Polarizing filter unit for a camera system, a camera system and a manufacturing process

Abstract

The invention relates to a polarization filter unit (10) for a camera system (100), comprising two filter sections (12, 14) for a receiver module (102) and an illumination module (104) of the camera system (100), wherein the polarization directions (20, 22) of the two filter sections (12, 14) are aligned orthogonally to each other by a polar angle (V).In this invention, a first filter section (12) is formed from a film element (11) with a predetermined first polarization direction (20), wherein a second filter section (14) can be removed from the first filter section (12) together with two engagement contours (30, 32) offset from each other by the polar angle (V) such that the second filter section (14) with a second engagement contour (32) can be positively inserted or is inserted into a first engagement contour (30) of the first filter section (12) in an operating position rotated by the polar angle (V) about an axis of rotation (S) in order to form the second filter section (14) with a second polarization direction (22). The invention further relates to a camera system (100) and a method for manufacturing the polarization filter unit (10).

Description

[0001] The invention relates to a polarization filter unit for a camera system, a camera system with a polarization filter unit and a method for producing the polarization filter unit.

[0002] Polarization filters for a time-of-flight camera system are known, for example, from DE 10 2019 108 324 A1. The time-of-flight camera system comprises an illumination module for emitting modulated light and a receiver module for receiving the light emitted by the illumination module and reflected from an observation area. The illumination module can comprise multiple light sources with and without polarization filters, which can be switched on and off as required. This allows the observation area to be captured with different contrast settings. The polarization filters are aligned perpendicular to each other and can be permanently installed in a camera housing. Filter sections with different polarization directions can be spatially separated from one another and assigned to the illumination module or the receiver module with different geometries.

[0003] US 5,541,419 A shows a reader with a plurality of illumination sources. A first polarizing filter receives unpolarized light from the illumination sources and transmits only light polarized in a first direction. Light reflected from the target object travels back to the reader, where it is received by a second polarizer oriented to block light polarized in the first direction and transmit only light polarized in a second direction orthogonal to the first polarization direction. The polarizing filters are implemented as individual pieces of laminar polarizing film attached to a transparent window base.

[0004] DE 10 2018 104 906 B3 discloses a camera comprising an image sensor for generating image data from received light from a detection area, an illumination unit with at least one light source for illuminating the detection area with transmitted light, and a polarization filter that polarizes the transmitted light and the received light. The polarization filter is configured as an additional module that can be subsequently replaced from the outside.

[0005] The polarization filters allow the light emitted by the illumination module and reflected by the illumination area to pass perpendicular to the polarization direction of the receiving module, where it is blocked. Specular or mirror-like reflections, in particular, have the same polarization direction as the light emitted by the illumination module and are thus filtered out by the polarization filter of the receiving module. This enables the receiving module to capture only the light diffusely scattered by the illumination area. This filtering has the advantage of reducing disruptive reflections on sharp contours or shiny objects and increasing the contrast of objects to be captured. In particular, a barcode structure, for example, can be more effectively captured using the camera system.

[0006] To further maximize contrast, illumination modules with light sources that emit light at different wavelengths can be used. For example, light sources with red, green, blue, white, or infrared light can be used. Depending on the light source, different polarization filters can be used. Measurements in the infrared range, in particular, have the advantage of not being affected by fluctuations in visible daylight. However, filters designed for the infrared range can be more expensive to manufacture.

[0007] In the prior art, the polarization filters mentioned are permanently installed in a camera housing, whereby the polarization directions for the illumination and reception module must be precisely aligned with each other with a predefined polar angle between the two polarization directions in order to achieve the desired filter effect. The alignment is performed based on the geometry or outer contour of the filter sections used. However, this can have the disadvantage of requiring high precision in the manufacture and assembly of the polarization filters, which can increase the manufacturing costs for the camera system. In particular, it may be necessary for the polarization direction to be precisely aligned with respect to the tailored geometry of the filter section. In this context, it is particularly challenging that the polarization directions are not visible and incorrect assembly cannot be visually corrected.

[0008] The object of the invention is to provide a polarization filter unit which simplifies the manufacture of polarization filters and their assembly for a camera system, in particular as a retrofit solution, while avoiding the problems known from the prior art.

[0009] Furthermore, the object is to provide a camera system with a polarization filter unit and a method for producing the polarization filter unit.

[0010] The problem is solved with regard to the polarization unit by the features of independent claim 1, with regard to the camera system by the features of claim 5 and with regard to the method by the features of claim 7.

[0011] Advantageous embodiments of the invention are specified in the subclaims.

