DE102019200664B3 - Sensor arrangement and method for measuring a measurement object - Google Patents

Abstract

A sensor arrangement for measuring a measurement object is disclosed, which comprises a light source (2), a detector lens (3) and a sensor surface (4). The light source (2) produces an illuminating light beam (8, 8 ', 8 ") emitted by the sensor arrangement (1, 1'), the detector lens (3) emitting a detection light beam (10, 10 ', 10") in the direction of Images sensor surface (4), the illuminating light beam (8, 8 ', 8 "), detector lens (3) and sensor surface (4) being arranged relative to one another such that a direction of propagation of the illuminating light beam (8, 8', 8") Cut a defined object plane (11), a lens plane (13) arranged perpendicular to an optical axis of the detector lens (3) and a detector plane (12) defined by the sensor surface (4) in an intersection line (14). The sensor arrangement further comprises a deflecting mirror (5) with a changeable direction of reflection, the deflecting mirror (5) being arranged optically on the cutting line (14) and in a beam path of a light beam generated by the light source (2), so that by changing the direction of reflection of the deflecting mirror ( 5) an illuminating light beam (8, 8 ', 8 ") with a variable direction of propagation and thus an object plane with a variable position is created.

Description

The invention relates to a sensor arrangement for measuring a measurement object, with a light source, a detector lens and a sensor surface, the light source producing an illuminating light beam emitted by the sensor arrangement, the detector lens imaging a detection light beam in the direction of the sensor surface, the illuminating light beam, detector lens and sensor surface being relative in this way are arranged relative to one another such that an object plane defined by a direction of propagation of the illuminating light beam, a lens plane arranged perpendicular to an optical axis of the detector lens and a detector plane defined by the sensor surface intersect in an intersection line. The invention further relates to a corresponding system and a corresponding method.

Sensor arrangements for measuring a measurement object, in particular for generating high-resolution three-dimensional images of measurement objects, are becoming increasingly important. For example, in quality assurance, the three-dimensional quality of manufactured workpieces must be monitored with regard to maintaining a specified flatness, a gap dimension, a specified profile profile or a specific surface quality. The recording is often carried out in ongoing production processes, so that it is not uncommon for time to be kept to a tight schedule. Optical measuring systems are therefore preferred because they offer clear advantages due to the contactless measuring principle, the high resolution that can be achieved in principle and the high measuring speed. Such optical measuring systems are available as point, line or area sensors. Point sensors measure a single point on the surface of the measurement object. With line sensors, measured values are generated along an illumination line or curve. Area sensors generate measured values in two directions simultaneously, for example within a rectangular area. The achievable resolution of point or line sensors is significantly higher than that of area sensors, so that these sensors are often combined with external actuators, such as industrial robots, coordinate measuring machines or linear tables. In the case of such mechanical scanning systems, the achievable measuring speed is significantly dependent on the performance of the external actuator.

Such a measuring device is for example in the US 9,989,356 B2 disclosed. A laser light source generates a laser line that is directed onto the measurement object.

A detector unit detects the reflected portions of the laser line and determines the profile of the measurement object from the illuminated detector elements. The illuminating light beam, detector lens and detector are arranged relative to one another in such a way that the Scheimpflug condition is fulfilled. In one exemplary embodiment, the beam expander is replaced by a mirror and a galvanomirror 1728, the galvanomirror being moved such that the laser beam swings back and forth within a predefined angular range and a laser line is thereby generated. The laser light source and the detector are arranged in a measuring head that can be moved in the three spatial directions.

US 2010/0149550 A1 discloses a method for contactless scanning of a three-dimensional object. A laser generates an illuminating laser beam that is directed onto the measurement object. A detector detects the portion of the illuminating laser beam reflected on the measurement object, the angle β between the illuminating laser beam and the detection beam should be as small as possible. The measurement object is rotated around its axis and shifted in height during the scanning process. The measurement object can also be tilted. In one embodiment, the illuminating laser beam and the detection beam are deflected by means of a mirror.

From the US 9,255,792 B2 a measuring arrangement is known with which the shape of a measuring object can be measured. A laser generates an illuminating light beam that is directed onto the measurement object. A detector measures a portion of the illuminating light beam that is reflected on the measurement object. Various shapes of the housing of the measuring arrangement are proposed for the measurement of reflecting measurement objects, by means of which multiple reflections of the illuminating light beam into the detector are made possible.

To improve the measuring speed, optically scanning sensors are known, in which the optical path of the sensor is influenced in order to generate an optical scanning movement. Since the mass to be moved is significantly lower with these systems than with mechanical scanning systems, higher scanning speeds are possible. In addition, very compact units can be implemented. Such optical scanning systems are known as confocal sensors. Basic ideas for triangulation sensors have also been proposed.

