DE19507742A1 - Objective lens with four lens groups - Google Patents

Abstract

Two lens groups are located in front and two behind the aperture plane. In the imaging direction, each of the first and fourth lens groups consist of two lenses. The nearest lens to the object or image plane is of positive refractive power, whose concave surface faces the aperture plane.Each of the second and third lens groups consist of a single lens. The objective lens meets three equations related to the refractive power of the first, second and third lens groups, and to total refractive power of the first two, or last two lens groups.

Description

The invention relates to a lens with four Lens groups, two of which are in front of and two behind Aperture plane are arranged.

In particular, the invention relates to an object tive, in which the following features are implemented:

• - the - in the imaging direction - first and fourth Lens groups each consist of two lenses, from those of the object plane or the image plane next lens a lens with positive refractive power is, the concave surface of which is the diaphragm plane is turned towards
• - The second and third lens groups consist of one lens each.

Lenses of this type are well known. After this However, the current state of knowledge remains with such gen lenses provided uncorrectable aberrations these lenses with variable image scales be set. Please refer to the article "Irredu cible aberrations of a lens used for a range of magni fications "by A. Walther in Optical Society of Ameri ca, Vol. 6, No. 3, 1989, p. 415 are referred to as follows.

Probably because of this prejudice, they are different most modifications of the preamble of the patent has been proposed according to the presupposed type:

Only by way of example is the US-PS 51 21 257 or the Reference is made to DE 39 34 168 C2. In both publications are modifications of the preamble of the patent Claim 1 required type described in which more than six lenses are used.

The invention is based on the object of a generic to develop appropriate lens in such a way that even without an increase in the number of lenses an improvement in the Image quality and especially the longitudinal color defects Lers as well as the lateral chromatic aberration is achieved.

An inventive solution to this problem is in the independent claims. Advanced training of the invention are the subject of the subclaims.

In the solution characterized in claim 1 are the following conditions are met at the same time:

| F₁ / F₂ | 0.75

1.0 | F₂ / F₃ | 1.5

2.0 | F _v / F _h | 40

here mean:
F _{1-3 is} the refractive power of the first, second or third lens group,
F _v , F _{h are} the total refractive power of the first and second or third and fourth lens groups.

Another solution is given in claim 2. the Compliance with the conditions specified in this claim gen is of course also used in a lens according to claim 1 advantageous. In particular, are in accordance with Claim 2 fulfills the following features:

The two lenses of the first and fourth lens groups are each cemented together. The refractive indices of the Lenses cemented to one another are different less than 0.06 and Abbe's numbers by more than 6.0. The refractive indices of the lenses of the second and third Lens groups differ by more than 0.1.

The objective according to the invention with four lens groups is particularly useful for information processing in suitable for technical devices. For example with the industrial image processing are templates ver different sizes on an electronic image recording mer, such as B. a CCD chip or a CCD line forms. In order to be able to take full advantage of the image recorder, the templates are adapted to their size Scale shown.

Different from the known generic lenses the lens according to the invention to a large extent area for the aforementioned applications corrected superbly. In addition, it is low in stray light, vignetting-free and has a rough measure bar area low color longitudinal and minimal color transverse error on.

In typical applications, the inventive Lens with a focal length of approx. 75 mm and one F-number of 4 used.

According to claim 3, there are the second and the fifth as well as the third and the sixth lens each from the same material. An advantageous choice of material - expressed by specifying the refractive index or refractive index pay as well as the Abbe's numbers is in claim 4 marked, according to which the following applies:

1.64 <n1 <1.68 47 <v1 <55
1.59 <n2 <1.64 40 <v2 <47
1.60 <n3 <1.65 58 <v3 <67
1.44 <n4 <1.53 65 <v4 <75
1.59 <n5 <1.64 40 <v5 <47
1.60 <n6 <1.65 58 <v6 <67.

