object side to the image side, and a diaphragm is provided between the third and fourth lenses, and the first lens has a convex surface directed toward the object side. A positive meniscus lens, a second lens is a negative lens, a third lens is a positive lens, and a fourth lens is a negative meniscus lens with a concave surface facing the object side. It is composed of a converter lens system detachable between four lenses, and does not change the relative positional relationship of each lens in the master lens system and the relative positional relationship of the master lens system and the converter lens system in the optical axis direction. A variable magnification lens characterized in that the converter lens system is inserted into a master lens system to realize a focal length shorter than that of the master lens system alone. 3. The variable power lens according to claim 1, wherein the converter lens system in the master lens system is inserted between the stop and the fourth lens. 4. The variable power lens according to claim 1, 2 or 3, wherein the maximum aperture diameter of the aperture of the master lens system is reduced when the converter lens system is inserted. 5. The variable power lens according to claim 1, 2 or 3, wherein the converter lens system has a fixed diaphragm on the object side, and the diaphragm diameter of the fixed diaphragm is smaller than the maximum diaphragm diameter of the master lens system. A variable power lens characterized by this. 6. The variable power lens according to claim 1, 2 or 3 or 4 or 5, wherein when the converter lens system is not inserted, the entire master lens system is displaced in the optical axis direction, and the converter lens system is used. A variable magnification lens characterized by performing focusing by displacing the entire variable magnification lens by a master lens system and a converter lens system in the optical axis direction when inserting. 7. The variable power lens according to claim 1, 2 or 3 or 4 or 5 or 6, wherein a part of the fourth lens of the master lens system outside the effective image forming range is cut away to form a converter lens system. A variable power lens characterized in that it constitutes a part of a detachable space. 8. A variable power lens according to claim 1, 2 or 3 or 4 or 5 or 6 or 7, wherein the converter lens system comprises a positive lens and a negative lens arranged in order from the object side. A variable power lens featuring. 9. A variable power lens according to claim 1, 2 or 3 or 4 or 5 or 6 or 7 or 8, wherein one or more lens surfaces in the converter lens system are aspherical surfaces. Double lens. 10. The variable power lens according to claim 1, 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, wherein at least the object side surface of the fourth lens of the master lens system is aspherical. Variable magnification lens. 11. A first through a first system from the object side to the image side.
A fourth lens is arranged and a diaphragm is provided between the third lens and the fourth lens. The first lens is a positive meniscus lens having a convex surface facing the object side, the second lens is a negative lens, and the third lens is a positive lens. The fourth lens is composed of a master lens system, which is a negative meniscus lens with a concave surface facing the object side, and a converter lens system of this master lens system, which is detachable between the third and fourth lenses. Without changing the relative positional relationship of each lens in the system, by inserting the converter lens system into the master lens system, it is configured to realize a focal length shorter than the focal length of the master lens system only, The object side surface of the fourth lens of the master lens system is an aspherical surface having a curvature increasing with distance from the optical axis, and the amount of deviation from the reference spherical surface in the periphery: δ ₄ satisfies the condition (1) 0.05 <δ ₄ < Zoom lens satisfies the .4. 12. From the object side to the image side, the first to
A fourth lens is arranged and a diaphragm is provided between the third lens and the fourth lens. The first lens is a positive meniscus lens having a convex surface facing the object side, the second lens is a negative lens, and the third lens is a positive lens. The fourth lens is composed of a master lens system, which is a negative meniscus lens with a concave surface facing the object side, and a converter lens system of this master lens system, which is detachable between the third and fourth lenses. Without changing the relative positional relationship of each lens in the system, by inserting the converter lens system into the master lens system, it is configured to realize a focal length shorter than the focal length of the master lens system only, The object side surface of the fourth lens of the master lens system is an aspherical surface whose curvature becomes gentler as it goes away from the optical axis, and the amount of deviation from the reference spherical surface at the periphery: δ ₄ ′ satisfies the condition (2) 0.05 <δ ₄ ' Zoom lens satisfies the 0.3. 13. The variable power lens according to claim 11 or 12, wherein a surface of the converter lens system closest to the image side is an aspherical surface, and the aspherical surface first has a strong curvature as the distance from the optical axis increases. , When the curvature becomes weaker and exceeds the midpoint, it intersects with the reference spherical surface and the amount of deviation from the reference spherical surface in the periphery:
[delta] _c is the condition (3) 0.001 <δ _c <zooming lens satisfies the 0.005.