Laser triangulation sensors are the most common optical sensors for dimension measurement and quality control tasks and are available as point or line sensors. They achieve both high resolutions as well large measuring ranges. Such sensors, as exemplified in 1 typically consist of a laser diode ( A ) (including associated beam shaping optics), a lens ( B ) (or a set of lenses) and a detector ( C. ). The laser beam generated by the laser diode and influenced by the beam shaping optics leaves the triangulation sensor as an illuminating light beam and strikes a measurement object ( D ). In 1 is the measurement object ( D ) with a solid, dashed and dotted line at different distances from the triangulation sensor. Part of the illuminating light beam is reflected on the surface of the measurement object ( D ) diffusely reflected and used as a detection light beam. The detection light beam is transmitted through the lens ( B ) on the detector ( C. ) projected. The result is that the lens ( B ) for different distances of the measurement object from the triangulation sensor at different distances to the lens ( B ) a sharp image on the detector ( C. ) generated. So that as many measuring points as possible on an object level ( E ) sharp on the detector ( C. ), the so-called Scheimpflug condition must be met, which is an extension of the lens equation to describe the imaging behavior of thin lenses. To meet the Scheimpflug condition, the individual components of the triangulation sensor are arranged in such a way that the object plane ( E ), a lens plane ( F ) and a detector level ( G ) in a single line ( H ) to cut. The object level ( E ) defined by the direction in which the illuminating light beam leaves the triangulation sensor. The lens plane ( E ) is defined by a plane perpendicular to the optical axis of the lens and the detector plane ( G ) through a plane in which the sensor surface of the detector ( C. ) lies. In 1 the planes are drawn as straight lines, whereby the planes ( E , F , G ) each extend perpendicular to the plane of the drawing.

If such a sensor is to be used to create an optical scanning system that can produce a three-dimensional image, the optical path must be redirected. Such optical scanning systems are, for example, from the article "Optical scanning of laser line sensors for 3D imaging" by J . Schlarp, E . Csencsics and G . Schitter, which was published in Applied Optics, Volume 57, No. 18, pages 5242 to 5248 in 2018. The systems disclosed there are in the attached 2nd and 3rd and offer the decisive advantage that conventional triangulation sensors can be used.

According to the system 2nd directs a fixed mirror ( I. ) the illuminating light beam on a 2-axis tilting mirror ( J ; also known as a tip / tilt mirror), which then pivots the illuminating light beam and enables different illuminating directions. The detection light beam enters the detector without an additional mirror. Since the diameter of the laser beam (with a point sensor) or the width of the laser line (with a line sensor) is relatively small, a 2-axis tilting mirror with a relatively small aperture can be used, which enables high scanning speeds. However, the scanning system does not meet the Scheimpflug condition at every measuring point, which leads to additional measurement errors.

According to the system 3rd is a 2-axis tilting mirror ( K ) arranged at a relatively large distance from the triangulation sensor and deflects both the illuminating light beam and the detection light beam. As a result, this scanning system fulfills the Scheimpflug condition. In this embodiment, however, the lateral measuring area corresponds to the aperture of the deflecting mirror. If large lateral scanning ranges are required, a correspondingly large mirror is required, which in turn affects the scanning speed and the cost of the system.

DE 10 2014 207 896 A1 shows a laser scanner for detecting the three-dimensional shape of an object. A laser beam is moved in a scanning movement over the measurement object by means of a mirror and the reflected light beam is detected and evaluated by a specially designed detection device.

US 2012/0307260 A1 discloses a method and system for measuring an object using structured light. From the deformation of the structured light on the surface of the measurement object, conclusions are drawn about its shape. Micromirror arrays are used both in the illumination beam path and in the detection beam path.

US 2002/0180987 A1 deals with the acquisition of the profile of a measurement object. A laser generates an illuminating light beam that is directed onto the measurement object. A detector measures a portion of the illuminating light beam that is reflected on the measurement object. A movable mirror directs the illuminating light beam and the detection light beam.

The present invention is based on the object of designing and developing a sensor arrangement, a system and a method of the type mentioned at the outset in such a way that even when the direction of propagation of the illuminating light beam is changed, measurement of a measurement object, in particular a three-dimensional measurement, with high measurement accuracy and high measurement speed is possible.

According to the invention, the above object is achieved by the features of claim 1. Thereafter, the sensor arrangement in question is characterized by a deflecting mirror with a variable direction of reflection, the deflecting mirror being arranged optically on the cutting line and in a beam path of a light beam generated by the light source, so that by changing the direction of reflection of the deflecting mirror, an illuminating light beam with a variable direction of propagation and thus one Object level with changeable position is created.

With regard to the system, the above object is achieved by the features of claim 16. The system in question then comprises a sensor arrangement according to the invention and a measurement object, the illuminating light beam being directed onto a surface of the measurement object and the detection light beam being produced by diffuse reflection of the illuminating light beam on the surface of the measurement object.

• Erzeugen eines Beleuchtungslichtstrahls und Lenken des Beleuchtungslichtstrahls auf eine Oberfläche des Messobjekts,
• Detektieren eines Detektionslichtstrahls mittels einer Sensorfläche der Sensoranordnung, wobei der Detektionslichtstrahl durch diffuse Reflektion des Beleuchtungslichtstrahls an der Oberfläche des Messobjekts hervorgerufen wird,
• Erzeugen eines Messwerts aus einer Position einer Auftreffstelle des Detektionslichtstrahls auf der Sensorfläche und
• Bestimmen eines Abstandswerts eines durch den Beleuchtungslichtstrahl beleuchteten Punkts der Oberfläche des Messobjekts von der Sensoranordnung.

