JP2019032507A - Self-centering lens structure for permeable deflection optical unit - Google Patents

Abstract

It is easy to arrange lenses with high accuracy with respect to a common optical axis, and this process provides a lens structure that is less susceptible to damage when temperature changes. A lens structure (1) for an optical unit includes at least two lenses (11-14) and a common case (15) in which at least two lenses (11-14) are continuously arranged. . The lenses (11 to 14) are arranged at an inclination angle in the axial direction. The lenses form contact surfaces (2) that face each other, and the adjacent lenses (11 to 14) contact each other through the contact surfaces. A series of remaining lenses (12-14) are aligned with each other by the facing abutment surfaces (2) of each adjacent lens (11-14) so that all the series of lenses (11-14) are aligned. , With respect to the common optical axis (16), arranged in the radial direction, in the axial direction and at an inclination angle. [Selection] Figure 1

Description

The present invention relates to a lens structure for an optical unit that operates to be transparent and refracted in a predetermined spectral range, the lens structure comprising:
-At least two lenses each made of a material that is transparent in a predetermined spectral range;
A common case in which at least two lenses are arranged in series,
The lenses are aligned at least substantially radially, axially, and at a tilt angle with respect to a common optical axis.

  Such a lens structure is disclosed in Patent Document 1 (US 2016/0282593 A1).

  The transmissive refractive optical unit serves to construct an optical image of the object. Light (eg, visible light or infrared light) propagates through the lens of the optical unit and in the process, at the lens interface based on the difference between the refractive index of the lens material and the refractive index around each lens. Refract. The polarization of light is determined by the interface shape and the difference in refractive index at the interface. The interface through which light is refracted for optical imaging can also be referred to as an optically effective surface.

  In the simplest case, a transmissive refractive optical unit can comprise only a single lens, but in order to combine the characteristics, a plurality of lenses are usually arranged in succession. When applied within the visible light range, the refractive powers of multiple lenses are often combined for particularly significant magnification or reduction.

  To continuously combine multiple lenses in the direction of light propagation, sufficiently accurate radial and axial alignment and sufficiently accurate for these lenses or their tilt relative to the common optical axis of the lens structure Alignment is necessary.

  In order to ensure this, different positioning and fixed deformations of the optical element (lens) over time have been developed. A summary of these is provided in Non-Patent Document 1 (Carl Hanser Verlag, Munich, 7th edition, 2014, by H. Naumann et al.

  In one variant, which is also realized in US Pat. No. 6,022,593 A1, the optical element is supported axially within a common case. All other optical elements in the common case are supported by their respective preceding optical elements via spacers, and the fasteners engage axially behind the last optical element. Each optical element is individually aligned in the radial direction by a common case. In this design, possible errors (eg, different spacer and optical element edge thicknesses) can propagate additively in the optical assembly, and the position of the optical axis of the final optical element is relatively significantly tilted. May be a position.

  If each optical element has a dedicated stop surface and a dedicated fixed part in the common case, error propagation is avoided. However, this design requires a larger diameter between the optical elements to ensure assembly.

  In both designs, radial alignment of the optical elements is provided by the common case inner wall to the radial edges (sides) of the respective optical elements. The local distance between the radial edge and the optical axis of the optical element is subject to manufacturing tolerances, so that a deviation of the optical axis of the optical element appears with respect to the common optical axis.

  In addition, there remains a significant radial gap between the edge (side) of the optical element and the inner wall of the common case, which also facilitates the displacement of the optical element with respect to the common optical axis, Generally results in optical aberrations. This gap compensates for manufacturing tolerances of the structural element and also a corresponding accumulation of tension in the optical element when radial clamping of the optical element and relative thermal expansion of the optical element relative to the common case occurs. If this is not necessary, the optical element is distorted and the imaging characteristics are adversely affected. If the radial gap is too small, the optical element can even be destroyed, especially considering temperature changes that can occur during storage, transportation, and normal use. On the contrary, when the gap in the radial direction is very large, decentering and thus optical aberration also increases.

  In Patent Document 2 (German Patent Application Publication No. 10 2004 048 064 A1 Specification) or Patent Document 3 (German Patent Application Publication No. 10 2005 023 972 A1 Specification), each lens is mounted on a mount (holder). Disclosed is a microscope objective arranged and mounted radially in a common case by respective mounts.

  Each individual lens is fixed to a dedicated mount within the so-called lathe centering, and its external contour is post-processed on a special alignment lathe. During this process, the optical axis of the optical element is measured. Post-processing of the mount is performed such that the orientation determination contour on the post-processed mount is more accurately placed with respect to the optical axis of the optical element. In the case of so-called alignment adhesive bonding, the optical axis of the optical element is likewise measured, the optical element is glued in its mount, and the optical element is accurately placed in the mount. As a result of this, it is possible to minimize tolerances at the radial position of the optical axis of the optical element, relative to the mount or to the edge of the mount, which determines the arrangement within the common case.

US Patent Application Publication No. 2016 / 0282593A1 German Patent Application Publication No. 10 2004 048 064 A1 German Patent Application Publication No. 10 2005 023 972 A1

H. H., published in Carl Hanser Verlag, Munich, 7th edition, 2014. Handbuch Baulementer der Optik [Optical component handbook] by Naumann et al.

  Lathe centering and alignment adhesive bonding reduce optical aberrations of the optical system, especially by minimizing the tolerance of the radial distance of the optical axis of the optical element from the side of the mount related to radial alignment in the common case It is an option to do. However, the different (radial) thermal expansion of the optical element and mount, or mount and common case, remains a problem in these designs. Furthermore, lathe centering and alignment adhesive bonding are complex and expensive.

