DE3126566C2 - Lens for an electron optical imaging system - Google Patents

Abstract

An electron-optical imaging system is described with an electron picture tube, the luminescent screen and / or photocathode of which are curved in such an aspherical-rotationally symmetrical concave manner towards the electron picture tube that the radius of curvature increases from the inside to the outside. The object field or the image field of the downstream or upstream optical system is curved in accordance with the curvature of the fluorescent screen of the photocathode. The type of curvature provided according to the invention allows not only a compact construction of the electron picture tube, but also enables a simple optical system with a high relative aperture and low image defects.

Description

The invention relates to an objective for an electron-optical imaging system according to the preamble of claims I and 9. Such lenses are used, for example, in image converters or residual light intensifiers used.

Lenses are known from practice whose electron picture tube has a fluorescent screen that is concave towards the tube with spherical curvature has eJectron picture tubes with a concave luminescent screen can be due to more favorable electron-optical conditions, much tisiner and lighter than tubes with planar Fluorescent screen can be built. However, it has turned out to be difficult, the object field of the downstream Objective to adapt the spherically curved luminescent screen, since the required curvature of field is opposite to the "natural curvature of field" of a lens.

Such lenses are therefore inferior to lenses with a flat object or image field in terms of their imaging quality. Therefore, in the vast majority of cases, electron optical imaging systems are used flat luminescent screen and corresponding image or object field of the lenses despite the overall large Dimensions of the imaging system used.

The above explanations apply analogously to the photocathode of the electronic picture tube or the image field of the upstream optical recording system.

The invention is based on the object of a lens according to the preamble of patent claims 1 or 9 of this type to develop that with small dimensions a good image quality is achieved even with a high aperture will.

According to the invention, this object is achieved in the case of lenses according to the preamble of patent claims 1 and 9, respectively solved by the features specified in the characterizing part of claim 1 and 9, respectively. Optical Systems with aspherically-rotationally symmetrically curved object or image field, its radius of curvature increases from the inside to the outside, an equally good image quality can - as was recognized according to the invention like optical systems with a flat object or image field. In addition, such optical Build systems relatively simple, even with a high aperture, so that the optical system has small dimensions may have. The small dimensions of the picture tube are (largely) consistent With the curvature of the object or image field, the curvature of the luminescent screen or the photocathode possible. Thus, the electron-optical imaging system provided with the objective according to the invention excellent image quality with small dimensions.

Developments of the invention are given in the sub-claims.

For example, an advantageous shape of the object field or of the luminescent screen is specified in claim 2. Given the curvature of the luminescent screen in the near-axis area due to electron-optical conditions, the aspheric parameter K is determined as a function of the focal length and the image angle of the optical system in such a way that the image quality of the optical system is as good as that of a system with a flat object field.

According to claim 3, the faceplate on which the luminescent screen is applied, as an element of the optical System be trained.

By arranging at least one biconcave lens near the luminescent screen according to claim 6, the Image quality further improved.

The structure according to claim 7 allows an angled beam path · τη optical system, so that the electron-optical imaging system can be adapted to special requirements or can also be constructed in a space-saving manner.

The invention is described below using an exemplary embodiment with reference to the drawing, in which the embodiment is shown in section, described in more detail.

An electron picture tube (not shown in more detail) has a fluorescent screen 3 that has been used on a faceplate 2. The surface r 1 of the screen support 2 carrying the luminescent screen 3 is curved in such an aspherical-rotationally symmetrical concave manner towards the electron picture tube (on the left in the figure) that the radius of curvature increases from the inside to the outside.

The visible image produced by the electron beam of the picture tube in a known manner on the luminescent screen 3 is displayed by means of the optical system shown in the drawing, the sharply imaged object field of which is the fluid. r \ or the luminescent screen 3 coincides, shown.

The optical system has a relatively high aperture, so that there is a bright image of the screen image. The screen carrier 2, the second surface rl is also curved concavely, is included in the calculation of the optical system.

In the figure, S is the common axis of the optical system shown as well as that of the individual shown designated picture tube.

In detail, the optical system consists of two lens groups I and II arranged at a large distance. The radii ri of the individual surfaces of the optical system, the assigned lens thicknesses dt or the air gaps // and the refractive indices n,. and the Abbe's numbers v _{e of} the materials used for the individual lenses are given in the following table.