With regard to the method, the above object is achieved by the features of claim 17. A sensor arrangement according to the invention is then used in the method in question and the method comprises the steps:

• Generating an illuminating light beam and directing the illuminating light beam onto a surface of the measurement object,
• Detecting a detection light beam by means of a sensor surface of the sensor arrangement, the detection light beam being caused by diffuse reflection of the illuminating light beam on the surface of the measurement object,
• Generating a measured value from a position of an impact point of the detection light beam on the sensor surface and
• Determining a distance value of a point of the surface of the measurement object illuminated by the illuminating light beam from the sensor arrangement.

To change the radiation direction when scanning a measurement object, it is not absolutely necessary to influence both the illuminating and the detection light beam via a deflecting mirror in order to comply with the Scheimpflug condition. Rather, it is sufficient if only the direction of propagation of the illuminating light beam is influenced by means of suitable means. These means act in such a way that all (or at least some of) the illuminating light beams emitted by the sensor arrangement intersect at a common point, this common point being arranged optically on the intersection line of an object plane, a detector plane and a lens plane. This can be achieved by means of a mechanism with which the entire lighting unit is pivoted. However, these means can also “only” affect the light beam generated by the light source. For this purpose, corresponding optical means can be arranged in the beam path of a light beam generated by the light source. In principle, these optical means can be designed in various ways.

In a particularly preferred embodiment of the invention, these optical means are realized by a deflecting mirror, the direction of reflection of which can be changed. Therefore, the following statements and the appended claims relate to the use of a corresponding deflection mirror. This deflecting mirror is optically arranged in a special way, namely on the intersection of an object plane, a detector plane and a lens plane. In this way, an illuminating light beam is created, and thus an object plane, which always complies with the Scheimpflug condition, since the object plane will have an invariable intersection with the lens plane and the detector plane even when the radiation direction of the illuminating light beam changes.

Similar to a conventional triangulation sensor, the sensor arrangement according to the invention comprises a light source, a detector lens and a sensor surface which functions as a detector. The light source generates a light beam which forms an illuminating light beam by reflection on the deflecting mirror and possibly after being influenced by further, intermediate optical means (for example a color or polarization filter or a lens connected downstream of the light source). The illuminating light beam produced in this way is directed onto a surface of a measurement object on which the illuminating light beam is diffusely reflected. If the illuminating light beam is reflected in the direction of the detector lens and sensor surface, a detection light beam is created as part of the diffusely reflected illuminating light beam. The detection light beam is imaged by the detector lens in the direction of the sensor surface and illuminates an impact point on the sensor surface. This point of impact can comprise one or more sensor elements of the sensor surface. The position of the impact point is used - using the geometry of the sensor arrangement - to determine the distance of the point illuminated on the surface of the measurement object from the sensor arrangement. By changing the direction of reflection of the deflecting mirror, the direction of propagation of the illuminating light beam and thus the point illuminated on the surface of the measurement object can be influenced. In this way, the surface of the measurement object or parts thereof can be scanned and can be measured and three-dimensional measurement data can arise from the measurement object.

By optically arranging the deflecting mirror on the intersection of the object plane, lens plane and detector plane, the Scheimpflug condition remains fulfilled even when the illuminating light beam is pivoted. The lens plane is formed by a plane that is perpendicular to an optical axis of the detector lens. If the detector lens is formed, for example, by a classic converging lens, the lens would extend in the direction of the plane, the center line of the lens lying on the plane and the curvatures of the lens extending on both sides of the lens plane. If the detector lens is formed, for example, by a gradient index lens (also referred to as a GRIN lens), the optical axis is formed by the center line of the cylindrical GRIN lens and the lens plane is parallel to the base or top surfaces of the GRIN Lens, an essentially identical portion of the GRIN lens extending on both sides of the lens plane. Regardless of whether the detector lens is formed by a single lens or a lens system, an optical axis of the detector lens can be defined, which can determine the position of the lens plane.

The detector level is defined by the sensor area. This means that the detector plane is arranged parallel to the sensor surface. The area of the sensor surface in which the detection of incident light is effectively effected will lie on the detector level. Since this area is very thin compared to the overall dimensions of the sensor arrangement and will be only a little below the surface of the sensor surface, it is sufficient in practice if this area is equated with the surface of the sensor surface. This would make the surface of the sensor surface part of the detector plane.

The object plane is defined by the direction of propagation of the illuminating light beam. Even if a single line segment (in the present case the illuminating light beam) cannot clearly define a plane, but only defines a set of planes, there is still a plane from the set of planes that can intersect two further planes in a single section line. Therefore, the direction of propagation in combination with the requirement of a single cutting line can clearly determine the position of the object plane. When the sensor arrangement is used as intended when measuring a measurement object, a point which is illuminated on the surface of the measurement object by the illuminating light beam lies on the object level.