  The present invention facilitates lens positioning with good accuracy with respect to a common optical axis in a simple and cost-effective manner, and this process eliminates the effects of errors and damage as the temperature changes. The object is to provide a lens structure that is difficult to receive.

This object is achieved simply and effectively using a lens structure of the type described above, in which case the lenses adjacent to each other in the sequence are mounted so as to allow relative movement between them, The lenses form contact surfaces that face each other with the transparent material, and adjacent lenses contact each other by the contact surfaces,
An elastic tension applying means for pretensioning a series of lenses in the axial direction is provided,
Only one of the series of lenses is arranged axially through the common case, and only a part of the series of lenses is arranged radially through the common case,
The rest of the series of lenses is arranged with respect to each other by the abutting surfaces of each adjacent lens so that all the series of lenses are radially, axially and inclined with respect to a common optical axis. It is arranged at an angle.

  The present invention proposes to form a loose stack of lenses that are arranged in a common case and elastically pretensioned (along a common optical axis) in the axial direction by means of tensioning means. A lens axially aligned by the case (preferably directly or indirectly but not by another lens but axially supported on the case) forms the base of the stack.

  If there is a difference in the axial expansion between the common case and the lens stack as a result of different thermal expansion coefficients and temperature changes, the tensioning means will expand without damaging the lens as a result of the compressive stress being too high. These differences can be compensated for. Here, the difference in the axial expansion can be directly attributable to the axial thermal expansion in this case, otherwise it faces each other and acts in a wedge-like or funnel-like form, for example. In the case of an abutting surface of an adjacent lens, there is a possibility that it is caused by thermal expansion in the radial direction of the lens causing axial displacement between the lenses.

  A part of the lens, typically one or two lenses, is radially aligned by the common case, i.e. limited in terms of radial movement due to the inner wall of the case. For this part of the lens or its permeable material, select a case material having a coefficient of thermal expansion approximately equal to the coefficient of thermal expansion of the permeable material (eg, up to 25% difference from the case material). be able to. In this case, in the case of an expected temperature change (during storage, transport or normal operation), a relatively small radial gap is sufficient to prevent radial clamping of each lens in the common case. The typical radial gap width (for example 20 ° C. for the desired temperature Tsoll) is usually 15 μm or less, or 1/1000 of the lens diameter. The possible deviation of the optical axis of the lens will be reduced accordingly and thus the optical aberration can be kept small.

  The remaining (residual) portions of the lens (usually two or more lenses) are not radially aligned by the common case, and without compromising the radial arrangement of these lenses, There can be a substantially arbitrary radial gap in between. In particular, in the case of anticipated temperature changes (eg even during storage or transport, even if they are out of the intended temperature interval for the intended operation), they will definitely be so large that there is no radial contact with each other. Thus, a radial gap to the common case can be realized. A typical radial gap to the common case is 150 μm or more for the rest of the lens. This radial alignment of the remaining part of the lens is only effected via the abutment surface against the adjacent lens. For example, by properly designing the abutment surfaces of adjacent lenses facing each other with abutment surfaces that act like wedges or funnels, the different radial thermal expansions of the lenses do not become radial tensions, It can be ensured that there is an axial displacement of the associated lens, which is possible for the elastic tensioning means without risk of damage.

  Within the scope of the present invention, individual lens mounts (holders) are not required. In the case of an assembly in a common case, the lens can generally be easily inserted into a substantially cylindrical cavity open on one side in the common case or as a loose stack, and ( Typically, it can be substantially fixed (eg, by closing and / or tightening the tensioning element by tightening screws).

  By radial alignment is meant the (correct) positioning of the lens (lens optical axis) relative to the displacement relative to the (desired) common optical axis perpendicular to it. Axial alignment means (correct) positioning of the lens with respect to displacement along the common optical axis relative to a desired position along the common optical axis. Positioning at an inclination angle means the (correct) inclination of the optical axis of the lens with respect to the (desired) common optical axis.

  In many applications, only one lens is aligned radially through the case. Often this lens is also axially aligned by the case. Note that lenses that are axially aligned by the case are typically also aligned by the case at a tilt angle and / or set the orientation of the common optical axis within the common case.

Preferred embodiments of the invention In a preferred embodiment of the lens structure according to the invention, the predetermined spectral range is in the infrared, in particular the whole or part of the predetermined spectral range comprises a wavelength range of 2 μm to 13 μm. In particular, the present invention is suitable for use with an infrared microscope objective. Furthermore, since the surface roughness remaining after lathe processing generally tends to be insignificant in the infrared spectral region due to long wavelengths, suitable lenses in the infrared spectral range are suitable for lathe methods, especially It can be easily manufactured with a diamond lathe. Spectroscopic information about the sample can be obtained using infrared light, and this information can be used, for example, in determining the chemical composition of the sample. For this purpose, the sample can in particular be examined with an infrared microscope. In order to orient itself on the surface of the sample, it is usually desirable that the sample can be observed at a small magnification. Mirror objectives for microscope applications that can be used in the visible and infrared spectral ranges are not suitable for small magnifications due to their large central obscuration. Infrared transparent lens materials usually have a wavelength dependence with a strong refractive index over a wide spectral range. As a result, a single lens results in strong chromatic aberration. In order to compensate for these, it is possible to combine lenses made of different transmissive materials in the lens structure according to the invention (see also in this regard). It is therefore possible within the scope of the invention to use the lens-based objective lens or lens structure according to the invention in an IR microscope.

