DE102020111130A1 - Optoelectronic system and optoelectronic sensor - Google Patents

Abstract

Optoelectronic system (1) with at least one circuit card (2) with several light transmitters (3) and / or several light receivers (4), which are arranged at least in a row and with at least one one-piece optical component (5) made of plastic for the several light transmitters ( 3) and / or light receiver (4), with at least one lens (6) being provided in the optical component (5) per light transmitter (3) and / or light receiver (4), the optical component (5) mechanically closing at least at one point the printed circuit board (2) is fixed, the printed circuit board (2) having a first positive thermal coefficient of linear expansion and the optical component (5) having a second positive thermal coefficient of linear expansion, the second positive thermal coefficient of linear expansion being greater than the first positive thermal coefficient of linear expansion, the Optical component (5) particles (7) made of a secondary material (8) are mixed in, which are made of a different material s ind as a primary material of the optical component (5), the secondary material (8) of the particles (7) having a smaller thermal coefficient of linear expansion than the second thermal coefficient of linear expansion of the primary material of the optical component, so that the resulting second positive linear expansion coefficient of the optical component (5) is reduced .

Description

The present invention relates to an optoelectronic system according to the preamble of claim 1 and an optoelectronic sensor according to the preamble of claim 13.

The problem with such optoelectronic systems or optoelectronic sensors is that, due to the expansion coefficients of the materials used, optics expand differently than materials used on a printed circuit board on which the light transmitters and / or light receivers are arranged in the event of temperature changes.

Thermal expansion (also called thermal expansion) is understood to mean the change in the geometric dimensions (length, surface area, volume) of a body, caused by a change in its temperature.

The coefficient of expansion or coefficient of thermal expansion, also known colloquially as the expansion factor, is a characteristic value that describes the behavior of a substance with regard to changes in its dimensions when there are changes in temperature, which is why it is often called the coefficient of thermal expansion. The effect responsible for this is thermal expansion. The thermal expansion depends on the material used, so it is a material-specific or substance-specific material constant. Since the thermal expansion of many materials does not take place uniformly over all temperature ranges, the coefficient of thermal expansion itself is also temperature-dependent and is therefore specified for a certain reference temperature or a certain temperature range.

In the present case, the coefficient of thermal expansion (also the coefficient of linear thermal expansion) is relevant.

For example, polycarbonate (PC) has a coefficient of thermal expansion of approx. 70 ppm / K. Polyamide (PA) has a thermal coefficient of linear expansion of approx. 110 ppm / K.

For example, electrical circuit boards, which are for example non-conductive material made of FR-4, expand due to an increase in temperature. This also shifts the position of components that are assembled on the circuit board. A displacement of optoelectronic components in relation to other components such as lenses can have a very detrimental effect on the behavior and availability of a sensor.

FR-4 or FR4 denotes a class of flame-retardant and flame-retardant composite materials, consisting of epoxy resin and glass fiber fabric. The abbreviation FR stands for English flame retardant (dt. Flame retardant) and meets the requirements of UL94V-0. FR-4 is available on the market in different versions. To improve the flame retardancy, chemical substances such as polybrominated diphenyl ethers based on bromine are added to the composite material; this additive is omitted in the halogen-free variant. The FR-4 composite material was specified by the National Electrical Manufacturers Association (NEMA) in the properties in the NEMA LI1 specification.

Epoxy resins (EP resins) are synthetic resins that carry epoxy groups. They are curable resins (reaction resins) that can be converted into a thermosetting plastic with a hardener and, if necessary, other additives. The epoxy resins are polyethers with usually two terminal epoxy groups. The hardening agents are reaction partners and together with the resin form the macromolecular plastic.

The thermosets produced by crosslinking have good mechanical properties as well as good temperature and chemical resistance and are considered to be high-quality plastics. The composite materials for the circuit boards are then formed in conjunction with the fiberglass fabric. FR4 has, for example, a thermal coefficient of linear expansion of 12 to 17 ppm / K. The thermal expansion coefficients also differ depending on the direction.

One object of the invention is to provide an optoelectronic system or an optoelectronic sensor which is more available in the event of temperature changes and can be manufactured more cheaply.

