Photographic lens, image recording device and method for producing the same

Abstract

A method for producing a photographic lens (11), comprising a light-transmitting base body (12) and image-forming optical elements (3a-h) arranged along a folded optical axis (OA), wherein the angle (α) between sections of the optical axis (OA1 - OA9) before and after folding is less than 180 degrees, and wherein the image-forming optical elements (3a-h) comprise reflective elements, at least one of which has a non-rotationally symmetrically curved reflective surface, the method comprising: - manufacturing the translucent base body (12) using an injection molding process and / or RIM process and - Forming the image-forming optical elements (3a-h) in the base body (12).

Description

[0001] The present invention relates to a method for producing a photographic lens, a method for producing an image recording device, a photographic lens and an image recording device.

[0002] A camera lens is a focusable lens, where focusing—i.e., setting the distance or focusing—can be achieved, for example, by moving optical elements within the lens. In addition to camera lenses with a fixed focal length, there are also camera lenses with a variably adjustable focal length. Zoom lenses are also known, where the focal length can be continuously adjusted within a range. Furthermore, there are camera lenses in which the focal length can only assume certain discrete values, e.g., three different focal lengths. To limit the cross-section of beams of rays, i.e., to stop down, the camera lens can have an aperture.

[0003] The above-mentioned properties are implemented in today's common camera lenses. These camera lenses are mostly dioptric camera lenses, i.e., camera lenses that have only refractive elements as imaging optical elements. Camera lenses that have both refractive and reflective elements as imaging optical elements are called catadioptric camera lenses. Due to the use of reflective elements, catadioptric camera lenses allow for folding of the optical path, which allows for smaller dimensions of a catadioptric camera lens compared to a dioptric camera lens of the same focal length.

[0004] A dioptric optical image recording system that can be used as the lens of a compact, flat camera is disclosed, for example, in DE 697 15 198 T2. The optical image recording system has a front lens group and a rear lens group, as well as a folded optical axis. Two planar reflective elements fold the optical axis at an angle of approximately 90°, with the planar reflective elements contributing nothing to the image. The image-forming optical elements are therefore all dioptric elements, i.e., refractive elements.

[0005] A camera system for capturing stereoscopic images, in which each imaging beam path has a three-dimensionally folded optical axis, is described in US Pat. No. 7,856,181 B2. Planar reflective surfaces are used as the elements folding the optical axis, and dioptric elements, i.e., refractive elements, are used as the image-forming optical elements.

[0006] Dioptric systems exhibit chromatic aberrations due to dispersion passing through the lenses. While these chromatic aberrations can be largely minimized by using multiple lenses with different dispersion properties, increasing the number of lenses results in increased weight and thus relatively heavy lenses.

[0007] US Pat. No. 4,690,516 A discloses a catadioptric photographic lens with an optical axis folded by 180 degrees. A primary mirror reflects the imaging beam path coming from the lens aperture back toward the lens aperture. A secondary mirror is located in the area of ​​the lens aperture, which deflects the beam path back to its original direction. This secondary mirror creates an obscuration in the beam path, sometimes also called an obstruction, which leads to a loss of aperture area and, due to diffraction effects, to a reduction in contrast.

[0008] A catoptric optical element is known from DE 696 18 689 T2, which is suitable, for example, for photo cameras, video cameras, or copiers. The use of numerous reflective surfaces and their special arrangement enables a compact design of the optical element. The interior of the optical element is filled with a translucent material, e.g., glass, so that a translucent body is formed. This enables the use of molding processes, thus increasing productivity and reducing manufacturing costs. As an alternative to the translucent body, the optical element can comprise a hollow core block.

[0009] US 5 078 502 A also describes a catoptric system that enables production in a compact size.

[0010] DE 697 28 804 T2 discloses an optical magnification system with at least two optical elements, one of which has reflective surfaces and the other has refracting surfaces. The reflective surfaces can be formed in a rigid transparent body. To achieve magnification, the optical elements can move relative to each other.

[0011] JP 2004 - 258 541 A describes a reflective optical system in which the reflecting surfaces do not have a common optical axis.

[0012] US Pat. No. 6,301,064 B1 discloses an optical device comprising an optical unit with a light entrance surface, light reflection surfaces, and a light exit surface, all integrally formed from transparent material. The optical unit has an internal refractive surface for refracting light. Since a light beam travels through the optical unit from the light entrance surface to the light exit surface via the internal refractive surface and the light reflection surfaces along a folded optical axis, the optical device is reduced in size and improved in optical performance, particularly with good correction for chromatic aberration.

[0013] In order to provide a compact photographic lens which has neither a chromatic aberration (e.g. lateral chromatic aberration or longitudinal chromatic aberration) nor an obscuration, an improved photographic lens was also developed, which was filed for patent by the co-applicant of the present patent application under the PCT file number PCT / EP2019 / 061863, filing date May 8, 2019.

[0014] This photographic lens comprises image-forming optical elements arranged along a folded optical axis. The optical axis is divided into at least two sections. The angle between the sections of the optical axis before and after folding is less than 180°. The image-forming optical elements comprise reflective elements. At least one image-forming optical reflective element has a non-rotationally symmetrically curved reflective surface. Non-rotationally symmetrically curved surfaces are to be regarded as both surfaces that are sections of rotationally symmetrical surfaces, i.e., surfaces that can be combined to form a rotationally symmetrical surface, and surfaces that cannot be combined to form a rotationally symmetrical surface.

[0015] If the camera lens uses only reflective elements as image-forming optical elements, chromatic aberrations are eliminated, which is particularly advantageous for camera lenses with long focal lengths. At the same time, the camera lens enables an obscuration-free imaging system. Furthermore, a catoptric camera lens can be constructed with fewer optical elements than a dioptric or catadioptric camera lens, since chromatic aberration induced by a dioptric element does not need to be compensated for by another dioptric element.

