Abstract:
The aim of the invention is to improve a projector lens, comprising an optical element for shaping radiation fields emitted from light guides, such that the light guide may be optimally coupled to the optical element. Said aim is achieved, whereby the optical element is embodied in a monolithic body, comprising a radiation field forming region and a connector region for the light guide, which form part of the optical element and the connector region comprises a connector surface for a front face of the light guide which approximately matches a diameter of the light guide and is arranged offset from a vicinity of the connector region.

Description:
The present disclosure relates to the subject matter disclosed in PCT application No. PCT/EP01/15043 of Dec. 19, 2001, which is incorporated herein by reference in its entirety and for all purposes. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a projector lens comprising an optical element for shaping radiation fields emitted from light guides. 
   Projector lenses of this type are known from the prior art, but these always have the problem of coupling the light guide optimally onto the optical element. 
   SUMMARY OF THE INVENTION 
   This problem is solved in the case of a projector lens of the type described at the beginning according to the invention by the optical element being formed in a monolithic body which has a radiation-field-shaping region and a connecting region for the light guide which are part of the optical element, and by the connecting region having a connecting area for a front face of the light guide which is adapted approximately to a diameter of the light guide and is disposed offset from a vicinity of the connecting region. 
   The advantage of this solution is to be seen in that, provision of the monolithic body makes the optical element particularly easy to produce and, in spite of this easily producible optical element, the light guide can also be fixed in the desired exact position in relation to the optical element in an easy way. 
   With regard to the formation of the connecting region carrying the connecting area, a wide variety of possibilities are conceivable. For instance, one advantageous solution provides that the connecting region forms a projection which goes beyond the vicinity of the connecting region and to which the light guide can be easily fixed in a centered manner, in particular if, according to the invention, the projection has a diameter corresponding approximately to the diameter of the light guide. 
   As an alternative to this, it is conceivable for the connecting region to be formed as a depression with respect to the vicinity of the connecting region, so that centering, and consequently exact positioning, of the light guide in relation to the optical element is possible by introducing the end of the respective light guide that carries the front face into a depression of this type. 
   With regard to the formation of the optical element, a wide variety of possibilities are conceivable. 
   A preferred solution provides that the optical element is part of a monolithic body extending beyond said element, the monolithic body itself having further regions, such as for example a carrier region. 
   In this case, the vicinity of the connecting region is formed by one side of the monolithic body, for example the carrier region, in particular a rear side of the same. 
   As an alternative to this, it is also conceivable however for the monolithic body to be held in a carrier which is not part of the monolithic body, since the production of the monolithic body is simplified in this way. 
   In such a case, the vicinity of the connecting region is preferably formed by one side of the carrier, preferably a rear side of the carrier. 
   One particularly advantageous variant of the solution according to the invention provides that the optical element is formed by a monolithic body which is approximately cylindrically constructed and encloses both the radiation-shaping region and the connecting region, and is for its part held in a carrier. 
   In this case, the cylindrical body itself forms the connecting area, which is then for its part offset from the vicinity, that is to say from a rear side of the carrier. 
   Such offsetting of the connecting area may take place either by the monolithic body extending beyond the rear side, in a way similar to a projection, or being set back from the rear side, and consequently a depression which extends up to the connecting area being formed from the rear side. 
   With regard to the formation of the radiation-field-shaping region, no further details have been specified in connection with the exemplary embodiments so far described. 
   It is for instance preferably provided that the radiation-field-shaping region has an area curved in the manner of a lens for radiation field shaping. 
   Another preferred solution provides that the radiation-field-shaping region has a refractive index gradient for radiation field shaping. 
   The radiation-field-shaping region is preferably formed by a cylindrical monolithic body with a GRIN optic. 
   Furthermore, no further details have been specified in connection with the exemplary embodiments so far concerning the way in which the optical elements are disposed. 
   One advantageous solution for instance provides that the optical elements are individual optical elements. 
   These individual optical elements are preferably held by a common carrier. 
   However, a particularly advantageous solution provides that the optical elements are formed by segmental regions of a unitary monolithic body. 
   The manner of radiation field shaping has not been defined in any more detail in connection with the exemplary embodiments described so far. 
   For instance, in principle all types of beam shaping such as focusing, defocusing, etc. are conceivable. 
   It is particularly advantageous if the radiation-field-shaping region has boundary surfaces shaped in such a way that rays reflected on them are substantially not reflected back directly into the light guide, and consequently the projector lens operates without backreflection with respect to the light guide. 