The object is achieved according to claim 1 by an optoelectronic system with at least one printed circuit board with several light transmitters and / or several light receivers which are arranged at least in a row and with at least one one-piece optical component made of plastic for the several light transmitters and / or light receivers, in which Optics component per light transmitter and / or per light receiver at least one lens is provided, the optics component being mechanically fixed at least at one point to the circuit board, the circuit board having a first positive thermal coefficient of linear expansion and the optical component having a second positive thermal coefficient of linear expansion, the second positive thermal coefficient of linear expansion is greater than the first positive thermal Coefficient of linear expansion, the optical component being admixed with particles made of a secondary material that are made of a different material than a primary material of the optical component, the secondary material of the particles having a smaller thermal coefficient of linear expansion than the second thermal coefficient of linear expansion of the primary material of the optical component, so that the resulting second positive The coefficient of linear expansion of the optical component is reduced.

The object is further achieved with an optoelectronic sensor with an optical system according to claim 13.

The secondary material of the particles has a positive or negative thermal coefficient of linear expansion, so that the resulting second positive coefficient of linear expansion of the optical component is reduced. In the case of a positive coefficient of thermal expansion of the secondary material, the coefficient of thermal expansion of the secondary material is smaller than the second coefficient of thermal expansion of the primary material of the optical component.

According to the invention, the first coefficient of thermal expansion of the optical component is reduced by the added particles. The optical component consists of at least a portion of primary material and a portion of secondary material. As a result, the different linear expansion of the optical component and the printed circuit board is minimized in the event of temperature fluctuations. As a result, the optical axes that run from the light emitters or from the light receivers through the center of the respectively assigned lens are each more directionally stable within a required tolerance range. For example, mutually parallel light axes remain almost parallel to each other even with temperature fluctuations, since the circuit board and the optical component expand or contract to the same extent, depending on the temperature change.

The optical component and the printed circuit board are referenced to one another in that the optical component is mechanically fixed at least at one point to the printed circuit board. For example, the circuit board and the optical component are connected to one another at a single end of an elongated shape. However, the optical component and the printed circuit board can be connected to one another at any point.

For example, the first coefficient of thermal expansion of the circuit board is less than 17 ppm / K.

The resulting second positive coefficient of linear expansion of the optical component is, for example, less than 40 ppm / K. The resulting second positive coefficient of linear expansion of the optical component is preferably less than 20 ppm / K.

The difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion is particularly preferably less than 5 ppm / K, particularly preferably less than 2 ppm / K.

The optical component has, for example, a proportion of 5 to 30 percent by volume of secondary material. In particular, the optical component has a proportion of 5 to 20 percent by volume and in particular a proportion of 5 to 10 percent by volume of secondary material.

In a further development of the invention, the particles for the secondary material are glass particles and / or crystal particles. These materials each have negative coefficients of thermal expansion.

In a further development of the invention, the particles are smaller than 50 nm in diameter.

Particles with a diameter of less than 50 nm lead to a particularly effective effect in reducing the expansion of the optical component. The optical properties of the optical component are hardly affected by the very small particles. This means that homogeneous materials can be produced for the optical component. Glass particles and / or crystal particles are also advantageously transparent, so that the optical properties of the optical component are hardly impaired by the secondary materials.

In a further development of the invention, the lenses are plano-convex, biconvex or convex plan.

Such lenses are converging lenses, the received light being bundled onto the light receiver and / or transmitted light from a light transmitter leading to a directed beam.

A converging lens, also called a collimator lens, convex lens or positive lens, is a cast lens with positive refractive power, for example. Light incident in parallel is collected in its focal plane. Specifically, light emitted parallel to the optical axis is focused at the focal point.

With the lens shapes plano-convex, biconvex or convex-plane, for example, only a single lens is necessary per light transmitter or per light receiver.

In a further development of the invention, the surface shape of the lens is spherical, aspherical or a free-form surface.