  In one embodiment, it is equally possible for the predetermined spectral range to be in the visible range, in particular so that all or part of the predetermined spectral range includes a wavelength range of 390 nm to 780 nm. .

  An advantageous embodiment is provided that at least a part of the at least two lenses are made of different materials that transmit in a predetermined spectral range. The refractive index is highly wavelength dependent in many optical materials, particularly in the infrared spectral range. In that case, significant chromatic aberration must be accepted in the case of individual lenses or optical systems in which all lenses are made from the same optical material. In contrast, within this embodiment, if different transmissive materials with different wavelength-dependent refractive behaviors are combined in an appropriate way, overall (compared to individual lenses) chromatic aberration It is possible to provide a lens structure with reduced (wavelength dependent) mutual (at least partial) compensation. In addition, different permeable materials typically have different coefficients of thermal expansion. This makes it easy to find or select a case material having a coefficient of thermal expansion that fits well with one of the permeable materials (lens materials), in which case the lens material is radially aligned by the common case. It is shown that it can be used for guided lenses or multiple lenses.

  An optically effective surface is formed in the radially inner region of the adjacent lens, and the adjacent lenses are in contact with each other only at the contact surfaces facing each other, but are not in the optically effective surface, but are formed in the radially outer region of the lens. Embodiments that provide opposing abutment surfaces for adjacent lenses to be powered are also preferred. This design has proven its value in practice. The optically effective surface and the abutment surface are separated from each other both spatially and functionally and can therefore be designed geometrically independently of each other.

Embodiments providing a series of adjacent lenses in each case to form first abutting surfaces facing each other are also advantageous, at least of the first abutting surfaces facing each other. One is realized in each case to be substantially flat and substantially perpendicular to the optical axis of the respective lens,
In particular, the maximum local inclination angle α of the first abutment surface does not exceed an absolute value of 15 °, and the local inclination angle α is measured in a cross section including a reference plane extending perpendicular to the optical axis of the lens and the optical axis of the lens. ,
In particular, the first contact surface is realized rotationally symmetrically with respect to the optical axis of each lens. The lenses can be aligned axially and at an angle of inclination with respect to adjacent lenses via the first abutment surface. Due to the substantially flat (especially no step) and substantially vertical embodiments, there is no axial offset for the first abutment surface (or no axial offset when the tilt angle is at most 15 °). A slight sliding) is possible with respect to each other in the radial direction. Typically, the two first contact surfaces facing each other are structured to be substantially flat and substantially perpendicular to the optical axis of each lens. It should be noted that the first abutment surfaces may have partial surfaces that are offset from each other or spaced from each other. A rotationally symmetric contact surface is particularly easy to manufacture and avoids misalignment between lenses.

  In a preferred construction, at least one of the first abutment surfaces facing each other in each case extends perpendicular to the optical axis of the respective lens, in particular the first abutment surface is a ring-shaped plane. It is formed as. In the case of a (precisely) vertical first abutment surface, a planar (surface) abutment without axial offset can be achieved at each radial displacement position of the adjacent lens, resulting in local Pressure load is kept low. This structure helps to avoid deformations often found in use in the IR spectral range, in the case of lenses, especially soft lens materials, so that good imaging properties can be obtained. The ring-shaped plane is easy to manufacture and allows a uniform pressure distribution over the entire circumference of the lens.

  An embodiment in which a series of adjacent lenses form a second abutment surface facing each other is equally advantageous, wherein one of the second abutment surfaces forms an opening that extends toward the other lens, And / or forming a protrusion in which one of the second surfaces tapers toward the other lens. The second abutment surface can also be referred to as a “centering” or “inclined” abutment surface. Typically, one of the second abutment surfaces facing each other is realized with an opening and the other is realized with a protrusion. The second abutment surface may have partial surfaces that are separated from each other or offset from each other, but the second abutment surface is typically on the optical axis of the respective lens. It should be noted that this is realized rotationally symmetrically. The second abutment surface serves to align each lens in the radial direction with respect to the adjacent lens. In particular, the radial movement relative to each other is limited by the interengagement of the lens or the second abutment surface. Here, in particular, the relative radial expansion of adjacent lenses can be converted into axial sliding by mutual induction, using a widened opening and / or a tapered protrusion, and a wedge-like or funnel-like mutual. Can lead to induction.

  In a preferred construction of this embodiment, at least one local inclination angle α of the second abutment surface has an absolute value between 25 ° and 65 °, preferably between 30 ° and 60 °, The local tilt angle α is measured in a cross section including a reference plane extending perpendicular to the optical axis of the lens and the optical axis of the lens. Here, it is only necessary to consider the local inclination angle α in the region where the adjacent lenses can contact each other. In principle, a good deflection function of the axial offset of the lens or a radial extension to good mutual sliding can be achieved in a specified tilt angle range and the radial play can be kept low at the same time. When the tilt angle is steeper (larger), radial play is reduced, and when the tilt angle is flatter (smaller), sliding of adjacent lenses with respect to each other is improved (slidability is a material-dependent friction) Both aspects can be combined with each other within a certain tilt angle range (depending on the factor). In particular, a frustum side surface with an inclination angle α = 45 ° can be set as the second contact surface.

  In a preferred structure, one or more of the second abutment surfaces are formed at least substantially in accordance with the frustum and / or the side surface of the spherical segment and / or the annular segment. These forms have proven to be valuable in practice and are easy to manufacture.