[0012] According to the invention, a polarization filter unit for a camera system is claimed, which has two filter sections with different polarization directions for a receiving module and an illumination module of the camera system, wherein the polarization directions are aligned orthogonally offset from one another by a polar angle in order to filter the emitted and specularly reflected light of the illumination module at the receiving module.In this case, a first filter section is formed from a film element with a predetermined first polarization direction, wherein a second filter section is detached from the first filter section together with two engagement contours in such a way that the second filter section with a second engagement contour can be or is inserted in a form-fitting manner into a first engagement contour of the first filter section in an operating position rotated with the polarity angle about a rotation axis in order to form the second filter section with a second polarization direction.

[0013] In other words, the two filter sections are manufactured from a common film element, with the engagement contours being rotated or offset relative to each other by the polar angle in a manufacturing position. The engagement contours thus serve as alignment aids to align the two filter sections perpendicular to each other in the rotated operating position. This allows the filter sections with different polarization directions for the camera system to be manufactured from a single film element.

[0014] The axis of rotation for the polar angle is preferably formed as a central axis of the second filter section.

[0015] The invention has recognized the advantage that the two polarization directions can be set by a defined detachment and rotation of the second filter section from the first filter section. It is advantageously not relevant at which angle the first filter section is aligned on a film element during the manufacturing process. Thus, the contiguous alignment has the advantage over separately manufactured filter sections that the first filter section can be aligned as desired. Furthermore, detaching the two filter sections from the same film element has the advantage that production is particularly resource-efficient and can be produced with little waste. Another advantage is that the mutual alignment with engagement contours ensures precise alignment of the two filter sections, which is why mounting the polarization filter unit on a camera system can be simplified without an alignment step.

[0016] According to the invention, the second filter section is circular and protrudes from the first filter section, with an alignment projection serving as the second engagement contour, wherein an alignment notch offset by the polar angle is formed as the first engagement contour in the first filter section. A circular shape has the advantage that the two filter sections can be adapted in a particularly space-saving manner to a camera system with a central receiving module and several illumination modules arranged in a circle around the receiving module. Particularly preferably, the circular shape of the second filter section is adapted to a circular shape of the receiving module, in particular a camera lens.

[0017] In principle, it is conceivable that alignment notches could also be formed in the second filter section. It is essential that the positive alignment is enabled in the rotated state, while the positive alignment in the operating position prevents rotation or adjustment of the polarization directions around the rotation axis.

[0018] Preferably, a semicircular recess is formed within the first filter cutout adjacent to the second engagement contour in order to remove the second filter cutout with the second engagement contour without damage.

[0019] Further preferably, the film element is made of a plastic material with a predetermined first polarization direction and a material thickness between 0.4 mm and 0.6 mm, preferably 0.5 mm. In particular, film elements made of a plastic material can be cut to size using cutting methods and with minimal manufacturing effort.

[0020] According to a further development, the film element is preferably designed to polarize infrared light. Reducing waste is particularly advantageous for such film elements in order to reduce manufacturing costs.

[0021] The invention also relates to a camera system with a polarization filter unit as described above, wherein the film element divided into a first and a second filter section is arranged in an operating position in a frame structure which can be mounted or is mounted on a front side of the camera system as a retrofit solution.

[0022] Preferably, the polarization filter unit can be inserted into the frame structure in a materially bonded manner, in particular by gluing at provided adhesive points, whereby the two filter sections can also be fixed to each other for long-lasting use.

[0023] In this context, it may be preferable for the camera system to be designed as a barcode reader with a search light, wherein the polarization filter unit has search cutouts to prevent filtering in the area of ​​the search light. Especially for infrared light, alignment of the camera system can be facilitated by using the search light with light beams in the visible wavelength range.

[0024] The invention further relates to a method for producing a previously described polarization filter unit for a camera system having two filter sections with different polarization directions for a receiving module and an illumination module of the camera system, wherein the polarization directions are offset from one another by a polar angle in order to filter specular reflections. The polarization filter unit can be produced from a film element with a predetermined first polarization direction using the following steps. According to a preferred first step, the film element is divided and cut into a first filter section and a second filter section that can be removed therefrom, together with two engagement contours offset by the polar angle. In particular, the cutting of the film element with the first and second filter sections is carried out in a common cutting step.Furthermore, it can be advantageous to cut several polarization filter units with two filter sections next to each other in one cutting process. This can have the advantage of minimizing waste.

