Lens device

Abstract

To enhance the variety of imaging lenses and the added value by enabling the normal imaging lens function and the soft focus lens function to be switched with the attachment / detachment of an image conversion ring for lens, avoid the adverse effect of upsizing and complication and achieve reduction in the size and cost of the imaging lens.SOLUTION: A lens device comprises an image conversion ring for lens 1 including: an imaging lens Mo that generates a soft focus effect by generating a prescribed aberration; a lens attachment / detachment part 3 which is attached / detached to / from a front end part 2f of a lens barrel 2 in the imaging lens Mo; and an outer diaphragm ring part 4 which is provided integrally with the lens attachment / detachment part 3, restricts an input light quantity C incident on the imaging lens Mo at the attachment to the front end part 2f of the lens barrel 2 and resolves the soft focus effect by removing the prescribed aberration.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lens device suitable for use in a digital still camera or the like.

Background Art

[0002] Conventionally, a normal imaging lens that performs sharp imaging and a soft focus lens that enables soft focus imaging are known. As this type of soft focus lens, the soft focus lens described in Patent Document 1 previously proposed by the applicant is known. This soft focus lens aims to significantly reduce costs associated with design and manufacturing by sharing the optical elements of the normal imaging lens and the soft focus lens, ensuring lens performance, and obtaining high-quality soft focus imaging. Specifically, with respect to the optical system of a normal photographing lens in which a first lens group with positive refractive power and a second lens group with positive refractive power are arranged front and back, by adding or replacing one soft focus forming lens, the spherical aberration of the entire optical system is set to be within a predetermined aberration in the aperture region where the aperture value is three times or more of the open F value, and to be more than a predetermined aberration when open.

[0003] In addition, there is also a so-called variable soft-focus lens in which the soft-focus effect of the soft-focus lens can be varied, that is, the aberration can be varied. As this type of lens, an aberration-variable optical system described in Patent Document 2 is known. This aberration-variable optical system has a sufficiently large angle of view and is intended to provide an aberration-variable optical system that can continuously change the spherical aberration from a negative value to a positive value across a sharp image quality state. Specifically, it includes a master lens group having a first partial lens group with positive refractive power, a second partial lens group with negative refractive power, and a third partial lens group with positive refractive power, and also includes a converter lens group having a positive lens component and a negative lens component. By changing the axial air gap between the positive lens component and the negative lens component, the spherical aberration can be mainly changed. When Fm is the focal length of the master lens group in the infinitely focused state and Fc is the focal length of the converter lens group in the infinitely focused state and at the lens position state where the amount of spherical aberration generated is the smallest, it is set so that -1 < Fm / Fc < 0.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional variable soft-focus lenses, including the lens described in Patent Document 2 mentioned above, had the following problems.

[0006] That is, since the aberration is varied by moving a specific lens or lens group inside the lens barrel, the structure for moving the lens group or the like becomes complicated. In particular, there is a risk of interfering with other adjustment mechanisms such as a focus adjustment mechanism that moves a lens or lens group to perform focus adjustment, which tends to lead to complication and enlargement of the optical system and further deterioration of accuracy.

[0007] Therefore, even if it is possible in the case of a lens barrel with a certain amount of space margin, when applied to an imaging lens for the purpose of miniaturization and compactness, it becomes a major obstacle to miniaturization and compactness, and there is a limit to realizing the target miniaturization and compactness. Moreover, even if a certain degree of miniaturization and compactness is achieved, the cost increase cannot be ignored, and there are problems such as the risk of adversely affecting the optical performance of the lens system. An object of the present invention is to provide a lens device that solves the problems existing in such background art.

Means for Solving the Problems

[0008] In order to solve the above-described problems, a lens device M according to the present invention is a lens device including an imaging lens Mo having a plurality of lenses L1, L2, ... arranged therein, and a lens image conversion ring that is attached to and detached from a front end portion 2f of a lens barrel 2 of the imaging lens Mo. The plurality of lenses L1, L2, ... are composed of a first cemented lens J1 formed by cementing a biconvex lens L1 and a biconcave lens L2, a second cemented lens J2 formed by cementing a positive meniscus lens L3 and a biconcave lens L4, and a third cemented lens J3 formed by cementing a negative meniscus lens L5 and a biconvex lens L6 from the object OBJ side to the image IMG side. An internal aperture stop STD is disposed between the first cemented lens J1 and the second cemented lens J2, and an imaging lens Mo that generates a soft focus effect in which a predetermined aberration is generated to cause blurring on the peripheral side is provided. A lens attachment / detachment portion 3 that is attached to and detached from the front end portion 2f of the lens barrel 2 of the imaging lens Mo, and an external aperture ring portion 4 that is integrally provided with the lens attachment / detachment portion 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates a predetermined aberration to eliminate the soft focus effect when attached to the front end portion 2f of the lens barrel 2. The lens device is characterized by comprising a lens image conversion ring 1 having the same.

[0009] Further, according to a preferred aspect of the present invention, the lens attachment / detachment portion 3 in the lens device M can be formed by a male screw portion 3s that is screwed into a female screw portion 6n provided on an inner peripheral surface of an accessory attachment portion 6 at the front end portion 2f of the lens barrel 2.

[0010] Furthermore, the external aperture ring portion 4 can be configured to be assembled to the lens attachment / detachment portion 3 by selecting from a plurality of external aperture ring portions 4... having different incident light amounts C to be restricted.

Effects of the Invention

[0011] According to the lens device M according to the present invention having such a configuration, the following remarkable effects can be obtained.

[0012] (1) For shooting with a soft focus effect, it is sufficient to remove the lens image conversion ring 1 attached to the front end 2f of the lens barrel 2. Therefore, it is possible to easily switch between the soft focus lens function (blurring function) that obtains the soft focus effect and the normal shooting lens function that performs sharp imaging. As a result, the diversity of the imaging lens Mo, and further the added value, can be enhanced more.

[0013] (2) Structurally (in terms of components), it can be implemented by preparing a lens detachable part 3 that is detachable from the front end 2f of the lens barrel 2 in the imaging lens Mo, and an external aperture ring part 4 that is integrally provided in this lens detachable part 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates predetermined aberrations to cancel the soft focus effect when attached to the front end 2f of the lens barrel 2. Therefore, it can be implemented without changing the configuration of the optical system inside the imaging lens Mo, etc., and it is possible to avoid the adverse effects of enlargement and complexity as much as possible, and to realize miniaturization and cost reduction of the imaging lens Mo.

[0014] (3) As a plurality of lenses L1... in the imaging lens Mo, from the object OBJ side to the image IMG side, a first cemented lens J1 formed by cementing a biconvex lens L1 and a biconcave lens L2, a second cemented lens J2 formed by cementing a positive meniscus lens L3 and a biconcave lens L4, and a third cemented lens J3 formed by cementing a negative meniscus lens L5 and a biconvex lens L6 are provided, so that the entire optical system can be constructed only by three sets of cemented lenses J1, J2, J3 without including single lenses. As a result, further miniaturization of the imaging lens Mo having an aberration variable function can be achieved.

[0015] (4) Since an internal aperture stop STO is arranged between the first cemented lens J1 and the second cemented lens J2 in the imaging lens Mo, it is possible to combine the internal aperture stop STO having a normal aperture function and the second aperture function by the external aperture ring part 4 in the lens image conversion ring 1. As a result, it is possible to perform various types of shooting including soft focus shooting.

[0016] (5) In a preferred embodiment, when configuring the lens attachment / detachment portion 3 in the lens image conversion ring 1, if it is formed by a male screw portion 3s that is screwed onto a female screw portion 6n provided on the inner peripheral surface of the accessory attachment portion 6 at the front end portion 2f of the lens barrel 2, the imaging lens Mo can be attached and detached with the feeling of an accessory such as a lens filter. Therefore, it is excellent in ease of handling and also excellent in convenience and usability.

[0017] (6) In a preferred embodiment, as the external aperture ring portion 4 in the lens image conversion ring 1, if it is configured to be selectable from a plurality of external aperture ring portions 4... with different restricted incident light amounts C and assembled to the lens attachment / detachment portion 3, a substantial variable soft focus function can be obtained, such as being able to select the degree of the soft focus effect (for example, strong, medium, weak), and the multifunctionality and diversity can be further enhanced.

