Method for producing an optical position encoder

Abstract

The invention relates to a method for producing an optical position encoder 100, which has an optoelectronic component 1 and has a measurement scale 101 which is illuminated by LED light sources 2 of the optoelectronic component 1, wherein the LED light sources 2 are embedded in a molded housing 11 in such a way that a light exit surface 5 of the LED light sources 2 is exposed to the outside, wherein the light exit surface 5 is coated and uncoated in regions to provide a light exit window 10. A further content of the invention is an optical position encoder 100, which has an optoelectronic component 1, which has a molded housing 11, in which LED light sources 2 are arranged in such a way that a light exit surface 5 of the LED light sources 2 is exposed to the outside, and which has a measurement scale 101 which is illuminated by the LED light sources 2 of the optoelectronic component 1.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an optical position encoder having optoelectronic components and a measuring scale illuminated by an LED light source of the optoelectronic components, wherein the LED light source is embedded in a molded housing with its light-emitting surface exposed to the outside. An optical position encoder having optoelectronic components forms another subject of the invention, wherein the optoelectronic components have a molded housing in which the LED light source is arranged with its light-emitting surface exposed to the outside, and the optical position encoder has a measuring scale illuminated by the LED light source of the optoelectronic components. Background Technology

[0002] Such optoelectronic components are commonly used in optical position encoders to detect the movement of components. For this purpose, a measuring scale illuminated by an LED light source from the optoelectronic component is arranged on the component. The measuring scale is designed in such a way that the light from the LED light source incident on the measuring scale is modulated according to a specific pattern. Therefore, the measuring scale can include, for example, bright and dark areas, where line patterns are particularly advantageous. The modulated light can then be detected by a sampling receiver in the form of at least one light sensor. In this way, a large number of sine and cosine signal forms can be generated that can be evaluated and thus provide information about the position of the component.

[0003] Such position encoders can be designed as linear position encoders to detect the linear motion of a component, or as rotary encoders to detect the rotational motion of a component. Therefore, the measurement scale can be formed by mutually parallel lines, having an overall rectangular shape, or formed as a disk with radially extending lines. Furthermore, the position encoder can be designed as an incremental encoder or an absolute encoder. In incremental encoders, a reference can also be performed at the beginning of the measurement process to obtain local absolute information items. This is unnecessary if the encoder is absolute throughout the entire sampling range.

[0004] The measurement scale can also be designed according to different applications. Therefore, on one hand, a transmitted light arrangement is known, in which the measurement scale is positioned between an LED light source and a photosensitive sensor that receives modulated light. The light region is then typically formed by a slotted light transmission region of the measurement scale. Alternatively, the measurement scale can also be designed as a reflective arrangement, in which the light from the LED light source is reflected at these light plates and reaches the sensor.

[0005] To protect the sensitive microelectronic components of a component from negative impacts, it is known to arrange these components in a molded housing that encapsulates the entire component.

[0006] The term "molding" is generally understood here to refer to molding methods, particularly injection molding, in which liquid material is injected under pressure into a mold, also known as an injection mold. Due to cooling or cross-linking reactions, the material solidifies again within the mold and is removed as the final part after the mold is opened. Shells produced in injection molding offer advantages in terms of processing speed and forming quality, particularly compared to shells produced solely by so-called "casting," in which liquid material is poured into a mold and solidifies therein. However, individual parts undergo significantly higher pressures in molding because not every part is suited to this production method.

[0007] For example, an arrangement in which these individual components are arranged in a molded housing is known from DE 102012107578A1. The LED light source is located on a carrier and is enclosed on all sides by the molded housing. To enable the light from the LED light source to be emitted upward in a defined manner and to prevent damage to the LED light source during the manufacturing process, a structured glass plate is positioned above the LED light source.

[0008] Of course, it has been proven that such components are used solely as LED lights; however, it has also been shown to be disadvantageous in this arrangement, specifically when used in position encoders, due to potential damage to light emission caused by the glass plate positioned above the LED light source. This is because, on the one hand, undesirable refraction of the light beam can occur at the transition points between the LED light source and the glass plate, and between the glass plate and the surrounding environment. On the other hand, reflections can occur, causing, for example, external light to deflect in the direction of the measurement scale, thereby damaging the measurement results.

[0009] To avoid damage to light emission caused by a glass plate arranged above the LED light source, for example, as known from DE102015103253A1, the light-emitting surface of the LED light source is exposed to the outside, through which light is emitted from the LED light source. Since the light-emitting surface is exposed to the outside, it is no longer located inside the mold housing, and in addition to structural simplification, it allows the LED light source to emit light in all directions. Possible refraction, shading, coupling, or other damage caused by scattered light can be prevented by avoiding components arranged on or above the LED light source.

[0010] The emission characteristics of an LED light source are affected by the precise dimensions of its light-emitting surface, which are essentially defined by the manufacturing method and tolerances. In this case, differences exist not only between LEDs from different manufacturers, but also between different batches from the same manufacturer, and even between individual LEDs within the same batch. These differences in the light-emitting surface affect the signal quality in position encoders and limit the resolution of optoelectronic components; in particular, a large light-emitting surface leads to low resolution. Summary of the Invention

[0011] In view of this background, the object of the present invention is to provide a method for producing an optical position encoder and an optical position encoder that improves the emission characteristics of an LED light source to achieve higher resolution.

[0012] This is achieved in the type of method mentioned at the beginning, where the light-emitting surface is coated and decoated in some areas to provide a light-emitting window.

[0013] Because the LED light source (especially the semiconductor LED chip) is coated, it can still be exposed to the outside. The coating thus forms the outer surface of the coated LED light source. Undesirable refraction of the beam can be avoided at transitions between the LED light source and covering elements such as glass plates, and between the covering element and the surrounding environment. The resolution of the optoelectronic component is no longer limited by the manufacturing method and manufacturing tolerances of the uncoated LED light source, especially the semiconductor crystal of the semiconductor LED chip, but by the coating and decoating processes and the dimensions of the light exit window. The tolerances for coating and decoating can be lower than the manufacturing tolerances. Better emission characteristics, especially better signal quality and higher resolution, can be achieved.