In contrast to a spherical lens, an aspherical lens is a lens with at least one refractive surface that deviates from a spherical or plane shape. Due to the largely freely shapable surface, imaging errors can be avoided or reduced, which are unavoidable with spherical lenses. In particular, you can correct the spherical aberration.

By means of a free-form surface, the lens can be adapted very specifically to the optical requirements and the required geometry.

In a further development of the invention, the light transmitters and / or the light receivers are arranged in a matrix with several rows and several columns.

In this way, flat lighting can be implemented with light transmitters and flat monitoring areas can be implemented with light receivers.

Any two-dimensional geometry can be formed via the selected number of several rows and several columns and the distances between the respective light transmitters or light receivers.

In a further development of the invention, an elongated at least two-part housing is provided, the two-part housing having at least two housing parts, the first housing part having the optical component and the second housing part having the printed circuit board. The circuit card is inserted into the first housing.

The housing parts are each open along one long side. As a result, necessary components, namely the optical component and the printed circuit board, can be inserted directly over the respective open long side. This simplifies assembly.

The two housing parts each have similar or almost identical positive coefficients of thermal expansion.

In a further development of the invention, the optical component is integrated in the first housing part, so that the first housing part and the optical component are a one-piece component. The first housing part is transparent to the light used. The one-piece first housing part with the integrated optical component eliminates the need for assembly steps. Furthermore, the first housing part and the optical component are already aligned with one another in terms of production technology.

The first housing part with the integrated optical component can be made from two different materials or materials or from a single material or material.

In a further development of the invention, the first housing part and the second housing part are connected by means of mechanical clip closures, by means of an adhesive connection, by means of an ultrasonic weld seam or by means of a laser weld seam.

Clip closures have the advantage that they can be installed very easily without additional devices. The clip closures are integrated, for example, in the respective housing parts.

A tight connection between the housing parts can easily be established by means of an adhesive connection, ultrasonic weld seam or laser weld seam. In this way, a tight housing can easily be produced.

In a further development of the invention, the first housing part is produced as a plastic injection-molded part by means of a plastic injection molding process. Using plastic injection molding processes, precise lens shapes with high quality can also be manufactured inexpensively. With a plastic injection molding process, high-quality parts can be produced, for example with a limited length, for example less than 500 mm. These parts can be connected to form a longer housing part. Another plastic injection process is 'Exjection', with which components <3 m long can be produced in one step.

The first housing part and the optical component can be produced with different materials in a two-component injection molding process. However, the first housing part and the optical component can also be produced from a single material in a one-component injection molding process.

In a further development of the invention, the second housing part is produced by means of an extrusion process. The mechanical accuracy requirements for the second housing part are lower than for the first housing part, since the second housing part does not have any optical components such as lenses. As a result, the second housing part can be produced more cheaply by means of an extrusion process. The only requirement here is that the cross-section has a uniform contour.

In a further development of the invention, the second housing part has a larger volume than the first housing part. Since the second housing part is cheaper to manufacture than the first housing part and the materials used for the second housing part are cheaper than for the first housing part, it is provided that the second housing part has a larger volume than the first housing part, whereby the costs for the overall housing are reduced.

According to the invention, an optoelectronic sensor is provided with an optical system.

For example, a first housing with the light transmitters and a second housing with the light receivers forms an optoelectronic sensor, such as a light barrier, a reflection light barrier, a light sensor, a camera system with lighting, or, for example, a solid state laser scanner with a plurality of light transmitters and light receivers, whereby no moving parts such as a rotating deflector are provided.

In a further development of the invention, the optoelectronic sensor is a light grid.

Light grids comprise a multiplicity of light transmitters or transmitting elements and assigned light receivers or receiving elements, so that in each case a pair of a transmitting element and a receiving element forms a light barrier that detects whether the light beam spanned between the transmitting element and the receiving element is or is interrupted by an object not. The transmitting elements and receiving elements are each combined in a transmitting unit and a receiving unit, which are mounted opposite one another.

There are also light grids in which the light emitter and light receiver are housed in two opposing, mixed sending and receiving units. Furthermore, reflective light grids are known in which transmitting and receiving units are mounted on one side of a monitored area and a retroreflector on the opposite side.

An important field of application for light grids is automation technology for measuring objects and objects or for dimensional control, but also for object detection and, in particular, for object counting.

Another important field of application for light grids is safety technology. The parallel light beams serve as a kind of virtual wall, and if an object is interrupted, for example, a source of danger is secured. In automation technology, light grids are used to measure the expansion of objects based on the number of interrupted beams. For example, the height of objects moving on a conveyor belt can be determined in this way, to be precise with an accuracy that is given by the spacing of the light beams.

The idea of a light beam from the individual sending elements is idealized. In fact, depending on the opening angles of the beam-shaping optics, transmit and receive lobes are created. Given the usual distances between the transmitting unit and the receiving unit, it is often impossible to avoid a receiving element receiving transmitted light not only from the assigned transmitting element but also from its neighbors due to the transmission beam divergence. In order to avoid incorrect evaluations, the transmission elements are therefore activated cyclically. In this case, individual light pulses or packets are sent out one after the other from each transmission element, and only the associated receiving element is activated for a certain time window in order to determine whether there is an object in the respective channel.

• 1 bis 4 jeweils ein optoelektronisches System;
• 5 ein zweiteiliges Gehäuse;
• 6 ein erstes Gehäuseteil;
• 7 einen optoelektronischen Sensor;
• 8 ein optoelektronisches System nach dem Stand der Technik.

The invention is explained below also with regard to further advantages and features with reference to the accompanying drawings using exemplary embodiments. The figures in the drawing show in:

• 1 until 4th one optoelectronic system each;
• 5 a two-part housing;
• 6th a first housing part;
• 7th an optoelectronic sensor;
• 8th a state-of-the-art optoelectronic system.

In the following figures, identical parts are provided with identical reference symbols.

8th shows an optoelectronic system according to the prior art. In the case of such optoelectronic systems or optoelectronic sensors, it is the case that optics 16 in the event of temperature changes due to the expansion coefficients of the materials used, it expands differently than the materials used in a printed circuit board 2 on which light transmitter 3 and / or light receivers 4th are arranged. This is the optical axes 17th according to 8th are no longer aligned parallel to one another, but are disadvantageously each at an acute angle to one another.

1 shows an optoelectronic system 1 according to the invention with a printed circuit board 2 with several light transmitters 3 and / or several light receivers 4th , which are arranged at least in a row and with at least one integral optical component 5 made of plastic for the multiple light transmitters 3 and / or light receivers 4th , wherein in the optical component 5 per light transmitter 3 and / or per Light receiver 4th at least one lens 6th is provided, the optical component 5 mechanically at least at one point to the circuit board 2 is fixed, with the circuit board 2 has a first positive coefficient of thermal expansion and the optical component 5 has a second positive thermal coefficient of linear expansion, wherein the second positive thermal coefficient of linear expansion is greater than the first positive thermal coefficient of linear expansion, wherein the optical component 5 Particles 7th from a secondary material 8th are added that are made of a different material than the optical component 5 , the secondary material 8th the particle 7th has a negative thermal coefficient of linear expansion, so that the resulting second positive coefficient of linear expansion of the optical component 5 is reduced in size.

According to 1 is the first coefficient of thermal expansion of the optical component 5 due to the added particles 7th reduced. The optical component 5 consists of at least a portion of primary material 9 and a proportion of secondary material 8th . This means that the length expansion of the optical component is different 5 and the circuit board 2 minimized in the event of temperature fluctuations. This is the optical axes 17th by the light emitters 3 or from the light receivers 4th each through the center of the respectively assigned lens 6th run, each directionally stable in a required tolerance range. For example, light axes that are parallel to one another remain almost parallel to one another even in the event of temperature fluctuations, since the circuit board is 2 and the optical component 5 expand or contract to the same extent, depending on the temperature change.

The optical component 5 and the circuit board 2 are referenced to one another by the optical component 5 mechanically at least at one point to the circuit board 2 is fixed. For example, the circuit board 2 and the optical component 5 interconnected at a single end of an elongated shape. However, the optical component 5 and the circuit board 2 connected to each other at any point.