   It is particularly advantageous in the case of a collimating radiation-field-shaping region if exact collimation does not takes place, since consequently there is substantially no reflection at the boundary surfaces of the radiation coming from the light guide back into the light guide. 
   The connection between the light guide and the connecting area of the connecting region may take place in a wide variety of ways. 
   A substantially reflection-free connection is particularly advantageous. 
   A connection of this type can be advantageously realized by adhesive bonding or welding by melting. 
   One possible way of achieving melting is for a heatable material by means of which the material in the region of the areas to be connected can be heated up to be provided in the region of the areas to be connected. 
   The heatable material may in this case have been applied in the form of a layer. 
   One particularly advantageous solution provides in this case that a collar of a heatable material by means of which the material in the region of the areas to be connected can be heated up is provided in the region of the areas to be connected. A collar has the great advantage that it can run around the region of the areas to be connected and consequently ensures optimum heating. 
   Another advantageous solution provides that the light guide is provided with a collar of heatable material in the region of its front face. Providing the light guide with a collar of this type can be realized in a particularly advantageous way. 
   The heatable material can in this case be heated up, for example, by an electric current or by an electrical discharge. 
   It is even more advantageous if the heatable material can be heated up by absorption of rays. 
   Such an absorbed beam may, for example, also be a particle beam or an electron beam. One advantageous variant provides that the absorption of a beam takes place by absorption of electromagnetic radiation. 
   It is particularly advantageous in this case if the electromagnetic radiation lies in the wavelength range of light. 
   One particularly advantageous solution provides that the material can be heated up by laser radiation. 
   Laser radiation may impinge on the material from the outside. 
   It is also conceivable, however, to pass the laser radiation through the light guide. 
   One particularly advantageous solution provides that the laser radiation passes through the monolithic body in order to heat up the heatable material. 
   One possibility for the provision of the radiation-absorbing layer is to provide this layer on the front faces to be connected. 
   It is particularly suitable when producing a welded connection to provide a collar which can be heated up by radiation in the region of the connection to be established. 
   Further features and advantages of the invention are the subject of the description which follows and of the graphic representation of some exemplary embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a longitudinal section through a first exemplary embodiment of a projector lens according to the invention; 
       FIG. 2  shows a plan view of the first exemplary embodiment in the direction of the arrow A in  FIG. 1 ; 
       FIG. 3  shows a section similar to  FIG. 1  with a representation of reflections at a boundary surface and an optical element of the projector lens according to the invention; 
       FIG. 4  shows a representation similar to  FIG. 1  of a second exemplary embodiment of a projector lens according to the invention; 
       FIG. 5  shows a representation similar to  FIG. 2  of the second exemplary embodiment; 
       FIG. 6  shows a representation similar to  FIG. 3  of the second exemplary embodiment; 
       FIG. 7  shows a representation similar to  FIG. 1  of a third exemplary embodiment of a projector lens according to the invention; 
       FIG. 8  shows a representation similar to  FIG. 2  of the third exemplary embodiment; 
       FIG. 9  shows a representation similar to  FIG. 3  of the third exemplary embodiment; 
       FIG. 10  shows a section along the line  10 — 10  in  FIG. 11  through a fourth exemplary embodiment of a projector lens according to the invention; 
       FIG. 11  shows a plan view in the direction of the arrow B in  FIG. 10 ; 
       FIG. 12  shows a representation similar to  FIG. 1  through the fourth exemplary embodiment; 
       FIG. 13  shows a representation similar to  FIG. 12  with a representation of laser welds for the connection of the light guide and optical element; 
       FIG. 14  shows a section along line  14 — 14  in  FIG. 15  through a fifth exemplary embodiment of a projector lens according to the invention; 
       FIG. 15  shows a plan view in the direction of the arrow C in  FIG. 14 ; 
       FIG. 16  shows a representation similar to  FIG. 1  of the fifth exemplary embodiment and 
       FIG. 17  shows a representation of a variant of the fifth exemplary embodiment in the form of a plan view in the direction of the arrow D in  FIG. 14 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A first exemplary embodiment of a projector lens according to the invention comprises an optical element, designated as a whole by  10 , which, as represented in  FIGS. 1 to 3 , formed in a monolithic body  12 , which has a radiation-field-shaping region  14  and a connecting region  16  for a light guide, designated as a whole by  18 , and also a carrier region  19  lying outside these regions. 
   The connecting region  16  is in this case provided with a connecting area  20 , which is adapted with regard to its cross-sectional area to a cross-sectional area of a front face  22  of the light guide  18 , the light guide  18  preferably having a core  24  and a cladding  26  and the front face  22  having a front face  28  of the core  24  and, enclosing the latter, a front face  30  of the cladding  26 . 
