GB2491976A

GB2491976A - Adaptation optical lens unit for upstream chromatic aberration correction

Info

Publication number: GB2491976A
Application number: GB1210629.0A
Authority: GB
Inventors: Bertram Achtner
Original assignee: Carl Zeiss Optronics GmbH
Current assignee: Hensoldt Optronics GmbH
Priority date: 2011-06-16
Filing date: 2012-06-14
Publication date: 2012-12-19
Anticipated expiration: 2032-06-14
Also published as: DE102011106585A1; DE102011106585B4; GB201210629D0; GB2491976B

Abstract

The adaptation optical unit 10 is designed to be added on to an imaging lens 1 (which images a first spectral range) in order to produce a supplementary image of a second spectral range. The combined system includes a beam splitter element B02 for splitting the first spectral range along a first optical axis and the second spectral range along a second optical axis, which is inclined relative to the first optical axis. The adaptation optical unit 11, which is arranged along the second optical axis and which images the second spectral range onto a detector B06 is additionally designed for the correction of the chromatic aberration of the components B01 of the imaging lens which are upstream of the beam splitter element B02.

Description

Adaptation lens The invention relates to an adaptation lens for the supplementary imaging of a second spectral range in an imaging lens that imagines a first spectral range. The detectable spectral range of the imaging lens present is intended to be extended by means of the adaptation lens.

There are known technical realizations for multispectral lenses. By way of example, multispectral lenses having a fixed focal length are known from EP 0935772 BI for the visible and the JR (infrared) range, from US 5,781,336 for a wavelength range of 0.55 pm to 5.35 pm and from US 6,950,243 B2 for a wavelength range of 0.7 pm to 5.0 pm. Suitable material selection makes it possible, in particular, to minimize the chromatic imaging aberrations for the spectral range to be imaged.

US 5,847,879 discloses a multispectral reflective lens having a fixed focal length.

A wide-angie lens for the visible range and for the lR range is specified therein. ln that case, a beam splitter element separates the visible range from the lR range.

Both spectral ranges are reflected onto a compact detector..

Multispectral lenses are generally comparatively complex and expensive.

Moreover, they have to be designed specifically in each case as a whole for the concrete application.

The problem addressed by the invention is that of providing a cost-effective multispectral lens with the least possible complexity.

This problem is solved according to the invention by means of an adaptation lens for the supplementary imaging of a second spectral range in an imaging lens that images a first spectral range, comprising for this purpose a beam splitter element for splitting the first spectral range along a first optical axis and the second spectral range along a second optical axis, which is inclined relative to the first optical axis, and an adaptation optical unit, which is arranged along the second optical axis and which images the second spectral range onto a detector. In this case, provision is made for additionally configuring the adaptation optical unit for correction of the chromatic aberration of the components of the imaging optical unit upstream of the beam splitter element.

in this case, in a first step, the invention proceeds from known lenses having an element for deflecting rays or for coupling out rays in an imaging beam path.

Lenses of this type are known for example from US 6,856,468, US 6,333,823 or US 4,749,268. Generally, such lenses are optimized to the effect that the imaging aberrations for the spectral range to be imaged, in particular the chromatic aberration, are minimized.

In a second step, the invention recognizes that-presupposing the spectral transmissivity of the optical components present -such a lens can be extended to the imaging of a further spectral range if the beam splitter element is used for spatially splitting the two spectral ranges. As far as the beam splitter element, both spectra) ranges are guided jointly through the optical components of the imaging optical unit present. At the beam splitter element, the second spectral range is separated and imaged separately. Rays of the first spectra) range are continued along the first optical axis in the imaging optical unit present. With regard to the imaging characteristic, nothing changes for the existing lens. Rays of the second spectral range are continued along the second optical axis and focused onto a separate detector.

In a third step, the invention recognizes that the optical components of the imaging optical unit present upstream of the beam splitter element lead to imaging aberrations in the second spectral range, since said components are optimized with regard to the imaging of the first spectral range. If the adaptation optical unit for imaging the second spectral range is designed for additional correction of the chromatic aberration of the upstream components of the imaging optical unit, then the chromatic aberrations thereof are taken into account. Through correspondingly optimized optical components of the adaptation optical unit, the second spectral range is imaged onto the detector with the desired quality.

