JPS62112114A - Photographing system having soft focusing function - Google Patents

Abstract

PURPOSE:To efficiently obtain soft focusing effect and to simplify the structure of a lens barrel by specifying the constitution of lenses and moving a part of lens groups in normal photographing without arranging specific lens group. CONSTITUTION:The titled system is constituted of the 1st lens group I having positive refractive force, the 2nd lens group II turning its convex surface to the object side and having a meniscus-like lens, an aperture diaphragm, and the 3rd lens group which are arranged successively from the object side and the soft effect is generated by moving the 2nd lens group on the optical axis. Thus, the soft effect is obtained by moving a part of lens groups in the normal photographing without arranging a specific lens group to obtain the soft effect and the structure of the lens barrel is prevented from being complexed by independently arranging the lens group for focusing and the one to obtain the soft effect.

Description

[Detailed Description of the Invention] <Industry> 2 Field of Application) The present invention relates to a photographing system having a soft focus function suitable for photographic cameras, video cameras, etc., and particularly to a photographing system that moves some lens groups of the photographing system. In particular, this relates to a photographing system having a soft focus mechanism that mainly changes spherical aberration to produce a soft effect.

(Prior Art) Various photographic systems have been proposed to obtain images with a soft effect, which are softer-looking images than conventional ones. The soft effect is optically delayed, and produces a certain aberration, mainly a spherical aberration of a certain shape (q). -Photographing system with a scrap function was published in 1983-7
This method has been proposed in Japanese Patent Publication No. 6921, Japanese Patent Publication No. 5B-1402, Japanese Patent Application Laid-Open No. 55-52013, etc.

Among these, in Japanese Patent Application Laid-open No. 52-76921, an air gap is provided between two concave lens surfaces at the position where the principal ray intersects the optical axis when opened, and two lens groups sandwiching this air gap are A soft effect is obtained by moving along the optical axis at different speeds. Focusing is achieved by extending the entire lens system. This method requires a separate lens group to obtain an air gap and a soft effect, which is unnecessary for maintaining performance in normal shooting.Furthermore, the same lens group must be moved at different speeds to obtain a soft effect and when focusing. Because of this, the lens system and the lens mirror tend to have extremely complicated structures.

In Japanese Patent Publication No. 5B-1402, a soft effect is obtained by using parallel planes having 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 clothing shadows.

In Japanese Patent Application Laid-open No. 55-52013, the positive refractive power is 11η.
A soft effect is obtained by changing the spacing between the lens groups and the rear group with negative refractive power, and focus is achieved by moving the entire lens system. This method tends to require a complicated lens barrel structure for moving the lens groups.

(Problems to be Solved by the Invention) The present invention generally solves the problem by appropriately setting the lens configuration.
An object of the present invention is to provide an imaging system having a soft focus function with a simplified lens barrel structure that efficiently obtains a soft effect by simply moving some of the lens groups in m jJ2 on the optical axis.

(Means for solving the problem) A first lens group having a positive refractive power, a second lens group having a meniscus-shaped lens with a convex surface facing the object side, an aperture diaphragm, and a third lens group are arranged in order from the object side. The second lens group is moved along the optical axis to produce a soft effect.

Other features of the invention are described in the Examples.

(Example) 1st. Second. FIG. 3 is a cross-sectional view of lenses of numerical examples 1 to 3 of the present invention, respectively. In the figure, I, II, and I[[ are the first
．． Second. This is the third lens group.

In this embodiment, the second lens group is composed of a single meniscus-shaped lens A with a convex surface facing the object side, and this lens A is moved on the optical axis to obtain a soft effect. In addition, the third lens group is composed of two lens groups I[1-1, l with negative and positive refractive powers.
11-2, of which the front lens group 11-1 having a negative refractive power is moved toward the image plane side to perform orcus.

In this example, the refractive power of the first lens group is positive, the total refractive power of the second and third lens groups is negative, and the overall lens length is shortened by configuring the photographing system as a telephoto type. We are trying to By using so-called rear focusing, in which focusing is performed by moving the small lens group 01-1 having a negative refractive power of light π in the third lens group, rapid focusing is possible. By configuring the second lens group with a meniscus-shaped B-lens with a convex surface facing the object side, aberration fluctuations ji when focusing is performed by moving the lens group lll-1 are reduced.