[0025] In a preferred second step, the second filter section with the second engagement contour is removed from the first filter section and rotated about the rotation axis by the polar angle. In a preferred third step, the second filter section with the second engagement contour is positively inserted into the first filter section with the first engagement contour to form the second filter section with a second polarization direction. In this case, an orthogonal arrangement of the two polarization directions can preferably be ensured by the engagement contours, and an assembly or adjustment step can be simplified while maintaining consistent precision. In other words, the alignment of the polarization directions is predetermined by the manufacturing process and preferably the predefined cutting process.

[0026] Particularly preferably, the film element is divided using a laser cutting process. This advantageously allows the engagement contours for aligning the polarization directions to be produced in a single process step, particularly to prevent slippage or displacement of the polarization directions relative to one another during the manufacturing process.

[0027] The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

[0028] They show schematically: Fig. 1: Front view of a polarization filter unit with two divided filter sections in a manufacturing state, Fig. 2: Front view of the polarization filter unit according to the Fig. 1 with the filter sections in an operating state within a frame structure, Fig. 3: Perspective view of the front of a camera system Fig. 4: Perspective view of the camera system according to the Fig. 3 with a polarization filter unit.

[0029] In the following description of the preferred embodiments, like reference numerals designate like or comparable components.

[0030] The Fig. 1 shows a polarization filter unit 10 in a manufacturing state, wherein a first and a second filter section 12, 14 are shown cut or divided from a film element 11 with a first polarization direction 20. In other words, the polarization filter unit 10 is in a delivery state or a manufacturing position prior to installation in a camera system 100 according to the Fig. 3 or the Fig. 4 shown.

[0031] The polarization filter unit 10 has a circular second filter section 14 within a first filter section 12, wherein the second filter section 14 has an alignment projection 16 as a second engagement contour 32. The first filter section 12 has, corresponding to a contour of the alignment projection 16, an alignment notch 18 offset about the rotation axis S as the first engagement contour 30. A polar angle V between the alignment projection 16 and the alignment notch 18 is 90°. The alignment projection 16 is preferably jagged or V-shaped, protruding adjacent to a circular shape.

[0032] To the Fig. To cut the filter sections 12, 14 shown in Figure 1, a cutting process, in particular a laser cutting process, is preferably used, which divides the film element 11, preferably in one manufacturing step. This ensures that the filter sections 12, 14 remain in a defined position relative to one another during production.

[0033] The film element 11, in particular made of a plastic material, preferably has a material thickness t between 0.4 mm and 0.6 mm, preferably 0.5 mm. Such a material can be cut quickly and precisely using a laser cutting process.

[0034] Preferably, a semicircular recess 28 can be introduced into the first filter section 12 adjacent to the alignment projection 16 of the second filter section 12 in order to enable the alignment projection 16 to be removed without causing damage.

[0035] The Fig. 2 shows the polarization filter unit 10 in an operating position 34, wherein the two filter sections 12, 14 are arranged rotated about the rotation axis S and the polar angle V for the filter operation for a camera system 100. In comparison to the manufacturing state according to the Fig. 1, the second filter section 14 is removed from the first filter section 12 and, by aligning the alignment projection 16 with the alignment notch 18 in a rotated position, is reinserted into the first filter section 12 in a form-fitting manner. This allows the second filter section 14 to be aligned with a defined second polarization direction 22 perpendicular to the first polarization direction 20. This alignment of the polarization directions 20, 22 relative to one another can advantageously be ensured by the two engagement contours 30, 32.

[0036] The first polarization direction 20 is in the Fig. 1 and the Fig. 2 is preferably drawn horizontally, but can vary as desired. It is essential that the polar angle V between the two polarization directions 20, 22 is defined by the engagement contours 30, 32. Accordingly, during the manufacturing process and when cutting the filter sections 12, 14 out of the film element 11, there is no need to align cutting tools with respect to a polarization direction. This enables significantly simpler production, with the engagement contours 30, 32 still enabling simplified assembly and alignment of the polarization directions 20, 22.

[0037] The Fig. 2 it can further be seen that the polarization filter unit 10 is preferably mounted on a front side 106 of the camera system 100 by means of a frame structure 24 according to the Fig. 3 or the Fig. 4 can be attached. The frame structure 24 has the advantage that the film-shaped polarization filter unit 10 can be fixed in a dimensionally stable manner and can be screwed onto the camera system 100 as a retrofit component.

[0038] Additionally, it may be provided that a plurality of search recesses 26 are formed in the first filter section 12 to enable unfiltered illumination of an observation area in these areas by the camera system 100. In particular, for infrared light, visually visible illumination can thus be used for camera alignment.