An optical arrangement of the deflecting mirror on the cutting line means that the cutting line lies in the effective effect of the deflecting mirror on a reflecting surface of the deflecting mirror. This can be implemented in various ways. In the simplest case, this optical arrangement is achieved in that the cutting line is arranged on the reflecting surface of the deflecting mirror. In this embodiment, a light beam generated by the light source and reflected on the reflecting surface would directly form the illuminating light beam.

In an alternative embodiment, the optical arrangement of the deflecting mirror on the cutting line is achieved using a further mirror. In this embodiment, a light beam caused by the light source first strikes the deflecting mirror, which reflects this light beam onto the further mirror. Deflecting mirror, further mirror and cutting line are arranged relative to one another in such a way that the cutting line mirrored on the further mirror is arranged on a reflecting surface of the deflecting mirror. In this way, the deflecting mirror appears optically as if it were arranged directly on the cutting line. This enables a relatively free positioning of the light source, deflection mirror, control electronics and / or other components of the sensor arrangement. Even if the use of a single further mirror represents a preferred embodiment, it is understood that this optical arrangement can also be implemented with a plurality of further mirrors. As long as the other mirrors and the deflecting mirror are arranged relative to one another in such a way that the optically effective position of the deflecting mirror lies on the cutting line, the arrangement fulfills the requirements of the sensor arrangement according to the invention.

If one or more other mirrors are used, inaccuracies in the installation of the individual mirrors can add up. In a further development, the deflecting mirror is therefore arranged such that a point of impact at which a light beam caused by the light source strikes a reflecting surface of the deflecting mirror is no further than a maximum distance from the cutting line. This maximum distance is preferably less than or equal to 50 mm, very particularly preferably less than or equal to 30 mm.

The deflecting mirror can be formed in a wide variety of ways. Since only the illuminating light beam is influenced in its direction of propagation, a deflecting mirror with a small aperture can be used. It is only essential that the deflecting mirror enables a changeable direction of reflection, as a result of which an incoming light beam can be controlled and reproducibly directed in a changeable direction. In the simplest case, this can be done by a reflective surface that is in at least one direction can be pivoted. For this purpose, actuators can be provided which move a reflecting surface in a suitable manner. These actuators can be formed by a wide variety of means, which convert an electrical control signal from a control device into a mechanical movement. Reference is made to the use of a stepping motor and the use of capacitive effects by way of example only.

The deflecting mirror and its pivoting mechanism is preferably designed such that a point of impact of a light beam caused by the light source on the reflecting surface of the deflecting mirror remains essentially unchanged during the pivoting of the reflecting surface. Since the point of impact is usually known very precisely by the arrangement of the individual optical means of the sensor arrangement, the requirement of this development can usually be easily met.

In one configuration, the deflecting mirror is formed by a 1-axis tilting mirror or a 2-axis tilting mirror. 1-axis tilt mirrors are also known as "tip mirror" and 2-axis tilt mirrors as "tip / tilt mirror". A 1-axis tilting mirror can be swiveled around a swivel axis and a 2-axis tilting mirror can be swiveled around two swivel axes. With 2-axis tilting mirrors, the two swivel axes are usually arranged perpendicular to each other. In both cases, it is advisable in the sensor arrangement according to the invention if the pivot axis or one of the pivot axes is arranged parallel or perpendicular to the cutting line.

In a further development, the deflecting mirror is constructed from an array of individual mirrors, which together fulfill the function of changing a direction of reflection. It is largely irrelevant how the array is constructed. In the simplest case, the deflecting mirror can consist of a matrix of square or rectangular individual mirrors. However, it is also conceivable that the deflecting mirror is formed as a honeycomb-like structure by a series of hexagonal individual mirrors. It is even conceivable that not all individual mirrors are constructed identically, but that different individual mirrors are present.

Such deflection mirrors constructed from individual mirrors can be implemented relatively easily by means of a MEMS (micro-electro-mechanical system). Such a MEMS is, for example, a DMD (Digital Mirror Device), in which an array of individual mirrors can be pivoted between two stable end positions by means of capacitive actuators. By using suitable control signals, for example a voltage with a sinusoidal curve, a defined dynamic pivoting between the two end positions can be achieved.

Regardless of the shape of the individual mirrors, they can be pivoted by means of one or more actuators. If a single actuator were used, this would move all of the individual mirrors together. If several actuators are used, a separate actuator can be provided for each individual mirror, which pivots the respectively assigned individual mirror. However, it is also possible for one of the several actuators to move several individual mirrors together, for example individual mirrors of a row or a column or several neighboring individual mirrors as a mirror cluster.

Regardless of the specific configuration of the deflecting mirror, the deflecting mirror can preferably be controlled by means of control electronics in such a way that an illuminating light beam can be generated which can be pivoted between two maximum deflections. In this way, the illuminating light beam can be pivoted back and forth in a defined manner, so that a scanning movement can be carried out. The illuminating light beam can be swiveled dynamically between the maximum deflections, i.e. the illuminating light beam is continuously moved without discrete intermediate stages. By suitable selection of a control signal, the dynamic movement of the illuminating light beam can take place largely uniformly over the measurement object. However, depending on the design of the deflecting mirror, the illuminating light beam can also be pivoted in several discrete intermediate stages between the maximum deflections. In this way, the illuminated pixels can be clearly delimited. Regardless of the type of movement, this development enables a complete or at least partial scanning of the surface of the measurement object. If a 2-axis tilting mirror is used, pivoting about the one pivot axis can pivot the illuminating light beam between two maximum deflections, while pivoting about the other pivot axis moves the illuminating light beam successively. In this way, defined scan paths can be generated on the measurement object, for example a meandering scan path.