Ideally, the beam splitter element used in the lens present can be used for the adaptation lens. This presupposes that the beam splitter element of the lens present is transmissive to the second spectral range, if the first spectral range is deflected or diverted, or alternatively is transmissive to the first spectral range, and deflects or diverts the second spectral range. In all other cases, the beam splitter element present is replaced by a correspondingly configured beam splitter element.

For the invention it is merely presupposed that the cOmponents of the imaging optical unit present or of the (ens present which are disposed upstream of the beam splitter element are transmissive both to the first and to the second spectral range. By contrast, the optical components of the adaptation lens need merely be transmissive to the second spectral range.

In the lens present, by way of example, the visible spectral range of 0.4 pm to 0.7 pm can be imaged onto the detector, while an IR range, for example the MR range (0.7 pm to 1.4 pm)or the SWIR range (1.4 pm to 3.0 pm), is imaged in the adaptation lens. In particular, it is also possible for the lens present to image both the visible spectral range and one part of the MR range, that is to say e.g. a spectral range of 0.4 pm to 0.9 pm, and for the adaptation lens to image another part of the N1R range and of the SWIR range, that is to say e.g. a spectral range between 1.0 pm and 3.0 pm.

The extension of an existing lens in the visible spectral range for imaging an IR spectral range is desirable particularly for target seeking devices, periscopes, etc., since it is thereby possible to increase the amount of information yielded about the surroundings or to use the optical-unit already present for example for laser tracking or the like. Since components of the imaging optical unit already present are also used for imaging the second spectral range, the demands on structural space are kept within limits fl Conjunction with comparatively low expenditure in terms of costs.

The use of existing components of the imaging optical unit designed for the first spectral range simultaneously has the further advantage that the existing optical properties are also transferred to the adaptation lens. By way of example, if the focal length of the lens present is variable, then the focal length of the system with the adaptation optical unit is also variable. By way of example, adaptation of a zoom lens for a first spectral range gives rise to a zoom lens both for the first and for the second spectral range.

If the optical system is used for example for imaging laser radiation, or example as a tracking system in laser communication, it may become necessary to image only a portion of the second spectral range, for example a partial range of the SWIR spectrum between 1.53 pm and 1.57 pm, onto the detector. This can preferably be achieved by pivoting in a filter either upstream of, downstream of, or in, the adaptation optical unit, said filter selecting the narrower spectral range.

Generally, in the present case the terms imaging lens and adaptation lens are used in the sense of the entire imaging components, while the terms imaging optical unit and adaptation optical unit respectively refer to a portion of the components of the lens.

Preferably, the beam splitter element deflects the first spectral range and transmits the second spectral range. In this case, the transmissive properties of the beam splitter element are used for imaging the second spectral range and in this respect, if the beam splitter element is exchanged for the one originally present, do not disturb the imaging properties of the lens present. If the lens present uses the deflected or diverted ray for imaging, then the structural space conditions for adding the adaptation lens are more favourable.

Preferably, the beam splitter element is also used for the correction of imaging aberrations for the second spectral range. in particular, for this purpose provision is made for inclining an entrance surface and an exit surface of the beam splitter element relative to one another at an angle, such that a wedge shape is formed.

The astigmatism correction of the imaging can be improved by such a wedge shape, provided that the beam splitter element is not situated in a parallel beam path. In the latter case, a plane-parallel configuration of the beam splitter element is expedient.

In one advantageous configuration of the adaptation lens, the beam splitter element is a partly transmissive reflector plate or a splitter prism. The reflector plate is coated for example for the reflection of the first spectral range, while it is embodied as transmissive to the second spectral range. The splitter prism is embodied for example as a beam splitter cube, the two spectral ranges being split by interface effects.

If the adaptation lens is designed for imaging an IR spectral range, in particular an SWIR spectral range, then all optical glasses and Si (silicon), ZnS (zinc sulphide), CaFI (calcium fluoride), ZnSe (zinc selenide) or BaFl (barium fluoride) can be used for the adaptation optical unit.

Advantageously, the adaptation optical unit for correction of the chromatic imaging aberrations comprises at least one correction lens element arranged along the second optical axis and having a diffractive surface. A diffractive surface of this type, for example a grating structure, formed by variation of the layer thickness, of the refractive indices or of the transmissivity, leads, particularly as a result of the condition of constructive interference, to different focal lengths for rays having different wavelengths and can therefore be used for the correction of chromatic imaging aberrations.