[0039] According to the Fig. 3, the camera system 100 preferably has a receiving module 104 and several, in particular four, illumination modules 102. The receiving module 104 is preferably arranged centrally on a front side 106 of a camera housing 107, wherein the first filter section 12 is preferably assigned to the illumination modules 102 and the circular second filter section 14 is assigned to the circular receiving module 104 in a space-saving manner.

[0040] The Fig.4 shows the camera system 100 with the polarization filter unit 10 in the frame structure 24 prior to a mounting step on the front side 106 of the camera housing 107. Particularly preferably, a separating element 108 with separating webs 109 can be formed between the polarization filter unit 10 and the camera housing 107 in order to optically separate the illumination module 104 from the receiving module 102. The separating webs 109 can advantageously prevent stray light from the illumination module 104 from reaching the receiving module 102. The separating element 108 is preferably formed from a foam material. The frame structure 24 can advantageously be retrofitted to an existing camera system 100 with a closed front side 106, in particular a front screen. List of reference symbols 10 Polarizing filter unit 11 Slide element 12,14 first and second filter section 16 Alignment projection 18 Alignment notch 20,22 first and second polarization direction 24 Frame structure 26 search cutouts 28 semicircular recess 30,32 first and second engagement contours 34 Operating position of the filter sections 100 camera system 102 Receiver module 104 lighting modules 106 Front of the camera system 107 camera bodies 108 Separator 109 dividers V Polar angle S axis of rotation t material thickness

Claims

[1] Polarization filter unit (10) for a camera system (100), with two filter sections (12, 14) for a receiving module (102) and an illumination module (104) of the camera system (100), wherein polarization directions (20, 22) of the two filter sections (12, 14) are aligned orthogonally offset from one another by a polar angle (V) in order to filter specularly reflected light at the receiving module (102), characterized byin that a first filter section (12) is formed from a film element (11) with a predetermined first polarization direction (20), wherein a second filter section (14) is detached from the first filter section (12) in a circular manner with an alignment projection (16) as a second engagement contour (32), wherein an alignment notch (18) offset by the polar angle (V) is formed as a first engagement contour (30) in the first filter section (12), wherein the second filter section (14) with the second engagement contour (32) in an operating position (34) rotated about an axis of rotation (S) with the polar angle (V) can be or is inserted in a form-fitting manner into the first engagement contour (30) of the first filter section (12) in order to form the second filter section (14) with a second polarization direction (22). [2] Polarization filter unit according to claim 1, characterized bythat a semicircular recess (28) is formed within the first filter cutout (12) adjacent to the second engagement contour (32) in order to remove the second filter cutout (14) with the second engagement contour (32) without causing damage. [3] Polarization filter unit according to claim 1 or 2, characterized by that the film element (11) is made of a plastic material with a predetermined first polarization direction (20) with a material thickness (t) between 0.4 mm and 0.6 mm, preferably 0.5 mm. [4] Polarization filter unit according to one of claims 1 to 3, characterized by that the film element (11) is designed to polarize infrared light. [5] Camera system with a polarization filter unit (10) according to one of claims 1 to 4, wherein the film element (11) divided into a first and a second filter section (12, 14) is arranged in an operating position (34) in a frame structure (24) which can be mounted or is mounted on a front side (106) of the camera system (100) as a retrofit solution. [6] Camera system according to claim 5, characterized by that the camera system (100) is designed as a barcode reader with a search illumination, wherein the polarization filter unit (10) has search recesses (26) in order to avoid filtering in the area of the search illumination. [7] Method for producing a polarization filter unit (10) for a camera system (100) according to one of claims 1 to 4 with two filter sections (12, 14) with different polarization directions (20, 22) for a receiving module (102) and an illumination module (104) of the camera system (100), wherein the polarization directions (20, 22) are aligned offset from one another by a polar angle (V) in order to filter specular reflections, wherein the polarization filter unit (10) is produced from a film element (11) with a predetermined first polarization direction (20) with the following steps: - cutting and dividing the film element (11) into a first filter section (12) and a second filter section (14) which can be removed therefrom, together with two engagement contours (30, 32) offset by the polar angle (V), - removing and rotating the second filter section (14) with a second engagement contour (32) with the polar angle (V) around the rotation axis (S), - Aligning and positively inserting the second engagement contour (32) into a first engagement contour (30) of the first filter section (12) in order to form the second filter section (14) with a second polarization direction (22). [8] Method according to claim 7, characterized by that the film element (11) is divided using the laser cutting process.

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