DD301804A7 - HIGHLY FLOATING SCAN OBJECTIVE SMALL CONSTRUCTION - Google Patents

Abstract

The invention relates to a high-resolution scanning lens of small length with front panel, consisting of four lens elements. The invention is applicable in the field of information and image recording. The aim of the invention is a lens with a small outer diameter and short length and small focal length and far in front of the system entrance pupil. The object is to provide a new constructive solution in which a consistently good correction over the entire field of view is ensured at the same time short length and large field angle. The structural design of an objective that fulfills the above task is specified. The necessary design data is contained in a table. Fig. 1

Description

For this 2 pages tables and 1 page drawing

Field of application of the invention

The invention relates to a Abtastobjektiv small length, consisting of four lens elements. The invention is applicable in the field of information and image recording.

Characteristic of the known technical solutions

Lenses with a small focal length and entrance pupil far in front of the system are known. They are used, for example, as eyepieces in microscopes or afocal systems and as magnifiers e.g. used for viewing picture tubes.

The eyepieces usually have a considerable Petzvalvölbung and only small opening ratios. They are thus not applicable as scanning lenses. Of the magnifiers, cathode ray tube viewing systems appear to be suitable for scanning purposes. However, this also results in problems with respect to the correction state. Thus, for example, the constructions disclosed in the published specifications DE-OS 2300203, DE-OS 2708691 and DE-OS 2657206 have considerable astigmatism that is disadvantageous for scanning objectives.

In the invention descriptions DE-OS 3151 221 and DE-OS 2849801 usable as scanning lenses systems are given with their design data. Although the correct correction properties required for scanning systems and a large aperture ratio are achieved, it is disadvantageous that the angle of view is much too small.

In addition, the former system is technologically difficult to implement.

Object of the invention

The aim of the invention is a lens with a small outer diameter and short length and small focal length and far in front of the system entrance pupil. The resolution should be at least 150 lines per millimeter, an aperture ratio of 1: 3.5 and a field angle of 2 σ = 52 ° should be realized.

Essence of the invention

The invention is based on the object to provide a new constructive solution in which a consistently good correction over the entire field of view is ensured at the same time short length and large field angle. In this case, it is technologically difficult to avoid special designs to avoid and to aim for a low centering and adjustment sensitivity. According to the invention, the object is achieved by a high-resolution scanning lens of small length with front panel, consisting of four members, characterized in that the first lens member is a scattering bent meniscus, the hollow side facing the object that the second lens member is a biconvex lens, the third Lens member is a downstream of a biconvex lens and a bent meniscus cemented cemented element, wherein the biconvex lens of the cemented element facing the object, and that the fourth lens member is a plano concave lens, which faces its face to the image.

The design data resulting for a scanning objective according to the invention are given in Table 1. With the solution according to the invention specified above, a lens can be realized which has a small outer diameter and a short overall length and a small focal length. It satisfies the demands placed on a scanning system in terms of short overall length and large field angle while at the same time providing good correction over the entire field of view. In particular, the chromatic aberrations are low, there is no vignetting and the distortion increases monotonically over the entire field of view without short-term rapid changes

 In addition, the specified lens centering insensitive and technologically manageable in production.

embodiment

The invention will be explained in more detail with reference to a drawing. It shows the

Fig. 1: a sectional view of the lens according to the invention with front panel.

InderTabellei the necessary for the objective of the invention according to FIG. 1 design parameters are given. The design parameters are defined over a wide range of parameters and provide for any, arbitrary value of Pi (i = 1 ... 4) inventive lenses with the aforementioned advantageous properties.

Referring to Fig. 1 and Table 1, the lens includes four lens members. The first member consists of a dissipative bent meniscus of a glass with the refractive index n, from 1.6 to 1.7 and the Abbezahl \ 7 "from 30 to 39. This diffusing meniscus must have a focal length of -2.5 · f to -4 f and turn its hollow side to the object. The second lens member is a biconvex lens, consisting of a glass with the refractive index n _e of 1.7 to 1.77 and a Abbe number v ~ _e

from 45 to 65. This lens has a focal length of 0.97 x f to 1.06 x f '.

The third lens member is a cemented member consisting of a biconvex lens and a flexed meniscus. The biconvex lens consists of a crown glass with the refractive index n _e between 1.53 to 1.59 and a Abbe number v "between 58 and 70.

The meniscus is made of a flint glass of refractive index n "1.73 to 1.83 and a Abbe number v. between 20 and 30. In the cemented component, the biconvex lens is turned toward the object and has a focal length of 0.82 · Γ to 0.98 · f. The focal length of the meniscus is

-0.94-f to-1.44-f.

The fourth lens member is shown in FIG. 1 and Table 1 from a Plankonkavlinse, the plane surface facing the image.

The refractive index of their glass is between 1.73 and 1.83 and their focal length is -0.84 · f to -0.04 · f.

Throughout the lens, the distances between the first three lens members are chosen as small as possible. The distance between the third and fourth lens element is about 0.5 · f. In detail, this is chosen so that the image plane is located directly behind the plane. Most of the positive refractive power is concentrated in the front part of the lens, so that the length of the lens could be kept very low. It is about 1.8 · f to 1.9 · f.

Table 1 focal length: f

Position of the EP: S _E p =

radii

Cutting distance: s' = 0.035 angle of view 2 σ = 52 °

-1.2 aperture ratio 1: 3.5

Distances and airspaces

Refractive indices n »pay off v _e

P ₁ -8.6177 -61.4096 ^Гі ~ 16.017-P ₁

г ₂ = (-7.376 + P ₁ ) -0.2-f

₌ P ₂ -3,7214-20,1916 .Q ₂ -V ^{з z} P ₂ - 2,3396

г ₄ = (-6.061 + P ₂ ) · 0.2 · f

₆ = (0.13723 - P ₃ x 0.53114) - 'x 0.2 x f

г ₆ = (-0.293 + P ₃ ) "'· 0.2 · f

X ₁ = (-0.06753 + P ₃ x 0.91544) "'x 0.2 x f

r ₈ = (-0.26932 - P ₃ 0.96508) "'0.2 f

d, = (0.7 + P ₄ ) · 0.2 · f

1 ₁ = (0.2-1.29 -P ₄ ) - 0.2 -fd ₂ = (1.5 -0.25 -P ₄ ) - 0.2 f

1 ₂ = (0.15 + 1.24 -P ₄ ) - 0.2 · f 'd ₃ = (2.1 - 0.44 · P ₄ ) · 0.2 · V d ₄ = (0.9 - 0.77 · P ₄ ) · 0.2 · f

1 ₃ = (2.5 - 2 · P ₃ ) 0.2 · f

d ₆ = (0.9 - 0.35 · P ₄ ) · 0.2 · f

1.62507

1 1.73444

35.69

52,00

1.57086 62.87 1.79192 25.52 1 1.79192 25.52 1

Value range of the parameters Pi:

-1 <P ₁ <1 -0.2 <P ₂ <0.3 -0.1 <P ₄ <0.1 -0.02 <P ₃ <0.02

Claims (2)

1. High-resolution scanning lens of small length with front panel, consisting of four lens members, characterized in that the first lens member is a scattering bent meniscus, the hollow side facing the lens, that the second lens member is a biconvex lens, the third lens member of a from a Subordinated biconvex lens and a bent meniscus cementing member, wherein the biconvex lens of the cemented element facing the object, and that the fourth lens member is a Plankonkavlinse, which faces its plane to the image. 2. High-resolution scanning lens of small length according to item 1, characterized in that the lens members have the design data given in Table 1.