In particular, the diffractive surface of the correction lens element is embodied with a kinoform profile, wherein the diffractive surface is described by the phase profile function w: (p_ECr2fl, where A denotes the reference wavelength and C denote&the coSicients of the phase polynomial. In this case, the radius of the m-th ring is calculated from m=1,2,3,...

There are a maximum of N rings N = where denotes half the lens element diameter. The groove depth d at each ring is d= where n0 indicates the refractive index of the material for A0 With further preference, the adaptation optical unit comprises a lens element group having a first lens element having positive refractive power and a second lens element having negative refractive power and a field lens element group having negative refractive power.

With further preference, the first and second lens elements are embodied in convexo-concave fashion, that is to say that they have a convex entrance surface and a concave exit surface in the propagation direction.

Advantageously, the concave exit surfaces of the first and second lens elements are in each case embodied in aspherical fashion in order to perform a further correction of the imaging aberrations.

Preferably, in the first tens element group, the first lens element having positive refractive power is embodied as the abovementioned correction lens. Particularly for imaging a second spectral range in the infrared from a lens present for imaging the visible and/or the NIR range, preferably the first lens element consists of ZnS and the second lens element consists of Si.

In a first embodiment variant, the field lens element group comprises a third lens element having negative refractive power and a fourth lens element having positive refractive power. In this case, a further configuration variant provides for the third lens element to be embodied in concavo-convex fashion and the fourth lens element to be embodied in convexo-concave fashion.

Expediently, for the correction of imaging aberrations, the convex entrance surface of the fourth lens element is embodied in aspherical fashion.

In order, by means of the adaptation lens, to image an SWIR range relative to a visible spectral range of the lens present, furthermore advantageously the third lens element is produced from CaFl and the fourth lens element is produced from Si.

In another configuration variant, the field lens element group is expediently formed from a cemented element having negative refractive power, comprising a third lens element having positive refractive power and a fourth lens element having negative refractive power, and from a fifth lens element having positive refractive power.

In this case, preferably, the third lens element is embodied in convexo-convex fashion, the fourth lens element is embodied in concavo-concave fashion and the fifth lens element is embodied in convexo-concave fashion.

Particularly preferably, the convex entrance surface of the fifth lens element is embodied in aspherical fashion.

For optimizing the imaging of an SWIR range, the third and fourth lens elements consist of optical glass of differing dispersion. The fifth lens element is produced from Si.

Overall, as a result of changing the lens element materials within the adaptation optical unit, the differing dispersions are used for the further correction of the chromatic aberrations.

Embodiments of the present invention will now be described by way of further example only and with reference to the accompanying drawings, in which: Figure 1 shows an optical system comprising an imaging lens present and an adaptation lens in accordance with a first embodiment variant, Figure 2 shows an optical system comprising an imaging lens present and an adaptation lens in accordance with a second embodiment variant, Figure 3 shows a known imaging lens in accordance with the prior art, Figure 4 shows the integration of an adaptation lens in accordance with a third embodiment variant, Figure 5 shows in enlarged fashion the adaptation lens in accordance with Figure 4, Figure 6 shows the integration of an adaptation lens in accordance with a fourth variant, and Figure 7 shows in enlarged fashion the adaptation lens in accordance with Figure 6.

In accordance with Figure 1, an existing imaging lens 1 for imaging a first spectral range comprises the individual components 601, 802, 803 and B04. The imaging lens I present can be a lens having a fixed focal length or a lens having a variable focal length. The imaging lens I images the first spectral range onto the detector 604 by means of the optical components BOl and 603. The component 602 is designed for deflecting rays in the first spectral range.

An adaptation lens 10 comprising the components 605 and 806 is adapted in the place of the ray deflection of the component 802. The component 602 for ray deflection becomes an element for ray deflection and for ray transmission as a result of the adaptation. The first spectral range is deflected. A second spectral range, which is different from the first spectral range, is transmitted. The second spectral range is imaged by the component 605 onto the detector 806. The focal length of the component 805 is, depending on the size of the detector 806, less than, equal to or greater than the focal length of the component 603.

The components 801, 503 and 805 in each case consist at least of one lens element or of an arrangement of a plurality of lens elements.