The sensor surface can be formed in different ways. It is essential that the sensor surface can carry out a spatially resolved measurement of the position of an impact point of a detection light beam on the sensor surface. This should mostly be done by the sensor surface consisting of a series of light-sensitive sensor elements, the sensor elements being arranged in a row or an array, for example a matrix. Suitable sensor surfaces of this type are For example, CCD (Charge Coupled Device) sensors designed as line or area sensors.

In principle, the light source can be formed in a wide variety of ways, as long as a light beam with sufficient intensity and sufficient homogeneity can be generated. What means sufficient intensity and sufficient homogeneity depends on the respective requirements for the measurement accuracy and the resolution of the sensor arrangement. So it may be sufficient to implement the light source using an LED (light-emitting diode) with downstream optics. However, a laser is preferably used, particularly preferably a laser diode. Beam shaping optics can be arranged downstream of the laser diode.

To homogenize a light beam generated by the light source, an optical means can be arranged in the beam path of the light beam, which reduces intensity fluctuations of the illuminating light beam. Even with lasers, their intensity fluctuates periodically. These fluctuations are known as "laser speckles". Even if these intensity fluctuations are relatively small, they can negatively influence the measuring accuracy of the sensor arrangement. Optical means are available to reduce these laser speckles, for example from OptiTune Switzerland AG, Dietikon, Switzerland. Such “laser speckle reducers” are formed, for example, by rapidly moving or rotating plates. In a development of the sensor arrangement according to the invention, such a laser speckle reducer is arranged in the beam path of an illuminating light beam caused by a laser.

In another development, means for determining an angular position are provided, with which the angular position of the deflecting mirror can be determined. This angular position indicates how one or more reflecting surfaces of the deflecting mirror are oriented. The angular position is thus a measure of the direction in which the deflecting mirror reflects an incident light beam and thus the direction of propagation of the illuminating light beam and the position of the object plane. The angular position can be obtained as a measured value or as an estimated value. A measured value would arise, for example, if the means for determining an angular position are formed by an angle sensor or an angle sensor that detects the angular position of the deflecting mirror. An estimated value can be obtained via an estimator which, for example, estimates a resulting angular position based on a control signal applied to an actuator. If the angular position of the deflecting mirror is set by regulation, it is also conceivable to obtain the estimated value by specifying a setpoint, i.e. If a setpoint is specified for the control, it is assumed that the control difference is small and the actual angular position is close to the setpoint. In the case of 2-axis tilting mirrors in particular, the angular position of the deflecting mirror, which causes the illuminating light beam to shift in directions parallel to the cutting line, can also be determined via the sensor surface, provided that the sensor surface enables location measurement in two directions. This is because appropriate tilting of the deflection mirror leads to a displacement of the point illuminated on the sensor surface, as a result of which the tilting can be inferred from the illuminated point.

Measured or estimated values for the angular position obtained in this way can be used to carry out an error correction and / or an adaptation of optical means of the sensor arrangement. Although the Scheimpflug condition is always met by the optical arrangement of the deflecting mirror according to the invention on the section line, the plane on which the detector lens sharply images the detection light beam varies with different orientations of the object plane. This creates measurement errors. Depending on the extent of the deviation between the detector level and the imaging level, these measurement errors can be partially or completely compensated for by an error correction. Appropriate correction polynomials are known from practice. The determined angular position can be used for this. On the other hand, it is possible to optically compensate for measurement errors arising from different positions of the object plane. For this purpose, optical means can be arranged in the beam path of the detection light beam, and the angular position determined is used when adapting them.

In principle, the detector lens can be formed in a wide variety of ways, as long as the detector lens is suitable for imaging a detection light beam in the direction of the sensor surface. The detector lens can be constructed by a single lens or a lens system consisting of several single lenses connected in series. The individual lens (s) can also be constructed in various ways. As an example, but not limited to these, reference is made to classic lenses and gradient index lenses.

In a further development, the detector lens has an adjustable focal length. Detector lenses of this type are known in practice, both in the form of individual lenses and in the form of lens systems. In particular, the imaging effects already mentioned due to different positions of the object plane can be compensated for by a detector lens equipped in this way. If measuring / If estimates of the angular position are known or determined, a detector lens with an adjustable focal length can be adapted as a function of the current angular position. Since the effects of a change in the position of the object plane are easy to describe, a control signal for adapting the focal length can be determined easily.

In another development, a cylindrical lens is arranged downstream of the detector lens, which projects the detection light beam onto points on a projection line. In this context, “subordinate” means that the cylindrical lens is arranged between the detector lens and the sensor surface. "Upstream" means that the detector lens is arranged between the cylindrical lens and the sensor surface. Suitable cylindrical lenses are known from practice. By using such a cylindrical lens between the detector lens and the sensor surface, it can be achieved that the detection light beam illuminates only points of the sensor surface lying on a line. As a result, a much cheaper line detector ( 1 D detector) can be used. It is advisable that the line detector is arranged parallel to the cylinder lens.