Further, in this embodiment, the axial light beam exiting the first lens group is in a convergent state. For this reason, in order to obtain a soft effect, the second
When the lens group has negative refractive power, it is moved toward the image plane to obtain undercorrected spherical aberration, or moved toward the object side to obtain overcorrected spherical aberration. When the second lens group has a positive refractive power, the movement of the second lens group causes spherical aberration in the opposite direction to the above, so it is necessary to move each lens group in a direction according to the purpose to obtain the desired amount of spherical aberration. I have to.

In the numerical examples described later, the spherical aberration is changed in both the 1fli positive and undercorrected direction and the overcorrected direction.

In this example, the lens A of the second lens group has a meniscus shape with a convex surface facing the object side, and an aperture stop is placed behind the second lens group, so that the spherical center of the lens A is directed toward the aperture stop side. There is. This greatly refracts the axial rays and minimizes refraction of the off-axis rays, making use of the difference in height of the axial rays from the optical axis to reduce spherical aberration when moving lens A to obtain a soft effect. This reduces the chances of other political differences arising.

As described above, in this embodiment, in order to obtain a soft effect, a special lens group is not arranged δ, but a soft effect is obtained by moving some lens groups in the normal wt shadow. The lens group for focusing and the lens group for obtaining the soft I effect are separated, thereby preventing the lens barrel structure from becoming complicated.

Although the object of the present invention is achieved as described above, in order to obtain the effect on the soft+ more efficiently, when the focal lengths of the second lens group and the entire system are fll and f, respectively, -0,1< f/ fI
I < 0.1 (1
) It is better to satisfy the following conditions.

Conditional expression (1) is 1b, which reduces fluctuations in aberrations other than spherical aberration when moving the second lens group on the optical axis, and also satisfactorily corrects fluctuations in aberrations when rear focusing is adopted.
It's something. The refractive power of the second lens is the conditional expression (1
) and become too strong, or 2N< too much, the second lens group is moved to create a soft effect. I don't like it because it gets bigger.

In this practical hh example, at least one lens surface in the second lens group is preferably provided with an aspheric surface whose refractive power gradually becomes stronger toward the lens periphery and (1) whose refractive power becomes weaker toward the periphery of the lens. According to this, it has a large effect only on spherical aberration, and has almost no effect on other political differences! It is now possible to very easily obtain any soft effect that does not require d3%.

In this example, the refractive power of the second lens group is expressed by conditional expression (1).
The refractive power may be positive or negative as long as it satisfies the following, but in the numerical examples described later, negative refractive power is used, especially within the range of -0,1 <f/'fU< 0, to efficiently soften the refractive power with less moving arsenal. It's getting an effect.

In this example, in order to satisfactorily correct the various political differences of the entire screen and further correct the aberration fluctuations during focusing, the details of the second lens are two lenses, both of which have convex surfaces, and two lenses whose both lens surfaces are convex. Consists of three concave lenses, the third
It is preferable that the lens group m-t of the lens group is composed of a bonded lens in which a positive lens and a negative lens are bonded together.

Note that the second lens group may be composed of a plurality of lenses including a positive lens or a negative lens, and in this case, the second lens detail and the final lens surface of this group have a convex shape toward the object side. That's fine.

Next, numerical examples of the present invention will be shown. In numerical examples R
4 is the radius of curvature of the first lens surface from the object side, D
i is the first lens thickness and air gap from the object side, Ni
and vi are the refractive index and Abbe number of the first lens from the object side, respectively.