For example, the first coefficient of thermal expansion is the circuit board 2 less than 17 ppm / K. The resulting second positive coefficient of linear expansion of the optical component 5 is according to 1 for example less than 40 ppm / K, or less than 20 ppm / K.

The optical component 5 has, for example, a proportion of 5 to 20 percent by volume of secondary material 8th on, being 95 to 80 percent by volume due to the primary material 9 are formed.

According to 1 are the particles 7th for the secondary material 8th Glass particles and / or crystal particles. These materials each have negative coefficients of thermal expansion.

For example, the particles are 7th less than 50 nm in diameter.

Because of the very small particles 7th are the optical properties of the optical component 5 hardly affected. This allows homogeneous materials for the optical component 5 getting produced. Glass particles and / or crystal particles are also advantageously transparent, so that the optical properties of the optical component 5 are hardly affected by the secondary materials 8th .

According to 1 are the lenses 6th plano-convex or convex plan.

According to 1 are the lenses 6th are converging lenses, whereby received light on the light receiver 4th is bundled and / or transmitted light from a light transmitter 3 leads to a directed beam.

With the lens shape according to 1 is only a single lens, for example 6th per light transmitter 3 or per light receiver 4th necessary.

According to 1 is the surface shape of the lens 6th spherical or aspherical.

According to an embodiment not shown, the light transmitters and / or the light receivers are arranged in a matrix with a plurality of rows and a plurality of columns.

2 shows another embodiment according to the invention similar to FIG 1 . 2 shows an optoelectronic system 1 with a circuit board 2 with several light transmitters 3 and / or several light receivers 4th , which are arranged at least in a row and with at least one integral optical component 5 made of plastic for the multiple light transmitters 3 and / or light receivers 4th , wherein in the optical component 5 per light transmitter 3 and / or per light receiver 4th at least one lens 6th is provided, the optical component 5 mechanically at least in two places to the circuit board 2 is fixed

According to 3 is an elongated at least two-part housing 11 provided, the two-part housing 11 at least two housing parts 12th and 13th having, wherein the first housing part 12th the optical component 5 and the second housing part 13th the circuit board 2 having.

The housing parts 12th and 13th are each open along one long side. This allows necessary components, namely at least the optical component 5 and the circuit board 2 can be inserted directly over the respective open long side. This simplifies assembly.

The two housing parts 12th and 13th each have similar or almost identical positive thermal expansion coefficients.

According to 3 is in the first housing part 12th the optical component 5 integrated so that the first housing part 12th and the optical component 5 is a one-piece component. The first housing part 12th is transparent to the light used. Through the one-piece first housing part 12th with the integrated optical component 5 assembly steps are no longer necessary. Furthermore, the first housing part 12th and the optical component 5 already aligned with one another in terms of production technology.

The first housing part 12th with the integrated optical component 5 can be made from two different materials or from a single material or material.

According to 4th are the first part of the housing 12th and the second housing part 13th connected by means of mechanical clip fasteners, by means of an adhesive connection, by means of an ultrasonic weld seam or by means of a laser weld seam.

The clip closures are integrated, for example, in the respective housing parts. A tight connection between the housing parts can easily be achieved by means of an adhesive connection, ultrasonic weld seam or laser weld seam 12th and 13th getting produced.

According to 3 is the first part of the housing 12th manufactured as a plastic injection-molded part using a plastic injection molding process. The first housing part 12th and the optical component 5 can be manufactured in a two-component injection molding process with different materials. However, the first housing part 12th and the optical component 5 can also be manufactured from a single material in a one-component injection molding process.

According to 3 is the second part of the housing 13th produced by means of an extrusion process. The mechanical accuracy requirements for the second housing part 13th are less than on the first housing part 12th , because the second housing part 13th has no optical components such as lenses. The only requirement here is that the cross-section has a uniform contour.

According to 3 has the second housing part 13th for example, a larger volume than the first housing part 12th .

5 shows a further embodiment of a two-part housing 11 in the assembled state in cross section. The second part of the housing 13th further has fastening receptacles.