  One of the second contact surfaces facing each other spreads toward the other lens to form an opening corresponding at least substantially to the side surface of the truncated cone, and the other of the second contact surfaces facing each other is the other Particularly preferred is a structure that is tapered toward the lens and that forms a protrusion at least substantially corresponding to the side of the coronal disc. In the case of “lifting”, this design allows the setting of a circumferential, linear (and not just point) contact between the two lenses in a simple manner, which is reliable. Helps to avoid tension peaks, as would occur as a result of the abutment surfaces being arranged in a punctiform fashion relative to each other, thus helping to reduce stress at the abutment surfaces.

  In an advantageous construction of the embodiment with the first and second abutment surfaces, the lens structure has the desired temperature Tsoll, and the first abutment surfaces facing each other in adjacent lenses abut against each other in series. In particular, it is realized such that play is left between the second contact surfaces of the adjacent lenses that are in contact with each other in plan and that are adjacent to each other. In particular, the intended temperature Tsoll is 20 ° C. As a result of play (nominal gap) between the second abutment surfaces, a certain amount of play remains in the lens centering (radial array). Usually, small centering errors are acceptable in many applications. Correspondingly, the play is greatly reduced at the desired temperature Tsoll (or the desired temperature interval, eg 15-40 ° C.) so that the centering error allowed for the desired imaging characteristics of the lens structure is not exceeded. Must be small. Then, for small temperature deviations from the desired temperature (or desired temperature interval) when the coefficients of thermal expansion of the transmissive materials of the lenses are different, the gap is the second abutment surface (usually non-surface). The lens lift due to contact (i.e., lifting of the first abutment surfaces from each other) is avoided, and as a result, local pressure buildup on the lens is avoided. The axial alignment and the alignment at the tilt angle are maintained very precisely via the first abutment surface, in the case of adjacency, in particular in the case of plane (plane) adjacency. However, it should be noted that the lifting of the lens can be justified to some extent. In the lifted state, the radial alignment is accurately maintained, but the axial alignment is changed and the lenses can be tilted with respect to each other, but this is allowed within certain boundaries. Furthermore, it should be noted that the intended temperature Tsoll (or the desired temperature interval) depends on the desired application. Typical play (nominal gap width in the case of the center position) at the desired temperature Tsoll is usually 15 μm or less.

  The transmissive material of all the lenses of the lens portion radially aligned by the common case has a thermal expansion coefficient, and the difference between the thermal expansion coefficient of the case material and the lens portion is not radially aligned by the common case. Embodiments that are smaller than the corresponding differences in the transmissive material of all lenses are also advantageous. In other words, the coefficient of thermal expansion of one or more transparent materials of the lenses radially aligned by the common case is closest to the coefficient of thermal expansion of the case material. As a result, it is possible to minimize the radial gap that must be set as a compensation space for various radial thermal expansions of the lens and case. Therefore, the optical aberration of the lens structure according to the present invention is minimized as a whole.

  In a preferred embodiment, a lens axially aligned by the case is arranged at the first end of the series of lenses, and the lens to which the elastic tensioning means is associated is located opposite the first end. Located at the second end of the series of lenses. This design has proven to be valuable in practice and typically the elastic element bears against the second end of the array.

Commonly applied is that the elastic tensioning means may have different structures, typically they are axial in the at least one elastic element (eg spring or elastomeric body) and the case. And a series of lenses (lens stack) and elastic elements are axially aligned between the adjustable tensioning element and the (stationary) opposing bearing of the case. The tensioning means is preferably in the lens stack as uniform as possible (especially uniform over the periphery and / or uniform over the contact surface) in order to prevent local tension peaks and deformations of the lens arising therefrom. Apply contact pressure. The tension applying means is
A contact ring that abuts against a lens at one end of the series of lenses, in particular a lens with a planar abutment ring surface extending perpendicular to the optical axis of the lens;
A tensioning ring that is screwed into the reverse screw of the case via a screw, in particular a male screw;
At least three spring elements, in particular leaf spring elements interconnecting the abutment ring and the tensioning ring;
An embodiment comprising is preferred. The spring elements are typically arranged in a uniform distribution around the circumference of the abutment ring and the tensioning ring. Usually, exactly three spring elements with the same spring constant are provided. The spring element is usually at an angle and / or over a range of circumferential angles between the abutment ring and the tensioning ring, preferably approximately between the abutment ring and the tensioning ring, e.g. Approximately extends on the side of the virtual cylinder, with a spiral path having the radius of the abutment or tensioning ring.

  An embodiment in which all optically effective surfaces and abutment surfaces are generated with the same clamping action during the manufacture of one side of the lens is particularly preferred. Thereby, a particularly high alignment accuracy of the optically effective surface can be obtained. The introduction of manufacturing tolerances due to re-clamping is avoided. It is also preferred that the lens edges (outer cylindrical surface) associated with radial alignment within the common case are similarly generated with the same clamping action.

  Furthermore, an embodiment is preferred in which the lens is produced at least partially, preferably completely, by a lathe, in particular by a diamond lathe. The lathe is cost-effective and allows for relatively accurate production of rotationally symmetric surfaces that are very suitable as both optically effective surfaces and abutment surfaces within the scope of the present invention. For a given spectral range in the infrared, the roughness left after the lathe does not significantly affect the imaging characteristics. In the case of a predetermined spectral range within the range of visible light, a post-treatment can be performed to reduce the surface roughness, for example by a mild post-polishing.

