Self-centering lens arrangement for a transmitting, refractive optical unit
A lens arrangement for an optical unit operating in a predetermined spectral range, includes at least two lenses ( 11 - 14, 114 ) of material, which transmits in the spectral range, and a common casing ( 15 ), in which the lenses are arranged sequentially. The lenses are at least substantially aligned radially, axially and angularly inclined relative to a common optical axis. Adjacent lenses in the sequence are mounted to allow relative movement therebetween. Abutment faces ( 2 ) of the lenses rest against one another. An elastic tensioner ( 21 ) pretensions the sequence of lenses in the axial direction. Only one of the lenses ( 11 ) in the sequence is axially aligned by way of the common casing. Only a portion of the lenses ( 11, 114 ) in the sequence are radially aligned by the common casing; the remaining lenses are aligned with respect to one another by the abutment faces of the respectively adjacent lenses.
1. A lens arrangement for an optical unit operating transmissively and refractively in a predetermined spectral range, comprising:
at least two lenses, wherein each of the at least two lenses transmits in the predetermined spectral range,
a common casing, in which the at least two lenses are arranged in sequence, wherein the lenses are at least substantially aligned radially, axially and angularly inclined with respect to a common optical axis,
wherein adjacent lenses of the at least two lenses form respective abutment faces that face one another, and wherein the adjacent lenses rest against one another by way of the respective abutment faces, and
an elastic tensioner configured to provide axial pressure to the sequence of lenses,
wherein a first of the lenses is axially aligned by the common casing;
wherein a first subset of the lenses in the sequence are radially aligned by the common casing,
wherein a gap is formed between each lens of a second subset of the lenses and the common casing such that each lens of the second subset of the lenses is not radially aligned by the common casing, and
wherein the second subset of the lenses in the sequence are aligned by the respective abutment faces of the respectively adjacent lenses, such that all lenses of the sequence are aligned radially, axially and angularly inclined with respect to the common optical axis.
2. The lens arrangement as claimed in claim 1 , wherein the predetermined spectral range lies in the infrared spectral range.
3. The lens arrangement as claimed in claim 2 , wherein the infrared spectral range comprises at least part of the wavelength range from 2 μm to 13 μm.
4. The lens arrangement as claimed in claim 1 , wherein at least some of the at least two lenses comprise different materials which transmits in the predetermined spectral range.
5. The lens arrangement as claimed in claim 1 , wherein the respective abutment faces of the respectively adjacent lenses are formed in radially outer regions of the lenses, wherein optically effective faces of the lenses are formed in radially inner regions of the respectively adjacent lenses, and wherein the respectively adjacent lenses rest against one another only with abutment faces that face one another, but excluding the optically effective faces.
6. The lens arrangement as claimed in claim 1 , wherein the adjacent lenses in the sequence respectively form first abutment faces that face one another, wherein at least one of the first abutment faces is embodied as substantially flat and substantially perpendicular to a respective optical axis of the respective lens.
7. The lens arrangement as claimed in claim 6 , wherein a maximum local gradient angle α of a first abutment face does not exceed an absolute value of 15°, wherein the local gradient angle α is measured in relation to a reference plane, which extends perpendicularly to the optical axis of the lens, and within a sectional plane, which contains the optical axis of the lens.
8. The lens arrangement as claimed in claim 6 , wherein the first abutment faces are rotationally symmetric in relation to the respective optical axis of the respective lens.
9. The lens arrangement as claimed in claim 6 , wherein at least one of the first abutment faces that face one another respectively extends perpendicularly to the optical axis of the respective lens.
10. The lens arrangement as claimed in claim 9 , wherein the first abutment faces are ring-shaped plane faces.
11. The lens arrangement as claimed in claim 6 , wherein lenses that are respectively adjacent in the sequence form second abutment faces that face one another, wherein one of the second abutment faces forms an opening that widens toward the other lens and/or one of the second faces forms a projection that tapers toward the other lens, and wherein the lens arrangement is embodied such that, at a temperature T soll , the first abutment faces that face one another of adjacent lenses rest against one another in the sequence, and play remains between the second abutment faces that face one another of adjacent lenses.
12. The lens arrangement as claimed in claim 11 , wherein, at the temperature T soll , the first abutment faces that face one another of the adjacent lenses rest against one another in a planar fashion, and wherein the temperature T soll is 20° C.
13. The lens arrangement as claimed in claim 1 , wherein lenses that are respectively adjacent in the sequence form second abutment faces that face one another, wherein one of the second abutment faces forms an opening that widens toward the other lens and/or one of the second faces forms a projection that tapers toward the other lens.
14. The lens arrangement as claimed in claim 13 , wherein a local gradient angle α of at least one of the second abutment faces has an absolute value of between 25° and 65°, wherein the local gradient angle α is measured in relation to a reference plane, which extends perpendicularly to the optical axis of the lens, and within a sectional plane, which contains the optical axis of the lens.
15. The lens arrangement as claimed in claim 14 , wherein the local gradient angle α of at least one of the second abutment faces has an absolute value of between 30° and 60°.
16. The lens arrangement as claimed in claim 1 , wherein a lateral face of at least one of the second abutment faces is substantially in the form of at least one of a frustum, a spherical layer, or a toroidal disk.
17. The lens arrangement as claimed in claim 1 , wherein one of the second abutment faces that face one another forms an opening that widens toward the other lens and corresponds substantially to the lateral face of a frustum, and the other of the second abutment faces that face one another forms a projection that tapers toward the other lens and corresponds substantially to a lateral face of a toroidal disk.
18. The lens arrangement as claimed in claim 1 , wherein a difference between a coefficient of thermal expansion of the common casing and the lenses of the first subset is less than a difference between the coefficient of thermal expansion of the common casing and the lenses of the second subset.
19. The lens arrangement as claimed in claim 1 , wherein the lens which is axially aligned by the common casing is arranged at a first end of the sequence of lenses, and a lens, at which the elastic tensioner engages, is arranged at a second end of the sequence of lenses which lies opposite the first end.
20. The lens arrangement as claimed in claim 1 , wherein all optically effective faces and abutment faces of a given one of the lenses are produced in a same clamping operation during manufacturing of one side of the given one of the lenses.