JPH02167516A - Microfilm projection lens system - Google Patents

Abstract

PURPOSE:To make a projection optical system compact on the whole by satisfying specific conditions as to the focal length of a 1st lens, the focal length of the whole system, the radius of curvature of the enlargement-side surface of a 5th lens, and the radius of curvature of the reduction-side surface of the 5th lens. CONSTITUTION:A stop is arranged at the front to form a type suitable to front stop constitution; and 1st - 3rd lenses are triplet lenses and 4th and 5th lenses are a positive lens and a negative lens for compensating an off-axis aberration. Each condition of 0.5<f1/f<0.95 and -1.2<r9/r10<-0.4 is satisfied by assuming the focal length of the 1st lens as f1, the focal length of the whole system as (f), the radius of curvature of the enlargement-side surface of the 5th lens as r9, and the radius of curvature of the reduction-side surface of the 5th lens as r10. Consequently, a lighting system is easily made common together with a projection lens system of other magnifications and the wide-view-angle lens system can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microfilm projection lens system used in a microleague or reader printer having an image rotation mechanism for reproducing images of microfilm.

[Prior Art] Many microfilms are recorded in such a way that each frame of the original is not aligned vertically and horizontally when it is created, and is often photographed in an irregular manner. For this reason, conventionally, when reproducing images using league or league blink, an image rotation prism is placed between the projection lens and the screen, that is, on the magnifying side of the projection lens, to correct the vertical and horizontal positions of the reproduced image projected onto the slurry. It is common to do so.

However, in conventional projection lens systems, the entrance pupil is located almost at the center of the projection lens system, so when the angle of view is wide, the inserted image rotation prism is placed close to the end surface on the enlarged side of the projection lens system. If the image rotation prism is disposed in the center of the prism, the light beam will be spread, and the size of the image rotation prism will increase. In addition, an image rotation prism is equivalent to a flat plate parallel to the optical axis tilted at 45 degrees, and its performance varies depending on the location even within the same image circle diameter, and the larger the image rotation prism, the more on-axis astegmatism will occur. The problem is that the axial astegmatism becomes large (axial astegmatism is proportional to the length of the bottom surface of the prism), leading to image deterioration, and the entire projection optical system including the mirror becomes larger.

For this reason, various so-called front aperture type projection lens systems have been proposed in which the entrance pupil position where the light beam is most converged in the projection lens system is located at the end face of the projection lens system. (
For example, Japanese Patent Publication No. 47-35027, Japanese Patent Publication No. 47-35027,
(Refer to Japanese Patent Laid-open No. 35028 and Japanese Patent Application Laid-Open No. 57-4016) [Problem 1 to be Solved by the Invention] By the way, in general, a front aperture type projection lens system cannot have a wide usable angle of view, resulting in field curvature.

Astigmatism becomes large, and it is difficult to correct coma aberration in a wide-angle lens system. Furthermore, there were also difficulties in making it compact. Furthermore, since it is a front diaphragm, the combination of glass materials for simultaneously correcting axial chromatic aberration and lateral chromatic aberration is limited, which is extremely difficult in terms of design.

This invention was made in view of these points, and the entrance pupil is placed at the end of the projection lens system to miniaturize the image rotation prism, and the angle of view 2ω = 278° and the F number 3.3 to 3.
．． It is an object of the present invention to provide a high-magnification projection lens system in which various aberrations are well corrected and the performance is good.

[Means for Solving the Problems] The invention of item 1 of the present invention includes a first lens that is a positive lens with a convex surface stronger than the magnifying side facing the magnifying side, and a second lens that is a biconcave lens.
It is composed of a lens, a third lens that is a biconvex lens, a fourth lens that is a biconvex lens, and a fifth lens that is a biconcave lens, and the aperture is located between the magnifying side end of the first lens and between the first lens and the second lens. This is a microfilm projection lens system arranged in such a manner that the focal length of the first lens is f+, the focal length of the entire system is f, and the radius of curvature of the enlargement side surface of the fifth lens is r9. The radius of curvature of the reduction side surface of the fifth lens is rl. Then, it is a microfilm projection lens system that satisfies the following conditions: (1) 0.5<f+/f<0.95 (2) -1,2<re/rho<0.4.

In addition, the invention of item 2 of this invention provides a first lens that is a positive lens with a convex surface stronger than the magnification side facing the magnification side, a second lens that is a biconcave lens, a third lens that is a biconvex lens, and a biconvex lens. A lens system for microfilm projection consisting of a fourth lens made of a cemented double-concave lens, with an aperture disposed from the enlargement side end of the first lens between the first lens and the second lens. where, the focal length of the first lens is f+, the focal length of the entire system is f, the radius of curvature of the enlargement side surface of the fifth lens in the fourth group is re, and the curvature radius of the reduction side surface of the fifth lens r,. This is a microfilm projection lens system that satisfies the following conditions: (1) o, 5<f, /f<0.95 (2) -2,0<re /r to<1.2.

[Example] Hereinafter, the present invention will be described in detail based on the drawings. 1st
3, 5, and 7 are cross-sectional views showing the configurations of Examples 1 to 4 of microfilm projection lens systems using the image rotation prism of the first aspect of the present invention. In order from the left screen side, which is the magnification side, the first lens is a positive lens with its strongly convex surface facing the magnification side, the second lens is a biconcave lens, the third lens is a biconvex lens, the fourth lens is a biconvex lens, and The parallel plane glass on the right side represents a microfilm holder.

The diaphragm S is disposed from the enlargement side end of the first lens to between the first lens and the second lens. That is, in Example 1 shown in FIG. 1, after the first lens, the lenses shown in FIGS.
In the lens systems of Examples 2 to 4 shown in the figure, a diaphragm is installed in front of the first lens.

The projection lens system of this invention has a diaphragm in front, an aperture efficiency of 100%, and an F number of 3.3.
It is bright at ~3.8 and is inexpensive with only 5 sheets.

The first to third lenses are triplet lenses, and the fourth lens is a type suitable for a front aperture.

The fifth lens is configured with a positive lens and a negative lens, respectively, in order to correct off-axis aberrations. In these lens systems, the focal length of the first lens is fl, the focal length of the entire system is f, the radius of curvature of the enlargement side surface of the fifth lens is ra, and the fifth lens is
When the radius of curvature of the surface on the reduction side of the lens is r+o, the following conditions are satisfied: (1) 0.5<f, /f<0.95 (2) -1,2<rs /r'+o<o, 4.

The above conditional expression defines an appropriate range of the focal length of the first lens, and is a condition for facilitating correction of spherical aberration at the front aperture.

If this upper limit is exceeded, the power of the first lens will be insufficient,
It becomes difficult to correct spherical aberration and coma aberration occurring in the first lens group from the second lens onward. If the lower limit is exceeded,
The power of the first lens becomes too strong, and the power of the first lens becomes too strong.
Control of the tolerance of parallel eccentricity of the lens becomes extremely strict.

Moreover, the above conditional expression (2) is a condition for maintaining the Petzval sum, which is shifted in the positive direction between the third lens and the fourth lens, at an appropriate value. If this upper limit is exceeded, the incident light beam to the fifth lens will be sharply bent by the 19th surface, and the air gap and eccentricity tolerance, which is the axial surface distance d9 between the fourth and fifth lenses, will be extremely large. It will be tough. Moreover, when the lower limit is exceeded, the astigmatism difference increases, leading to an increase in lateral chromatic aberration, both of which become difficult to correct.

Lens specifications of Examples 1 to 4 that satisfy each of these conditional expressions are shown in Tables 1 to 4. In each of these tables, the radius of curvature is r+, r2, etc. in order from the enlarged side of the screen.
, rl. , axial surface spacing dd2..., d, 2, the refractive index of the glass material at the d-line is NN2. ..., N6, the number υ1 to the roughness of the glass material. ν2゜..., shows the numerical value on each side of the white,
S indicates an aperture.

Aberration curve diagrams of spherical aberration, sine condition, astigmatism, and distortion of Examples 1 to 4 are shown in FIG. 2, Section 4, FIG. 6, and FIG. 8, respectively.

Next, FIG. 9 shows the configuration of a microfilm projection lens system using the image rotation prism of the second invention.

In this example, the fourth lens, which is a biconvex lens, and the fifth lens, which is a biconcave lens, are configured as a cemented lens.
-Different from the lens system of Example 4. That is, in order from the magnification side on the left screen side, the first lens is a positive lens with its strongly convex surface facing the magnification side, the second lens is a biconcave lens, the third lens is a biconvex lens, and the fourth lens is a biconvex lens. and a fourth group of cemented lenses consisting of a fifth lens that is a biconcave lens, and a diaphragm S that is arranged from the enlargement side end of the first lens between the first lens and the second lens. In this lens system, the focal length of the first lens is fl
, the focal length of the entire system is f, the radius of curvature of the enlargement side surface of the fifth lens of the fourth group of cemented lenses is re, and the radius of curvature of the reduction side surface of the fifth lens is rlQ, then ■0.5 <f, /f
<0.95 ■ -2,0<r9/rho<1.2.

The above conditional expression (2) is a condition for facilitating correction of spherical aberration at the front aperture. If this upper limit value is exceeded, it becomes difficult to correct spherical aberration and coma aberration, and if the lower limit value is exceeded, control of the eccentricity tolerance of the first lens and the second lens becomes extremely difficult.

Moreover, the above conditional expression (2) is a condition for maintaining the Petzval sum, which is shifted in the positive direction, at an appropriate value in the third lens and the fourth lens. If this upper limit is exceeded, the axial distance and eccentricity tolerance between the fourth and fifth lenses, which are cemented lenses, will become extremely severe. Moreover, when the lower limit is exceeded, astigmatism increases and lateral chromatic aberration increases, both of which become difficult to correct.

Table 5 shows the lens specifications of Example 5 that satisfy each of these conditional expressions, in order from the enlarged side of the screen, the radius of curvature r+, ri..., r12, and the axial distance d1.
．． d2..., d1□, the refractive index of the glass material at the d-line is Nl
, N2. ..., N6, the temperature of the glass material υ1. ν2.
. . . indicates the numerical value on each side of the white, and S indicates the aperture.

The longitudinal aberration curve of Example 5 is shown in correspondence with FIG. 10.

Further, the numerical values of each conditional expression of each of the above embodiments are summarized and shown in Table 6.

(Margin below) f=18.3 Radius of curvature r 10.75 r2-74.54 1st Table FNO,=3. 3 Axis top surface distance Refractive index (Nd) 7-point number (νd) d,
2.30 Nl 1.7435 171 49.
2 apertures rs -io, sa r, 10.61 rs 473.34 ra -11, [18 19,02 re (3,24 re -11,86 rho 22.92 r(X) d20.O di 1.55 d4 1.00 N2 1.7552 ν2
27.5ds 2.10d, 2.60Ns 1.8061 v33
3.3d? 0.75 d, 2.80 N41.7435 υ449.
2d9 1.60 d, o 1.50 Ns 1.7618 1/s
26.6d++ 7.90d, 23. (to Na 1.5168 νg
64.2 (Film holder) Σd = 27.10 (White 1it!I) f = 18.2 Radius of curvature S Aperture 12, 13 r2-21.57 rs -8,61 12,39 rt, 460.58 re - 9,81 r719.74 ra (3,11 r9-11.16 rho 18.14 FNO, = 3.3 Axial spacing Refractive index (Nd) 7-point number (νd) 1,6
667 1, 7552 1, 8061 1.7433 1.7618 3.0 [l N61.5168 White 64°2 (film holder) Σd = 27.68 (white glass) f = 18.2 Radius of curvature S Aperture r+ 14. 12 r2 -36.07 rs -17,02 r4 85.08 rr, 131.75 re (6,50 rt 12.00 rs 114.99 ra -14,71 rho 12.4O r++ (1) r+z (1) Table FNO, = 3.3 Axis spacing Refractive index (Nd) 7-beam number (νd) d24
．． 14 N.

da 0.60 (L O,90 ds 6.28 d62.90 d70.63 da 2.49 d, 1.47 d,, 1.56N5 d++ 4.00 d1□ 3.00 Na 1.5168 υ66
4.2 (Film holder) 29.3 51.7 47.3 27.6 1.6734 1.6710 1.7883 1, 7006 1.6405 N.