Preferably, the focal length of the component B05, depending on the size of the detector B06, is less than, equal to or greater than the focal Jength of the component 803. In the case of detectors for different spectral ranges, the formats, that is to say e.g. the height and width of the detector, are different. What can be achieved by adapting the focal length is that the imaged horizontal or vertical field is identical in both spectral ranges. If both detectors have the same aspect ratio, what can be achieved is that the imaged horizontal and vertical field is identical in both spectral ranges.

The components 801 and 603 are chromatically corrected for the first spectral range, but not for the second spectral range. In the component 805, in other words in the adaptation optical unit 11 of the adaptation lens 10, the chromatic aberration of the component 601 is additionally corrected for the second spectral range.

In the imaging lens I present, e.g. the visible spectral range between 0.4 pm and 0.7 pm can be imaged onto the detector 604. In the adaptation lens 10, by way of example, the MR range between 0.7 pm and 1.4 pm or the SW1R range between 1.4 pm and 3.0 pm is imaged onto the detector 806. it is likewise possible that, in the imaging lens I present, the visible spectral range and one part of the MR range are imaged onto the detector 604, e.g. a range between 0.4 pm and 0.9 pm in the imaging lens I present and in the adaptation lens 10 a range of 1.0 pm to 3.0 pm.

If the focal length of the imaging lens I present is variable, then the focal length of the system with the adaptation lens 10, as illustrated in Figure 1, is also variable.

By way of example, a zoom lens for both spectral ranges arises.

Figure 2 illustrates a further optical system comprising an imaging lens 2 present and an adaptation lens 12. The imaging lens 2 present comprises the components AOl, A02, A03 and A04. The adaptation lens 12 is inserted in place of the component A02 and additionally comprises the components A05 and ADS.

The explanations concerning Figure 1 with regard to the components 601, 603, 804, 805 and 806 can analogously be applied to the components AOl, A03, A04, ADS and A06 of the embodiment variant in accordance with Figure 2. The element A02 in accordance with Figure 2, in contrast to the element 802 in accordance with Figure 1, is embodied as an element for coupling out rays. In this case, it comprises the functions of coupling out rays for the first spectral range and transmission for the second spectral range.

Figure 3 illustrates, by way of example, a known imaging lens 1 in accordance with the prior art. This lens 1 images part of the visible spectral range and part of the MR range, namely a range between 0.45 pin and 0.75 pm, onto the detector 804. In this case, it comprises the components BOl, 602 and 603, which correspond in terms of their function and their properties to the components provided with identical reference signs in the embodiment variant in accordance with Figure 1.

The illustrated imaging lens 1 present is a zoom lens comprising a deflection group B02. The zoom groups ZOl and Z02 are correspondingly provided. Figure 3 illustrates one zoom position.

In the imaging lens 1 present, the chromatic correction of the components soi is designed for a first spectral range between 0.45 pm and 0.75 pm, but not for the second spectral range between 1.4 pm and 1.7 pm. In the component eoi, the chromatic aberrations for the second spectral range are significantly greater than those for the first spectral range. The lens illustrated can be found in us 6,856,468, for example.

Figure 4 illustrates the integration of an adaptation lens 10 into the existing lens I in accordance with Figure 3. From the imaging lens, the components of the imaging optical unit 13 upstream of the component 602 for ray deflection are shown. The component for ray deflection 602 is replaced by a component for ray deflection which is additionally embodied as transmissive to a second spectral range between 1.4 pm and 1.7 pm. In the adaptation optical unit 10, the chromatic aberrations of the components BOl or of the imaging optical unit 13 of the lens 1 upstream of beam splitting are corrected.

The exact construction of the adaptation lens 10 in accordance with Figure 4 becomes evident from Figure 5. The adaptation lens 10 for coupling to the lens I present in accordance with Figure 3 comprises the component for ray deflection and for transmission 602, a first Lens element group L composed of a convexo-concave first lens element L01 and a convexo-concave second lens element L02 and a field lens element group F, consisting of a concavo-convex third lens element L03 and a convexo-concave fourth tens element L04. The lens elements L0I to L04 form the component B05 in accordance with Figure 1. The detector B06 is depicted.