[0014] LED light sources can be equipped with an integrated shielding element consisting of a coated light-emitting surface and an uncoated light-emitting window. Uncoating allows for precise fabrication of the light-emitting window, particularly enabling it to have sharp edges, thereby improving emission performance.

[0015] This method can be used with LED light sources from different manufacturers and / or batches. Due to coating and decoating, optoelectronic components with uniform emission characteristics can be produced despite the use of different manufacturing methods and LED light source manufacturing tolerances. A light emission window with dimensions substantially independent of the LED light source used and below the size of the light emission surface can be achieved. In the case of producing multiple optoelectronic components in series, a uniform light emission window can be achieved in all optoelectronic components despite differences between individual LED light sources.

[0016] According to one embodiment of the invention, a portion of the light-emitting surface may be coated. Specifically, a portion of the light-emitting surface used to provide the light-emitting window may be left uncoated from the outset. To provide the light-emitting window, the coated portion of the light-emitting surface may be decoated in areas. In particular, the edges of the light-emitting window surrounding the uncoated portion of the light-emitting surface may be decoated to achieve sharp edges. This method can be performed in a material- and time-saving manner by coating only a portion of the surface, particularly in the case of larger light-emitting windows.

[0017] The molded housing is preferably formed from a molding compound for embedding an LED light source. For this purpose, the molding compound can be injected into an injection mold in which the LED light source has already been arranged. The manufacturing of the molded housing and the embedding of the LED light source can be carried out in a single process step in a time-saving manner.

[0018] Advantageously, a light-emitting surface is coated on the entire surface or part of the surface, and this coating is particularly substantially opaque and / or reflective. If the light-emitting surface is coated on the entire surface, the light-emitting window can be freely positioned on the light-emitting surface by corresponding decoating, without considering the position of the uncoated portion of the light-emitting surface. Light emission from the coated portion of the light-emitting surface can be prevented by the substantially opaque coating. Light escape from the LED light source can be limited by the opaque coating on the light-emitting window. The emission characteristics of the LED light source can be defined by the size of the light-emitting window, which is substantially independent of the size of the entire light-emitting surface. A reflective coating, particularly one that reflects in the direction of the LED light source inward, causes light to be reflected into the interior of the LED light source if a single beam of light is incident on the coating but not on the decoated light-emitting window. The light output of the LED light source can be increased by reflection within the LED light source. Especially in the case of multiple reflections, a beam of light reflected inside the light source can be reflected again in such a manner that it can exit from the LED light source through the light-emitting window. This method allows for the focusing of light generated by the LED light source onto the light exit window.

[0019] A light-emitting surface can be coated with multiple coatings on its entire surface or part of its surface, resulting in a multi-layered coating that specifically produces a light-emitting surface. The effect of a single coating, particularly the effect of improving the emission performance of an LED light source, can be achieved by combining multiple coatings, especially multi-layered coatings, in a simple manner.

[0020] The coating and / or these coatings may specifically consist of non-organic compounds.

[0021] In this paper, it is particularly advantageous to use metallic coatings, especially those made of gold or gold alloys, to coat light-emitting surfaces. Metallic coatings, especially those made of gold or gold alloys, can be applied to light-emitting surfaces using simple methods. Thin coatings of the light-emitting surface can be achieved in a material-saving manner, resulting in a very small volume. Opaque and / or reflective coatings can be achieved easily using metallic coatings, especially those made of gold or gold alloys, particularly with layer thicknesses of a few hundred nanometers. Chromium-gold alloys have proven particularly advantageous for coating light-emitting surfaces. Chromium-gold coatings can be used to increase the light output of LED light sources through multiple reflections in a particularly simple manner.

[0022] In another embodiment of the invention, at least one peripheral surface of the LED light source is coated. The same or different coatings used to coat the light-emitting surface can be used to coat the peripheral surface. Specifically, the peripheral surface can be coated using multiple layers and / or several layers. Depending on the shape of the LED light source, the light path exiting the LED light source that does not extend through the light-emitting window can be suppressed by a coating on the peripheral surface that extends substantially laterally to the light-emitting surface. This prevents unwanted scattered light from incident on adjacent photosensors and causing damage to the output signal. The coated peripheral surface can alternatively or additionally be used to reflect the light beam in a direction within the LED light source to increase the light output of the LED light source through multiple reflections.

[0023] Furthermore, it is advantageous that the four peripheral surfaces of the LED light source, and in particular all peripheral surfaces, are coated. The coatings on the individual peripheral surfaces can be applied differently or identically to each other. In particular, the peripheral surfaces can be coated simultaneously.

[0024] Furthermore, it may be advantageous to continuously coat at least one peripheral surface and the light-emitting surface of the LED light source. The peripheral surface can be coated first, followed by the light-emitting surface. Similarly, the light-emitting surface can be coated first, followed by the peripheral surface. In the case of continuous coating of the peripheral surface and the light-emitting surface, different coatings can be applied to both the at least one peripheral surface and the light-emitting surface.

[0025] Furthermore, it is advantageous that the light-emitting surface is coated with a different coating than at least one peripheral surface of the LED light source. Since the peripheral surface is embedded in and in contact with the molded housing, while the light-emitting surface is exposed to the outside, such different arrangements of the various surfaces in the optoelectronic component can be considered through the different coatings of at least one peripheral surface and the light-emitting surface. The coating of the light-emitting surface can be designed to be as opaque as possible, so that no more light, except for light emanating through the light-emitting window, is emitted from the LED light source via the light-emitting surface exposed outside the molded housing. Conversely, the coating of the peripheral surface can be designed to be primarily reflective, thereby increasing the total light output of the LED light source. In contrast, the opacity of the peripheral surface can have a backing, as the peripheral surface presses against the molded housing, so that, in addition to the coating of the peripheral surface, the molding material also helps to reduce unwanted scattered light.

[0026] According to another embodiment of the invention, the light-emitting surface is proposed to be coated by physical vapor deposition, particularly by sputtering. Coating, particularly thin coating, can be used to coat the light-emitting surface in a simple manner via physical vapor deposition. By physical vapor deposition, particularly by sputtering, coatings and / or structured coatings with substantially uniform and previously defined layer thicknesses can be obtained. Chemical reactions with the light-emitting surface can be avoided by physical vapor deposition. By using physical vapor deposition for coating, changes in the surface structure of the light-emitting surface after decoating in certain areas can be avoided, particularly changes in the surface structure in the area of ​​the light-emitting window.