  In one embodiment, it is likewise possible to produce the lens at least partly, preferably completely, by means of a mold press. The press tool predetermines both the optically effective surface and the abutment surface so that they can be aligned with each other with good accuracy. The pressing can be performed in particular under the application of heat in order to soften and / or homogenize the initial lens material.

  Likewise preferred is an embodiment in which the lens is at least partly, preferably completely manufactured, by a manufacturing method adjusted by an interferometer. As a result, particularly high accuracy can be achieved during tool feeding.

  Further advantages of the present invention will become apparent from the description and the drawings. Similarly, the features described above and further described below can be used individually or together in any combination according to the invention. The embodiments shown and described are not to be understood as a comprehensive list, but as exemplary features describing the invention.

1 is a schematic longitudinal sectional view of a first embodiment of a lens structure according to the present invention in which only one lens is radially aligned by a common case. FIG. It is a schematic perspective view of the lens structure of FIG. 1 provided with a disengagement tension applying device. FIG. 2 is an enlarged view of a cross section of the lens structure of FIG. 1 in the region of the lens stack. FIG. 6 is a longitudinal cross-sectional view of two adjacent lenses in a lifted state. Fig. 4 shows a longitudinal section of two adjacent lenses that are lifted and tilted. FIG. 6 is an enlarged view of a cross-section of a second embodiment of a lens structure according to the invention in the region of a lens stack comprising two lenses aligned radially by a common case. FIG. 7 is an enlarged view of a cross-section of a third embodiment of a lens structure according to the invention in the region of a lens stack comprising a lens having a first abutment surface with a small tilt angle.

  The invention is illustrated in the drawings and will be explained in more detail on the basis of exemplary embodiments.

  All figures show schematic diagrams that are not to scale. In particular, the gap is exaggerated for the sake of clarity.

  1 and 2 show a lens structure 1 according to the present invention in the first embodiment, and in this case, four lenses 11, 12, 13, and 14 arranged in a common case 15 are provided. ing. The lenses 11, 12, 13, and 14 are continuously arranged along a common optical axis 16. The lenses 11-14 set optical imaging in which light (in this case infrared light) propagates along the substantially common optical axis 16 (from right to left in FIG. 1) through the lens structure 1. work. For this optical imaging, the lenses 11-14 are arranged in a radial direction (i.e. perpendicular to the optical axis 16) and in an axial direction (i.e. transverse to the optical axis 16) and at a tilt angle (i.e. common Are aligned with respect to the common optical axis 16 at an inclination angle of the optical axes of the lenses 11 to 14). Here, light refraction occurs at the lens surface.

  Only one of the lenses, i.e. the lens 11 at the first end 3 of the lenses 11-14, is arranged axially by the common case 15 in the illustrated embodiment. For this purpose, the lens 11 is in contact with the circumferential shoulder 17 of the common case 15 which in this case has a circumferential contact surface 18 on the left side. By this axial contact, the lens 11 is simultaneously set with respect to the tilt angle (that is, the tilt angle of the optical axis of the lens 11 is set with respect to the common optical axis 16). Furthermore, only one of the lenses, in this case the lens 11, is arranged radially by the common case 15, ie the common case so that the desired radial positioning of this lens 11 is performed directly by the case 15. 15 is firmly held in the radial direction.

  A series of subsequent lenses 12 are held by the lens 11 and are thereby set in a radial direction, an axial direction and a tilt angle. For this purpose, the lenses 11 and 12 form contact surfaces 2 that face each other. Similarly, the lens 13 is held by the lens 12, and the lens 14 is held by the lens 13. In particular, the lenses 12, 13, and 14 are not held radially or axially by the case 15 (see also FIG. 3 in this regard).

  The lenses 11 to 14 that are in contact with each other are also referred to as a lens stack 20, and are tensioned in the axial direction by the tension applying means 21. For this purpose, the tension applying device 22 presses the lens 14 from the right side with some force at the second right end 4 of the lens stack 20. Here, the tension applying means 21 or the tension applying device 22 includes a contact ring 23 disposed on the contact surface 24 of the lens 14 having a flat contact ring surface 23a. The abutment ring 23 is connected to the tensioning ring 26 via a plurality of spring elements 25, in this case three leaf spring-like spring elements 25. The tension applying ring 26 serves as a tension applying element adjustable in the axial direction of the case 15. For this purpose, the tensioning ring 26 comprises a screw 27 (in this case a male screw), so that it can be screwed in the case 15 into a corresponding counter screw 28 (in this case a female screw). The force with which the contact ring 23 presses the lens 14 can be set by the screwing depth of the tension applying ring 26. The screwing position can be fixed by an adhesive spot (not shown in more detail).

  In the illustrated embodiment, the case 15 further includes an end-side connection screw (in this case, a male screw) 29 for attaching to the optical structure.

  The arrangement of the lenses 11 to 14 in the common case 15 is described in more detail in FIG.

The lens 11 directly arranged in the radial direction and the axial direction by the case 15 is first brought into contact with the planar ring-shaped shoulder 17 of the case 15 having the planar ring-shaped contact surface 18. Second, the lens 11 substantially abuts the inner wall 31 of the case 15 with its radial edge (outer cylindrical side) 30 and in practice (assuming the center position of the lens 11 in the case 15). A minimum gap 32 of about 10 μm remains in the radial direction, and in particular enables the lens 11 to be guided to the shoulder 17 in the case 15 (inserting the lens). Further, the minimum gap 32 is caused by manufacturing variations with respect to the inner diameter of the inner wall 31 of the case 15 and the outer diameter of the lens 11, and the radial direction between the lens 11 and the case 15 (initially during normal operation, but also during transport and storage This is sufficient to compensate for possible thermal expansion differences (in the case of expected temperature fluctuations) without the lens 11 being radially clamped by the inner wall 31. The materials of the case 15 and the lens 11 are preferably matched to each other so that the (linear) coefficients of thermal expansion are as similar as possible, so that the thermal expansion coefficient of the lens material is maximized from the thermal expansion coefficient of the material of the case 15. It is preferable that the difference is 25%. The remaining lenses 12-14 are typically made of any different material and have specifications that allow all of the lenses 11-14 to transmit (pass) in the spectral range provided in the lens structure. Typical materials for lenses in the case of infrared include germanium (eg, for lens 12, thermal expansion coefficient α = 5.5 × 10 ⁻⁶ 1 / K), zinc selenide (eg, for lens 13, Thermal expansion coefficient α = 7.6 × 10 ⁻⁶ 1 / K), and GASIR® 1 (for example, in the case of lenses 11 and 14, the coefficient of thermal expansion α = 17 × 10 ⁻⁶ 1 / K). . Next, brass is suitable for a case material having a thermal expansion coefficient of α = 18.5 × 10 ⁻⁶ 1 / K. In the case of a combination of materials of GASIR (registered trademark) 1 and brass, the thermal expansion coefficient. The difference is only about 8.1% with respect to the case material.

  A first contact surface 41 and a second contact surface 42 of the adjacent lens 12 are provided in the radially outer region of the lens 11. Here, the first contact surface 41 is realized as a flat ring surface 41a that is perpendicular to the optical axis 71 of the lens 11 (here, coincides with the common optical axis 16). Here, the second contact surface 42 is realized as a protrusion 42 a that tapers toward the lens 12, and in this case, the protrusion corresponds to the side surface of the annular portion. Further, the lens 11 includes an optically effective surface 43 in the radially inner region, and the optically effective surface faces the lens 12 but does not contact the lens 12.

  The lens is manufactured from a uniform material, in which both the abutment surfaces 2, 41, 42 and the optically effective surface 43 are machined. In general, all contact surfaces 2, 41, 42, optically effective surfaces 43, 53, optionally case (cylinder side) 30, and optionally contact to case 15 or tensioning means 21 The edges associated with the radial alignment by the surfaces 18, 24 are produced with only one clamping action or with only one clamping action per lens side (front side, rear side), minimizing manufacturing tolerances, where Typical manufacturing methods include lathes, especially diamond lathes.

  The first contact surface 51 and the second contact surface 52 of the adjacent lens 11 are formed again on the lens 12 in the radially outer region. Similarly, the first contact surface 51 is realized as a flat ring surface 51a that is perpendicular to the optical axis 72 of the lens 12 (coincident with the common optical axis 16). Here, the second contact surface 52 is realized here as an opening 52a that expands toward the lens 11 in the form of a side surface of a truncated cone. Facing the lens 11, the lens 12 forms an optically effective surface 53 located in the radially inner region.

  Usually, it is at room temperature (20 ° C.), but can be selected depending on the application. In the case of an intended temperature, the first contact surfaces 41 and 51 are in contact with each other, and the protrusion 42a is open. Engage with the portion 52a. Here, a small gap 61 remains between the second contact surfaces 42 and 52 facing each other. The small gap 61 typically has a width BR of about 10-15 μm assuming the center position (ie, the gap 61 is exaggerated in FIG. 3). Therefore, when the first contact surfaces 41 and 51 are in contact with each other, only a small radial play that allows the lenses 11 and 12 to slide in the radial direction by the first contact surfaces 41 and 51 only. Remains. This ensures radial alignment of the lenses 12 on the common optical axis 16 even if the lenses 12 are not directly set by the case 15. In particular, the radial edge 62 of the lens 12 is separated from the facing inner wall 63 by a large gap 64, which typically does not clamp the lens 12 within the case 15 and tightens due to manufacturing tolerances. In other words, the lens 12 has a radial gap width of 150 μm or more so that the lens 12 is not clamped even if it slides in the radial direction with respect to the lens 11 and is not clamped by the influence of thermal expansion.

  Due to the planar contact of the lens 11 via the first contact surfaces 41 and 51, alignment in the axial direction and alignment of the inclination angle of the lens 12 is ensured.

  Similarly, the lens 13 is arranged with respect to the lens 12 via corresponding first and second abutment surfaces, and the lens 14 is attached to the lens 13 via appropriate first and second abutment surfaces. Placed against. The abutting ring 23 pressed in the axial direction on the lens 14 ensures that the lenses 11-14 of the lens stack 20 face each other without any axial play. As a result, all the lenses 11 to 14 are aligned in the common case 15, in particular along the common optical axis 16, with respect to the radial direction, the axial direction and the tilt angle, which depends on the case 15. No further contribution is required (self-centering).

  What can happen in the case of relatively strong temperature changes, and when the materials of the lenses 11-14 are different, is that the lens 11 forming the protrusion 42a is more than the lens 12 forming the associated opening 52a. It expands relatively strongly in the radial direction (or does not shrink so strongly). As a result, the gap 61 between the second contact surfaces 42 and 52 decreases until the second contact surfaces 42 and 52 finally contact each other.

  In the state of contact between the second contact surfaces 42 and 52, the lens 12 is displaced away from the protrusion 42a in the axial direction due to further relative radial expansion of the lens 11 with respect to the lens 12. 4 (only the lenses 11 and 12 are shown for simplicity), the (surface) contact of the first contact surfaces 41 and 51 is lost (raised). Accordingly, the lenses 11 and 12 slide on each other at the second contact surfaces 42 and 52.

  Here, the axial displacement of the lens 12 against the force of the tension applying means can be easily performed without damaging the lenses 11 and 12. Due to the tilt angle α (and sufficiently small friction) of the second abutment surfaces 42 and 52, the lenses 11 and 12 will also not move, and again referring to FIG. I want. A typical inclination angle α of the second contact surfaces 42 and 52 is 30 ° to 60 °, preferably about 45 °. In this case, the frustum side surface opening 52a has a uniform inclination angle α = 45 °, and the annular disk side surface protrusion 42a forms a local inclination angle α between 35 ° and 50 °. . The local inclination angle α is determined with respect to the reference surface BE extending perpendicularly to the optical axes 71 and 72 of the lenses 11 and 12 at each of the contact surfaces 42 and 52, in this case, the second contact surface (for example, tangential line). ) And determined by a cross-section SE (in this case the plane of the figure) containing the optical axes of the lenses 11, 12.

  It should be noted that the thermal expansion of the lenses 12-14 of FIG. 3 is not important not only for the other lenses 11-14, but also for the case 15 because these lenses are not guided radially. .

  As a result of the lifting, that is, due to the use of the contact contact between the lenses 11 and 12 by the second contact surfaces 42 and 52, the lenses 11 and 12 may be inclined with respect to each other. 71 is significantly inclined with respect to the optical axis 72 of the lens 12. In this regard, please refer to FIG. 5 (for the sake of simplicity, only the lenses 11 and 12 are shown here again, and the tilt is exaggerated). However, here, the inclination is limited by the first contact surfaces 41 and 51, because the first contact surfaces 41 and 51 finally have points in the lower region in this case. This is for mutual contact with each other. As a result, in the individual case, it is possible to still maintain the predetermined specifications for the lens structure despite “lifting”.

  FIG. 6 shows a second embodiment of the lens structure according to the present invention, which substantially corresponds to the lens structure of FIGS. 1 to 3 in the region of the lens stack 20. Therefore, it is intended to explain only the essential differences.

  Also in this case, the four lenses 11, 12, 13, 114 are arranged in the common case 15. The lens 11 is disposed directly in the axial direction by the case 15 as a lens only. In this embodiment, two lenses, namely lenses 11 and 114, are arranged directly in the radial direction by case 15. The remaining lenses 12 and 13 are arranged in the radial direction by the lenses 11 and 114. The radial alignment of the lens stack 20 can be more accurate overall as a result of the radial alignment of the two lenses 11, 114 by the case 15. However, in this embodiment, as a result of the radial clamp in the case 15 for both lenses 11, 114, it is ensured that there is no radial tension, in particular by the choice of material that matches the case 15. is necessary. As a result, in this embodiment, the material selection of the lenses 11, 12, 13, and 114 is slightly limited as a whole. Furthermore, the various parts of the inner walls 31, 81 of the case 15 must be manufactured with high accuracy relative to each other.

  FIG. 7 shows a region of the lens stack 20 in the third embodiment of the lens structure according to the present invention. Only the essential differences from FIG. 6 will be described.

  Here, the lenses 11 and 12 are in contact with each other by the first contact surfaces 41 and 51. Here, the first abutment surface 41 of the lens 11 is measured relative to a reference plane BE, which is perpendicular to the optical axis 71 of the lens 11 (in this case coincident with the common optical axis 16). In this case, it is realized as a conical side with a very small inclination angle α of about 7 °. The cross section SE (in this case, the plane in the figure) where the tilt angle α is measured includes the optical axis 71 of the lens 11. Here, the first contact surface 51 of the lens 12 is realized as a side surface of an annular segment. The small tilt angle α of the first abutment surface 41 is such that the lenses 11, 12 are relatively over the radial play of the lenses 11, 12 (see the small gap 61 between the second abutment surfaces 42, 52). It only allows a small tilt. However, this possible tilt is usually allowed if the tilt angle α is sufficiently small.

DESCRIPTION OF SYMBOLS 1 Lens 2 Contact surface 3 1st edge part 4 2nd edge part 11 Lens (aligned in radial direction and axial direction with a case)
12-14 lens 15 common case 16 common optical axis 17 shoulder 18 contact surface 20 lens stack 21 tension applying means 22 tension applying device 23 contact ring 23a contact ring surface 24 contact surface 25 spring element 26 tension applying ring 27 screw 28 Counter screw 29 Connection screw 30 Radial edge 31 Inner wall 32 Gap (Inner wall / radial edge in lens 11)
41 First contact surface 41a Flat ring surface 42 Second contact surface 42a Projection 43 Optically effective surface 51 First contact surface 51a Flat ring surface 52 Second contact surface 52a Opening 53 Optical Effective surface 61 gap (second contact surface)
62 Radial edge 63 Inner wall 64 Gap (radial edge / inner wall in lens 12)
71 Optical axis (lens 11)
72 Optical axis (lens 12)
81 Inner wall 114 lens (radially aligned by case)
α Inclination angle BE Reference plane BR width (gap 61)
SE cross section

Claims (14)