The adaptation lens 10 is additionafly corrected for correction of the chromatic aberration with regard to the second spectral range between 1.4 pm and 1.7 pm by the optical components BOl of the imaging lens I present, and images this spectral range onto the detector 606 by means of the first lens element group L

and the field lens element group F.

The adaptation lens 10 in accordance with Figure 5 comprises a total of four lens elements, namely a first lens element LOl having positive refractive power composed of ZnS, a second lens element L02 having negative refractive power composed of Si, and the field lens element group F having overall negative refractive power. The field lens element group F consists of the third lens element L03 having negative refractive power composed of CaFl and the fourth lens element L04 having positive refractive power composed of Si. The element B02 is designed as a splitter plate. The entrance surface and the exit surface of this splitter plate B02 are inclined at a wedge angle with respect to one another, in order to improve the astigmatism correction. The lens element L01 is embodied as a correction lens element KL having an aspherical, diffractive exit surface having a kinoform profile.

The configuration of the individual optical components in accordance with Figure becomes evident from Table 1 below, wherein an aspherical surface is identified by the abbreviation ASP, and a diffractive surface is identified by the abbreviation DOE. An aspherical surface is described by the so-called sagitta formula: ph +Ah4+Bh6÷Ch8+Dh'°, 1+JTi(1+K)P2h2 where z denotes the sagitta, K denotes the eccentricity, p denotes the vertex curvature, h denotes the height and A, B, C, D denote the coefficients for higher-order terms. In this case, the surfaces 22. . .23 describe the wedge-shaped splitter plate B02, the surfaces 24. . .25 describe the first lens element LOl, the surfaces 26.. .27 describe the second lens element L02, the surfaces 28.. .29 describe the third lens element L03 and the surfaces 30... 31 describe the fourth lens element L04.

Table I

Radius Thickness Glass 22: INFiNiTY 5.000000 NFK5_SCHQTT ADE: 37.500000 BDE: 0.000000 cDE: 0.000000 23: INFINITY 9.000000 ADE: 37.446842 BDE: 0.000000 CDE: 0000000 24: 2251527 5.000000 ZNS_SPEC1AL 25: 35.93188 13.584422 ASP: K: 0.000000 A:-.147485E-05 B:-.107236E-08 c: 0.361681E-ii DOE: NOR: 1.000000 NWL: 1550.00 I-CT: R 6LI: (DEAL HCO Ci: -2.6772E-04 26: 25.54382 2.000000 SILICON SPECIAL 27: 15.41 141 32.462092 ASP: K: 0.000000 A:0.303527E-04 8:0.304204E-06 C:-.261946E-09 D:0.308784E-10 28: -1 3.81 476 2.000000 CAFL SPECIAL 29: -128.92526 0.100000 30: 32.66272 4.853486 SILICON SPECIAL ASP: K: 0.000000 CUF: 0.000000 A:0.744503E-04 B:-.531015E-06 C: 0.457757E-08 D:-.146431E-10 31: 43.62753 6.000000 1MG: iNFiNITY 0.000000 The dispersion in the spectrum between 1.4 pm and 1.7 pm with the average wavelength HWL of 1.55 pm is calculated from n -1 = where fl1.4 -fl1.7.

n155 indicates the refractive index of the material at a wavelength of 1.55 pm, n14 indicates the refractive index of the material at a wavelength of 1.4 pm and n7 indicates the refractive index of the material at a wavelength of 1.7 pm. The material silicon has, for example, a dispersion of v1 = 97.9. The material CaFI has a dispersion v,5 =302.8.

What is essential to the colour correction is the positive refractive power of the first lens element LOl composed of a material having low dispersion v1 > 150, the negative refractive power of the second lens element L02 composed of a material having high dispersion v155 <150, the negative refractive power of the third lens element L03 composed of a material having low dispersion v155 >150 and the positive refractive power of the fourth lens element L04 composed of a material having high dispersion V155 <150.

Figure 6 illustrates the integration of a further adaptation ens 10' into the imaging lens I in accordance with Figure 3. The exact construction of the adaptation lens 10' becomes evident from Figure 7.

The components 602 and 806 correspond to those illustrated in Figure 5.