[0027] Another embodiment provides decoating of the light-emitting surface by etching, machining, and / or laser. Decoating of some areas of the light-emitting surface by etching, machining, and / or laser can be used to decoat the entire surface of the portion of the light-emitting surface forming the light-emitting window. Alternatively, the decoating method can be used to expand the uncoated portion of the light-emitting window, particularly to define sharp edges of the light-emitting window in the transition to the coated area of ​​the light-emitting surface. When the LED light source is already embedded in a molded housing, etching, machining, and / or laser processing can be used to decoat some areas of the light-emitting surface. In decoating by etching and / or laser, photolithography methods can be used, which allow the size and geometry of the light-emitting window to be predetermined in a simple manner, and the light-emitting surface can be decoated in areas of the light-emitting window. Decoating the light-emitting surface by laser enables the provision of one or more small-area light-emitting windows, which can increase the resolution of optoelectronic components. A light-emitting window with a width in the range of 50 μm and smaller, particularly with a slit width of 20 μm and smaller, can preferably be achieved by laser. For coating by mechanical processing, the coated light-emitting surface can be processed by ablation, particularly by grinding or sawing.

[0028] The light-emitting surface is preferably coated in rectangular, gapped, elliptical, and / or circular forms to provide a light-emitting window. The geometry of the light-emitting window can be individually adapted to the application requirements of the optoelectronic component by decoating some areas of the light-emitting surface in rectangular, gapped, elliptical, and / or circular forms. Rectangular, gapped, elliptical, and / or circular decoating forms can be combined to obtain light-emitting windows with more complex geometries. Different shapes of light-emitting windows can be achieved in a simple manner through combination.

[0029] In another embodiment of the invention, the light-emitting surface is coated before or after molding. The coating of the light-emitting surface before molding results in an overlap of the coating covering the light-emitting surface on the peripheral portion surfaces. Such overlap can be advantageous if one or more peripheral portion surfaces are also coated, particularly using the same coating used for coating the light-emitting surface. The LED light source can be thus covered between the light-emitting surface and the peripheral portion surfaces, particularly in known areas. The step of providing the light-emitting window can be performed concurrently with the coating of the light-emitting surface after molding.

[0030] Another embodiment provides decoating of the light-emitting surface in certain areas before or after molding. In the case of decoating before molding, the light-emitting window can be provided before the molding process. The light-emitting window can be disposed on an LED light source, which is fixed in a suitable position within the molded housing due to the decoating of the light-emitting surface after molding. The position and orientation of the light-emitting window of the LED light source can be generated at a predetermined position relative to the molded housing or, in the case of decoating after molding, at a photosensor arranged within the molded housing. Reproducible production of optoelectronic components with identical emission characteristics can be achieved by decoating after molding. The effects of differences between individual light sources and variations in the position of the LED light source relative to the molded housing or the photosensor on the position and / or orientation of the light-emitting window relative to the molded housing or the photosensor (which may occur during molding) can be avoided by decoating after molding.

[0031] In an advantageous embodiment of the invention, the coating of the light emitting surface and the decoating in some areas of the light emitting surface can both be performed before molding, the coating of the light emitting surface can be performed before molding, and the decoating in some areas can be performed after molding, or the coating of the light emitting surface and the decoating in some areas of the light emitting surface can both be performed after molding.

[0032] In optical position encoders of the type described at the beginning, in order to achieve the above objectives, it is proposed that the light-emitting surface is coated and has an uncoated light-emitting window.

[0033] Because the LED light source (especially the semiconductor LED chip) is coated, it can still be exposed to the outside. Undesirable refraction of the beam at transitions between the LED light source and covering elements such as glass plates, and between the covering element and the surrounding environment, can be avoided. The LED light source can be equipped with an integrated shielding element consisting of a coated light-emitting surface and an uncoated light-emitting window. Due to the coating of the light-emitting surface and the uncoating of the light-emitting window, the resolution of the optoelectronic component no longer depends on the manufacturing methods and tolerances in the fabrication of different LED light sources, especially the semiconductor crystals of the semiconductor LED chip, and no longer depends on the alignment of the LED light source with the photosensor. Instead, it depends on the coating and uncoating processes and the size of the light-emitting window, thus achieving better emission characteristics, especially better signal quality and higher resolution. The tolerances for coating and uncoating can be significantly lower than the manufacturing tolerances.

[0034] Uncoated light exit windows can be manufactured more precisely and, in particular, can have sharp edges, thus improving emission characteristics.

[0035] The features described in conjunction with the method according to the invention can also be used individually or in combination in optical position encoders, producing the same advantages already described.

[0036] According to one structural embodiment, a light-emitting surface is proposed to have a substantially opaque and / or reflective coating. This coating can extend not only on the light-emitting surface but also additionally cover the entire peripheral portion of the LED light source surface. The coating can advantageously cover all sides of the LED light source except for the contact side used for electrical contact with the LED light source, specifically covering the entire surface of these sides. The contact side of the LED light source can be radially opposite to the light-emitting surface, allowing the LED light source to be designed like a so-called flip-chip LED. Multiple reflections can be achieved within the LED light source through the coating on the peripheral surface, particularly the reflective coating. The light output of the LED light source, i.e., the intensity of the light emitted from the LED light source through the light-emitting window, can be increased. The coating can be multi-layered, particularly multiple layers.

[0037] Furthermore, it can be advantageous if the coating has a layer thickness of less than 600 nm, particularly less than 400 nm. Optoelectronic components can be designed with a layer thickness of less than 600 nm, and especially less than 400 nm, in a material-saving manner. This can save weight and cost.

[0038] In an advantageous embodiment, the side of the LED light source facing away from the light-emitting surface is the contact side of the LED light source. This side of the LED light source facing away from the light-emitting surface can be the side of the LED light source radially opposite to the light-emitting surface. The optoelectronic components can be equipped with a flip-chip-like LED light source on the contact side. Due to the geometry of the flip chip, contact lines and conductive channels for electrical contact with the light-emitting surface can be omitted. Shadows caused by contact lines can be avoided. The entire light-emitting surface can be used to provide a light-emitting window.

[0039] To avoid the risk of short circuits, the contact side can advantageously be constructed without a coating. Specifically, the coating on either the light-emitting surface or the coating on the peripheral surface may not extend to the contact side of the LED light source. The LED light source can advantageously be electrically contacted only via the contact side.

[0040] The molding compound of the molded housing is preferably opaque, especially within the wavelength range of the LED light source. Undesirable optical effects, such as scattered light, can be suppressed by using a molded housing made of an opaque molding compound. The molding compound can be particularly opaque, i.e., not translucent, so that light cannot pass through or escape from the molded housing, except from the light-emitting surface of the LED light source. Additional separation elements may be provided, but are not required, to suppress external light incident on the molded housing and / or the LED light source. The molding compound preferably has a low coefficient of thermal expansion, thus not providing temperature limitations. With an opaque, especially opaque, molding compound, negative effects such as scattering or reflection due to scratches on the surface of the molded housing can be reduced. Furthermore, it is advantageous to use standard materials, thereby achieving a reduction in production costs. The molding compound can be, in particular, epoxy resin.

[0041] In a preferred embodiment, at least one light sensor is arranged within a molded housing. Light reflected and modulated, particularly at a measuring scale, can be detected by the light sensor. The light sensor may have a photosensitive photoelectric surface for this purpose and may provide the received signal in the form of an electrical output signal. The light sensor may preferably comprise multiple partial surfaces and / or additional circuit elements. The partial surfaces of the light sensor may be arranged symmetrically to each other. Multiple partial surfaces may also be combined to form a group. The partial surfaces may be arranged mirror-symmetrically relative to each other, wherein the symmetry of the sensor surfaces will be taken into account for rotational arrangement in a rotary encoder. The individual sensor surfaces may be periodically electrically connected to each other.

[0042] In one improvement of the invention, a direct optical path between the LED light source and the photosensor is prevented, particularly by means of a molded housing. This prevents unwanted scattered light from incident on the sensor surface of the photosensor and causing damage to the output signal. The prevention of the optical path can be achieved by a coating on the outer surface of the LED light source facing the photosensor and / or by an opaque, particularly opaque, molded housing. For this purpose, a molding compound can be arranged between the various elements, for example, between the LED light source and the photosensor. The use of additional, particularly opaque and / or opaque, optical separation elements is possible but not necessary. In the case of a separation element, it can be arranged between the LED light source and the photosensor and can be designed, for example, as a web, wall, partition wall, etc.

[0043] Preferably, the molded housing has a recess in the region of the light sensor through which modulated light can reach the light sensor. The recess can be formed by a transparent auxiliary element, such as a plate made of glass, plastic, or transparent resin, disposed above the light sensor. The auxiliary element can terminate flush with the outer side of the molded housing, thereby creating a horizontal profile on the outer side of the housing. The auxiliary element can be designed such that the modulated light can only be incident on certain areas of the sensor. For this purpose, the auxiliary element can be designed as a shielding accessory. The auxiliary element designed as a shielding accessory can be made of, for example, an opaque material and can have a light-transmitting, particularly transparent, recess, or it can be made of a light-transmitting, particularly transparent material on which an opaque coating can be applied. Alternatively or additionally, the auxiliary element can serve as a protective element, particularly capable of protecting the light sensor from damage.

[0044] According to one structural embodiment, an auxiliary element arranged above the photosensor is proposed to have the same height as the LED light source. Specifically, the auxiliary element positioned above the photosensor can also terminate flush with the upper side of the molded housing, thereby creating a flat outer surface in the emission direction of the optoelectronic component. This auxiliary element can be arranged on a carrier together with the LED light source. The advantages of this arrangement are particularly evident in the production of optoelectronic components, and especially in positioning the LED light source and auxiliary element in the injection mold before molding.

[0045] Furthermore, embodiments providing multiple LED light sources and / or multiple light sensors are advantageous. By providing multiple LED light sources and / or light sensors, multiple code tracks can be implemented in the optoelectronic components, by means of which multiple position information items can be obtained and evaluated, particularly in conjunction with multiple measurement scales.

[0046] According to another structural embodiment, the LED light source and / or light sensor is arranged on a carrier. The carrier is preferably a chip formed from a semiconductor substrate. Alternatively, the carrier can be a lead frame, a base, or another element for defining the position. When the carrier is designed as a chip, this can in turn be arranged on a lead frame, such as a metal wire carrier that can be soldered in the form of a frame or insulating carrier. The LED light source and / or light sensor is preferably positioned relatively high, thereby facilitating the possibility in a simple manner that the LED light source and / or light sensor at least partially exposes its surface to the outside and / or terminates flush with the molded housing.

[0047] The LED light source is preferably disposed on a carrier including a photosensor and / or a signal processing unit. The carrier may be designed as a chip made of a semiconductor substrate. As a signal processing unit, the chip can evaluate position information items detected by the photosensor and provided as an electrical output signal. Alternatively or additionally, the photosensor and / or signal processing unit may be integrated into the chip. The LED light source may be disposed on a carrier designed as a chip-on-a-chip structure.

[0048] An advantageous embodiment provides a signal processing unit for an LED light source and / or a light sensor. The signal processing unit can process the signal detected by the light sensor, activate the LED light source, and / or perform further signal processing procedures. The signal processing unit can be an integrated circuit, particularly a carrier designed as a semiconductor chip. The LED light source and the light sensor can each be assigned a signal processing unit, which can be specifically connected to each other or to a control unit for data exchange.

[0049] LED light sources are preferably designed to emit light with wavelengths less than 700 nm, particularly less than 500 nm. Using this wavelength range allows for the detection of finer structures, especially for measuring scales. The light emitted by the LED light source can be in or below the visible light wavelength range. LED light sources preferably emit green, blue, or ultraviolet light. Due to the use of light with wavelengths less than 500 nm, the photosensor can resolve smaller dimensions or angular areas, such as corners or notches. The emitted light wavelength is preferably less than 480 nm; however, the emitted light wavelength can be greater than 400 nm, preferably greater than 425 nm, and particularly preferably greater than 450 nm. Furthermore, the advantage of using blue or even shorter wavelength LED light sources is that harder semiconductor materials can be used compared to other LED light sources, which are less prone to scratches and can withstand higher pressures during production, especially during molding.

[0050] In a circular measurement scale with a code track of 26 mm in diameter, by means of the optoelectronic component according to the invention, a linewidth of 37 μm on the measurement scale is resolvable under 1000 pulses, instead of the previously possible 60 μm.

[0051] In an advantageous embodiment, the measuring scale is made partially reflective and decoded. Due to the reflective design of the measuring scale, the LED light source and the light sensor can be arranged in a common optoelectronic component. Light emitted by the LED light source through the light exit window can be reflected by the measuring scale in the direction of the light sensor and thus detected. The measuring scale can be designed as an absolutely decoded measuring scale, through which a unique position value can be determined for each resolvable position. Referencing at the start of the measurement can be omitted, but it can still be performed.

[0052] In an advantageous embodiment of the invention, multiple optical sensors are provided for determining absolute position. Due to the presence of multiple optical sensors, multiple code tracks of the measurement scale can be sampled, and more precise position data can be detected. One or more LED light sources can be provided for the multiple optical sensors, groups of optical sensors, and / or the multiple code tracks of the measurement scale. Each code track of the measurement scale can be assigned a set of partial surfaces. The LED light sources can be arranged between the optical sensors, particularly in the middle between them, or symmetrically arranged relative to the sensor axes. This allows for more accurate position detection. The optical position encoder preferably has at least two optical sensors for absolute position detection. Attached Figure Description

[0053] The following will explain further details and advantages of the invention by way of example, based on exemplary embodiments of the invention shown in the accompanying drawings. (Figures:)

[0054] Figure 1a A first exemplary embodiment of the optical position encoder is illustrated in a schematic cross-sectional view.

[0055] Figure 1b A second exemplary embodiment of the optical position encoder is illustrated in a schematic cross-sectional view.

[0056] Figure 2a A schematic perspective view is shown according to Figure 1a Optical position encoder,

[0057] Figure 2b A schematic perspective view is shown according to Figure 1b Optical position encoder,

[0058] Figure 3 The region of the optoelectronic component according to the invention is shown in the region of the LED light source.

[0059] Figure 4 The LED light source, serving as the starting point of the method according to the invention, is shown in a schematic perspective view.

[0060] Figure 5A schematic cross-sectional view of an LED light source with a coated light-emitting surface is shown, and

[0061] Figures 6a to 6c Three exemplary embodiments of an LED light source having a coated light-emitting surface and an uncoated emission window are shown. Detailed Implementation

[0062] Figures 1 and 2 illustrate two exemplary embodiments of an optical position encoder 100 according to the present invention. These types of optical position encoders 100 are commonly used in industry to detect the position of components. For this purpose, the position encoder 100 can be designed as a linear position encoder or a rotary encoder.

[0063] To detect the position of a component, measuring scales 101 are arranged on the component with different regions 102, 103. Regions 102, 103 can be surfaces with high absorption (shown as light) and high reflection (shown as shadows), which are respectively differently affected by light incident on them by the LED light source 2. Each region 103 forms a code track, wherein during the movement of the measuring scale 101 perpendicular to the illustrated plane, the reflection and absorption fields alternate, thereby modulating the light incident thereon. One or more code tracks 103 can be provided to generate incremental signals or index signals, thereby enabling relative or absolute position determination. Figure 1a and Figure 2a In the first exemplary embodiment, the measuring dial 101 is formed in two tracks and moves orthogonally to the axis of the optoelectronic component 1 that connects the LED light source 2 and the light sensor 14.

[0064] According to Figure 1b and Figure 2b In a second exemplary embodiment, the measuring scale 101 further has two code tracks formed by regions 103. The optical position encoder 101 of this exemplary embodiment is an absolute encoder, wherein multiple code tracks on the measuring scale 101 are sampled, for example, to form pseudo-random codes. The measuring scale 101 is designated for absolute decoding, and its regions 103 have digital binary decoding, which is unique for each distinguishable position and consists of multiple simultaneously detected code points. In this case, the absorption field of the measuring scale 101 can generate a logic low signal, and the reflection field can correspondingly generate a logic high signal.

[0065] However, in both exemplary embodiments, the diffuse reflection or diffraction regions 102, 103 of the measurement scale 101 may also be used.

[0066] In order to detect the position of the component using the measuring scale 101, the optical position encoder 100 has an optoelectronic component 1 that emits light in the direction of the measuring scale 101. The optoelectronic component 1 has an LED light source for this purpose, for example in the form of an LED chip.

[0067] The LED chip used as the LED light source 2 is a light-emitting diode composed of a semiconductor crystal 3 having a base region 4. The pn junction of the LED light source is arranged such that the generated light is emitted substantially through the light-emitting surface 5 in the emission direction from the LED light source, and is thus emitted by the optoelectronic component 1 in the direction of the measuring scale 101.

[0068] In the optoelectronic component 1, the LED light source 2 is arranged on the carrier 13 such that the light emitting surface 5 is exposed to the outside. The light emitting surface 5 terminates substantially flush with the outer side 12 of the molded housing 11. This creates a smooth surface for the optoelectronic component 1 in the region of the LED light source 2. This substantially smooth surface of the optoelectronic component 1 provides advantages during the manufacturing process and in general handling during testing and assembly of printed circuit boards incorporating the optoelectronic component 1. The injection mold used in the manufacturing process can therefore be designed more simply, and in particular, no structure is required for defining position or for visual adjustment. Furthermore, guides and fixtures designed for handling standard surface-mountable components, as well as suction units for testing and assembly, can be used.

[0069] In the exemplary embodiment, the light emitting surface 5 is formed horizontally. Light emitting through the light emitting window 10 of the light emitting surface 5 can emit light with a beam smaller than the entire light emitting surface 5. Since the coated light emitting surface 5 of the LED light source 2 is exposed to the outside, it prevents, for example, the influence of other parts of the optoelectronic component 1 on the beam after it has been emitted. Therefore, it can be ensured that the beam is incident on the measuring dial 101 in a suitable manner.

[0070] Because a small, clearly defined beam of light can be provided through the light exit window 10 for modulation by the measuring scale 101 and detection by the photosensitive sensor 14 on the carrier 13 for position determination, a measuring scale 101 with a code track 103 can be used in the position encoder 100. The absorption and reflection field forming the decoded field has a significantly smaller dimension in the direction of movement of the measuring scale 101 at 37 μm than that of a conventional measuring scale. While accurate and high-resolution position determination can be achieved through the field of the smaller code track 103, this problem can still be addressed because the LED light source 2 has a light exit window 10.

[0071] Possible intensity loss of the light beam can be readjusted via the signal processing unit 15. In an exemplary embodiment, the signal processing unit 15 is part of the carrier 13, which is designed to include a semiconductor chip containing the signal processing unit 15. In addition to the signal processing unit 15, the carrier 13 also includes two light sensors 14, which are arranged along a common axis together with the LED light source 2, as shown in FIG2.

[0072] In this exemplary embodiment, the carrier 13 is arranged on the lead frame 16.

[0073] The LED light source 2 in the exemplary embodiment is designed to have a wavelength of 500 nm. By using an LED light source that emits light within this wavelength range, the efficiency of the photosensitive sensor 14 of the optoelectronic component 1 can be improved compared to using light with a larger wavelength. Therefore, light with a shorter wavelength does not penetrate deeply into the semiconductor substrate of the photosensitive sensor 14, allowing sufficient charge carriers to be generated and separated in the space charge region to increase the efficiency of light output. Furthermore, light with a shorter wavelength results in a clearer imaging of the structure of the code track 103, and thus a higher resolution for the position encoder 100.

[0074] Another advantage of the LED light source 2, which emits light with wavelengths less than 700 nm, particularly less than 500 nm, is the mechanical properties of the materials used. Compared to other LED light sources 2, these LED light sources 2 are manufactured to be more rigid, allowing them to better withstand the pressures that occur during molding. Therefore, a protected arrangement of the LED light source 2 inside the molding housing 11 is unnecessary. Instead, the LED light source 2 can be in direct contact with the injection mold (not shown) during molding. The LED light source can be constructed from carbides, for example, combined with II-VI or III-V semiconductors.

[0075] Light emitted by LED light source 2 is emitted in the direction of measuring dial 101 and reflected thereon. Due to the alternating field of code track 103, the light is modulated according to the decoding of measuring dial 101. The modulated light is reflected back in the direction of light sensor 14, which is also arranged in optoelectronic component 1, which detects the modulated light.

[0076] The light sensor 14 includes an integrated circuit and is implemented as part of a carrier 13 designed as a semiconductor chip. The light sensor 14 may also have groups of photosensitive partial surfaces, such as multiple photosensitive photodiodes. These partial surfaces may be located in the measurement direction, i.e., transverse to the axis extending between the light sensor 14 and the LED light source 2, and may detect multiple bits of code track 103, or may be positioned sequentially and interleaved, and may be electrically connected to each other in a manner that generates sine and cosine signals with phase shifts.

[0077] A light-transmitting plate (especially a glass or plastic plate) is arranged above the light sensor 14 as an auxiliary element 17. This auxiliary element 17 can be used to protect the light sensor 14 on the one hand, and as a shielding accessory on the other. As a shielding accessory, the auxiliary element 17 can cover a part of the light sensor 14, so that the modulated light is only incident on a specific area of ​​the light sensor 14.

[0078] In order to accommodate the auxiliary element 17, Figure 1a and 2a In an exemplary embodiment, the molded housing 11 has a single recess 19. An auxiliary element 17, housed in the recess 19, covers two light sensors 14.

[0079] According to Figure 1b and Figure 2b In an exemplary embodiment, the mold housing 11 has two recesses 19, in which an auxiliary element 17 may be arranged. In this exemplary embodiment, each auxiliary element 17 covers a separate photosensor 14 assigned to it. The auxiliary element 17 may have the same height as the LED light source 2 and may preferably be in the range of 150 μm to 140 μm. The auxiliary element 17 generates the horizontal outer side 12 of the optoelectronic component 1, even though the mold housing itself has one or more recesses 19.

[0080] The optoelectronic component 1 can be designed as an SMD component that can be arranged in a space-saving manner via solder-capable contacts or wires on a printed circuit board or similar carrier element. To achieve this contact, the molded housing 11 has a connection surface 18 opposite to the LED light source 2 and the photosensor 14. Through the connection surface 18, a signal processing unit 15 can be integrated into a data exchange network. The signal processing unit 15 can process photosensor data, adjust the LED light source 2, and / or perform other signal processing procedures, such as an adjustment system for adjusting the position of the component equipped with the measuring dial 101.

[0081] Aside from the different numbers of recesses 19 in the molded housing 11, the two exemplary embodiments differ in that, according to Figure 1b and Figure 2bIn an exemplary embodiment, the light sensor 14 is arranged on both sides of the LED light source 2. The LED light source 2 is not located on one side of the light sensor 14, as in the first exemplary embodiment, but is arranged between the light sensors 14, particularly in the middle between them. For this purpose, the LED light source 2 is arranged in the mesh portion of the molded housing 11 between the two recesses 19. The optical position encoder 100 designed according to this exemplary embodiment is particularly suitable for implementing an absolute encoder indicating absolute position. The first light sensor 14 can be designed as the main sensor, while the second light sensor 14 can be designed as a non-metallic sensor. Alternatively, the first light sensor 14 can detect pseudo-random trajectories, and the second light sensor 14 can detect incremental trajectories with regular patterns for interpolation, to increase the resolution of the position sensors. Thus, the absolute position of the component can be detected via the measuring dial 101.

[0082] Figure 3 The area of ​​optoelectronic component 1 is shown, in which LED light source 2 is arranged in a molded housing 11. Components of optoelectronic component 1 disposed below LED light source 2 opposite to the emission direction, particularly the light sensor 14, carrier 13, or lead frame 16, are not visible; these components may be part of the component according to an embodiment of optoelectronic device 1. The cross-sectional structure of LED light source 2 is evident, in which semiconductor crystal 3 has a trapezoidal cross-section and base region 4.