   The light guide  18  is preferably adhesively bonded or welded by its front face  22  to the connecting area  20 , in order to obtain a substantially reflection-free optical contact between the front face  28  of the core  24  and the connecting area  20 . 
   Furthermore, as represented in  FIG. 3 , the radiation-field-shaping region  14  of the monolithic body  12  is formed as a collimating element, which forms from a divergent radiation field  40  emanating from the front face  28  in the optical element  10  a substantially collimated radiation field  42 , which is emitted from the radiation-field-shaping region  14  on a front side  32  lying opposite the connecting area  20 . 
   In this case, to achieve the collimating effect, the front side  32  is preferably provided with a curved region  34  with respect to a plane  46  that is perpendicular to a beam axis  44 , it being possible, for example, to fix the collimating effect of the radiation-field-shaping region  14  by the curvature. 
   The curved region  34  forms a boundary surface between the material of the monolithic body  12  and the surrounding medium, so that undesired reflections of rays  48  emanating in the monolithic body  12  can occur at this region. 
   The curved region  34  is in this case preferably formed in such a way that the rays  48  emanating within the monolithic body  12  in the direction of the curved region  34  are reflected in such a way that the reflected rays  50  emanate in such a way that they can no longer enter the core  24  through the front face  28 , so that in the monolithic body  12  a back reflection of the radiation field  40  into the core  24  are substantially avoided in the region of the front side  32 . 
   In addition, it is also advantageous to provide an anti-reflection coating, which reduces the reflection. 
   In the case of the first exemplary embodiment, the connecting region  16  is preferably formed in such a way that the connecting area  20  is disposed at a spacing from a rear side  36  of the carrier region  19  of the monolithic body  12  in such a way that an approximately cylindrical free projection  38  is formed extending from the rear side  36  and for its part carries the connecting area  20 . 
   A connecting area  20  which is raised in such a way from the rear side  36  and the cross-sectional area of which corresponds substantially to the diameter of the light guide  18  has the advantage that, during fixing, in particular the melting of the front face  22  of the light guide  18  onto the raised and free connecting area  20 , a self-centering effect is obtained if the diameter of the connecting area  20  corresponds substantially to the diameter of the front face  22 , and consequently sufficiently precise positioning of the light guide  18  with respect to the optical element  10  can be achieved in an easy way. 
   In the case of a second exemplary embodiment of a projector lens, represented in  FIGS. 4 to 6 , by contrast with the first exemplary embodiment, the connecting region  16 ′ is formed in such a way that the connecting area  20  is offset with respect to the rear side  36  in the direction of the front side  32  and consequently forms a depression  38 ′ from the rear side  36 , into which the light guide  18  can be introduced with its front region  21 , carrying the front face  22 , in order to apply the front face  22  to the connecting area  20  and connect it to the latter, for example by adhesive bonding or welding or a similar method. 
   Furthermore, peripheral walls  39  of the depression  38 ′ effect a centering of the front region  21  of the light guide  18  for the connection of the front face  22  of the latter to the connecting area  20 . 
   Otherwise, the second exemplary embodiment is formed in the same way as the first exemplary embodiment, so that reference can be made to the full content of the statements made with respect to said first embodiment. 
   In the case of a third exemplary embodiment of a projector lens according to the invention, represented in  FIGS. 7 to 9 , the optical element  10  is held by a carrier  11 , fitted into which is the monolithic body  12 , which has the radiation-field-shaping region  14 ″ and the connecting region  16 ″, which both have approximately the same diameter and are realized by the monolithic body  12  of the same diameter. 
   In this case, the monolithic body  12  is disposed in the carrier  11  in such a way that the connecting region  16 ″ protrudes from a rear side  36  of the carrier  11  and consequently, in a way similar to the first exemplary embodiment, forms a free cylindrical projection  38 , to which the light guide  18  can be fixed with its front face  22  by welding. 
   It is also the case in the third exemplary embodiment that the radiation-field-shaping region  14 ″ of the monolithic body  12  is formed in such a way that it acts substantially in a collimating manner, the radiation-field-shaping region  14 ″ being formed by a GRIN optic, which, on account of a refractive index varying in the radial and/or axial directions, acts in a collimating manner. Such GRIN optics, also known as graded-index rod optics, are commercially available as GRIN lenses or GRIN fibers. 
   In the case of a fourth exemplary embodiment of a projector lens, represented in  FIGS. 10 to 12 , those elements which are identical to the previous exemplary embodiments are provided with the same reference numerals, so that reference can be made to the full content of the statements made with respect to these exemplary embodiments. 
