JPS61124914A - Telecentric zoom lens - Google Patents

Abstract

PURPOSE:To reduce the overall length of a lens by putting the 3rd lens group not in monotonous linear motion, but in reciprocal motion and suppressing the overall movement range small. CONSTITUTION:The lens consists of five positive, negative, positive, negative, and positive groups and the 1st and the 5th groups are fixed; as the whole system is varied in power from the long-focus end to the short-focus end, the 2nd and the 4th groups move monotonously toward the 1st group and the 3rd group enter reciprocal motion toward the 5th group while drawing a convex track. Then, a stop is fixed to the 3rd group. This lens meets requirements shown by inequalities (I)-(V) [where U is object image distance, fi the focal length of the (i)th group, n2 the mean refractive index of the 2nd group lens, and nu5 the mean Abbe number of the 5th lens group].

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a zoom lens used in a projector, etc., and mainly to a telecentric zoom lens.

(Conventional Kei*) In order to change the projection intensity in a projector, prepare multiple lenses for different @military use, and project the lens as necessary.
It is necessary to replace the lens by attaching it to and removing it from the turret, or by mounting multiple lenses on the turret. Developed a zoom lens that satisfies telecentric conditions and published Japanese Patent Application Publication No. 57-16581.
No. 0, No. 57-169717, 1Iij57-173
Published as No. 812. However, all of these were developed for a screen with a diameter of 300 mm.

If you want to use these Q telecentric zoom lenses for a φ510C1 projector with a screen size of 1.7 times, with the same -angle and p-number, you will need a lens that has a screen size of 1.7 times and a focal length of 1.78. All the storage units other than the distortion storage unit would be on the 167th floor, which would be unsuitable for practical use.

(Problems to be solved by the invention) The invention improves the telecentric zoom lens disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 57-169717, and has a focal length of 1.
Although K has increased to about 7@, the objective is to keep the overall length of the lens compact and to keep the various aberrations within the same range as the lens disclosed in the above-mentioned publication.

Structure of the Invention (Means for Solving the Problem) The telecentric zoom lens of the present invention has an eight-lens structure as disclosed in the above-mentioned Japanese Patent Laid-Open No. 57-169717 JIt.
It is similar to the O4, but by making the movement locus of the third group lens a reciprocating movement rather than a controversial linear movement, the total movement range is kept small, and the overall length of the lens can be made compact. In other words, the zoom lens system of this invention basically consists of five lenses: positive, negative, positive, negative, positive, the first group and the fifth group are fixed, and the entire system has t- As the focus changes from the long focus end to the short focus end, the second and fourth groups each move like a fist in the direction of the 1st I+, and the third group reciprocates toward the 5th IP side in a convex O trajectory. When the diaphragm is moved and the diaphragm is fixed to the 3rd group, it becomes a trap, U: Distance between storage units fi: Focal length of the 1st group 0.02 < fVU (0,04...
(1) o, oi <1fzl/U <α03
...9) 0.02 (l j'41 /
U (0,04...(0 that satisfies condition 3) In terms of the sail body, the first IP is a conductive lens and at least two
The second group consists of at least two negative main lenses, a doublet consisting of an upper tower lens and a negative lens, and the third
The group is a doublet consisting of a positive path lens and a negative single lens, and a positive path lens, the fourth group is a doublet consisting of a positive path lens and a negative lens, and a negative lens, and the fifth group is a doublet Q consisting of a positive path lens and a negative negative lens. It consists of a pair and one lens, and the above (1), (2), (31'Z) #! Sweat and co-K.

Acceptable: The uniform refractive index of the second detailed lens Acceptable: 1.75 <Acceptable (4) 45 <
Possible,...-(5) ■Article 11! F'? It is M plus.

<for f'F-) Conditions (1), (2), and (3) are OS conditions in order to make the total lens length compact; that is, No. 29. Third review,
If the focal length of the 4th lens is kept within the above conditions, the distance between the 2nd and 3rd lenses and the 4th lens and 5th lens spaces at the long focal length can be kept small, and , the group spacing between the first detail and second groups and the group spacing between the third detail and fourth groups at the short focus end can be kept small. Furthermore, when zooming from the long point end to the short focus end, the second group, the third group,
Even if the movable lid of the fourth group is kept small, it is possible to obtain a sufficient variable ratio, and as a result, the overall length of the lens can be made compact.