[0083] The light-emitting surface 5 of the LED light source 2 is radially opposite to the emission direction of the LED light source 2, and has a contact surface 7. On one hand, the contact surface 7 is used for electrical contact with the LED light source 2; for this purpose, at least two electrodes 8 are arranged on the contact surface 7. The LED light source 2 and... Figure 3 Other parts of the electro-optic component 1, not shown, particularly the electrical and / or mechanical contact with the carrier 13, can be established via the contact surface 7 and the electrode 8. The LED light source 2 is constructed in a flip-chip manner, with its electrical contact occurring only from one side via the contact surface 7.

[0084] The light emitting surface 5 and the peripheral surface 6 of the LED light source 2 have a coating 9. This coating 9 is a chromium-gold alloy applied by physical vapor deposition. Although the coating 9 is shown as a broad line in the figure for better illustration, the coating 9 actually has a layer thickness of only 400 nm.

[0085] The peripheral surface 6 of the LED light source 2, located between the light-emitting surface 5 and the contact surface 7 and which also emits light, is coated with a coating 9 across its entire surface. The coating 9 also extends to the base region 4 of the semiconductor crystal 3, which also emits light. Alternatively, one or more peripheral surfaces 6 may be uncoated or partially coated. In the case of partial coating, the coating 9 will extend only in a single area of ​​the peripheral surface 6, for example, only in a portion of the peripheral surface 6 associated with the base region 6 or the trapezoidal region. At least the contact surface 7 surrounding the electrode 8 remains uncoated, having a full-surface and partial-surface coating of one or more peripheral surfaces 6 using the coating 9. This prevents short circuits that might otherwise occur between the electrodes 8.

[0086] Peripherally of the LED light source 2, a molded housing 11 is directly adjacent to the coating 9 of the LED light source 2. Although the molded housing 11 itself is substantially opaque within the wavelength range of the LED light source 2, the opaque and / or reflective coating 9 prevents scattered light from escaping through the coated areas of the peripheral surface 6 and the light-emitting surface 5. Since the scattered light cannot escape from the LED light source 2, it cannot reach the photosensor 14 and cannot disrupt the measurements used for position determination.

[0087] Due to the reflective properties of coating 9, the scattered light is reflected back into the interior of LED light source 2. Because of internal reflection, light can be reflected here inside LED light source 2 until it can exit through the decoated light exit window 10 of light exit surface 5. The reflected scattered light is thus emitted from LED light source 2 together with the light emitted directly through light exit window 10, which was initially not reflected inside LED light source 2, thereby increasing the light output of LED light source 2, i.e., the number of photons emitted per unit area, compared to uncoated LED light source 2.

[0088] Although the light-emitting surface 5 and the peripheral surface 6 have the same coating 9 in the illustrated exemplary embodiment, the peripheral surface 6 may be uncoated or have a different coating 9 than the light-emitting surface 5. Therefore, the composition and / or layer thickness of the coating 9 on one or more peripheral surfaces 6 may differ from that on the light-emitting surface 5. The coating 9 on the light-emitting surface 5 and / or the coating 9 on one or more peripheral surfaces 6 may be composed of multiple layers.

[0089] In addition to increasing light output and providing a smaller beam to improve the overall resolution of the optical position encoder 100, the decoated light exit window 10 can also compensate for the manufacturing tolerances of the semiconductor crystal 3 of the LED light source 2 and the positioning tolerances of the LED light source 2 in the injection mold before molding. The following will be based on... Figure 4 The steps shown in section 6 illustrate how to achieve this compensation and how to provide the decoated light exit window 10.

[0090] exist Figure 4 The image shows an initially uncoated LED light source 2. A semiconductor crystal 3 with its base region 4 can be seen. The contact surface 7 (not shown) has a rectangular shape that serves as the base surface of the LED light source 2 and measures 240 μm × 320 μm. The semiconductor crystal 3, particularly above the base region 4, is in the form of a truncated pyramid and has a light-emitting surface 5 on the side opposite to the diameter of the contact surface 7. In the circumferential direction, the LED light source 2 has a peripheral surface 6 that extends substantially transversely to the light-emitting surface 5 and the contact surface 7.

[0091] In the first method step, a coating 9 is applied to the LED light source 2, which remains uncoated up to this point. This coating step can be performed before molding and before or after mounting or fixing the LED light source onto the carrier 13, which is particularly advantageous if at least one of the peripheral surface 6 is also coated. This is because after molding, the partial surface 6 is hidden by the molding compound of the molded housing 11 and thus no longer has the coating 9. Conversely, the coating 9 on the light emitting surface 5 can also be applied after molding, or, like the coating 9 on the peripheral surface 6, can be performed before molding and before or after mounting or fixing the LED light source onto the carrier 13. To obtain the most uniform possible coating 9, it is sputtered onto the uncoated light emitting surface 5.

[0092] After sputtering, coating 9 is applied to the light-emitting surface 5, such as... Figure 5 As shown. In the intermediate step shown, coating 9 is used to cover the entire light-emitting surface 5. To simplify and accelerate the method steps below, it is also possible that the area of ​​the light-emitting surface 5 that later forms part of the light-emitting window 10 remains uncoated. For this purpose, a shielding element can be introduced into the sputtering beam during sputtering, or a shielding element can be applied to the light-emitting surface 5 before sputtering. In both cases, the shielding element or shielding element prevents material of coating 9 from depositing on the covered area of ​​the light-emitting surface 5. The shape of the shielding element or shielding element can be similar to that of the light-emitting window 10 to be achieved, but it can have a smaller size.

[0093] After the light emitting surface 5 is coated, a portion of the light emitting surface 5 is decoated to provide the light emitting window 10. This decoating can even be performed before molding. To compensate for tolerances in the relative position of the LED light source 2 with respect to the photosensor 14 and the common carrier 13, decoating in some areas is preferably performed after molding, particularly as the final step in the production of the optoelectronic component 1, in order to also compensate for tolerances in the positioning of the LED light source 2 with respect to the injection mold and / or the outer side and edges of the optoelectronic component 1. In this case, the already coated LED light source 2 can be embedded in the molded housing 11, or the coating 9 can be applied first after molding.