Tabel

λI aspherical surface according to claim 2 with K = -2.0 and C - 1 / 37.57

v _r = 36.11 v _r = 54.5 v, = 54.5

25.2

v, = 54.5 v .. = 25.2 v _r = 60.0 v, = 60.0

15th rl = -37.57 d \ = 2.43 ", · ⁼ 1.624 ri = 78.37 W. = 3.4 i / • 4 = -56, lo dl = 1.58 n _r = 1.694 20th r5 = 120.74 / 2 = 1.96 rf, = -66.02 i / 3 = 2.50 n _r = 1.694 25th rl = -328.51 / 3 = 3.96 r% = -95.69 there = 3.20 "<■ = 1,813 1-9 = -116.60 / 4 = 2.11 30th HO = 36.79 dS = 7.47 n, = 1.694 r \\ = 97.81 / 5 = 66.54 J 5 r \ l - oo dk = 5.34 1,813 / • 13 = 985.79 / 6 = 0.59 / • 14 = 62.13 dl =! 2.80 /?,. = 1.623 40 / ■ 15 = 1922.35 Il = 1.07 / • 16 = 108.35 dS = 9.60 n, = 1.623 45 Relative Opening 1: 1.90 Focal length / = 100

1 sheet of drawings

50

Claims (9)

Patent claims: 1. Lens for imaging a visible image on a concave to an electron picture tube Luminescent screen on a flat image field, characterized in that the luminescent screen (3) and the The object field of the objective (4) roughly coincide and are curved in an aspherical-rotationally symmetrical manner are that the radius of curvature increases from the inside out. 2. Lens according to claim 1, characterized in that the distance ζ in the direction of the optical axis (5) between the vertex of the luminescent screen (3) or the object field and a point on the The fluorescent screen or the object field with the height A is given by: z = c A ² / (l + Vl- (A ^- + I) C ² A ² ) where c is the constant of curvature and K is the aspheric parameter, which has a value between -0.5 and -10. 3. Objekei i according to claim 1 or 2, characterized in that the luminescent screen (3) is arranged on a faceplate (2) whose second surface {rl) is also curved concavely. 4. Lens according to claim 3, characterized in that the second surface (rl) is spherical, and its radius of curvature is 0.5 to 5 times as large as the near-axis radius of curvature of the luminescent screen (3). 5. Lens according to claim 3, characterized in that the second surface (rl) has the same shape as the luminescent screen (3). 6. Lens according to one of the preceding claims, characterized in that the optical system (4) has at least one biconcave lens near the luminescent screen. 7. Lens according to one of the preceding claims, characterized in that the optical System (4) consists of two spaced apart lens groups (I, II) so that between the Lens groups a deflecting mirror or prism can be inserted 8. Object according to one of the preceding claims, characterized by the following data: 30 rl aspherical surface according to claim 2 with K = -2.0 and C = 1 / 37.57 dl - 2.43 n _c = 1.624 v _r = 36.11 Λ = -37.57 JS / 1 = 3.41 rl = 78.37 dl = 1.58 η, = 1.694 ν, = 54.5 / ■ 4 = -56.16 / 2 = 1.96 / · 5 = 120.74 dl = 2.50 n _r = 1.694 ν, = 54.5 Sj r6 = -66.02 ί / 3 = 3.96 * ■ ' rl = -328.51 </ 4 = 3.20 η,. = 1.813 ν, = 25.2 / • 8 = -95.69 / 4 = 2.11 / ■ 9 = -116.60 dS = 7.47 η, = 1.694 v _r = 54.5 / -10 = 36.79 / 5 = 66.54 / ■ 11 = 97.81 dS = 5.34λ, = 1.813 v _c = 25.2 / • 12 = οο / 6 = 0.59 / ■ 13 = 985.79 dl = 12.80 η, = 1.623 v _r = 60.0 / • 14 = 62.13 Π = 1.07 r 15 = 19.22.35 ί / 8 = 9.60 η ,. = 1.623 ν ,. = 60.0 / ■ 16 = 108.35 relative aperture 1: 1.90 focal length / = 100 with ri are the radii of curvature, dl the lens thickness, // the air gaps n _{c are} the refractive indices, and with v _r the Abbe's numbers are designated. 9. Objective for imaging a flat object field on the photocathode of an electronic picture tube, characterized in that both the image field of the objective and the photocathode are aspherically rotationally symmetrical in this way are concavely curved towards the picture tube that the radius of curvature of increases inside out.