[0016] At least one of the non-rotationally symmetrically curved reflective surfaces can be designed as a freeform surface. With the help of freeform surfaces, monochromatic imaging errors such as spherical aberration, astigmatism, coma, etc. can be corrected. A freeform surface can be understood in the broader sense as a complex surface that can be represented in particular by means of region-defined functions, in particular twice continuously differentiable region-defined functions. Examples of suitable region-defined functions are (in particular piecewise) polynomial functions (in particular polynomial splines, such as bicubic splines, higher-order splines of fourth degree or higher, or polynomial nonuniform rational B-splines (NURBS)). These must be distinguished from simple surfaces, such asspherical surfaces, aspherical surfaces, cylindrical surfaces, toric surfaces that are described as a circle at least along one main meridian. In particular, a freeform surface does not need to have axial symmetry or point symmetry and can have different values ​​for the mean surface refractive index in different areas of the surface. The production of a freeform surface on an optical element is usually carried out by machining the optical element, for example by milling, as part of a CNC process in which the freeform surface is produced under numerical control based on a mathematical description of the surface. However, it is also possible to press the freeform blank. For this purpose, the negative press mold must be machined using CNC processes with appropriate allowances for temperature-dependent shrinkage.

[0017] The optical axis of the photographic lens can be folded at least twice. In this case, with each fold, the angles between the sections of the optical axis before and after the fold can be less than 180°. The second fold of the optical axis can occur in the same plane as the first fold, or it can lie in a different plane than the first fold, whereby a three-dimensional variant can be realized, in particular if at least one of the reflective elements has neither a rotationally symmetric nor an axially symmetric curved reflective surface. In the photographic lens with an optical axis folded at least twice, the position of the object axis relative to the image axis can be freely selected, i.e. parallel to one another or with any angle between the object axis and image axis. This configuration therefore enables a very variable adaptation of the lens to a given installation space.

[0018] The reflective elements can comprise at least two reflective elements whose reflective surfaces are shaped such that different magnifications are present in the formed image in two directions perpendicular to each other and to the optical axis. This makes it possible to realize a so-called anamorphic image, i.e., an image with different magnifications along the axes of a two-dimensional coordinate system in the image plane.

[0019] Additionally or alternatively, the reflective elements may comprise at least two reflective elements whose reflective surfaces are shaped such that a different number of intermediate images is created for two mutually perpendicular image extension directions. Such imaging is called choristical imaging.

[0020] At least one of the image-forming optical elements of the camera lens can have a section of a rotationally symmetrically curved reflective surface, wherein the optical axis of the rotationally symmetrically curved reflective surface does not penetrate the image-forming optical element. This allows the camera lens to be reduced in size by a scaling factor of 0.1, allowing the camera lens to be used more effectively for mobile phone cameras or other miniaturized image capture devices.

[0021] The camera lens can have a telephoto factor of more than 3.

[0022] The camera lens can be dimensioned to have a maximum sensor area of ​​120 mm 2 , a maximum sensor area of ​​60 mm 2 or a maximum sensor area of ​​30 mm 2 an image sensor, whereby a sufficiently bright image of the recorded object is created.

[0023] For a focal point of the photographic lens, it can be assumed that the distance between the image plane and the focal point is less than a quarter, preferably less than a sixth, of the focal length of the photographic lens.

[0024] The folded optical axis of the photographic lens may have a three-dimensional fold.

[0025] The described camera lens is suitable for installation in a compact image recording device, e.g., a camera, or another electronic device that includes such a compact image recording device. The compact image recording device can, for example, have an image sensor with a maximum sensor area of ​​120 mm 2 , maximum 60 mm 2 or maximum 30 mm 2 includes.

[0026] For example, the photo lens can be used and installed in a mobile device, such as a mobile phone with a camera function, smartphone, tablet, etc., or another device of similar size with a camera function, such as a rear-view camera or other on-board camera of a vehicle, a camera or camera attachment (adapter) with multiple photo lenses, but also, for example, a camera on board a drone or other light flying object or a camera of a surveillance system or (part of) a 360° camera system.

[0027] The image recording device can also be designed to record image sequences, i.e. it can also be a film camera.

[0028] Due to the compact design of this camera lens from the co-applicant, conventional manufacturing processes for camera lenses can only be used to a limited extent. Furthermore, miniaturization requires the camera lens to be designed in such a way that it can be easily handled, e.g., integrated into a base unit.

[0029] Against this background, the object of the present invention is to provide methods for producing a photographic lens and an image recording device. Furthermore, a photographic lens with improved handling and an image recording device are to be specified.

[0030] This object is achieved by the subject matter of the independent claims. The dependent claims contain embodiments of these inventive solutions.

[0031] A first aspect of the invention relates to a method for producing a photographic lens, comprising a light-transmissive base body and image-forming optical elements arranged along a folded optical axis, wherein the angle between sections of the optical axis before and after folding is less than 180 degrees, and wherein the image-forming optical elements comprise reflective elements, at least one of which has a non-rotationally symmetrically curved reflective surface. The method comprises manufacturing a light-transmissive base body and forming image-forming optical elements in the base body.

[0032] For possible designs of the photographic lens, in particular the design and arrangement of the image-forming optical elements, reference is made to the above explanations with reference to the patent application with the PCT file number PCT / EP2019 / 061863, filing date May 8, 2019.

[0033] Preferably, the image-forming optical elements of the camera lens have free-form surfaces. Further preferably, the camera lens can have exclusively reflective elements as imaging optical elements. Particularly preferably, the camera lens can be dimensioned such that it has a maximum sensor area of ​​120 mm 2 , especially of a maximum of 60 mm 2 and preferably a maximum of 30 mm 2 , an image sensor.

[0034] To manufacture the photographic lens, a translucent base body is formed into which image-forming optical elements are inserted at predefined positions during or after its manufacture.

[0035] Translucent refers to the wavelength of the electromagnetic radiation for which the camera lens is intended to be used, for example, visible light. For this, the base body must be at least sufficiently translucent, i.e., transparent, so that an image of an object viewed with the camera lens can be recorded after the beam passes through the camera lens.

[0036] The base body can be made of a thermoplastic and / or thermosetting polymer material or glass material.