[0094] To decoat some areas of the light-emitting surface 5 and to provide the light-emitting window 10, the coating 9 is again removed from the light-emitting surface 5 in individual areas. This removal can be performed by machining, chemical etching, or laser bombardment. In particular, a laser can be used to achieve particularly precise and sharp boundaries for the light-emitting window 10. The shape and position of the light-emitting window 10 can be adapted during decoating to meet the corresponding requirements of the sensor 14, and thus to meet the corresponding requirements of the optoelectronic component 1.

[0095] therefore, Figure 6a The circular light exit window shown can be achieved by circular decoating. The circular light exit window 10 shown can also be achieved similarly through linear processing, such as laser scanning. Other geometries of the light exit window (e.g.) Figure 6b The rectangular light exit window shown is or Figure 6c The gap-shaped light exit window shown can also be achieved by decoating.

[0096] like Figure 6c As shown, using laser for decoating has proven particularly advantageous for obtaining the gap-shaped light exit window 10, because a thin gap with a short gap side length of 20 μm can be obtained in this way.

[0097] In addition to the simple geometry shown in Figure 6, other geometries of the light exit window 10 can also be achieved by removing the coating of the light exit surface 5 in some areas, which can be specifically composed of basic geometries such as rectangles, gaps, ellipses, and circles.

[0098] If a masking element or shielding member is used in the coating of the light emitting surface 5 such that the area of ​​the light emitting surface 5 associated with the light emitting window 10 is not coated, then the decoating of the light emitting window 10 thus occurs particularly in the edge region around the uncoated area, such that a clear boundary between the coated area and the uncoated area of ​​the light emitting window 10 on the light emitting surface 5 is achieved by a decoating method such as etching or laser action.

[0099] By using the above method and the optical position encoder 100, the emission characteristics of the LED light source 2 can be improved and the achievable resolution of the optical position encoder 100 can be increased.

[0100] List of reference numerals in the attached diagram:

[0101] 1. Optoelectronic components

[0102] 2 LED light sources

[0103] 3 Semiconductor crystals

[0104] 4 base regions

[0105] 5 light exit surface

[0106] 6 Partial Surfaces

[0107] 7 Contact Surface

[0108] 8 electrodes

[0109] 9. Coating

[0110] 10 light exit windows

[0111] 11. Molded shell

[0112] 12 External

[0113] 13 Carriers

[0114] 14. Light Sensor

[0115] 15 Signal Processing Unit

[0116] 16 Lead Frame

[0117] 17 Auxiliary Components

[0118] 18 Connecting surfaces

[0119] 19 concavity

[0120] 100 Optical Position Encoder

[0121] 101 Measurement Scale

[0122] 102 Code Channel Outside Area

[0123] 103 Regions with code tracks

Claims

1. A method for manufacturing an optical position encoder (100), the optical position encoder (100) having an optoelectronic component (1) and a measuring scale (101) illuminated by an LED light source (2) of the optoelectronic component (1), wherein the LED light source (2) is embedded in a molded housing (11) such that the light emitting surface (5) of the LED light source (2) is exposed to the outside. Its features are, The light emitting surface (5) is coated and decoated in some areas to provide a light emitting window (10), wherein light can be emitted in the form of a beam smaller than the entire light emitting surface (5) through the light emitting window (10) defined by the coating of the light emitting surface (5), and the emission characteristics of the LED light source (2) are defined by the size of the light emitting window (10), and the size of the light emitting window (10) is smaller than the size of the light emitting surface (5).

2. The method according to claim 1, characterized in that, The light-emitting surface (5) is coated with a coating (9) that is opaque and / or reflective.

3. The method according to claim 2, characterized in that, The light-emitting surface (5) is coated with a metal coating (9).

4. The method according to claim 1 or 2, characterized in that, At least one peripheral portion of the surface (6) of the LED light source (2) is coated.

5. The method according to claim 4, characterized in that, The at least one peripheral portion surface (6) and the light emitting surface (5) of the LED light source (2) are continuously coated.

6. The method according to claim 5, characterized in that, The light-emitting surface (5) is coated with a coating (9) that is different from the surface (6) of the at least one peripheral portion of the LED light source (2).

7. The method according to any one of claims 1, 2, 3, 5 or 6, characterized in that, The light-emitting surface (5) is coated by physical vapor deposition.

8. The method according to any one of claims 1, 2, 3, 5 or 6, characterized in that, The light-emitting surface (5) is decoated by etching, machining and / or laser.

9. The method according to any one of claims 1, 2, 3, 5 or 6, characterized in that, The light-emitting surface (5) is coated before or after molding.

10. The method according to any one of claims 1, 2, 3, 5 or 6, characterized in that, The light-emitting surface (5) is decoated in some areas before or after molding.

11. An optical position encoder having an optoelectronic component (1) having a molded housing (11), an LED light source (2) being arranged in the molded housing (11) such that the light emitting surface (5) of the LED light source (2) is exposed to the outside, and the optical position encoder having a measuring scale (101) illuminated by the LED light source (2) of the optoelectronic component (1). Its features are, The light emitting surface (5) is coated and has an uncoated light emitting window (10), wherein light can be emitted in the form of a beam smaller than the entire light emitting surface (5) through the light emitting window (10) defined by the coating of the light emitting surface (5), and the emission characteristics of the LED light source (2) are defined by the size of the light emitting window (10), and the size of the light emitting window (10) is smaller than the size of the light emitting surface (5).

12. The optical position encoder according to claim 11, characterized in that, The side of the LED light source (2) that is away from the light emitting surface (5) is the contact side (7) of the LED light source (2).

13. The optical position encoder according to claim 11 or 12, characterized in that, At least one optical sensor (14) is arranged in the molded housing (11).

14. The optical position encoder according to claim 11 or 12, characterized in that, The LED light source (2) and / or the light sensor (14) are arranged on the carrier (13).

15. The optical position encoder according to claim 11 or 12, characterized in that, The LED light source (2) is arranged on a carrier (13) including a light sensor (14) and / or a signal processing unit (15).

Images