In a departure from the adaptation lens 10 in accordance with Figure 5, the field lens element group F now comprises a cemented element K consisting of a third lens element L03 and a fourth lens element L04. The cemented element K is followed by a fifth lens element L05. The adaptation lens 10' likewise images the second spectral range between 1.4 pm and 1.7 pm onto the detector B06 and has for this purpose a corresponding correction of the chromatic aberration by the components BOl or of the imaging optical unit 13 of the imaging lens I present upstream of beam splitting.

The adaptation lens 10' consists of five lens elements, namely a first lens element LOl having positive refractive power composed of ZnS, a second lens element L02 having negative refractive power composed of Si, and a field lens element group F having overall negative refractive power, which contains a cemented element, comprising a third lens element L03 having positive refractive power and a fourth lens element L04 having negative refractive power, in each case composed of optical glass, and a fifth lens element L05 having positive refractive power composed of Si.

A prerequisite for the colour correction is the positive refractive power of the first lens element LOl composed of a material having low dispersion v155 >150, the negative refractive power of the second lens element L02 composed of a material having high dispersion v55 <150, the positive refractive power of the third lens element L03 composed of a material having high dispersion v155 <150, the negative refractive power of the fourth lens element L04 composed of a material having low dispersion v55 >150, and the positive refractive power of the fifth lens element LOS composed of a material having high dispersion v,55 <150.

The exact configuration becomes evident from Table 2 below. In this case, the surfaces 22. . .23 describe the wedge-shaped splitter plate 802, the surfaces 24...25 describe the first lens element LOl, the surfaces 26...27 describe the second lens element LO2, the surfaces 28.. .29 describe the third lens element LO3, the surfaces 29... 30 describe the fourth lens element L04, and the surfaces 30.. .31 describe the fifth lens element LOS. Once again the first lens element LO1 is formed as correction lens element KL having an aspherical, diffractive exit surface having a kinoform profile.

Table 2

Radius Thickness Glass 22: INFINiTY 5.000000 NFK5_SCHOTT AIDE: 37.500000 BDE: 0.000000 CDE: 0.000000 23: INFINITY 9.000000 ADE: 37.478775 BIDE: 0.000000 CDE: 0.000000 24: 21.59684 5.000000 ZNS_SPECIAL 25: 29.57899 13.404648 ASP: K: 0.000000 A:-.156776E-05 B:-.222609E-06 C: 0.181838E-11 DOE: HOR: 1.000000 HWL: 1550.00 HCT: R BLI: IDEAL HCO C1:-2.5154E-04 28: 22.41254 2.000000 SILICON_SPECIAL 27: 15.41 748 32.995352 ASP: K: 0.000000 A:0.228809E-04 B:0.228944E-06 C:-.210468E-09 D:0.248943E-10 28: 44.18024 5.000000. NFK5_SCHOTT 29: -16,72592 4.000000 NLASF31ASCHOTT 30: 54.95512 0.100000 31: 26.54505 2.500000 SILICON_SPECIAL ASP: K: 0.000000 A:0.947867E-04 B:-.674551 E-06 C: 0.707821 E-08 D:-.219976E-10 32: . 30.35493 6.000000 1MG: INFINITY 0.000000 The foregoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention.

List of reference signs I Imaging lens 2 Imaging lens Adaptation lens 10' Adaptation lens II Adaptation optical unit 12 Adaptation (ens 13 Imaging optical unit AOl imaging component A02 Ray coupling-out A03 Imaging component A04 Detector A05 Adaptation optical unit A06 Detector 801 imaging component 802 Ray deflection 603 Imaging component B04 Detector 805 Adaptation optical unit 606 Detector ZOl Zoom group Z02 Zoom group LOl First lens element L02 Second lens element L03 Third lens element L04 Fourth lens element L05 Fifth lens element L Lens element group