Brief Description of the Drawings

[0018]

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Mode for Carrying Out the Invention

[0019] Next, preferred embodiments according to the present invention will be given and described in detail with reference to the drawings.

[0020] First, the basic configuration of the lens device M according to this embodiment will be described with reference to FIGS. 1-10.

[0021] As shown in FIGS. 1 and 6, the lens device M according to this embodiment includes an imaging lens Mo and an image conversion ring 1 for the lens that is attached to and used with this imaging lens Mo. The imaging lens Mo shown in FIG. 1 is a cross-sectional side view in which the front half is shown by a solid line and the rear half, which is the other part, is shown by a virtual line. Note that the exemplary imaging lens Mo is an interchangeable lens that can be used in a digital still camera, and the arrow Ff indicates the front (object OBJ side) of the imaging lens Mo.

[0022] First, the imaging lens Mo includes a lens barrel 2, and 11 indicates a fixed barrel in the lens barrel 2. This fixed barrel 11 has an accessory mounting portion 6 at the front end where camera accessories such as a hood and a lens filter can be attached and detached, and a lens-side mount portion 22 at the rear end that is attached (detachable) to the camera-side mount. Further, the outer peripheral portion of the fixed barrel 11 is provided with a focus adjustment ring 23 shown by a virtual line, and a diaphragm adjustment ring 24 is provided on the front side of this focus adjustment ring 23. By rotating the focus adjustment ring 23, focusing adjustment can be performed, and by rotating the diaphragm adjustment ring 24, diaphragm adjustment of the internal aperture diaphragm STO provided in the optical system of the imaging lens Mo can be performed. On the other hand, inside the lens barrel 2 (fixed barrel 11), a plurality of lenses L1, L2,... held by lens holding portions 25, 26, 27 are arranged.

[0023] FIG. 7 and FIG. 8 show the configuration of the entire lens system 100 in the imaging lens Mo according to the present embodiment, and FIGS. 9 and 10 show the lens data and specification data of the entire lens system 100.

[0024] The entire lens system 100 includes, from the object OBJ side to the image IMG side, a first cemented lens J1 in which a biconvex lens L1 and a biconcave lens L2 are cemented, a second cemented lens J2 in which a positive meniscus lens L3 with a convexly curved image IMG side and a biconcave lens L4 are cemented, and a third cemented lens J3 in which a negative meniscus lens L5 with a convexly curved object OBJ side and a biconvex lens L6 are cemented. If the entire lens system 100 is configured in this way, the entire optical system can be constructed only with three sets of cemented lenses J1, J2, and J3 that do not include single lenses, so that the imaging lens Mo having an aberration variable function can be made smaller and more compact. And the above-described internal aperture stop STO is disposed between the first cemented lens J1 and the second cemented lens J2. In FIGS. 7 and 8, Dc indicates the optical axis, and the arrow Ff indicates the front side (object OBJ side).

[0025] Also, in the lens data shown in FIG. 9, the surface number of the lens surface counted from the object OBJ side is indicated by i, which corresponds to the symbols (numbers) shown in FIGS. 7 and 8. Corresponding thereto, the radius of curvature R(i) of the lens surface, the on-axis surface interval D(i), the refractive index nd(i) of the lens, and the Abbe number νd(i) of the lens are shown respectively. nd(i) and νd(i) are values with respect to the d-line (587.6 [nm]). The on-axis surface interval D(i) indicates the lens thickness or air space between the opposing surfaces. The units of the radius of curvature R(i) and the surface interval D(i) are [mm]. OBJ of the surface number indicates the object, STO indicates the internal aperture stop, and IMG indicates the position of the image. "∞" of the radius of curvature R(i) indicates a plane. The blanks for the refractive index nd(i) and the Abbe number νd(i) indicate that it is air.

[0026] Furthermore, as shown in FIG. 10, the specifications data of the entire lens system 100 at the infinite object point of the imaging lens Mo are as follows: focal length f: 50.5 [mm], F-number: F1.562, angle of view: 46.311 [°], image height: 21.633 [mm], overall lens length: 76.576 [mm], BF (back focus): 31.879 [mm].

[0027] On the other hand, as shown in FIGS. 1 and 6, the lens image conversion ring 1, as a main part configuration, includes a lens attachment / detachment part 3 that attaches to and detaches from the front end part 2f of the lens barrel 2 of the above-described imaging lens Mo, and an external aperture ring part 4 that is integrally provided with the lens attachment / detachment part 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates a predetermined aberration to cancel the soft focus effect when attached to the front end part 2f of the lens barrel 2.

[0028] As shown in FIG. 6 (FIG. 5), this lens image conversion ring 1 includes a conversion ring base 31 formed in a flat cylindrical shape having substantially the same outer diameter as the front end part 2f of the lens barrel 2. At the rear end of the conversion ring base 31, a lens attachment / detachment part 3 having a smaller diameter than the conversion ring base 31 is integrally formed. The lens attachment / detachment part 3 is integrally formed in a ring shape, and a convex screw part 3s that is screwed into a concave screw part 6n provided on the inner peripheral surface of the accessory attachment part 6 at the front end part 2f of the lens barrel 2 is formed on the outer peripheral surface. With this configuration, the lens image conversion ring 1 can be attached to and detached from the imaging lens Mo in the same way as an accessory such as a lens filter, so it is excellent in ease of handling, convenience, and usability.

[0029] Also, a ring-shaped attachment plate part 32 for attaching the external aperture ring part 4 is integrally formed on the inner peripheral surface of the lens attachment / detachment part 3. The external aperture ring part 4 is formed in a ring plate shape, a circular light incident opening 4s is formed on the inside, and a part to be attached 4c for overlapping the outer peripheral side with the attachment plate part 32 is formed. Therefore, by selecting the inner diameter Ec of the light incident opening 4s, the incident light amount C from the light incident opening 4s can be determined. In the exemplary case, as shown in FIG. 1 (FIG. 4), it is selected to have an inner diameter Ec that is substantially the same as the inner diameter of the lens holding part 25 that holds the first cemented lens J1.

[0030] Furthermore, on the inner peripheral surface of the conversion ring base 31, by forming a concave screw portion 33n identical to the concave screw portion 6n provided on the inner peripheral surface of the accessory mounting portion 6 described above, it is formed as an accessory mounting portion 33 for mounting (attaching and detaching) an accessory such as a lens filter. Then, a ring holding plate 34 having a convex screw portion 34s screwed to the concave screw portion 33n is prepared. After overlapping the attached portion 4c in the external aperture ring portion 4 on the attachment plate portion 32, the convex screw portion 34s of the ring holding plate 34 is screwed to the concave screw portion 33n of the accessory mounting portion 33, and the attached portion 4c (external aperture ring portion 4) is fixed to the attachment plate portion 32. Note that since the ring holding plate 34 is screwed to the latter half of the concave screw portion 33n in the accessory mounting portion 33, the first half of the concave screw portion 33n in the accessory mounting portion 33 can be used as the original accessory mounting portion.

[0031] If the lens image conversion ring 1 is configured in this way, a desired external aperture ring portion 4 can be selected from a plurality of external aperture ring portions 4... with different restricted incident light amounts C, that is, a plurality of external aperture ring portions 4... with different inner diameters of the light entrance opening 4s, and can be assembled to the lens attachment / detachment portion 3. In other words, by selecting from a plurality of external aperture ring portions 4..., the degree of soft focus effect (for example, strong, medium, weak) can be selected, so that a substantial variable soft focus function can be obtained, and the multifunctionality and diversity can be further enhanced.

[0032] As described above, a lens image conversion ring 1 in which the lens attachment / detachment portion 3 and the external aperture ring portion 4 are integrated with respect to the conversion ring base 31 can be configured.

[0033] In this way, as a basic configuration, the lens image conversion ring 1 includes a lens attachment / detachment portion 3 that attaches to and detaches from the front end portion 2f of the lens barrel 2 of the imaging lens Mo, and an external aperture ring portion 4 that is integrally provided with the lens attachment / detachment portion 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates a predetermined aberration to cancel the soft focus effect when attached to the front end portion 2f of the lens barrel 2.