[0037] As a thermoplastic material, e.g. B. PMMA (polymethyl methacrylate), PA (polyamide, e.g. Trogamid CX), COP (cycloolefin copolymers, e.g. Zeonex ® and topaz ® ), PC (polycarbonate, poly(bisphenol-A-carbonate), e.g. Makrolon ® ), LSR (Liquid Silicone Rubber, e.g. Siloprene ® , Elastosil ® ), PSU (polysulfone, e.g. Ultrason ®), PES (polyethersulfone) and / or PAS (polyarylenesulfone). Thermosetting materials such as ADC (allyl diglycol carbonate, e.g. CR-39), polyacrylate, PUR (polyurethane, e.g. Trivex ® ), PTU (polythiourethanes, e.g. MR-8, MR-7) and / or episulfide / polythiol-based polymers (e.g. MR-174).

[0038] A combination of polymer and glass materials, as well as different polymer and / or glass materials, is also possible. Production from glass can be achieved, for example, using compression molding.

[0039] To manufacture the base body, a primary forming process (such as injection molding, RIM, casting), a forming process (such as thermoforming, hot embossing) and / or an abrasive and / or separating process (such as diamond machining, ion bombardment, etching) can be used.

[0040] For the production of the base body, tools that allow the creation of the base body with an acceptable surface quality without the need for post-processing are preferred. Any material shrinkage should also be taken into account during production.

[0041] The image-forming optical elements, such as reflective surfaces, are formed in the base body, i.e., they are integrated into the base body. For example, the base body can be provided with a reflective coating at predefined positions, or reflective elements can be incorporated into the base body. An arrangement in the base body is also understood to mean an arrangement on the base body, i.e., on its outer boundary.

[0042] The reflective coating can be applied, for example, by vapor deposition, sputtering, CVD (chemical vapor deposition), wet coating, etc. The coating can be a single layer. However, it is also possible to apply multiple layers. Furthermore, at least one adhesion layer, one mechanical compensation layer, and a protective layer (diffusion / migration, thermal protection, chemical protection, UV protection, etc.) can be applied. The optically effective coating can be designed for specific wavelengths or spectral ranges.

[0043] At least one metal, at least one metal oxide, and / or at least one metal nitride can be used for the reflective coating. An organic material and / or a polymer material can also be used. Furthermore, so-called hybrid materials, such as organic-inorganic hybrid systems and organically modified silanes / polysiloxanes, can be used.

[0044] Preferably, the photographic lens is designed as a component so that it can be incorporated as a component into an image recording device.

[0045] After forming the image-forming optical elements, the camera lens can be completed. However, it is also possible to perform at least one material-removing processing step, for example, to create a desired external shape. Optionally, at least one surface-finishing process step can also be performed, such as applying an anti-reflective coating, a hard coating, etc.

[0046] A camera lens manufactured using this process is characterized by cost-effective production, as only a few parts, e.g., ≤ 3, need to be manufactured. The integration of the image-forming optical elements into the base body results in a one-piece camera lens, allowing for less effort in assembly and adjustment.

[0047] The entry and exit surfaces of the base body can be flat, spherical, or freeform. Each additional freeform surface can be used to better correct the wavefront.

[0048] The base body is manufactured using an injection molding process and / or a RIM process. This also applies to the possibility of manufacturing the base body from several sub-bodies as described below, i.e., one or more sub-bodies can also be manufactured by injection molding. Preferably, injection molding is carried out in conjunction with the use of a polymer material, i.e., as plastic injection molding.

[0049] Injection molding enables simple and cost-effective production of the component parts or the base body. It is particularly suitable for mass production, allowing the manufacture of camera lenses for mass applications, e.g., in mobile devices.

[0050] Injection molding can be performed, for example, as described in DE 10 2015 116 A1. Accordingly, the base body or a partial body can be created as a single body comprising a small-volume section and a large-volume section.

[0051] In a first step of such a process, a preliminary body is produced by injection molding, with a region omitted from this preliminary body compared to the finished body. The omitted region is located in the section of the preliminary body that corresponds to the large-volume section in the finished body. In a second step, the body is completed by adding the region omitted during injection molding to the preliminary body after the injection-molded preliminary body has solidified.

[0052] The terms "large-volume" and "small-volume" do not refer to the absolute volume of the sections. Instead, in the small-volume section, the distance of the volume element furthest from a surface of the corresponding section from the nearest surface should be at most half the distance of the volume element furthest from a surface of that section from the nearest surface in the large-volume section. In this sense, a small-volume section can even have a larger absolute volume than a large-volume section if the small-volume section has a significantly flatter geometry than the large-volume section.

[0053] Such a method offers the advantage that even bodies, e.g., base bodies or partial bodies within the meaning of this application, that have regions with greatly differing volumes or greatly differing geometries—and thus a large-volume region and a small-volume region—can be produced using an injection molding process. The differences in the volumes or geometries are reduced by omitting the region in the preliminary body to be produced using the injection molding process, thereby reducing the difficulties that arise during injection molding due to large volume differences or greatly differing geometries.In particular, the recess allows the volumes of the individual regions of the preliminary body to be equalized in such a way that the heat of the injection molding material can be dissipated from the individual regions at largely the same speed during cooling and solidification, thus reliably preventing the formation of hot zones within the injection molding material. This makes it possible for the injection molding material to solidify more evenly in the preliminary body, largely avoiding stresses in the cooled material that could impair the optical properties, and making volume shrinkage more uniform. By evening out the volume shrinkage, the formation of stresses that could impair the optical properties can also be reduced. Overall, the formation of mechanical stresses in the injection molded body that could lead to birefringence can thus be largely avoided.

[0054] For further details of such a procedure, reference is made to the content of DE 10 2015 116 402 A1.

[0055] The injection molding process can be carried out using a molding tool, such as that described in DE 10 2016 119 636 B3. The molding tool described in DE 10 2016 119 636 B3 has at least one controllable adjustment element with which the position of a mold core of the molding tool can be determined. The control can change the dimensions of the adjustment element and / or exert pressure on other elements to perform an adjustment. This enables adjustment of the molding tool without disassembly. Overall, the accuracy of the injection molding process can be increased, so that injection-molded parts with tolerances in the range of a few micrometers can be obtained.