(White group) f=18. 1 Radius of curvature r+ 8.01 r276.01 S Aperture ra -22,46 r'< 7.39 ra 210.18 ra -13,66 rt 16.23 r8-17.41 r910.71 r+o ■ r++ ω 5th Table FNO, = 3.3 Axis spacing Refractive index (Nd) 7' Tsupe number (νd) d,
2.07 N, 1.8350 ν, 4
3.0d20.10 ds 1.09 a40.63 N21.7618 C266ds
2.03 d, 1.91 N31.8042 ν346.
5d, 1.69 da 2.39 N41.8350 17-43
．． 0a91.79 N51. [l[134υ, 3
8. [ldl. 7.60 d++ 3.00 Na 1.5168 Va
64.2 (White set) (Film holder) Σd =24.30 f=20.6 Radius of curvature r112.09 r2 -80.92 S Aperture rs Jl, 91 r411.88 r5532.83 ra (2,34 rt 21 .38 r8-14.72 re (3,28 r,. 25.16 r o.

r+2 (1) Table 4 FNO, = 3.8 Axis top surface spacing Refractive index (Nd) 7-point number (νd) d,
2.50 N, 1.7433 ν, 49
．． 2631.71 (L 1.14 N2 1.7552 Sea 2F, 5a, 2.39 d, 2.85 Nz 1.8061 v,
33.3d, 0.85 d, 3.19 N4 1.7433 ν449
．． 2d, 1.71 d,, 1.71 NB 1.7618 ν,
26.6d 9.40 dl. 3.00 N61.5168 Shiro 64
．． 2 (White set) (Film holder) [Effects of the invention] As explained above, the lens system of this invention that projects a microfilm by disposing an image rotation prism on the enlargement side has an entrance pupil where the light flux is most converged. By arranging the image rotation prism at the enlarged side end face of the projection lens system and arranging the image rotation prism close to the end face, deterioration of the projected image can be minimized, and the image rotation prism and the entire projection optical system can be can be made more compact. Furthermore, despite the relatively high magnification and short focal length, the pupil position is relatively far from the microfilm surface, making it easier to share the illumination system with projection lens systems of other magnifications.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing the configuration of Example 1 of the present invention, FIG. 2 is an aberration curve diagram of the projection lens system shown in FIG. 1, and FIG. 3 is the configuration of Example 2 of the present invention. FIG. 4 is an aberration curve diagram of the projection lens system shown in FIG. 3, FIG. 5 is a side sectional view showing the configuration of Example 3 of the present invention, and FIG. FIG. 5 is an aberration curve diagram of the projection lens system. FIG. 7 is a side sectional view showing the configuration of Example 4 of the present invention. FIG. 8 is an aberration curve diagram of the projection lens system shown in FIG. 7. 10 is a side sectional view showing the configuration of Example 5 of the present invention, and FIG. 10 is an aberration curve diagram of the projection lens system shown in FIG. 9. Patent applicant Minolta Camera Co., Ltd.

Claims (2)

[Claims] (1) A first lens that is a positive lens with a convex surface that is stronger than the magnification side facing the magnification side, a second lens that is a biconcave lens, a third lens that is a biconvex lens, a fourth lens that is a biconvex lens, and a third lens that is a biconcave lens. [1] 0.5<f_1/f<0.95 [2] In a lens system composed of 5 lenses, with the aperture disposed between the enlargement side end of the first lens and between the first lens and the second lens, ] A microfilm projection lens system that satisfies the following conditions: -1.2<r_9/r_1_0<-0.4. However, f_1; focal length of the first lens f; focal length of the entire system r_9; radius of curvature of the enlargement side surface of the fifth lens r_1_0; radius of curvature of the reduction side surface of the fifth lens (2) A first lens that is a positive lens with a convex surface that is stronger than the magnification side facing the magnification side, a second lens that is a biconcave lens, a third lens that is a biconvex lens, a fourth lens that is a biconvex lens, and a fifth lens that is a biconcave lens. [3] 0.5<f_1/ in a lens system that is composed of a fourth group consisting of a cemented lens and in which the aperture is disposed from the magnifying side end of the first lens between the first lens and the second lens. A microfilm projection lens system that satisfies the following conditions: f<0.95 [4]-2.0<r_9/r_1_0<-1.2.