[0034] Therefore, the imaging lens Mo described above has an optical performance that generates a predetermined aberration to produce a soft focus effect. Thus, by using only the imaging lens Mo without the lens image conversion ring 1 attached, it can be used as a soft focus lens that obtains a soft focus effect (blurring effect). On the other hand, as shown in FIG. 5, if the lens image conversion ring 1 is attached to the front end portion 2f of the lens barrel 2 of the imaging lens Mo, the amount of incident light C incident on the imaging lens Mo is restricted, and by removing a predetermined aberration, the soft focus effect is eliminated, and it can be used as a normal photographing lens that performs sharp imaging. That is, the lens device M according to the present embodiment is based on the principle of causing a soft focus effect by including an aberration in advance with respect to the imaging lens Mo, and removing the aberration by attaching the lens image conversion ring 1 to convert it into a normal photographing lens.

[0035] Next, the functions and usage methods of the lens device 1 according to the present embodiment will be described with reference to FIGS. 1 to 12.

[0036] As shown in FIGS. 5 and 6, since the lens device 1 includes an imaging lens Mo and a lens image conversion ring 1 that is detachable from the imaging lens Mo, as shown in FIG. 5, if the lens image conversion ring 1 is attached to the imaging lens Mo and used, it can be utilized as a normal photographing lens that performs sharp imaging. In this case, since a relatively thin lens image conversion ring 1 is attached to the front end of the imaging lens Mo, it is integrated in appearance, and thus, in particular, there are no adverse effects such as an increase in size or damage to the shape.

[0037] When used as a normal photographing lens, as shown in FIG. 4, the amount of incident light C is restricted by the light incident opening 4s of the lens image conversion ring 1, like the light ray Cs indicated by the virtual line, so that the amount of light (brightness) on the peripheral side is cut, the aberration on the peripheral side is removed, and the soft focus effect is eliminated. That is, it can be used as a normal photographing lens that performs sharp imaging.

[0038] When using it as a soft focus lens, the lens image conversion ring 1 can be detached from the imaging lens Mo, and it can be used only with the imaging lens Mo shown in Fig. 6. As a result, as shown in Fig. 4, the incident light amount C becomes the light beam indicated by the solid line and is in a state where it is hardly restricted. Therefore, for the entire lens system 100 of the imaging lens Mo, it becomes the maximum brightness and the aberration can be increased. Thereby, it can be used as a soft focus lens (special effect lens) that causes blurring on the peripheral side.

[0039] In this case, when using only the imaging lens Mo, since the image conversion ring is removed, the lateral aberration characteristic at infinity can increase the aberration as shown in Fig. 12. That is, an aberration characteristic that produces a soft focus effect can be obtained. On the other hand, when used as the imaging lens Mo with the lens image conversion ring 1 attached, the axial surface interval D(i) with the surface number i = 1 in the lens data of Fig. 9 is 5.0 [mm], and the lateral aberration characteristic at infinity is such that the aberration is relatively small on the peripheral side as shown in Fig. 11.

[0040] Note that since the internal aperture stop STO described above is provided between the first cemented lens J1 and the second cemented lens J2, it is possible to combine the internal aperture stop STO having a normal stop function and the second stop function by the external stop ring portion 4 in the lens image conversion ring 1, and various types of photography including soft focus photography can be performed.

[0041] As described above, the lens device M according to this embodiment, as a basic configuration, includes an imaging lens Mo that generates a predetermined aberration to produce a soft focus effect, a lens attachment / detachment unit 3 that attaches to and detaches from the front end portion 2f of the lens barrel 2 of the imaging lens Mo, and an external aperture ring unit 4 that is integrally provided with the lens attachment / detachment unit 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates a predetermined aberration to cancel the soft focus effect when attached to the front end portion 2f of the lens barrel 2. Since it is provided with an image conversion ring 1 for a lens, for shooting with a soft focus effect, it is sufficient to remove the image conversion ring 1 for a lens attached to the front end portion 2f of the lens barrel 2. Therefore, it is possible to easily switch between a soft focus lens function (blur function) that obtains a soft focus effect and a normal shooting lens function that performs sharp imaging. Thereby, the diversity of the imaging lens Mo, and further the added value, can be enhanced more.