A lens structure (1) for an optical unit that operates to refract transparently within a predetermined spectral range,
At least two lenses (11-14, 114) each made of a material that transmits within the predetermined spectral range;
A common case (15) in which the at least two lenses (11-14, 114) are arranged in succession;
With
The lenses (11-14, 114) are arranged at least substantially radially, axially and at an angle of inclination with respect to a common optical axis (16),
In each case, a series of adjacent lenses (11-14, 114) are mounted to allow relative movement between them, said lenses facing each other with their permeable material ( 2), and the adjacent lenses (11 to 14, 114) are in contact with each other via the contact surface,
Elastic tension applying means (21) is provided so that a series of lenses (11-14, 114) is pretensioned in the axial direction,
Only one of the series of lenses (11) is arranged axially through the common case (15), and only a part of the series of lenses (11, 114) passes the common case (15). Arranged in a radial direction through
A series of the remaining lenses (12-14, 114) are aligned with each other by the abutting surfaces (2) facing each other of the adjacent lenses (11-14, 114), so that all of the series A lens structure (1) in which lenses (11 to 14, 114) are arranged in a radial direction, an axial direction, and at the inclination angle with respect to the common optical axis (16).   The lens structure (1) according to claim 1, wherein the predetermined spectral range is in the infrared, and in particular, the whole or part of the predetermined spectral range comprises a wavelength range of 2 µm to 13 µm.   3. The lens structure (1) according to claim 1 or 2, wherein at least a part of the at least two lenses (11-14, 114) are made of different materials that transmit in the predetermined spectral range.   The abutting surfaces (2) of the adjacent lenses (11-14, 114) facing each other are formed in a radially outer region of the lenses (11-14, 114), and the optically effective surfaces (43, 53) are adjacent to each other. Formed in the radially inner region of the lenses (11-14, 114), the adjacent lenses (11-14, 114) are not the optically effective surfaces (43, 53) but only the contact surfaces (2) facing each other. The lens structure (1) according to any one of claims 1 to 3, which abuts each other. A series of adjacent lenses (11-14, 114) in each case form a first contact surface (41, 51) facing each other, the first contact surfaces facing each other At least one of (41, 51) is realized in each case to be substantially flat and substantially perpendicular to the optical axis (71, 72) of the respective lens (11-14, 114);
In particular, the maximum local inclination angle α of the first abutment surface (41, 51) does not exceed an absolute value of 15 °, and the local inclination angle α is determined by the optical axis of the lens (11-14, 114). 71, 72) measured in a cross section (SE) including a reference plane (BE) extending perpendicularly to the optical axis (71, 72) of the lens (11-14, 114),
In particular, the first contact surface (41, 51) is realized rotationally symmetrically with respect to the optical axis (71, 72) of the respective lens (11-14, 114). 5. The lens structure (1) according to any one of 4 above.   At least one of the first contact surfaces (41, 51) facing each other in each case extends perpendicular to the optical axis (71, 72) of the respective lens (11-14, 114), In particular, the lens structure (1) according to claim 5, wherein the first abutment surface (41, 51) is realized as a ring-shaped plane (41a, 51a).   A series of adjacent lenses (11-14, 114) form a second abutment surface (42, 52) facing each other, one of the second abutment surfaces (42, 52) being the other An opening (52a) extending toward the lens (11-14, 114) is formed, and / or one of the second surfaces (42, 52) is in the other lens (11-14, 114). The lens structure (1) according to any one of claims 1 to 6, wherein a projection (42a) that tapers toward the surface is formed.   At least one local inclination angle α of the second abutment surface (42, 52) has an absolute value between 25 ° and 65 °, preferably between 30 ° and 60 °, and the local inclination A reference plane (BE) extending at right angles to the optical axes (71, 72) of the lenses (11-14, 114) and the optical axes (71, 72) of the lenses (11-14, 114) have an angle α. Lens structure (1) according to claim 7, measured in a cross section (SE) comprising   9. One or more of the second abutment surfaces (42, 52) are formed at least substantially in accordance with the side surfaces of a truncated cone and / or a spherical segment and / or an annular segment. Lens structure (1).   One of the second contact surfaces (42, 52) facing each other extends toward the other lens (11-14, 114) and at least substantially corresponds to the side surface of the truncated cone (52a). And the other of the second abutment surfaces (42, 52) facing each other is tapered towards the other lens (11-14, 114) and at least substantially corresponds to the side surface of the annular segment. The lens structure (1) according to any one of claims 7 to 9, wherein a projection (42a) is formed.   In the lens structure (1), the first contact surfaces (41, 51) facing each other of adjacent lenses (11-14, 114) are in contact with each other in order at a desired temperature Tsoll. The two abutment surfaces (42, 52) of the adjacent lenses (11-14, 114) that are in contact with each other in plan view are realized so that play remains between them. The lens structure (1) according to any one of claims 5 and 6, and 7 to 10, wherein the temperature Tsoll is 20 ° C.   The transmissive material of all the lenses (11, 114) of the portion of the lens (11, 114) aligned in the radial direction by the common case (15) has a coefficient of thermal expansion, and the case (15) The difference in thermal expansion coefficient of the material is that of the transparent material of all the lenses (12-14) of the part of the lens (12-14) that is not radially aligned by the common case (15). 12. Lens structure (1) according to any one of the preceding claims, wherein the lens structure (1) is smaller than a corresponding difference.   The lens (11) aligned in the axial direction by the case (15) is disposed at the first end (3) of the series of lenses (11 to 14, 114), and the elastic tension applying means (21 ) Are engaged with the second end (4) of the series of lenses (11-14, 114) located on the opposite side of the first end (3). The lens structure (1) according to any one of claims 1 to 12, which is arranged.   All optically effective surfaces (43, 53) and abutment surfaces (2) are produced with the same clamping action during the manufacture of one side of the lens (11-14, 114). The lens structure (1) described in the item.