   In particular, the fourth exemplary embodiment is based on the concept of the first exemplary embodiment, though not just a single optical element  10  is provided in the monolithic body  12  but a multiplicity of optical elements  10 ′ are formed in a unitary monolithic body  12 ′, the monolithic body  12 ′ having for each individual one of the optical elements  10 ′ a  to  10 ′ c  a dedicated radiation-field-shaping region  14   a–c  and a dedicated connecting region  16 , and the connecting region  16   a–c  and the radiation-field-shaping region  14   a–c  being formed in the same way as in the case of the first exemplary embodiment. 
   Furthermore, the fixing of the light guides  18  also takes place in the same way as in the case of the first exemplary embodiment on the respectively dedicated connecting areas  20  of the connecting regions  16 . 
   The advantage of this solution can be seen in particular in that the self-centering of the end of the light guide  18  carrying the respective front face  22  in relation to the connecting region  16  is of considerable significance in this solution, since it allows a large number of light guides  18  to be connected to a large number of connecting regions  16  in an easy way, without inadequate results being obtained on account of inadequate centering of the front face  22  in relation to the connecting areas  20 . 
   In the case of the fourth exemplary embodiment of the projection lens, the connection between the light guides  18  and the individual connecting areas  20  preferably takes place by means of welding, with melting of the material of the front face and/or of the light guide  18  preferably being required in the region  21  of the light guide  18  near the front face  22 . 
   Such melting of the light guide  18  takes place as represented in  FIG. 13  on the basis of the optical element  10   b  by a divergent laser beam  60  being coupled in via the front side  32   b  of the optical element  10   b  and focused onto the front face  22  of the light guide  18  and the front face  22   b  consequently being heated up by the laser radiation being absorbed by a layer  62 , for example of SiO 2 , applied to the front face  22   b , in order to melt the material in this region. 
   However, as an alternative or in addition to this, it is conceivable, as likewise represented in  FIG. 13  on the basis of the optical element  10   a , to couple the diverging light beam  60  into the radiation-field-shaping region  14   a  in such a way that it not only impinges on the front face  22   a  of the light guide  18   a  but also impinges on a collar  64  which encloses the connecting region  16   a  and the end of the light guide  18   a , carrying the front face  22   a , and is formed in such a way that it absorbs the laser beam  60  and consequently serves the purpose of heating the end of the light guide  18   a , carrying the front face  22   a , by thermal coupling in the region of the front face  22   a  and the connecting area  20   a , and consequently of contributing to the advantageous welding of the front face  22   a  to the connecting area  20   a , so that welding with laser radiation  60  coupled in through the optical element  10  is possible even with low absorption of the laser beam  60  in the light guide  18 . 
   In the case of a fifth exemplary embodiment, represented in  FIGS. 14 to 16 , those elements which are identical to those of the previous exemplary embodiments are provided with the same reference numerals, so that reference can be made to the full content of the statements made with respect to the previous exemplary embodiments with regard to the description of these elements. 
   The fifth exemplary embodiment of a projector lens is based in principle on the second exemplary embodiment, with the individual optical elements  10 ″ being combined into a single monolithic body  12 ′ and the connecting regions  16 ′ forming depressions  38 ′ in a way corresponding to the second exemplary embodiment, into which the light guides  18  can be introduced with their front regions  21  bordering the front face  22 , can be positioned and can be placed against the connecting area  20 . 
   In the case of one variant of the fifth exemplary embodiment, represented in  FIG. 17 , provided in addition to the depressions  38 ′, to be precise to the side of them, preferably in a region  70  respectively lying between four depressions  38 ′, are markings  72 , which serve for example as a positioning aid for an introducing device, in order when introducing the light guides  18  with their front face  22   a  into the depressions  38 ′, to align the light guides  18  exactly in relation to the depressions  38 ′ and consequently allow them to be introduced precisely into the latter. 
   The markings  72  are preferably formed by two marking segments  74  and  76 , running in directions perpendicular to each other, so that a point in the respective area region  70  can be uniquely defined by each marking  72 . 
   The markings  72  are preferably disposed in such a way that at least two such markings  72  are associated with each of the depressions  38 ′. 
   The markings  72  described in connection with the fifth exemplary embodiment may, however, also be provided in the same way for positioning the light guides  18  in the case of the fourth exemplary embodiment according to  FIGS. 10 to 13  in intermediate regions between the connecting regions  16  or, in the case of monolithic micro-optics, without additional structuring of the connecting region.