[0056] In a RIM process (RIM, Reaction Injection Moulding), two or more mixed components are injected into a mold as a reaction mass and cured, i.e., crosslinked. Crosslinking of the polymer can be induced not only by mixing the components, but also, for example, thermally and / or by UV exposure. Due to their low viscosity, RIM reaction masses exhibit more favorable flow behavior than thermoplastic melts used in injection molding processes. A RIM process can also be used to enclose bodies with a component formed from the reaction mass.

[0057] A RIM process can be carried out, for example, based on the process described in DE 10 2014 113 966 A1. This makes it possible to apply a protective layer made of a thermosetting material by casting. The RIM process can also be carried out in successive sub-steps, thus reducing the shrinkage associated with production.

[0058] For example, two components, such as a polyol and an isocyanate, can be mixed together and then injected into a mold under pressure. The two components react to form the desired chemically crosslinked polymer (here, for example, polyurethane). Using the RIM process, the base body can be formed as such, or the base body can be provided with a coating, such as a protective layer. For this purpose, the base body can be positioned in the mold in such a way that the desired protective layer is formed.

[0059] Depending on the design, the base body can be manufactured from several sub-bodies. After production, the sub-bodies are assembled and connected to each other to form the base body. The above and following statements regarding the production of the base body, e.g., regarding materials and manufacturing processes, apply accordingly to the production of the sub-bodies.

[0060] For example, the partial bodies can be joined together to form a compact, monolithic base body. Such a solid body prevents particle deposits and other contamination of the optical elements.

[0061] The parts can be joined by a material bond, e.g., by bonding, cementing, or casting. A form-fitting connection or a combination of the above techniques is also possible.

[0062] Acrylic, polyurethane, epoxythiol, epoxyamine, or silicone adhesives can be used as adhesives. The adhesive can be cured thermally or by UV radiation, for example. Adhesives whose refractive index matches the refractive index of one of the parts to be bonded are preferred.

[0063] The bonding of the partial bodies can be carried out, for example, in accordance with the process described in DE 10 2015 102 032 A1 or in DE 10 2015 114 990 A1.

[0064] According to the method of DE 10 2015 114 990 A1, an elongated recess can be provided that at least partially surrounds at least one of the surfaces to be bonded. The adhesive can then be applied over the entire surface of one or both of the surfaces to be bonded, with excess adhesive being absorbed by the recess. The adhesive is then cured.

[0065] The elongated recess allows for the use of an excessive amount of adhesive. This allows for a slightly excessive amount of adhesive to be applied, thereby preventing the application of too little adhesive, which can, among other things, lead to insufficient bond strength, especially at the edges of the surface to be bonded. The elongated recess can be considered an adhesive reservoir, preventing air from penetrating the joint gap, i.e., between the two surfaces to be bonded, in the event of adhesive retraction, e.g., due to shrinkage.

[0066] For further details of such a procedure, reference is made to the content of DE 10 2015 114 990 A1.

[0067] The partial bodies can also be connected based on the method described in DE 10 2014 207 494 A1. Accordingly, the partial bodies can be manufactured separately, e.g., using an injection molding process, with one partial body being manufactured as the main part and another partial body being manufactured as an insert element for insertion into a corresponding recess in the main part. The two partial bodies can be glued after assembly, preferably only those surfaces that are not traversed by the light beam during the virtual image formation.

[0068] The partial bodies can also be provided with a reflective coating, at least in sections, so that an image-forming optical element is formed and positioned by connecting the partial bodies.

[0069] A positive connection of partial bodies can be achieved, for example, by forming one of the partial bodies with a recess and the other partial body with a protruding section complementary to the recess, and then inserting the two partial bodies into one another. Optionally, the facing contact surfaces can be glued. Such a method is disclosed, for example, in DE 10 2014 114 238 B3 for spectacle lenses and can be applied accordingly to the partial bodies of the camera lens.

[0070] It is also possible to connect the partial bodies at least partially at a distance from one another, creating a cavity between the partial bodies that can optionally be filled with gas, e.g., air. The partial bodies can be connected, for example, by plugging them together, gluing them together, or enclosing them with a pot. Such a cavity advantageously exhibits no dispersion and therefore does not cause chromatic aberration. By arranging cavities, the weight of the camera lens can be reduced compared to a camera lens of the same dimensions with a solid body without a cavity.

[0071] Preferably, the geometric shapes of the partial bodies can be defined in such a way that undercuts can be avoided during their production and, depending on the production process, easy demoulding is possible without impairing the properties.

[0072] According to further embodiments, the partial bodies can be made of different materials, e.g., materials with different refractive indices. It is also possible to form multiple groups of partial bodies, with the partial bodies of a group each having the same properties, e.g., being made of the same material.

[0073] Various materials can be used, for example, for chromatic correction.

[0074] According to further embodiments, an interface of at least one partial body, for example, an interface at the boundary between two directly adjacent partial bodies or an interface between a partial body and a cavity, can be formed as a flat, spherical, or freeform surface. For the definition of the term "freeform surface," please refer to the explanations in the introductory description.

[0075] Planar interfaces are less sensitive to translation and are suitable for larger manufacturing tolerances. Freeform surfaces are significantly more sensitive in this regard, but in return, they enable good wavefront correction. Spherical interfaces allow a compromise between the properties of planar interfaces and freeform surfaces. The possibility of manufacturing the base body from several sub-bodies, as well as the described various design variants of the sub-bodies and their connection to the base body, advantageously enable a wide variety of variations in the optical properties of the camera lens, so that it can be adapted to different applications and installation and environmental conditions.

[0076] According to further embodiments, at least one partial body can be designed to be actuatable.

[0077] For example, it is possible to move individual parts of the body with the image-forming optical elements incorporated therein depending on a sensor signal, e.g., an acceleration sensor. This can achieve image stabilization.

[0078] Another aspect of the invention relates to a method for manufacturing an image recording device. The method comprises incorporating a photographic lens manufactured by a method according to the above description into a base unit.

[0079] The term basic device refers to the remaining components of the image recording device to be manufactured, so that the image recording device is created by adding the camera lens and, if necessary, other components.

[0080] The image recording device may comprise an image sensor, wherein the sensor surface has an area of ​​preferably a maximum of 120 mm 2 , more preferably a maximum of 60 mm 2and particularly preferably a maximum of 30 mm 2 has.