In claim 5 is a particularly advantageous condition for the radii of the first and last lens of the object tivs: according to this claim applies to the Radii of the first surface of the first lens group and the last surface of the last lens group:

1.05 | R _v / R _h | 1.75

The invention is hereinafter described without limitation general inventive concept based on execution examples with reference to the drawing exempla risch described to the rest of the Revelation of all not further explained in the text he inventive details are expressly referenced will. Show it:

Fig. 1 shows a lens section of the beam path, and

FIG. 2 shows the modulation transfer function for the objective shown in FIG.

The lens shown in section in FIG. 1 has the following data.

Table 1

The f-number of this lens is 4, the focal length is 74.6 mm.

In table 1 and the following table 2 mean:
ri radius of the i-th surface,
di lens thickness or air gap between the i-th and the (i + 1) -th surface,
ni refractive index of the material between the i-th and the (i + 1) -th surface for the d-line, and
vi Abbe's number of the material between the i-th and the (i + 1) -th area for the d-line.

The modulation transfer function is shown in Fig. 2 Darge. The excellent Abbildlei stungen of the lens according to the invention can be clearly seen.

Table 2

Plane-parallel plate, thickness 2.0 made of BK 7

The plane-parallel plate that has the function of a deck glass is included in the optical calculation.

For the version specified in Tables 1 and 2 For example, the individual lenses consist of the same Materials. Only the radii of curvature are varied ri and the thicknesses or air gaps di.

Of course, it is also possible to use the Krüm measurement radii ri and the thicknesses or air gaps di unchanged changes to let, and the materials that make up the individual There are lenses to change:

Thus, in the case of the tables 1 and 2 reproduced Embodiments without changing the geometry data the following materials were chosen for the individual lenses will:

Lens 1 SSKN5, DBC6585,
Lens 2 KzFSN4, BPM51,
Lens 3 PHM52, PSK53A,
Lens 4 FK5, FSL5
Lens 5 KzFSN4, KzFSN5
Lens 6 PHM52, PSK53A.

Of course, this information is only an example that are intended to illustrate the range of variation that are possible within the conditions according to the invention.

To further clarify within the fiction possible range of variation in the Table 3 shows a further exemplary embodiment given in which both the materials of the individual lenses and the geometry data compared to the examples according to the Tables 1 and 2 are changed.

Table 3

Claims (9)

1. Lens with four lens groups, two of which are arranged in front of and two behind the diaphragm plane, with the following features:

• - the - in the imaging direction - first and fourth lens groups each consist of two lenses, of which the lens closest to the object plane or the image plane is a lens with positive refractive power, the concave surface of which faces the diaphragm plane,
• - the second and third lens groups each consist of one lens,

characterized in that the following conditions are met: | F₁ / F₂ | 0.75
1.0 | F₂ / F₃ | 1.5
2.0 | F _v / F _h | 40 mean:
F _{1. . . 3} the refractive power of the first, second and third lens groups,
F _v , F _{h are} the total refractive power of the first and second or third and fourth lens groups. 2. Lens according to the preamble of claim 1 or claim 1, characterized by the combination of the following features:

• - the two lenses of the first and fourth lens group are cemented together,
• - the refractive index of the lenses cemented together differ by less than 0.06 and the Abbe's numbers by more than 6.0,
• - The refractive indices of the two lenses in the second and third lens groups differ by more than 0.1.

3. Lens according to claim 2, characterized in that the second and the fifth as well as the third and the sixth lens each from the consist of the same material. 4. Lens according to claim 2 or 3, characterized in that the following applies to the refractive indices and Abbe's numbers: 1.64 <n1 <1.68 47 <v1 <55
1.59 <n2 <1.64 40 <v2 <47
1.60 <n3 <1.65 58 <v3 <67
1.44 <n4 <1.53 65 <v4 <75
1.59 <n5 <1.64 40 <v5 <47
1.60 <n6 <1.65 58 <v6 <67. 5. Objective according to one of claims 1 to 4, characterized in that the following applies to the radii of the convex surface of the meniscus lens of the first and fourth lens group: 1.05 | R _v / R _h | 1.75 6. Lens according to one of claims 1 to 5, characterized by the following data: 7. Lens according to one of claims 1 to 5, characterized by the following data: Plane-parallel plate, thickness 2.0 made of BK 7 8. Lens according to one of claims 1 to 5, characterized by the following data: