Optical code carrier

Abstract

Optical code carrier (11) for a position transmitter, comprising a carrier body (13) and a dimension medium (15) formed by a sequence of transparent areas (16) and opaque areas (17) of the carrier body (13), wherein the carrier body (13) is formed from a transparent material and has structures in the form of protrusions (40) or depressions (30) opposite a base surface (33) of the carrier body (13), and wherein, to form the sequence of transparent areas (16) and opaque areas (17) of the carrier body (13), an opaque layer (35) is provided on the structures (30, 40) while leaving the areas (37) of the base surface (33) located between the structures (30, 40) exposed.

Description

[0001] The present invention relates to an optical code carrier for a position sensor, comprising a carrier body and a measuring embodiment formed by a sequence of transparent regions and non-transparent regions of the carrier body.

[0002] Such code carriers are generally used in conjunction with an optical scanning device to determine the position of a first object relative to a second object. Typically, the optical code carrier is attached to the first object, while the optical scanning device is attached to the second object. Optical scanning can be performed by transmission or reflection.

[0003] Position sensors with optical code carriers are known in a wide variety of designs, with a distinction being made between linear and rotary systems. A linear sensor determines a displacement along an axis, whereas a rotary encoder or rotary angle sensor is used to detect a rotation angle or angular position, for example, the angular position of a motor shaft. An important application area for position sensors is so-called motor feedback systems, in which a rotary encoder in a servo motor reports the actual speed of the motor shaft back to the control system.

[0004] Optical code carriers can be manufactured using lithography, but this involves high manufacturing costs. Alternatively, a plastic carrier can be printed with a pattern to produce an optical code carrier. This is relatively inexpensive, but results in comparatively low dimensional accuracy, which is unacceptable for certain applications.

[0005] It is an object of the invention to provide an optical code carrier which can be produced simply and inexpensively and which nevertheless enables a high position resolution.

[0006] The problem is solved by an optical code carrier having the features of claim 1.

[0007] According to the invention, the carrier body is formed from a transparent material and has structures in the form of elevations or depressions relative to a base surface of the carrier body, wherein, in order to form the sequence of transparent regions and non-transparent regions of the carrier body, an non-transparent layer is provided on the structures while leaving free the regions of the base surface located between the structures, or on the regions of the base surface located between the structures while leaving free the structures.

[0008] Creating the structures in the base surface of the carrier body is possible with relatively little effort and, at the same time, with high precision. In particular, the structures can be molded, for example, from a particularly dimensionally accurate matrix or master. Since the provision of the opaque layer is based on the structures, the accuracy requirements for the process of applying or creating the layer are reduced. Thus, an optical code carrier according to the invention is relatively easy to manufacture, even with high dimensional accuracy specifications.

[0009] The carrier body can be molded from a transparent plastic, which allows for particularly simple production. For example, the transparent plastic can be polycarbonate.

[0010] According to one embodiment of the invention, the carrier body is an injection-molded part or a stamped part. The dimensional accuracy of the resulting structures depends solely on the quality of the associated tool and is therefore highly reproducible. This facilitates large-scale production. Depending on the specific application, the carrier body can be manufactured using an injection-compression molding process, a UV imprinting process, or a hot-stamping process.

[0011] The non-transparent layer can be a layer made of an absorbent material or a reflective material. If a layer made of an absorbent material is present, the optical code carrier can be used in a transmitted-light arrangement according to the light barrier principle. In this case, a light source is arranged on one side of the carrier body, while a light receiver is arranged on the other side of the carrier body. If, however, a layer made of a reflective material is present, the optical code carrier can be used in a reflected-light arrangement. The scanning device is designed such that the light source and the light receiver are located on the same side of the carrier body. The term "non-transparent" is to be understood broadly in the present disclosure to also include "reflective" or "highly scattering." The non-transparent regions can, in particular, be opaque to visible light.

[0012] According to one embodiment of the invention, the carrier body is disc-shaped, and the base surface is formed on a flat side of the disc-shaped carrier body. Such a code disc is particularly suitable for mounting on a rotating component in order to determine the angular position or rotational speed of the component.

[0013] The disc-shaped carrier body may have a central passage and / or a centering structure to facilitate centering of the disc-shaped carrier body with respect to a rotating shaft or the like.

[0014] For example, for particularly secure centering, a central passage can be provided into which a rotating shaft can be accommodated.

[0015] A centering structure can be a raised or recessed portion relative to the base surface of the support body. Such a centering structure of the support body can interact with a counter-structure of the shaft, such as a shoulder, to achieve centering. If a centering structure is present, a central feedthrough can be omitted; however, in certain applications, a central feedthrough, for example, with a reduced diameter, can be provided despite the centering structure.

[0016] The central feedthrough and / or the centering structure can be created in the same manufacturing step as the structures. For example, the central feedthrough and / or the centering structure can be molded from a die. Since this is possible with high dimensional accuracy if the die is of sufficient quality, subsequent adjustment of the disc-shaped carrier body to achieve concentricity of the dimensional standard is unnecessary. This saves time and costs during assembly. A centering structure is particularly easy to create if it has the same height / depth as the code structures.

[0017] According to a further embodiment of the invention, a toothing is formed into a peripheral surface of the disk-shaped carrier body. Code disks with toothing are particularly required for gears in multi-turn encoders. It is advantageous that the toothing can be produced in the same manufacturing step as the structures, for example, by molding a die.

[0018] In an edge region of the disc-shaped carrier body, a peripheral elevation can be provided relative to the base surface. The peripheral elevation can serve as a casting barrier, so that, for example, the structures formed as elevations can be cast with an opaque fluid. A further casting barrier can be provided towards the center of the disc. In particular, a further peripheral elevation can be provided relative to the base surface, preferably extending completely around the base surface, in an area surrounding a central passage. It is understood that applying an opaque liquid to the entire base surface can be accomplished more quickly and easily than selectively applying it in limited areas.

[0019] One embodiment of the invention provides that the structures are elevations, and the opaque layer is selectively applied to the elevations. For example, an opaque material can be printed onto the elevations.

[0020] According to an alternative embodiment of the invention, the structures are elevations, and the opaque layer is selectively applied to the area surrounding the elevations. For example, the elevations can be encapsulated with an opaque liquid.

[0021] A further embodiment of the invention provides that the structures are recesses, and the opaque layer is selectively introduced into the recesses. This means that the opaque layer can be located at the bottom of the recesses.

[0022] According to a further embodiment of the invention, the structures are recesses, and the opaque layer is selectively applied to the area surrounding the recesses. In particular, the base surface can be printed with an opaque material either completely or only in the area of ​​the recesses.

[0023] The measuring embodiment of an optical code carrier according to the invention can comprise a plurality of code tracks or measuring tracks, which preferably run parallel to one another or concentrically to one another.

[0024] A method for producing an optical code carrier according to the invention for a position sensor can comprise the following steps: Forming a carrier body from a transparent material to form structures in the form of elevations or depressions relative to a base plane, Creating a dimensional embodiment formed by a sequence of transparent areas and non-transparent areas of the carrier body by applying a non-transparent layer to the structures while leaving the areas of the base surface located between the structures exposed, or to the areas of the base surface located between the structures while leaving the structures exposed.

[0025] The molding of the carrier body can involve an injection molding process. This enables particularly fast and cost-effective production.

[0026] Shaping the carrier body may include forming a toothing on the carrier body. A carrier body with toothing can be used in a multi-turn gearbox.

[0027] The structures can be designed as raised areas, and the raised areas can be cast with an opaque material. Casting is easier to accomplish than selectively applying the material in specific areas.

[0028] It can be provided that the structures are raised areas and the raised areas are covered with an opaque material, and the opaque material is removed from the raised areas after the covering. For example, the opaque material can be ground down to a desired level after the covering.

[0029] The structures can also be formed by molding from a matrix. The dimensional accuracy of the structures is then determined solely by the quality of the matrix. Since the matrix does not need to be manufactured multiple times, it can be created using a particularly precise process such as 3D microfabrication, for example, using a two-photon polymerization process or by growing a 2D structure, despite the associated effort.

[0030] The invention proves to be particularly advantageous in rotary systems, i.e. in rotary encoders.

[0031] Further developments of the invention can also be found in the dependent claims, the description and the accompanying drawings.

[0032] The invention is described below by way of example with reference to the drawings. Fig. 1 is a plan view of an optical code carrier according to the invention. Fig. 2 is a partial sectional view of an optical code carrier according to a first embodiment of the invention. Fig. 3 is a partial sectional view of an optical code carrier according to a second embodiment of the invention. Fig. 4 is a partial sectional view of an optical code carrier according to a third embodiment of the invention. Fig. 5 is a partial sectional view of an optical code carrier according to a fourth embodiment of the invention. Fig. 6 shows the optical code carrier according to Fig. 5 in an overall view obliquely from above.

[0033] Fig. 1 shows a plan view of an optical code carrier according to the invention, as it can be used in a rotary encoder.

[0034] The Fig. The optical code carrier 11 shown in Figure 1 comprises a carrier body 13 and a measuring embodiment 15, which is formed by a sequence of transparent areas 16 and non-transparent areas 17, which in Fig. 1 is shown only schematically in a small section. The carrier body 13 is disc-shaped and has a central passage 19 and a circular outer edge 21. The upper flat side 23 of the disc-shaped carrier body 13 is essentially flat.

[0035] The optical code carrier 11 can be placed on a rotating shaft, for example a motor shaft, via the central feedthrough 19 and connected to it in a drive-effective manner. A scanning device (not shown) is capable of optically scanning the measuring embodiment 15. This can be done in transmission or reflection, depending on the application, with the opaque regions 17 being absorbent for transmission scanning and reflective for reflection scanning. An electronic evaluation unit of a position sensor can be in signal communication with the scanning device. This evaluation unit receives signals from the scanning device, reads an absolute code from the signals, and determines the rotational position of the shaft based on the absolute code. In the illustrated embodiment, the measuring embodiment 15 comprises two concentric code tracks 26, 27. However, more than two code tracks 26, 27 could be provided.For certain applications, only one code track may be provided.

[0036] The carrier body 13 is formed from a transparent material, preferably a transparent plastic. The type of plastic is selected depending on the application requirements, such as strength, temperature resistance, and UV resistance. The carrier body 13 can be an injection-molded part.

[0037] Fig. 2 shows a first embodiment of a carrier body 13 in cross-section. It can be seen that the carrier body 13 has depressions 30. The upper flat side 23 of the carrier body 13 forms a base surface 33, to which the term "depression" refers. A layer 35 made of absorbent or reflective material is introduced into the depressions 30. The regions 37 of the base surface 33 located between the depressions 30, however, are free of an absorbent or reflective layer. This means that these regions 37 are transparent due to the transparent material of the carrier body 13. The previously specified sequence of transparent regions 16 and non-transparent regions 17 is thus formed by the layer 35 located exclusively in the depressions 30.

[0038] At the Fig. In the second embodiment of the invention shown in Figure 3, the recesses 30 are free of an absorbing or reflective layer, whereas such a layer 35 is applied to the regions 37 between the recesses 30. In particular, the entire flat side 23 of the carrier body 13 could be provided with the layer 35, with only the recesses 30 being left out.

[0039] The Fig. The carrier body 13 shown in Figure 4, designed according to a third embodiment of the invention, has elevations 40 opposite the base surface 33 instead of the depressions 30. A layer 35 of absorbent or reflective material is selectively applied to the elevations 40. The regions 37 between the elevations 40, however, are free of an absorbent or reflective layer, i.e., these regions 37 are transparent. For example, the layer 35 could be printed onto the elevations 40.

[0040] At the Fig. 5, elevations 40 are also provided opposite the base surface 33 on the carrier body 13. In contrast to the embodiment according to Fig. 4, however, the layer 35 of absorbing or reflective material is not provided on the elevations 40, but exclusively in the areas 37 of the base surface 33 located between the elevations 40.

[0041] Fig. 6 shows the carrier body 13 according to Fig.5 in a perspective overall view. A peripheral elevation 41 can be seen, extending completely around the periphery. The absorbent layer 35 covers the carrier body 13 such that the elevations 40 protrude beyond the layer 35. The layer 35 can be easily applied to the carrier body 13 by pouring a light-absorbing liquid, with the edge elevation 41 forming a pouring barrier. This means that the elevations 40 can be easily encapsulated with the absorbent material.

[0042] In principle, the carrier bodies 13 shown could be provided with a toothing, although this is not depicted in the figures. It is also understood that the shape of the recesses 30 and the elevations 40 is purely exemplary. In particular, the flanks of the recesses 30 and elevations 40 could also extend obliquely to the base surface 33. Furthermore, the recesses 30 and elevations 40 could have chamfers or curves or generally have a round, for example, semicircular, cross-section.

[0043] To produce an optical code carrier 11 according to the invention, the carrier body 13 is first molded from a transparent plastic. This can be done in a generally known manner in an injection molding tool on which negatives of the recesses 30 or the elevations 40 are formed. Thus, during injection molding, both the external dimensions of the carrier body 13, including the central passage 19 and any toothing provided, as well as the recesses 30 or the elevations 40 are formed. The dimensional accuracy of the arrangement of recesses 30 or elevations 40 is determined exclusively by the quality of the injection molding tool. The recesses 30 or elevations 40 could also be molded from a die or master using another process.

[0044] To produce the matrix, a particularly precise process is preferably chosen, for example a 3D microfabrication process or a 2-photon polymerization process.

[0045] After forming the carrier body 13 and forming the depressions 30 or elevations 40, the dimensional scale 15 is created by applying an opaque layer 35 either to the structures formed by the depressions 30 or elevations 40 or to the regions 37 therebetween, for example, by printing or casting. The accuracy requirements for this process are reduced because the dimensional accuracy of the code pattern is determined by the depressions 30 or elevations 40 and not by the application process of the layer 35.

[0046] Depending on the application, more than two code tracks 26, 27 could be provided or only one code track could be provided.

[0047] The shape of the carrier body can be adapted to specific requirements, for example to expansion behavior at elevated temperatures.

[0048] Furthermore, an optical code carrier according to the invention can also be designed for linear movement. For example, an elongated measuring scale could be applied to a strip-shaped carrier body.

[0049] The invention provides an optical code carrier which has a particularly high dimensional accuracy and is nevertheless relatively light and inexpensive to produce. List of reference symbols 11 optical code carrier 13 carrier bodies 15 Measurement embodiment 16 transparent area 17 non-transparent area 19 central implementation 21 outer edge 23 upper flat side 26 Code track 27 Code track 30 Deepening 33 base area 35 shift 37 Area between depressions 40 Survey 41 Marginal elevation

Claims

[1] Optical code carrier (11) for a position sensor, with a carrier body (13) and a measuring embodiment (15) which is formed by a sequence of transparent regions (16) and non-transparent regions (17) of the carrier body (13), wherein the carrier body (13) is formed from a transparent material and has structures in the form of elevations (40) or depressions (30) opposite a base surface (33) of the carrier body (13), and wherein, to form the sequence of transparent regions (16) and non-transparent regions (17) of the carrier body (13), an non-transparent layer (35) is applied to the structures (30, 40) while leaving free the regions (37) of the base surface (33) located between the structures (30, 40) or to the regions (37) of the base surface (33) located between the structures (30, 40) while leaving free the structures (30, 40). [2] Optical code carrier according to claim 1, wherein the carrier body (13) is formed from a transparent plastic. [3] Optical code carrier according to claim 1 or 2, wherein the carrier body (13) is an injection-molded part or a stamped part. [4] Optical code carrier according to one of the preceding claims, wherein the non-transparent layer (35) is a layer of an absorbent material or of a reflective material. [5] Optical code carrier according to one of the preceding claims, wherein the carrier body (13) is disc-shaped and the base surface (33) is formed on a flat side (23) of the disc-shaped carrier body (13). [6] Optical code carrier according to claim 5, wherein the disc-shaped carrier body (13) has a central passage (19) and / or a centering structure. [7] Optical code carrier according to one of claims 5 or 6, wherein a toothing is formed in a peripheral surface of the disc-shaped carrier body (13). [8] Optical code carrier according to one of claims 5 to 7, wherein in an edge region (21) of the disc-shaped carrier body (13) an edge elevation (41) extending in the circumferential direction is provided opposite the base surface (33). [9] Optical code carrier according to one of the preceding claims, wherein the structures are elevations (40) and the non-transparent layer (35) is selectively applied to the elevations (40). [10] Optical code carrier according to one of claims 1 to 8, wherein the structures are elevations (40) and the non-transparent layer (35) is selectively applied to the surroundings of the elevations (40). [11] Optical code carrier according to one of claims 1 to 8, wherein the structures are depressions (30) and the non-transparent layer (35) is selectively introduced into the depressions (30). [12] Optical code carrier according to one of claims 1 to 8, wherein the structures are depressions (30) and the non-transparent layer (35) is selectively applied to the surroundings of the depressions (30).

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