The sensor arrangement according to the invention can be used not only for a point sensor, but also for a line sensor. In this development, the sensor arrangement comprises an optical means that expands the light beam generated by the light source in one direction. This optical means is preferably formed by line optics, the use of which in triangulation sensors is known. This line optics expands a light beam generated by the light source in one direction in such a way that line-shaped illumination of the measurement object is possible by means of the expanded illuminating light beam which is thereby produced. The line optics are preferably arranged such that the expanded illuminating light beam lies in the object plane.

When using the sensor arrangement according to the invention in the context of the method according to the invention, a measurement object can be successively measured. The deflecting mirror of the sensor arrangement can be controlled in such a way that the illuminating light beam is directed over at least part of the surface of the measurement object in a scan movement. The scan paths created by the scanning movement can have different structures. Meandering, triangular or sawtooth-shaped scan paths are preferably used.

The distance values obtained by the sensor arrangement can be combined into a profile of the measurement object by means of an evaluation unit. Measured values at different points on the surface of the measurement object, which have been obtained, for example, during a scan movement, are combined in such a way that three-dimensional image information is generated from the measurement object. This evaluation unit can be part of the sensor arrangement or can be connected to the sensor arrangement via a correspondingly suitable communication interface.

• 1 eine schematische Darstellung eines bekannten Triangulationssensors,
• 2 eine schematische Darstellung eines scannenden Triangulationssensors gemäß Stand der Technik, bei dem der Beleuchtungslichtstrahl mittels eines Umlenkspiegels in seiner Ausbreitungsrichtung beeinflusst wird,
• 3 eine schematische Darstellung eines scannenden Triangulationssensors gemäß Stand der Technik, bei den sowohl Beleuchtung- als auch Detektionslichtstrahl mittels eines Umlenkspiegels beeinflusst wird,
• 4 eine schematische Darstellung eines ersten Ausführungsbeispiels eines erfindungsgemäßen Triangulationssensors und
• 5 eine schematische Darstellung eines zweiten Ausführungsbeispiels eines erfindungsgemäßen Triangulationssensors.

There are now various possibilities for advantageously designing and developing the teaching of the present invention. For this purpose, reference is made on the one hand to the claims subordinate to the independent claims and on the other hand to the following explanation of preferred exemplary embodiments of the invention with reference to the drawing. In connection with the explanation of the preferred exemplary embodiments of the invention with reference to the drawing, generally preferred refinements and developments of the teaching are also explained. Show in the drawing

• 1 1 shows a schematic illustration of a known triangulation sensor,
• 2nd 1 shows a schematic representation of a scanning triangulation sensor according to the prior art, in which the illuminating light beam is influenced in its direction of propagation by means of a deflecting mirror,
• 3rd 1 shows a schematic representation of a scanning triangulation sensor according to the prior art, in which both the illumination and detection light beam are influenced by means of a deflection mirror,
• 4th a schematic representation of a first embodiment of a triangulation sensor according to the invention and
• 5 is a schematic representation of a second embodiment of a triangulation sensor according to the invention.

4th shows a first embodiment of a sensor arrangement according to the invention 1 which uses a deflection mirror as a means for influencing the direction of propagation of the illuminating light beam. The sensor arrangement 1 includes a light source 2nd in the form of a laser diode (including any downstream beam shaping optics), a detector lens 3rd , a sensor surface 4th and a deflecting mirror 5 . The deflecting mirror 5 is pivotable about an axis in the illustrated embodiment (by the double arrow in the deflecting mirror 5 indicated), which is formed perpendicular to the plane of the drawing. The light source 2nd creates a beam of light 6 on a reflective surface 7 of the deflecting mirror 5 meets. By reflection of the light beam 6 on the reflective surfaces 7 becomes an illuminating light beam 8th generated. For further discussions is in addition to the illuminating light beam 8th an illuminating light beam 8th' drawn in by pivoting the mirror 5 would arise around the pivot axis. The illuminating light beam 8th is on a symbolic object 9 diffusely reflected, creating a detection light beam 10th arises. The detection light beam 10th hits the detector lens 3rd and is going through this towards the sensor surface 4th pictured. The detector lens 3rd passing detection light beam 10th illuminates a point of impact on the sensor surface 4th . From knowledge of the geometry of the sensor arrangement 1 and the angular position of the deflecting mirror 5 can on the distance of the measurement object 9 from the sensor arrangement 1 getting closed.