[0042] Also, in terms of configuration (component-wise), it can be implemented by preparing a lens attachment / detachment unit 3 that attaches to and detaches from the front end portion 2f of the lens barrel 2 of the imaging lens Mo, and an image conversion ring 1 for a lens that is integrally provided with the lens attachment / detachment unit 3 and restricts the incident light amount C incident on the imaging lens Mo and eliminates a predetermined aberration to cancel the soft focus effect when attached to the front end portion 2f of the lens barrel 2. Therefore, it can be implemented without changing the configuration of the optical system inside the imaging lens Mo, and it is possible to avoid the adverse effects of enlargement and complication as much as possible, and to achieve miniaturization and cost reduction of the imaging lens Mo.

[0043] As described above, the preferred embodiment has been described in detail, but the present invention is not limited to such an embodiment, and can be arbitrarily changed, added, or deleted within the scope not departing from the gist of the present invention in terms of detailed configuration, shape, material, quantity, numerical value, etc.

[0044] For example, although the lens image conversion ring 1 has been shown in the case where the lens attachment / detachment portion 3 and the external aperture ring portion 4 are assembled, the case of integrally molding is not excluded. Further, although the lens attachment / detachment portion 3 of the lens image conversion ring 1 has been shown as being formed by a male screw portion 3s that is screwed into a female screw portion 6n provided on the inner peripheral surface of the accessory mounting portion 6, other attachment means such as a type that fits onto the outer peripheral surface of the front end portion 2f of the lens barrel 2 are not excluded. Furthermore, although an example has been shown in which the external aperture ring portion 4 is configured to be assembled to the lens attachment / detachment portion 3 by selecting from a plurality of external aperture ring portions 4... having different restricted light input amounts C, it may be configured such that the positions before and after the external aperture ring portion 4 can be changed.

Industrial Applicability

[0045] The lens device according to the present invention can be used as a dedicated lens or an interchangeable lens in various optical devices such as digital still cameras and video cameras.

Explanation of Reference Numerals

[0046] 1: Lens image conversion ring, 2: Lens barrel, 2f: Front end portion of the lens barrel, 3: Lens attachment / detachment portion, 3s: Male screw portion, 4: External aperture ring portion, 6: Accessory mounting portion, 6n: Female screw portion, M: Lens device, Mo: Imaging lens, C: Light input amount, OBJ: Object, IMG: Image, STO: Internal aperture stop, L1: Double convex lens, L2: Double concave lens, L3: Positive meniscus lens, L4: Double concave lens, L5: Negative meniscus lens, L6: Double convex lens, J1: First joining lens, J2: Second joining lens, J3: Third joining lens

Claims

1. A lens device comprising an imaging lens having a plurality of lenses and a lens image conversion ring that is attachable to and detachable from the front end of a lens barrel of the imaging lens, wherein the plurality of lenses are composed of, from the object side to the image side, a first cemented lens formed by cementing a biconvex lens and a biconcave lens, a second cemented lens formed by cementing a positive meniscus lens and a biconcave lens, and a third cemented lens formed by cementing a negative meniscus lens and a biconvex lens, and an internal aperture stop is disposed between the first cemented lens and the second cemented lens, and an imaging lens that generates a soft focus effect in which a predetermined aberration is generated to cause blurring on the peripheral side, a lens attachment / detachment portion that is attachable to and detachable from the front end of the lens barrel of the imaging lens, and an external aperture ring portion that is integrally provided in the lens attachment / detachment portion and limits the amount of incident light entering the imaging lens when attached to the front end of the lens barrel and eliminates the soft focus effect by removing the predetermined aberration, characterized in that the lens device is provided with a lens image conversion ring having the external aperture ring portion.

2. The lens attachment / detachment portion is formed by a male screw portion that is screwed into a female screw portion provided on the inner peripheral surface of an accessory attachment portion at the front end of the lens barrel, according to the lens device of Claim 1.

3. The external aperture ring portion is configured to be assembled to the lens attachment / detachment portion by selecting from a plurality of external aperture ring portions having different amounts of incident light to be restricted, according to the lens device of Claim 1.

Images