[0081] The image capture device can be designed as a still camera or as a mobile device with a camera function, such as a mobile phone, smartphone, tablet, etc. with a camera function, or as another device of similar size with a camera function. The image capture device can also be designed to record image sequences, i.e., it can also be a film camera.

[0082] The advantages mentioned with reference to the method for producing the photographic lens are correspondingly associated with the method for producing the image recording device.

[0083] A further aspect of the invention relates to a photographic lens comprising a base body having a plurality of partial bodies and image-forming optical elements. The optical elements are arranged along a folded optical axis, wherein the angle between sections of the optical axis before and after folding is less than 180 degrees, and wherein the image-forming optical elements comprise reflective elements, at least one of which has a non-rotationally symmetrically curved reflective surface. The partial bodies are connected to one another at least in sections, spaced apart from one another.

[0084] Such a camera lens can be manufactured, for example, using one of the methods for manufacturing a camera lens described above. All statements regarding the method according to the invention can be applied analogously to the camera lens according to the invention.

[0085] Depending on the design, the parts can be made of different materials.

[0086] According to further embodiments, an interface of at least one partial body can be flat, spherical or designed as a free-form surface.

[0087] According to further embodiments, at least one partial body can be designed to be actuatable.

[0088] A further aspect of the invention relates to an image recording device with a photographic lens as described above.

[0089] Such an image recording device can be manufactured, for example, using one of the methods for manufacturing an image recording device described above. All statements regarding the method according to the invention can be applied analogously to the image recording device according to the invention.

[0090] Further features, properties and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying figures. Fig. 1 shows an exemplary photographic lens with a two-dimensional folding of the optical axis and a focal length of 800 mm and an aperture of 4.0. Fig. Figure 2 shows an exemplary photographic lens with a three-dimensional folding of the optical axis and a focal length of 300 mm and an aperture of 4.0. Fig. Figure 3 shows an exemplary image acquisition device with a catoptric lens. Fig. Figure 4a shows an example compact camera lens. Fig. 4b shows an image recording device with the photo lens of the Fig. 4a in a side view. Fig. 4c shows the image capture device of the Fig. 4b in frontal view. Fig. 4d shows the image-forming optical elements and the optical path of the camera lens of the Fig. 4a in enlarged frontal view. Fig. 4e shows the image-forming optical elements and the optical path of the camera lens of the Fig. 4a in enlarged side view. Fig. 5a shows an exemplary photo lens with a one-piece base body. Fig. 5b shows an exemplary photographic lens with a monolithic base body constructed from two partial bodies. Fig. 5c shows another exemplary photo lens with a monolithic base body constructed from two partial bodies. Fig. Figure 5d shows another exemplary photographic lens with a monolithic base body constructed from two partial bodies. Fig. Figure 5e shows another exemplary photographic lens with a monolithic base body constructed from two partial bodies. Fig. 5f shows another exemplary photographic lens with a monolithic base body constructed from two partial bodies. Fig. Figure 5g shows an exemplary photographic lens with a monolithic base body constructed from three sub-bodies. Fig. 6a shows an exemplary photographic lens with a base body constructed from two partial bodies of the same material, in which the partial bodies are connected to each other at a distance from each other. Fig. 6b shows an exemplary photographic lens with a base body constructed from two sub-bodies of different materials, in which the sub-bodies are connected to each other at a distance from each other. Fig. 6c shows another exemplary photographic lens with a base body constructed from two sub-bodies of different materials, in which the sub-bodies are connected to each other at a distance from each other. Fig. 6d shows another exemplary photographic lens with a base body constructed from two partial bodies of different materials, in which the partial bodies are connected to each other at a distance from each other. Fig. 6e shows an exemplary photographic lens with a base body constructed from three sub-bodies, in which the sub-bodies are connected to each other at a distance from each other. Fig. 6f shows another exemplary photographic lens with a base body constructed from three sub-bodies, in which the sub-bodies are connected to each other at a distance from each other. Fig. 6g shows an exemplary photographic lens with a base body constructed from two partial bodies, in which the partial bodies are connected to one another in sections spaced apart from one another. Fig. 7 shows a flowchart of an exemplary method for manufacturing a photographic lens.

[0091] The following will first be based on the Fig. 1 and Fig. 2, the beam path of an exemplary camera lens 11 is described. To improve clarity, only the image-forming optical elements, the object plane, the optical axis, and the image sensor are shown together with the beam path. For specific configurations of the camera lens 11, please refer to the explanations of the Fig. 4, Fig. 5a-g and Fig. 6a-g.

[0092] The photo lens 11 in Fig. 1 comprises reflective image-forming optical elements 3a-h, which are arranged along a two-dimensionally folded optical axis OA and which, at the location of an image sensor 2, generate an image of an object located in the object plane 1. To ensure the color purity of the photographic lens 11, only reflective elements are present as imaging optical elements 3a-h. The optical axis OA has several sections OA1 to OA9, with adjacent sections each folded by less than 180°. The two-dimensional folding means that all sections OA1 to OA9 of the optical axis OA lie in a common plane. This ensures that the image sensor 2 can be displaced as desired relative to the object plane 1 within this common plane. Furthermore, the image sensor 2 can be rotated relative to the object plane 1 about a rotation axis pointing out of the plane.

[0093] The surfaces of the reflective elements 3a-h are non-rotationally symmetrically curved reflective surfaces, which allows for folding of the beam path. Furthermore, it is possible for one or more of the surfaces of the reflective elements 3a-h to be designed as freeform surfaces, which allows for the correction of monochromatic aberrations.

[0094] By using sections of rotationally symmetrically curved reflective surfaces for the image-forming optical elements 3a-h, wherein the optical axis OA of the rotationally symmetrically curved reflective surfaces does not pass through the sections, the optical structure of the photo lens 11 can be kept small.