The 1111 third group is used to control the movement of the aperture lid, and O is also O in order to minimize fluctuations in the entrance pupil position and to shorten the overall length of the lens. If the refractive power of the third group becomes even stronger, the number of third detail Q movable lids will decrease and the fluctuation of the incident m position will increase, which will increase the diameter of the front lens and cause a decrease in aperture efficiency, as well as the front and back of the diaphragm. If the convergence fluctuation is large at υ, it becomes difficult to correct the distortion O. Conversely, if the upper limit is exceeded, the amount of movement of the third group increases, making it difficult to correct the entire lens length.

2nd tIp% 4th beyond the lower limit of Article P+(2) (3)
If the refractive power of the ip is strengthened, the aberration Q fluctuation due to the plate wave O system will be large before the diaphragm, and it will be difficult to correct the convergence, especially the distortion convergence. Moreover, when the refractive power becomes weak beyond the upper limit, the movement amount of the second detail and the fourth detail increases, making it difficult to convert the entire length of the lens.

Getting on and off (4) is 4ili! Based on Note (2), this lens is intended to increase the refractive power of the second F# without making it difficult to correct various aberrations, and it is necessary to maintain a sufficient variable power ratio in the second ridge even beyond the lower limit. If this is attempted, the Veravar sum of the entire system will not be sufficient, leading to astigmatism in the Q form, and the occurrence of barrel-shaped distortion becomes noticeable on the long focal point side.

Condition (5) relates to correction of chromatic aberration. Generally, in a zoom lens, it is necessary to correct chromatic aberration for each lens group, but in the zoom lens of this invention, the chromatic aberration is particularly difficult to correct in the fifth detail due to the large numerical aperture on the short focal length side. It becomes a problem. It is particularly important to correct chromatic aberration of magnification, and if it deviates from line # (5), it becomes extremely difficult to correct chromatic chromatic aberration of magnification Q on the short focus side, and the occurrence of distortion due to color cannot be ignored.

(Implementation row) Examples of the zoom lens according to the present invention will be shown below.

Actual m row 1 (from the enlarged screen side) f = 176.06 ~ 58.72 Magnification 10X ~ 30X
N, A, 0.074-0.115 Magnification ratio 3.0
@Screen radius 255 mm RDN ν 31 -250.637 Distance between object peaks 1i 2000.0 mm Lens total length 205.8*, 1) ~ *4): variable
@ at each @ rate is missing a, b20x (f = 89.74)
17.18 29.77 9.34 47.90
30X (f=58.72) 3.60 38.6
4 2.50 60.47R: Lens θ radius of curvature D: Lens thickness or lens spacing N: dil, l (wavelength 587.56 nm) ”rom
50/50 ν: Atsube number fy'U = 0.0267 n2 = 1.77421
f21/Ll=u, Ol 58 Possible=58.18If
, l/U=0.0384 The aperture is located 0.8 mm in front of the East 3 group, and moves in unison with variable magnification herbal medicine 3F#. =177.78 ~ 59.21 @ rate 40x ~ 30
XN, A, 0.078-0.125 Magnification ratio 3.
O@screen half & 255mm RDN ν 31 -548.724 object distance ill
! 2000.0rrs? Fs Lens total length 20
6.6mm*1) ~*4): variable
eThe values at each magnification are as follows *1) *ri *3)
*4) 10x (f=177.78) 26.63
10.62 42.65 23.2820X(, f=
90.43) 19.95 28.98 9.
32 44.4330X (f=59.21) 8
．． 20 37.96 2.50 54.79R:
Lens curvature D = lens thickness or lens spacing N: dI/IA (wave & 587.56 nn1) TeC)
Jm refractive index ν: Atsube ft7/LI=o, o 272 n2 = 1
゜77421f2 horn=0.0161 ν5=
58.181fn prisoner = 0.0329 The aperture is 0.8 mm in front of the 39th ■. 12) There is a reed at the position, and a mouth that moves as a trap with three variable magnification herbal medicines.

[Brief explanation of the drawing]

Figures 1 and 2 are the actual IM example 1 and the implementation column zQl, respectively.
The fr plane view and its movement locus, and Figures 3 and 4 are its aberration curve diagrams.〇Patent applicant Roku Konishi Photography Shiba Co., Ltd. Agent for the applicant
Patent attorney Fumio Sato (and one other person) to Hasso

Claims (1)

[Claims] It consists of five groups: positive, negative, positive, negative, and positive.The first and fifth groups are fixed, and as the entire system is changed from the long focus end to the short focus end, the second and fourth groups A telecentric zoom system in which the 3rd group moves monotonically in the direction of the 1st group, the 3rd group reciprocates in a convex trajectory toward the 5th group, and the aperture is fixed to the 3rd group. lens