JPS62205308A - Photography system with soft focusing function - Google Patents

Abstract

PURPOSE:To easily and speedily obtain excellent soft-focus effect without making a lens barrel complex by correcting variation of the best image plane at the time of variation from normal photography to soft-focus photography by utilizing a focus detecting means. CONSTITUTION:A photographic lens 1 consists of the 1st lens group I, the 2nd lens group II which is movable on the optical axis so as to obtain the soft-focus effect, a lens group III-1 for soft focusing, and a fixed lens group III-2. When soft-focusing effect is obtained, the variation of the best image at the time of the movement of the 2nd lens group II for obtaining the soft-focusing effect is detected by a focus detecting means 4, whose output signal is utilized to move the lens group III-1 for soft focusing by a driving means 7 and perform correction automatically, thus focusing the image. Consequently, the soft-focusing effect is easily and speedily obtained without making the lens barrel complex.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a photographing system having a soft focus function suitable for photographic cameras, video cameras, etc. ,! :YotJ This relates to an imaging system having a soft focus function that corrects fluctuations in the best image plane that occur when a soft effect is produced mainly by changing spherical aberration, and provides a good soft effect.

(Prior Art) Various photographic systems have been proposed that are designed to obtain images with a soft effect, which are images that give a softer feel than conventional ones. The soft effect is obtained by optically intentionally generating a certain aberration, mainly a spherical aberration of a certain shape. For example, a photographing system with a soft focus function that gradually changes the amount of spherical aberration to obtain a desired soft effect was published in Japanese Patent Application Laid-Open No. 52-769.
Publication No. 21, Japanese Patent Publication No. 1402-1982, Japanese Patent Application Publication No. 1987-1402
No proposals have been made in Publication No. 52013, etc.

Among these, in Japanese Patent Application Laid-Open No. 52-76921, an air gap is provided between two lens surfaces with concave surfaces at the position where the principal ray intersects the optical axis when the lens is opened. A soft effect is obtained by moving the groups along the optical axis at different speeds. The focus is the entire lens system'(i-
This method requires a separate lens group to obtain a desired distance and a soft effect, which are unnecessary for maintaining the performance of normal shooting. Because the same lens group was moved at different speeds, the lens system and lens barrel tended to have a very clumsy structure.

In Japanese Patent Publication No. 58-1402, a soft effect is obtained by using parallel planes with no refractive power in the center and moving optical members having refractive power toward the periphery in the optical axis direction. In this method, in order to obtain a soft effect, it was necessary to newly provide an optical member that is unnecessary in normal photography.

In Japanese Patent Application Laid-open No. 55-52013, a soft effect is obtained by changing the distance between the front lens group with positive refractive power and the rear lens group with negative refractive power. I'm going. This method tends to complicate the lens barrel structure for moving the lens groups.

In all of the above-mentioned shooting systems that have a soft focus function, spherical aberration is extremely severe during soft focus, so it is difficult to accurately focus even when using optical distance measuring means such as a micro prism or split prism. Can not. Therefore, in order to obtain the soft effect, it was first necessary to focus once in normal shooting conditions, and then move the soft focus lens group.

Furthermore, when changing from normal photography to soft focus, the best image plane changes depending on the amount of change in spherical aberration. Therefore, when using soft focus, it was necessary to refocus.

As described above, conventionally, in order to obtain a soft effect, the focusing lens group had to be operated many times, which was very troublesome.

(Problems to be Solved by the Invention) The present invention uses a focus detection means to correct variations in the best image plane when changing from normal shooting to soft focus, thereby easily achieving a nice soft effect. Moreover, it is an object of the present invention to provide an FC photographing system with a soft focus function that can be used quickly. The object of the present invention is to provide a photographing system having a soft focus function 1i, which provides a soft effect.

(Means for Solving the Problems) In addition to the photographic lens having two lens groups, a lens group SF for soft focus and a lens group F for focusing, soft focusing is achieved by the movement of the lens group SF. A method in which the amount of movement of the best image plane that occurs when the effect is obtained is detected by a focus detection means, and the lens group F is moved by a driving means to perform focusing using an output signal from the focus detection means. That's true.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, the rotary mirror x3 12 is a condenser lens, and has -7 mirrors 3a to 3a f inside. 4 is a focus detection means, 5 is a pentaprism X6 is a viewing lens, and 7 is a driving means.

The photographing lens 1 has the following features as described in Direct Fire Example 1, and includes a first lens group I, a second lens movable on the optical axis to obtain a soft effect, and a third lens group 3. It has two lens groups.

The third lens group (2) consists of two lens groups: a focusing lens group (1-1) and a fixed lens group (111-2).

The focus detection means 4 utilizes the light beam that passes through the photographing lens l and is reflected by the =7 mirror 31.
-155331 publication and Japanese Patent Application Laid-open No. 58-106511
Focus detection is performed using the method proposed in the publication.

Based on the output signal from the focus detection means 4, the driving means 7 moves the focusing lens group 1[-1 to perform focusing.

Generally, in order to efficiently obtain a soft effect, it is preferable for a d-photographing lens to have a shallow depth of field and a somewhat wide open F-number, for example FZ8 or higher.

In many photographic lenses for 35th-day film, spherical aberration is corrected to minimize spherical aberration so that good optical performance can be achieved in the range from infinity to close range during normal photography. On the other hand, when using soft focus, in order to obtain a good soft effect with a center at the center and a soft flare around it, the spherical aberration is adjusted to F2, for example.
．． ．． I try to make it occur for several minutes in the vicinity of 8.

Therefore, when the lens group is moved to obtain a soft effect, the best image plane, the so-called focus plane, changes.

However, since there is a lot of spherical aberration during soft focus, 1
It becomes very difficult to accurately focus with the naked eye using an optical member such as a split prism or a microprism.

Especially with many shooting lenses, F2 is used when soft focus is used.
For example, there is spherical aberration of several ff in the vicinity of -8, and at least one degree of spherical aberration exists even in the vicinity of iF8. Therefore, even if a light beam of F8 or less is used, it becomes difficult to achieve good focusing with the naked eye.

Therefore, in this embodiment, in order to obtain a soft effect, the change in the best image plane when the second lens group is moved is detected by the focus detection means 4, and the entire output signal from the focus detection means 4 at this time is used. (by driving means 7) lens group 1 for focusing
The lens is automatically corrected by moving l-1tfe and fully focused.

In particular, in this example, the photographic lens is configured so that the spherical aberration is in the range of 0.2 to 1 m when the F number of the axial light beam is 8 or less, and by using the light beam of F8 or less, accurate focus detection is achieved. Is going.

By employing such a configuration, this embodiment enables photographing with a good soft effect easily and quickly.

In this embodiment, the focusing lens group ff1-1 of the third lens group (3) has a negative refractive power, and the lens group 1-2 has a positive refractive power. Consists of a single shaped lens.

In addition, in this embodiment, the total lens length is shortened by setting the refractive power of the first lens group to be positive and the total refractive power of the second and third lens groups to be negative, and configuring the entire photographing system as a telephoto type. I'm planning everything. Rapid focusing is achieved by moving the lightweight lens group 111-1 with negative refractive power in the third lens group, and by utilizing the III/IJ focus.

By configuring the second lens group with a single meniscus lens with a convex surface facing the object side, lens group III
-1 is moved to reduce the amount of aberration variation when focusing.

Further, an aperture stop is arranged behind the second lens group, so that the center of the sphere of the lens is directed toward the aperture stop υ side.

As a result, the axial light beam is refracted to a large extent, and the off-axis light beam is not refracted as much as possible, and the difference in height from the optical axis of the 1-axis light beam is used to move lens A to obtain a soft effect on the spherical surface. This reduces the amount of aberrations other than aberrations.

As described above, in this embodiment, in order to obtain a soft effect, the υ soft effect is obtained by moving some of the lens groups during normal photography without arranging separate lens groups. The lens group for focusing and the lens group for obtaining a soft effect are separated to prevent the lens barrel structure from becoming complicated. In this embodiment, at least one lens surface in the second lens group It is preferable to provide an aspheric surface with a shape in which the refractive power gradually becomes stronger or weaker toward the periphery of the lens. According to this, it is possible to extremely easily obtain an arbitrary soft effect that greatly affects only spherical aberration and does not affect other aberrations at all.

In addition, the first lens group is composed of three lenses: two lenses with convex surfaces on both surfaces and a lens with concave surfaces on both surfaces, and the lens group m-i' of the third lens group is composed of positive and negative lenses. Consisting of laminated lenses, lens group 11 [
It is preferable to use a single-2k lens or a laminated lens made by laminating positive and negative lenses.

FIG. 4 is a lens sectional view of Numerical Example 2 of the photographing lens according to the present invention. In this figure, the same elements as those in FIG. 1 are given the same reference symbol -ti. The focus, soft focus, etc. are the same as those of the photographic lens of Numerical Example 1 shown in FIG.