[0095] The Fig. The photographic lens 11 shown in Figure 1 can also comprise at least two reflective elements 3a-h, whose reflective surfaces are shaped such that different magnifications are present in the formed image in two directions perpendicular to each other and to the optical axis OA. This allows for anamorphic images. Additionally or alternatively, the Fig. The photographic lens 11 shown in Figure 1 may comprise at least two reflective elements 3a-h, whose reflective surfaces are shaped such that a different number of intermediate images is created for two mutually perpendicular image extension directions. This enables choristic imaging.

[0096] In the photo lens 11 there is also an iris diaphragm 5 at an accessible location so that the photo lens 11 can be stopped down.

[0097] While in Fig. 1 shows a photographic lens 11 with a two-dimensional folded optical axis OA, Fig. 2 a photographic lens 11 with a three-dimensionally folded optical axis OA, ie a photographic lens 11 in which not all sections OA1 to OA9 of the optical axis OA lie in a common plane. Thus, the section OA8 has a directional component which lies in the plane of the drawing of the Fig. 2. This allows the image sensor 2 to be arranged displaced relative to the reflective elements 3a to 3f perpendicular to the plane of the drawing. By means of a suitable shape and orientation of the reflective elements 3a-h, it is also possible to achieve an orientation of the image sensor 2 at any angle relative to the orientation of the image plane 1, ie the surface normal of the image sensor 2 can be oriented in any direction relative to the surface normal of the image plane 1.

[0098] For the rest, please refer to the comments on Fig. 1.

[0099] Fig. 3 shows an image recording device 10 designed as a photo camera with an image sensor 2 and a photo lens 11. The photo lens 11 can in particular be a photo lens 11 as described with reference to the Fig. 1 and Fig. 2 or as described below with reference to the Fig. 4a-e, Fig. 5a-g and Fig. 6a-g will be described.

[0100] The camera lens 11 can be used for small-format image sensors. It is characterized by its lack of obscuration and its ability to be stopped down. By scaling the camera lens 11 by a factor of 0.1, the camera lens 11 can also be realized with focal lengths in the range of 15 to 20 mm, so that it can be used as a camera lens 11 for a mobile phone camera. The image capture device 10 can therefore also be realized as a mobile phone, tablet, or a similar device with a camera.

[0101] The photographic lens 11 has several advantages. As a catoptric lens, it exhibits no chromatic aberrations, which is particularly advantageous for lenses with a long focal length. Furthermore, the photographic lens 11 is an obscuration-free imaging system. Furthermore, the catoptric photographic lens 11 can be realized with fewer optical elements than a dioptric or catadioptric lens, so that the photographic lens 11 can be lighter than a dioptric or catadioptric photographic lens. Furthermore, the mirror surfaces are generally thinner than comparable lenses, which leads to additional weight savings. Furthermore, the photographic lens 11 enables the position and orientation of the image plane to be shifted and rotated relative to the position and orientation of the object plane 1. The existing coatings also allow high reflectivity even at large reflection angles, so that large reflection angles can also be used in the photographic lens 11.

[0102] The Fig. 4a-4e show an image recording device 10, which is a smartphone, with a compact photo lens 11.

[0103] The photographic lens 11 has a translucent base body 12 made of a polymer material and a plurality of image-forming optical elements 3a-3h, which are reflective elements and are formed as reflective freeform surfaces in the base body 12. The rays are guided through the entrance surface 17 into the base body and exit it again through the exit surface 4. After leaving the base body 12 through the exit surface 4, the rays are guided onto the image sensor 2. The entrance surface 17 and / or the exit surface 4 can be flat, spherical, or designed as a freeform surface. Advantageously, each additional freeform surface can better correct the wavefront.

[0104] The base body 12 is formed monolithically from a single body and was manufactured using a RIM process. Alternatively, an injection molding process would also be possible. The image-forming optical elements 3a-3h were formed on the base body 12 using a coating process, e.g., a sputtering process or a vapor deposition process.

[0105] The camera lens 11 is characterized by its compact size. Possible dimensions include, for example, 28 mm x 7 mm x 6 mm. The image sensor 2 can have a size of 4.8 mm x 3.6 mm, meaning that the camera lens 11 can be designed as a 1 / 3" lens. For such a camera lens 11, a focal length of 20 mm with a maximum adjustable aperture of 2.8 corresponds to a focal length of 150 mm with a maximum adjustable aperture of 2.8 in 35mm format (24 mm x 36 mm).

[0106] Fig. 4a shows a monochromatic photographic lens 11. However, an achromatic version is also possible.

[0107] Fig. 4b shows an image recording device 10 comprising a base body 16 and the photo lens 11 according to Fig. 4a. It can be seen that the camera lens 11 can be easily installed or integrated into the base body 16 despite its narrow design.

[0108] In Fig. 4c is the image recording device 10 of the Fig. 4b in a frontal view. The photo lens 11 can be present in addition to another photo lens in the image recording device 10 or can be the sole photo lens.

[0109] The Fig. 4d and Fig. 4e shows the image-forming elements 3a-3h and the beam path of the photo lens 11 in an enlarged frontal and side view.

[0110] As an alternative to the Fig. 4a-e can also be another photo lens 11, e.g., one of the Fig. 1, Fig. 2, Fig. 5a-g or Fig. 6a-g are installed in the basic unit 16 to create an image recording device 10.

[0111] The Fig. 5a-5g show photographic lenses 11 with a monolithic base body 12, wherein the base body 12 is made in one piece - as in Fig. 5a - or multi-part from partial bodies 13a-c - as in the Fig. 5b-5g. Different materials are represented by different hatchings. Each of the exemplary photo lenses 11 shown comprises, in addition to the light-transmitting base body 12, several image-forming optical elements 3a-h, each of which is a reflective elements. For an explanation of the entrance surface 17 and the exit surface 4, reference is made to the explanations for Fig. 4.

[0112] All photo lenses 11 of the Fig. 5a-5g also have in common that the image-forming optical elements 3a-h are arranged along a folded optical axis OA, wherein the angle α between the sections of the optical axis OA1-OA9 before and after folding is less than 180 degrees. At least one of the image-forming optical elements 3a-h has a non-rotationally symmetrically curved reflective surface.