6th shows a pre-assembly consisting of the printed circuit board 2 with the light transmitters 3 and / or the light receivers 4th and a tube 18th , namely a light trap and the first housing part 12th with the lenses 6th .

According to 7th is an optoelectronic sensor 14th provided with an optical system 1 .

According to 7th a first housing with the light transmitters and a second housing with the light receivers form an optoelectronic sensor 14th such as a light barrier with several optical axes or light beams.

According to 7th is the optoelectronic sensor 14th a light grid 15th . Light curtain 15th include a variety of light emitters 3 or transmitting elements and associated light receivers 4th or receiving elements, so that a pair of a transmitting element and a receiving element forms a light barrier that detects whether the light beam spanned between the transmitting element and the receiving element is interrupted by an object or not. The transmitting elements and receiving elements are each combined in a transmitting unit and a receiving unit, which are mounted opposite one another.

List of reference symbols

1

Optoelectronic system

2

Circuit board

3

Light transmitter

4th

Light receiver

5

Optical component

6th

lens

7th

Particles

8th

Secondary material

9

Primary material

11

two-part housing

12th

first housing part

13th

second housing part

14th

optoelectronic sensor

15th

Light curtain

16

optics

17th

optical axis

18th

Tube

Claims (14)

Optoelectronic system (1) with at least one circuit card (2) with several light transmitters (3) and / or several light receivers (4), which are arranged at least in a row and with at least one one-piece optical component (5) made of plastic for the several light transmitters ( 3) and / or light receiver (4), with at least one lens (6) being provided in the optical component (5) per light transmitter (3) and / or light receiver (4), the optical component (5) mechanically closing at least at one point the printed circuit board (2) is fixed, the printed circuit board (2) having a first positive thermal coefficient of linear expansion and the optical component (5) having a second positive thermal coefficient of linear expansion, the second positive thermal coefficient of linear expansion being greater than the first positive thermal coefficient of linear expansion, characterized that the optical component (5) particles (7) made of a secondary material (8) are admixed with are a different material than a primary material of the optical component (5), wherein the secondary material (8) of the particles (7) has a smaller thermal coefficient of linear expansion than the second thermal coefficient of linear expansion of the primary material of the optical component, so that the resulting second positive linear expansion coefficient of the optical component (5 ) is reduced. Optoelectronic system according to Claim 1 , characterized in that the particles (7) are glass particles and / or crystal particles. Optoelectronic system according to at least one of the preceding claims, characterized in that the particles (7) are smaller than 50 nm in diameter. Optoelectronic system according to at least one of the preceding claims, characterized in that the lens (6) is plano-convex, biconvex or convex plan. Optoelectronic system according to at least one of the preceding claims, characterized in that the surface shape of the lens (6) is spherical, aspherical or a free-form surface. Optoelectronic system according to at least one of the preceding claims, characterized in that the light transmitters (3) and / or the light receivers (4) are arranged in a matrix with several rows and several columns. Optical system according to at least one of the preceding claims, characterized in that an elongated at least two-part housing (11) is provided, the two-part housing (11) having at least two housing parts (12, 13), the first housing part (12) being the optical component (5) and the second housing part (13) has the printed circuit card (2). Optical system according to at least one of the preceding claims, characterized in that the optical component is integrated in the first housing part (12), so that the first housing part (12) and the optical component (5) are a one-piece component. Optical system according to at least one of the preceding claims, characterized in that the first housing part (12) and the second housing part (13) are connected by means of mechanical clip closures, by means of an adhesive connection, by means of an ultrasonic weld seam or by means of a laser weld seam. Optical system according to at least one of the preceding claims, characterized in that the first housing part (12) is produced as a plastic injection-molded part by means of a plastic injection molding process. Optical system according to at least one of the preceding claims, characterized in that the second housing part (13) is produced by means of an extrusion process. Optical system according to at least one of the preceding claims, characterized in that the second housing part (13) has a larger volume than the first housing part (12). Optolelectronic sensor (14) with an optoelectronic system (1) according to at least one of the aforementioned Claims 1 until 12th . Optolelectronic sensor (14) according to Claim 13 , characterized in that the optoelectronic sensor (14) is a light grid (15).

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