F Field lens element group

K Cemented element KL Correction lens element ZOl Zoom group Z02 Zoom group

Claims

Claims Adaptation lens (10, 10', 12) for the supplementary imaging of a second spectral range in an imaging ens (1) that images a first spectral range, comprising a beam splitter element (A02, 802) for splitting the first spectral range along a first optical axis and the second spectral range along a second optical axis, which is inclined relative to the first optical axis, and comprising an adaptation optical unit (11), which is arranged along the second optical axis and which images the second spectral range onto a detector (A06, 606), wherein the adaptation optical unit (11) is additionally designed for correction of the chromatic aberration of the components (AOl, BOl) of the imaging optical unit (13) upstream of the beam splitter element (A02, 802).
2. Adaptation lens (10, 10', 12) according to Claim 1, wherein the beam splitter element (A02, 802) deflects the first spectral range and transmits the second spectral range.
3. Adaptation lens (10, 10', 12) according to Claim 2, wherein the boundary surfaces of the beam splitter element (602) in the direction of the second optical axis form a wedge shape.
4. Adaptation lens (10, 10', 12) according to any of the preceding claims, wherein the beam splitter element (A02, 802) separates a first, visible spectral range from a second, infrared spectral range, and wherein the adaptation. optical unit (11) is designed for correction of the chromatic aberrations of the upstream components (AOl, 801) of the imaging optical unit (13) in the infrared spectral range.
5. Adaptation lens (10, 10', 12) according to Claim 4, wherein the beam splitter element (A02, 802) separates as second spectral range a range of 0.7 pm to 1.4 pm (N1R) or a range of lÀ pm to 3.0 pm (SWIR).
6. Adaptation lens (10, 10', 12) according to any of the preceding claims, wherein the beam splitter element (A02, 802) is a partly transmissive reflector plate or a splitter prism.
7. Adaptation lens (10, 10', 12) according to any of the preceding claims, wherein the adaptation optical unit (11) for correction of the chromatic imaging aberrations comprises at least one correction lens element (KL) arranged along the second optical axis and having a diffractive surface.
S. Adaptation lens (10, 10', 12) according to Claim 7, wherein the diffractive surface of the correction lens element (KL) is embodied with a kinoform profile.
9. Adaptation lens (10:10', 12) according to any of the preceding claims, wherein the adaptation optical unit (11) comprises a lens element group (L) having a first lens element (LO 1) having positive refractive power and a second lens element (L02) having negative refractive power and a field lens element group (F) having negative refractive power.
10. Adaptation lens (10, 10', 12) according to Claim 9, wherein the first and second lens elements (LOl and L02, respectively) are embodied in convexo-concave fashion.
11. Adaptation lens (10, 10', 12) according to Claim 10, wherein th concave exit surfaces are in each case embodied in aspherical fashion.
12. Adaptation lens (10, 10', 12) according to any of Claims 9 to 11, wherein the first lens element (LOl) having positive refractive power is embodied as correction lens element (KL).
13. Adaptation lens (10, 10', 12) according to any of Claims 9 to 12, wherein the first lens element (LOl) consists of ZnS and the second lens element (L02) consists of Si.
14. Adaptation lens (10, 10', 12) according to any of Claims 9 to 13, wherein the field lens element group (F) comprises a third lens element (L03) having negative refractive power and a fourth lens element (L04) having positive refractive power.
15. Adaptation lens (10, 10', 12) according to Claim 14, wherein the third lens element (L03) is embodied in concavo-convex fashion and the fourth lens element (L04) is embodied in convexo-concave fashion.
16. Adaptation tens (10, 10', 12) according to Claim 14, wherein the convex entrance surface of the fourth lens element (L04) is embodied in aspherical fashion.
17. Adaptation lens (10, 10', 12) according to any of Claims 14 to 16, wherein the third lens element (L03) consists of CaFl and the fourth lens element (L04) consists of Si.
18. Adaptation lens (10, 10', 12) according to any of Claims 9 to 12, wherein the field lens element group (F) consists of a cemented element (K) having negative refractive power, comprising a third lens element (L03) having positive refractive power and a fourth lens element (L04) having negative refractive power, and of a fifth lens element (L05) having positive refractive power.
19. Adaptation lens (10, 10', 12) according to Claim 18, wherein the third lens element (L03) is embodied in convexo-convex fashion, the fourth lens element (L04) is embodied in concavo-concave fashion and the fifth lens element (LOS) is embodied in convexo-concave fashion.
20. Adaptation lens (10, 10', 12) according to Claim 19, wherein the convex entrance surface of the fifth lens element (LOS) is embodied in aspherical fashion.
21. Adaptation (ens (10, 10', 12) according to any of Claims iSto 20, wherein the third and fourth lens elements (L03 and L04, respectively) consist of optical glass of differing dispersion and the fifth lens element (L05) is produced from Si.
22. A lens as hereinbefore described with reference to any one of the drawings.