[0113] The base body 12 or the partial bodies 13a-c can be manufactured, for example, from a polymer material by means of an injection molding process or RIM process. The image-forming optical elements 3a-h are formed on the base body 12 or the partial bodies 13a-c by providing the base body 12 or the partial bodies 13a-c with a reflective coating at predeterminable positions. Further details of the manufacturing process for photo lenses 11 are described below with reference to Fig. 7 explained.

[0114] The photo lens 11 of the Fig. 5a comprises a one-piece translucent base body 12.

[0115] The photo lenses 11 of the Fig. 5b-g each comprise a multi-part translucent base body 12, which consists of two partial bodies 13a, 13b ( Fig. 5b-f) or three partial bodies 13a-c ( Fig. 5g) that are connected to each other without a gap. In other words, the partial bodies 13a-c directly adjoin one another, whereby the respective boundary surfaces 14 can be flat, spherical, or designed as a free-form surface. The partial bodies 13a and 13b consist of two different materials. Materials with different dispersion or Abbe numbers can preferably be combined to correct chromatic aberrations.

[0116] The partial body 13c of the Fig. 5g consists of the same material as the partial body 13a. The partial bodies 13a-c can each be manufactured from a polymer material by injection molding and glued or cemented together. Optionally, it is possible to cast the entire camera lens 11 in another material to thereby connect the partial bodies 13a-c.

[0117] The photo lenses 11 of the Fig. 5b-g differ due to the arrangement of the partial bodies 13a-c.

[0118] Fig. Figure 5b shows an embodiment in which two approximately equally sized partial bodies 13a,b are connected to each other. The partial bodies 13a,b are arranged such that the image-forming optical elements 3a-h are arranged alternately in or on the first partial body 13a or the second partial body 13b. The beam path thus runs alternately through the two partial bodies 13a,b.

[0119] Fig. Figure 5c shows an embodiment in which a small partial body 13a and a large partial body 13b are connected to each other. The partial bodies 13a,b are arranged such that the image-forming optical elements 3a-g are formed in partial body 13b, while the image-forming optical element 3h is formed in partial body 13a. The beam path therefore first runs through partial body 13b and then through partial body 13a.

[0120] Fig. Figure 5d shows an embodiment in which a small partial body 13a and a large partial body 13b are also connected to one another. The partial bodies 13a,b are arranged such that the image-forming optical element 3a is formed in the partial body 13a, while the image-forming optical elements 3b-h are formed in the partial body 13b. The beam path therefore first runs through the partial body 13a and then through the partial body 13b.

[0121] Fig. Figure 5e shows an embodiment in which a small partial body 13a and a large partial body 13b are also connected to each other. All image-forming optical elements 3a-h are formed in partial body 13b. The beam path first runs through partial body 13a and then through partial body 13b.

[0122] Fig. Figure 5f shows an embodiment in which a small partial body 13a and a large partial body 13b are also connected to each other. The partial bodies 13a,b are arranged such that the image-forming optical element 3d is formed in partial body 13a, while the remaining image-forming optical elements 3a-c and 3e-h are formed in partial body 13b. The beam path first runs through partial body 13b, then through partial body 13a, and then again through partial body 13b.

[0123] Fig. Figure 5g shows an embodiment with three partial bodies 13a-c, wherein partial bodies 13a and 13c are made of the same material, and partial body 13b has a different material. The arrangement of the partial bodies 13a-c is such that the image-forming optical elements 3a, 3c, 3e, and 3g are formed in partial body 13a, while the image-forming optical elements 3b, 3d, 3f, and 3h are formed in partial body 13c. There are no image-forming optical elements in partial body 13b. The beam path runs from partial body 13a through partial body 13b into partial body 13c and from partial body 13c back through partial body 13b into partial body 13a, etc.

[0124] The Fig. 6a-6g show photographic lenses 11 with a base body 12 comprising a plurality of partial bodies 13a-c, wherein the partial bodies 13a-c are connected to one another at least in sections at a distance from one another, so that a cavity 15 is formed. The cavity 15 can be filled with a gas, e.g., air. Different materials are represented by different hatchings. Each of the exemplary photographic lenses 11 shown comprises, in addition to the light-transmitting base body 12, a plurality of image-forming optical elements 3a-h, each of which is a reflective elements. For an explanation of the entrance surface 17 and the exit surface 4, reference is made to the explanations for Fig. 4.

[0125] All photo lenses 11 of the Fig. 6a-6g also have in common that the image-forming optical elements 3a-h are arranged along a folded optical axis OA, wherein the angle α between the sections of the optical axis OA1-OA9 before and after folding is less than 180 degrees. At least one of the image-forming optical elements 3a-h has a non-rotationally symmetrically curved reflective surface.

[0126] The partial bodies 13a-c can, for example, be manufactured from a polymer material by means of an injection molding process or RIM process. The image-forming optical elements 3a-h are formed on the base body 12 or the partial bodies 13a-c by providing the base body 12 or the partial bodies 13a-c with a reflective coating at predeterminable positions. Further details of the manufacturing process for photo lenses 11 are described below with reference to Fig. 7 explained.

[0127] The photo lenses 11 of the Fig. 6a-d and the Fig. 6g each comprise a multi-part translucent base body 12, which is constructed from two partial bodies 13a, 13b, while the photo lenses 11 of the Fig. 6e and Fig. 6f are constructed from three partial bodies 13a-c. The respective interfaces 14 of the partial bodies 13a-c can be flat, spherical, or designed as free-form surfaces. The partial bodies 13a and 13b consist of two different materials. The partial body 13c consists of the same material as the partial body 13a. The partial bodies 13a-c can each be manufactured from a polymer material by injection molding and glued or cemented together. Optionally, it is possible to cast the entire photo lens 11 in another material in order to thereby create a connection between the partial bodies 13a-c.

[0128] The photo lenses 11 of the Fig. 6a-g differ due to the number and arrangement of the partial bodies 13a-c.

[0129] Fig. Figure 6a shows an embodiment with two partial bodies 13a and 13c made of the same material. The partial bodies 13a,c are arranged such that the image-forming optical elements 3a-h are arranged alternately in or on the first partial body 13a or the second partial body 13c. The beam path thus runs alternately through the two partial bodies 13a,c.

[0130] Fig. Figure 6b shows an embodiment with two partial bodies 13a and 13b made of different materials. The arrangement of the partial bodies 13a,b is such that the image-forming optical elements 3a-h are arranged alternately in or on the first partial body 13a or the second partial body 13b. The beam path thus runs alternately through the two partial bodies 13a,b.

[0131] Fig. Figure 6c shows an embodiment with a small partial body 13a and a large partial body 13b made of different materials. The partial bodies 13a,b are arranged such that the image-forming optical elements 3a-g are formed in partial body 13b, while the image-forming optical element 3h is formed in partial body 13a. The beam path therefore first runs through partial body 13b and then through partial body 13a.

[0132] Fig. Figure 6d also shows an embodiment with a small partial body 13a and a large partial body 13b made of different materials. The partial bodies 13a,b are arranged such that the image-forming optical element 3a is formed in the partial body 13a, while the image-forming optical elements 3b-h are formed in the partial body 13b. The beam path therefore first runs through the partial body 13a and then through the partial body 13b.

[0133] Fig. Figure 6e shows an embodiment with two small partial bodies 13a,b made of the same material and one large partial body 13c made of a different material. All image-forming optical elements 3a-h are formed in partial body 13b. The beam path first passes through partial body 13c, then through partial body 13b, and finally through partial body 13a.

[0134] Fig. Figure 6f also shows an embodiment with two small partial bodies 13a,b made of the same material and one large partial body 13c made of a different material. The partial bodies 13a-c are arranged such that the image-forming optical element 3d is formed in partial body 13c, while the remaining image-forming optical elements 3a-c and 3e-h are formed in partial body 13b. The beam path first runs through partial body 13b, then through partial body 13c, then again through partial body 13b, and finally through partial body 13a.

[0135] Fig. Figure 6g shows an embodiment with two partial bodies 13a,b of different materials, which are connected to each other in such a way that a large cavity 15 is formed. The image-forming optical elements 3a, 3c, 3e, and 3g are formed on the partial body 13a, while the image-forming optical elements 3b, 3d, 3f, and 3h are formed on the partial body 13b. The image-forming optical elements 3a-h are each arranged at the interface 14a,b of the partial bodies 13a,b to the cavity 15. Consequently, the beam path runs largely through the cavity 15.

[0136] Fig. 7 shows a flow chart of an exemplary method for producing a photographic lens 11, the base body 12 of which has a plurality of partial bodies 13a-c.

[0137] In a first process step S1, the partial bodies 13a-c are manufactured separately from a polymer material. For this purpose, an injection molding process or a RIM process can be used, for example.

[0138] Subsequently, in step S2, the partial bodies 13a-c are joined together to form the base body 12, e.g., by gluing or cementing them together. Optionally, the connection can be made such that the partial bodies 13a-c are spaced apart from one another at least in sections, and a cavity 15 is formed between the partial bodies 13a-c.

[0139] In the final step S3, the image-forming optical elements are formed in the base body 12. For this purpose, the base body 12 is provided with a reflective coating at predeterminable positions, which can be applied, for example, by means of a sputtering or vapor deposition process.

[0140] The present invention has been described in detail using examples for illustrative purposes. However, one skilled in the art will recognize that deviations from the examples are possible. For example, the catoptric photographic lens as described by way of example can also be combined with a few dioptric elements to create a catadioptric photographic lens. The invention is therefore not intended to be limited exclusively to the described examples, but only by the appended claims. List of reference symbols 1 object level 2 image sensors 3a-h image-forming optical element 4 Exit surface 5 aperture 10 Image capture device 11 Photo lens 12 basic bodies 13a-c Partial body 14, 14a-b interface 15 Cavity 16 basic unit 17 Entrance area OA optical axis OA1-OA9 section of the optical axis α Angle between sections of the optical axis S1 Manufacturing of partial bodies S2 Connecting the partial bodies to the main body S3 Formation of the image-forming optical elements in the base body

Claims

[1] A method for producing a photographic lens (11) comprising a light-transmitting base body (12) and image-forming optical elements (3a-h) arranged along a folded optical axis (OA), wherein the angle (α) between sections of the optical axis (OA1 - OA9) before and after folding is less than 180 degrees, and wherein the image-forming optical elements (3a-h) comprise reflective elements, at least one of which has a non-rotationally symmetrically curved reflective surface, the method comprising: - manufacturing the translucent base body (12) using an injection molding process and / or RIM process and - Forming the image-forming optical elements (3a-h) in the base body (12). [2] Method according to claim 1, wherein the base body (12) is manufactured from several partial bodies (13a-c). [3] Method according to claim 2, wherein the partial bodies (13a-c) are connected to one another at least in sections at a distance from one another. [4] Method according to claim 2 or 3, wherein the partial bodies (13a-c) comprise different materials. [5] Method according to one of claims 2 to 4, wherein an interface (14) of at least one partial body (13a-c) is formed planar, spherical or as a free-form surface. [6] Method according to one of claims 2 to 5, wherein at least one partial body (13a-c) is designed to be actuatable. [7] A method for manufacturing an image recording device (10), comprising: - Installing a photographic lens (11) manufactured by a method according to one of the preceding claims into a basic device (16). [8] Photographic lens (11), comprising: - a base body (12) having several partial bodies (13a-c) and - image-forming optical elements (3a-h) arranged along a folded optical axis (OA), wherein the angle (α) between sections of the optical axis (OA1 - OA9) before and after folding is less than 180 degrees, and wherein the image-forming optical elements (3a-h) comprise reflective elements, at least one of which has a non-rotationally symmetrically curved reflective surface, wherein the partial bodies (13a-c) are connected to one another at least in sections at a distance from one another. [9] Photographic lens (11) according to claim 8, wherein the partial bodies (13a-c) comprise different materials. [10] Photographic lens (11) according to claim 8 or 9, wherein an interface (14) of at least one partial body (13a-c) is planar, spherical or designed as a free-form surface. [11] Photographic lens (11) according to one of claims 8 to 10, wherein at least one partial body (13a-c) is designed to be actuatable. [12] Image recording device (10) with a photographic lens (11) according to one of claims 8 to 11.

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