DE1114337B - Four-lens afocal attachment system for shortening the focal length of a downstream lens - Google Patents

Description

Four-lens afocal attachment system to shorten the focal length of a downstream lens The invention relates to a lens consisting of four lenses afocal attachment system to shorten the focal length of a downstream, z. B. photographic lens, the individual lenses of which one after the other collecting, dispersing, have a dispersing and collecting effect and whose first lens is convex on the object side. Such header systems are required to be well corrected that the The diameter of your front lens is not too large and that your exit pupil is sufficient is far behind the last lens vertex, so that it can also be used in unfavorable cases can be placed in the entrance pupil of the downstream objective. The so far known, consisting of four lenses attachments meet these three requirements not in a satisfactory way.

The object of the invention is to improve the known attachments. Extensive calculations have shown that this goal will be achieved if the third Lens is bent meniscus-like so strongly towards the object that the radius of curvature their object-side area no longer than 10 times the length of the attachment system is.

It has also proven to be beneficial for the state of correction, the third lens standing alone, i.e. by clear vertex distances from theirs To arrange neighboring lenses separately.

The ratio of the vertex distances of the third is advantageous Lens from neighboring lenses between 2: 1 and 1: 2.

The first two lenses can be cemented in a manner known per se be.

The free diameter of the front lens of an attachment of the aforementioned Type does not need to be greater than 1.5 times the overall length 1, with the Overall length 1 is the distance between the first lens vertex and the last lens vertex of the Intent is understood. The good correction is achieved for an exit pupil, whose distance from the last lens is greater than 0.6 times the overall length 1.

In the drawing, an embodiment of the invention is in section shown.

The attachment system consists of a front dispersing member, whose two separately drawn lenses Li and Lir are also cemented together can, from a single standing meniscus Liii, which bent towards the object side. is, and from another converging lens Liv.

In the drawing and table, the individual lenses are designated with L, with Y the radii, with d the thicknesses and air gaps, with na, nd and ni, the refractive indices for the red hydrogen line C, the yellow helium line d and the blue hydrogen line F.

The components of the example carried out with the telescope magnification 1 '= 0.625 are listed in the following table. The free opening curvature Lens radius of curvature r K - 1 vertex distance d nC rtd rtr r Li r1 = + 1.69446-1 -I - 0.59016: 1 d, - 0.16977 - 1 1.72096 1.72830 1.74637 r2 = -11.003-1 -0.09088: 1 d2 = 0 r3 = -11.003-1 -0.09088: 1 Lii d3 = 0.02791-1 1.61980 1.62374 1.63306 r, _ + 0.56758-1 +1.76186: 1 d4 = 0.25884-1 Liii r5 = + 2.19549-1 -1-0.45548: 1 d5 = 0.03488-1 1.73904 1.74400 1.75561 r. = + 0.62774-1 +1.59301: 1 dg = 0.23186-1 Liv r7 = + 0.74607-1 -I-1.34036: 1 d7 - 0.27674-1 1.44424 1.44628 1.45088 r $ _ -1.06914-1 -0.93533: 1 1.3 - 1 of the front lens is sufficient to capture an angle of 75 ° on the object side.

In this example, the exit pupil is 0.7 # 1 behind the last lens vertex.

Claims (7)

PATENT CLAIMS: 1. An afocal attachment system consisting of four lenses to shorten the focal length of a downstream lens, its individual lenses one after the other collecting, dispersing, dispersing and collecting work and its first Lens is convex on the object side, characterized in that its third lens after the object is bent so strongly meniscus that the radius of curvature their object-side area no longer than 10 times the length of the attachment system is. 2. Afocal attachment system according to claim 1, characterized in that the third lens standing alone, i.e. due to the clear air gap from its neighboring lenses is arranged separately. 3. Afocal attachment system according to claim 2, characterized in that that the ratio of the vertex distances of the third lens to the neighboring lenses is between 2: 1 and 1: 2. 4. Afocal attachment system according to claim 1, characterized characterized in that the first two lenses are cemented. 5. Afocal attachment system according to claim 1, characterized in that the free diameter of the front lens is not greater than 1.5 times the overall length 1 of the attachment system. 6. Afocal attachment system according to claim 1, characterized in that the distance of the exit pupil from last lens vertex is greater than 0.6 times the length 1 of the system. 7. Afocal attachment system according to claim 1, characterized in that its components come so close to the values of the example compiled in the table below that any curvature by no more than , each vertex distance d deviates by no more than ± 0.2 # 1 and each refractive index n by no more than ± 0.1 from the value given in the table, the refractive indices for the red hydrogen line C with hc, for the yellow Helium line d is denoted by na and for the blue hydrogen line F by nF and 1 is the length of the attachment. curvature Lens radius of curvature r K - 1 vertex distance d IIC nd ns r LI rl = + 1.69446-1 -I-0.59016: 1 dl = 0.16977 # 1 1.72096 1.72830 1.72096 r2 = -11.003-1 -0.09088: 1 r3 = -11.003-1 -0.09088: 1 d2 0 LII d3 = 0.02791 # 1 1.61980 1.62374 1.63306 r4 = + 0.56758-1 -F1.76186: 1 r5 = + 2.19549-1 -I-0.45548: 1 d4 = 0.25884-1 LIII re = -I-0.62774 # 1 -I-1.59301: 1 d5 = 0.03488-1 1.73904 1.74400 1.75561 de = 0.23186-1 LIV r7 = + 0.74607-1 -I-1.34036: 1 d7 = 0.27674-1 1.44424 1.44628 1.45088 r8 = -1.06914-1 -0.93533: Z Documents considered: German Patent No. 702 436.