Next, numerical examples of the photographic lens according to the present invention will be shown. In the numerical example, Ri is the radius of curvature of the first lens surface from the object side, Di is the thickness and air gap of the i-th lens from the object side, and N1 and νl are the radius of curvature of the first lens surface from the object side, respectively. These are the refractive index and Atsube number of glass.

Numerical Example I F-135FNO-1:Z8 2ω-18,2”Rl-
65,00D I-7,00N 1-1.62299
C1-5&2R2--158Z 72 D 2-0
．． 15R3-62, 93D3-8.00 N 2-1
．． 60311 Shi2-60.7R4--211,82
D 4-0.43R5--189,57D 5-2.2
0 N 3-1.80518 v 325.4R6
-114,60D6-7 R7-28,78D 7-2.69 N 4-1.6
0311 Shi4-60.7R8-25,64D 8-
8.37 R9-Aperture stop D9-3 R1()--230,51DIO-3,12N 5-L
75520 Shi5-27.5R11--50,13
Dll-1,39N 6-1.60311 Jiro 6
0.7R12-37, 77012-IL5 R13= 17a 55 Di3-6.50
N 7-1.69680 v 7”55.5R1
4--33,07D14-1.50 N8-1.5
9551 Shi8-39.2R15--190,88 f■--574,96 f/f■-o, zas 2nd lens sty 6-order movement toward the body side during soft focus R8; Aspheric coefficient -O B-2 ,6405XlO-7 C-LO613Kari 0-10 D-Z4158X10-12 E-λ2353XlO-16 Numerical Example 2 F-135FNO-1:Z8 2ω-1&τR1~5
0.94 DI-9,00N l-1,62299
C1-58.2R2--256L 76 D 2-0
．． 15R3-941103-5,50N 2-1.62
299 Shi2-5&2R4--37&42
D 4-1.92R5--189,92D 5-Z
20 N 3-1.80518 v 3=25
．． 4R6-135,07D6-Variable R7-Aspherical D 7-2.60 N 4-158
313 Shi4-59.4R8-26,319D 8-
Variable R9-Aperture diaphragm D-Variable RIO--96,86DIO470N 5-1.755
20y 5-27.5R11--4192Dll
-1,39N 6-L 54072 v 6-47
．． 2R12-38゜39 D12 change R13-90,61Di3-5.30 N 7-1
．． 48749 v 7-70.2R1← -69,
19 Second lens group with soft focus from normal mode■
The amount of feed is approximately 24R7 from the side of the object; aspherical coefficient A-1,639X10-2 B~3.847X10-6 C-Z266XlO-9 D--LO51XlO-12 E-3,609XIO-15 ) According to the present invention, a good soft effect can be quickly obtained by using a focus detection means to detect changes in the best image plane when changing from normal shooting to soft focus, and furthermore, a good soft effect can be obtained quickly by using a focus detection means. By configuring the lens group and the focusing lens group independently, it is possible to achieve a soft-focus function with a simplified lens barrel structure, thereby achieving a solid photographic system.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention.
FIG. 3 is a diagram of various aberrations during normal photography and soft focus in Numerical Example 1 of the photographic lens according to the present invention. The fourth factor is the aberration diagram of Numerical Example 2 of the photographic lens according to the present invention. In FIG. 1, l is a photographing lens, 2 is a rotating mirror 13, a condenser lens 14 is a focus detection means 15, a pentaprism, 6 is an eyepiece, 7 is a driving means, and I, U, and Ill are 11th, 21st, and 3rd lenses, respectively. The lens group S is an aperture stop group. 3rd Haze Loss Absorption and Absorption 5 Figure

Claims (3)

[Claims] (1) In a taking lens that has two lens groups, soft focus lens group SF and focus lens group F, calculate the amount of movement of the best image plane that occurs when a soft effect is obtained by moving the lens group SF. A photographing system having a soft focus function, characterized in that focus detection is performed by a focus detection means, and focusing is performed by moving the lens group F by a drive means using an output signal from the focus detection means. (2) The photographing lens is arranged in order from the object side: a first lens group with positive refractive power, a second lens group having a meniscus-shaped soft focus lens group SF with a convex surface facing the object side, an aperture diaphragm, and a focus lens group. 2. An imaging system having a soft focus function according to claim 1, characterized in that the photographing system is constituted by three lens groups: a third lens group having a lens group F; (3) The detection of the amount of movement of the best image plane that occurs when a soft effect is obtained by the focus detection means is performed using a light beam of F8 or less among the axial light beams passing through the photographing lens. Photography system with soft focus function.