Numerical example IF=I35 FNO=l:
2.11 2w=18.2°RI=li5. oO
D + = 7.00 N l = 1.62
299 ν 1=5n), 2R2=-1582,7
2D 2= 0.15R3= 62.93
D3=8.00 N2=1
．． 603+1 ν 2=60.7R4=-21
1,82D 4= 0.4:IR5= -189
,57D 5=2.20 N :1=1
．． 80518 υ :1=25.4R6=1
14.60 D (i= 7R7=
28.78 D 7= 2.69 N
・I=1.60311 ν 4=60.7R8
= 25.64 D Il = 8.37
R9= Aperture diaphragm D9= : ] N
5=1.75520 ν co=27.5RIO
= −230,', +l DIO= :]
, 12 N 6 = 1.80311 ν 6
=IiO-7RII=-50,13DI]=
1.39R+2= 37°77 Di2=
15.5 N 7=1.69680
ν7=55.5RI3=176.55
D13=6.50R14=-:13.07
D-th = 1.50 N 8 = 1.5955
1 Shi8=:+9.2R15=-190,88 fn==57L96 f/f11=-0,235
At soft focus, 2nd lens group 6m towards object side
+n movement R8 aspheric coefficient A=O B= 2.6405 x 10-' C= 1.0613 x 10" D= 2.4158 x 1O-12 E=-2,2:]53 x 10-" Numerical implementation Example 2 F=135 FNO=]
: 2.8 2w=18.2'Rl= 50.94
D l = 9.00 N 1 = 1.6
2299 ν 1=58.2R2=-2561,7
6D 2= 0.15R3= 94.11
D3=5.50 N2=1.62299
V2=58.2R4=-378,42D 4=
1.92R5=-189,92D5=2.2
0 N 3=1.80518 ν3==25.4
R6= 135.07 D6= 0.8
R7=oo D7=2.60
N4=1.58313 ν4=59.4R8
= 264I D B = 17.57R
9= Aperture diaphragm D 9= 6.3 N 5
=+, 7ss>o 5=27.5R10=-9
6,86DIO=2.70 N6=1.540
72 Shiro=47.2R1+= -42,920
11= 1.39R12= 38.39D
12 = 19.70 N 7 = 1.48749
Schiff = 70.2R13 = 90.61
D13=5.30RI4=-69,19 fII=-426,83f/fll=-0,316 At soft focus 2nd lens group 9.2m toward the image side
m movement R7 aspheric coefficient A= 1.63Q2 X 1O-2B= 3.
8471 x 1O-6 C= 2.2667 x 1O-9 D=-1,0517X 1O-12 E= 3.6097 x 10" Numerical Example 3 F-135FNO=I: 2.
8 2w=I8.2°Rl-50,56D +=
10.50 N 1=1.43:187
ν 1=95.1R2=-172,05D 2=
0.21R3=75.15D3
= 7.30 N 2 = 1.49700
ν 2=81.6R4=-500,28D 4
= 1.64R5= -148,li2D
5=2.43 N 3=1.72047
ν3=34.7R6=240.83
D6=4.3R7=29.54
D7=2.77 N4=1.58
913 ν 4=61. OR8=27.6
8 D 8= 12.66R9= Aperture stop D 9= 2.00 N 5=1.75520
C5=27. ! +RIO=-82, :TOD
lO = 3.12 N 6 = 1.6 + 340
υ 6=43.8RII=-30,32D
11= 1.39R12= 40.28
D12= 16RI3= 190.97
D13=6.00 N7=1.6968
0 ν 7=55.5RI4=-49,79
DI4=1.50 N0=1.69895
Z/8=30. IRI5- -77.57 f II = -1665, 02f/f II = -0,
081 At soft focus, 2nd lens group moves 6.2mm toward the image plane R8 aspheric coefficient A=O B= 7.669 x 1O-7C=-1,1
213x 10-" D = 7.5366 It has a soft focus function that efficiently obtains a soft effect by moving some of the lens groups during shooting, and also simplifies the lens barrel structure by configuring it separately from the focusing lens group. It is possible to achieve the shooting system.

[Brief explanation of drawings]

1st. Second. FIG. 3 is a cross-sectional view of lenses of numerical examples 1 to 3 of the present invention, and FIG. Z6. FIG. 8 is a diagram of various aberrations in the normal mode of numerical examples 1 to 3 of the present invention, and FIG. 7th. FIG. 9 is a diagram of various aberrations during soft focus of numerical actual hK examples 1 to 3 of the present invention. In the figure, I, I1. [are each the first
．． Second. In the third lens group, an arrow SF indicates a moving direction during soft focus, and an arrow F indicates a moving direction during focus during normal shooting.

Claims (4)

[Claims] (1) In order from the object side, the first lens group has a positive refractive power, and the second lens group has a meniscus-shaped lens with a convex surface facing the object side.
1. An imaging system having a soft focus function, comprising a lens group, an aperture stop, and a third lens group, and a soft effect is produced by moving the second lens group on the optical axis. (2) An imaging system having a soft focus function according to claim 1, wherein at least a part of the third lens group is moved to perform focusing. (3) A patent claim that satisfies the following condition: -0.1<(f/fII)<0.1, where fII is the focal length of the second lens group and f is the focal length of the entire system. A photographing system having a soft focus function according to item 2. (4) Claim 3, characterized in that at least one lens surface in the second lens group is provided with an aspherical surface.
Photography system with soft focus function as described in section.