So that the sensor arrangement can measure with high accuracy, there are detector lenses 3rd , Sensor surface 4th and deflecting mirror 5 arranged in a special way: an object level 11 , a detector level 12th and a lens plane 13 intersect in a common cutting line 14 , the cutting line 14 on the reflective surface 7 of the deflecting mirror 5 lies. The object level 11 , the detector level 12th and the lens plane 13 are in 4th shown as straight line sections and each extend perpendicular to the plane of the drawing. The cutting line 14 is shown as a point and also extends perpendicular to the plane of the drawing. The object level 11 is by the direction of propagation of the illuminating light beam 8th Are defined. The detector level 12th includes the sensor surface 4th . The lens plane 13 runs perpendicular to the optical axis of the detector lens 3rd that in the in 4th illustrated embodiment is formed by a conventional lens. The curvatures of this lens extend on both sides of the lens plane 13 and the center line of this lens lies on the lens plane 13 . This type of arrangement of the detector lens 3rd , the sensor surface 4th and the deflecting mirror 5 creates an illuminating light beam that is always a point of the cutting line 14 includes. In this way - regardless of the angular position of the deflecting mirror 5 - The Scheimpflug condition is met, so that at a given angular position of the deflecting mirror 5 an illuminating light beam 8th always sharp on the sensor surface 4th can be mapped.

In 4th is next to the illuminating light beam 8th nor the illuminating light beam 8th' drawn. It can be seen that depending on the distance of the illuminated impact point on the surface of the measurement object 9 a detection light beam 10th can arise despite the deviating direction of propagation of the illuminating light beam 8th' illuminates an identical point on the sensor surface. It is at different distances a ₁ and a ₂ the distance a ' identical to the sensor surface in both cases. This leads to measurement errors. Therefore, the detector lens 5 have an adjustable focal length so that the focal length can be readjusted depending on the direction of propagation of the illuminating light steel.

5 shows a second embodiment of a sensor arrangement according to the invention. The sensor arrangement 1' again includes a light source 2nd in the form of a laser diode, a detector lens 3rd and a sensor surface 4th . In 5 are three different illuminating light beams 8th , 8th' , 8th" and the associated detection light beams 10th , 10 ' , 10 " shown, which result from different angular positions of the deflecting mirror 5 surrender. Again is an object level 11 (in 5 for illuminating light beam 8th exemplified), a lens plane 13 and a detector plane 12th defined, which is in a common cutting line 14 to cut. The cutting line 14 is again perpendicular to the plane of the drawing 5 . In the second embodiment, the cutting line is 14 but not on the reflecting surface of the deflecting mirror 5 arranged. Instead is another mirror 15 present on the one from the light source 2nd generated and by the deflecting mirror 5 reflected light beam hits. The one at the other mirror 15 reflected light beam finally forms the illuminating light beam 8th , 8th' , 8th" which leaves the sensor arrangement. Nevertheless, the deflecting mirror 5 optically on the cutting line 14 arranged, because the on the other mirror 15 mirrored cutting line 14 (by double arrow 16 indicated) lies on the reflecting surface of the deflecting mirror 5 . So the deflecting mirror 5 optically the effect as if it were on the cutting line 14 arranged. The use of the wider mirror 15 has the advantage that the individual elements can be positioned more freely. In the in 5 The illustrated embodiment is the sensor surface 4th on a circuit board 17th arranged so that there would be no space for the laser diode. By using the additional mirror 15 can the laser diode next to the circuit board 17th be arranged without affecting the optical properties of the sensor arrangement 1' to change.

With regard to further advantageous configurations of the sensor arrangement according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

Finally, it should be expressly pointed out that the exemplary embodiments described above are only used to discuss the claimed teaching, but do not restrict them to the exemplary embodiments.

Reference list

1.1 '

Sensor arrangement

2nd

Light source

3rd

Detector lens

4th

Sensor surface

5

Deflecting mirror

6

Beam of light

7

Reflective surface

8, 8 ', 8 "

Illumination light beam

9

Target

10, 10 ', 10 "

Detection light beam

11

Object level

12th

Detector level

13

Lens plane

14

Cutting line

15

Another mirror

16

Double arrow

17th

Circuit board

Claims (19)

Sensor arrangement for measuring a measurement object, with a light source (2), a detector lens (3) and a sensor surface (4), the light source (2) emitting an illuminating light beam (8, 8 ', 8 emitted by the sensor arrangement (1, 1') "), whereby the detector lens (3) images a detection light beam (10, 10 ', 10") in the direction of the sensor surface (4), with the illumination light beam (8, 8', 8 "), detector lens (3) and sensor surface (4 ) are arranged relative to one another in such a way that an object plane (11) defined by a direction of propagation of the illuminating light beam (8, 8 ', 8 "), a lens plane (13) arranged perpendicular to an optical axis of the detector lens (3) and a plane through the Cut the sensor surface (4) of the defined detector plane (12) in a cutting line (14), characterized by a deflecting mirror (5) with a variable direction of reflection, the deflecting mirror (5) optically on the cutting line (14) and in a beam path one through the Light source (2) generated light beam is arranged so that by changing the direction of reflection of the deflecting mirror (5) an illuminating light beam (8, 8 ', 8 ") with a variable direction of propagation and thus an object plane with a variable position. Sensor arrangement after Claim 1 , characterized in that an optical arrangement of the deflecting mirror (5) on the cutting line (14) is achieved in that the cutting line (14) is arranged on a reflecting surface (7) of the deflecting mirror (5). Sensor arrangement after Claim 1 , characterized in that an optical arrangement of the deflection mirror (5) on the cutting line (14) is achieved by using a further mirror (15), a light beam caused by the light source (2) and reflected by the deflection mirror (5) being directed onto the meets another mirror (15) and the deflecting mirror (5) and the further mirror (15) are arranged relative to one another such that the cutting line (14) mirrored on the further mirror (15) on a reflecting surface (7) of the deflecting mirror ( 5) is arranged. Sensor arrangement after Claim 3 , characterized in that a point of incidence of a light beam caused by the light source (2) on a reflecting surface (7) of the deflecting mirror (5) is no further than a maximum distance from the cutting line (14), the maximum distance preferably being less than or equal to 50 mm is. Sensor arrangement according to one of the Claims 1 to 4th , characterized in that the deflecting mirror (5) achieves a change in the direction of reflection by pivoting a reflecting surface (7), the reflecting surface (7) preferably being designed to be pivotable in such a way that an impact point of a light beam caused by the light source (2) the reflecting surface (7) of the deflecting mirror (5) remains essentially unchanged during the pivoting of the reflecting surface (7). Sensor arrangement according to one of the Claims 1 to 5 , characterized in that the deflecting mirror (5) is formed by a 1-axis tilting mirror or a 2-axis tilting mirror, wherein a pivot axis of the tilting mirror is preferably arranged parallel to the cutting line (14). Sensor arrangement according to one of the Claims 1 to 6 , characterized in that the deflecting mirror (5) is constructed from an array of individual mirrors, the individual mirrors being pivotable by means of one or more actuators, the deflecting mirror preferably being designed as a MEMS - micro-electro-mechanical system. Sensor arrangement according to one of the Claims 1 to 7 , characterized in that the deflecting mirror (5) can be controlled by means of control electronics such that the illuminating light beam (8, 8 ', 8 ") is preferably periodically pivotable between two maximum deflections, so that the illuminating light beam (8, 8', 8") is one Executes scanning motion. Sensor arrangement according to one of the Claims 1 to 8th , characterized in that an optical means for reducing intensity fluctuations of the illuminating light beam is arranged in the beam path of a light beam generated by the light source (2). Sensor arrangement according to one of the Claims 1 to 9 , characterized by means for determining an angular position, the means determining a measured value or an estimated value for the angular position of the deflecting mirror (5), whereby measured / estimated values determined in this way can be used for error correction and / or adaptation of optical means of the sensor arrangement. Sensor arrangement according to one of the Claims 1 to 10th , characterized in that the detector lens (3) consists of a single lens or a lens system. Sensor arrangement according to one of the Claims 1 to 11 , characterized in that the detector lens (3) has an adjustable focal length, the focal length preferably being set as a function of an angular position of the deflecting mirror (5). Sensor arrangement according to one of the Claims 1 to 12th , characterized in that the detector lens (3) is followed by a cylindrical lens which projects the detection light beam (10, 10 ', 10 ") onto points on a projection line, and in that the sensor surface (4) is a line detector, the line detector is arranged on the projection line and preferably parallel to the cylindrical lens. Sensor arrangement according to one of the Claims 1 to 13 , characterized in that a line optics is arranged in the beam path of the light beam generated by the light source (2), the line optics expanding the light beam in a direction to an expanded illuminating light beam in such a way that a linear illumination of the measurement object is possible by means of the expanded illuminating light beam, wherein the expanded illuminating light beam is preferably arranged in the object plane. Sensor arrangement according to one of the Claims 1 to 14 , characterized in that the light source (2) is formed by a laser, preferably a laser diode. System comprising a sensor arrangement according to one of the Claims 1 to 15 and a measurement object, the illumination light beam (8, 8 ', 8 ") emitted by the sensor arrangement (1, 1') being directed onto a surface of the measurement object (9) and the detection light beam (10, 10 ', 10") being passed through Diffuse reflection of the illuminating light beam (8, 8 ', 8 ") on the surface of the measurement object (9) arises. Method for measuring a measurement object using a sensor arrangement according to one of the Claims 1 to 15 , comprising the steps: generating an illuminating light beam (8, 8 ', 8 ") and directing the illuminating light beam (8, 8', 8") onto a surface of the measurement object (9), detecting a detection light beam (10, 10 ', 10 ") ) by means of a sensor surface (4) of the sensor arrangement (1, 1 '), the detection light beam (10, 10', 10 ") by diffuse reflection of the illuminating light beam (8, 8 ', 8") on the surface of the measurement object (9) generating a measured value from a position of a point of impact of the detection light beam (10, 10 ', 10 ") on the sensor surface (4) and determining a distance value of a point of the surface of the surface illuminated by the illuminating light beam (8, 8', 8") Measurement object (9) from the sensor arrangement (1, 1 '). Procedure according to Claim 17 , characterized in that the deflecting mirror (5) of the sensor arrangement (1, 1 ') is controlled in such a way that the illuminating light beam (8, 8', 8 ") is guided in a scan movement over at least part of the surface of the measurement object (9) . Procedure according to Claim 17 or 18th , characterized in that a profile of the measurement object (9) is determined from a plurality of measurement values at different points on the surface of the measurement object (9).

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