WO2014023345A1 - Improved device for examining an object and method - Google Patents

Abstract

The present invention relates to a device (10) for optically examining an object (12), said device having an object support (14) to support the object (12), a pattern-generating unit (16) to illuminate the object (12) with a measuring pattern, an image recording unit (18) to record a plurality of images of the object (12), imaging optics (20) to influence a light beam path (22) between the object (12) and the image recording unit (18), and a data processing unit (24) designed to determine at least one property of the object (12) with the aid of the plurality of images, characterised in that the device (10) can be set at least at one first working distance (26) and one second working distance (28), and the device also has a scattering unit which can be changed between an active state, in which the scattering unit (30) influences the light beam path (22) upstream of the pattern-generating unit (16), and an inactive state in which the scattering unit (30) does not influence the light beam path (22) upstream of the pattern-generating unit (16). The present invention additionally relates to a method for changing an operating mode of a device (10) for optically examining an object (12).

Description

 Improved device for inspecting an object and method

The present invention relates to an apparatus for optically inspecting an object, comprising a slide for carrying the object, a pattern generation unit for illuminating the object with a measurement pattern, an image acquisition unit for taking a number of images of the object, an imaging optic for influencing a light beam path between the object and the image pickup unit, and a data processing unit configured to determine at least one property of the object based on the number of images.

Such a device is known for example from the document DE 10 2009 021 733 A1. According to a further aspect, the present invention relates to a method for changing an operating mode of an apparatus for optically inspecting an object.

In industrial manufacturing of products, product quality has been playing an increasingly important role for many years. On the one hand, high product quality can be achieved through suitably designed and stable production processes. On the other hand, the quality parameters of a product must be controlled as reliably and completely as possible in order to detect quality defects at an early stage. In many cases, the quality of a product surface plays a role. These may be decorative surfaces, such as painted surfaces in motor vehicles or household items, or technical surfaces, such as the surfaces of finely machined metallic pistons or bearing surfaces.

There are already a variety of proposals and concepts for inspecting surfaces.

The document DE 10 2009 021 733 A1 describes, for example, a deflectometric method and a corresponding device. In this method, a striped pattern having a sinusoidal brightness pattern is projected on a screen which is disposed obliquely over a surface to be inspected. The projected pattern is changed or moved so that correspondingly altered striped patterns fall on the surface. During or after changing / moving the pattern, an image of the surface with the reflected pattern is taken each time. By a mathematical combination of the images taken at different times, a result image is to be generated, on the basis of which defective areas and defect-free areas of the surface can be distinguished computationally and / or visually.

Further Deflektometrieverfahren are shown for example in the publications DE 10 2008 038 256 A1 and DE 10 2008 064 562 A1. Furthermore, in the prior art so-called strip imaging methods are known. For example, the publication DE 10 2010 007 922 A1 shows the use of such a strip image method. In this case, a striped pattern is projected onto the object to be inspected, for example by a lighting device being directed through a multigrip grid onto the object. In the multi-strip grid, light and dark stripes alternate. The width of the strips of the multi-strip grid determines - together with an angle between illumination and observation direction - the accuracy or the resolution of the three-dimensional detection of the object. From the position of a lighting device of the multi-strip grid and the position of the multi-strip grid, the position of a light plane extending from the illumination device through the strip of the multi-strip grid can be calculated. On the basis of the position of a pixel in the image of the first image recording device, in turn, the vector of a light beam can be calculated, which has generated this pixel. This in turn makes it possible to determine the point of intersection of this light beam with the calculated plane of the multigrip lattice. Thus one obtains the spatial coordinates of a specific pixel on the image of the image acquisition unit.

[0009] It can be provided that the fringe projection method is a Gray code fringe projection method. Basically, in a multi-strip pattern, only light and dark stripes alternate. Thus, however, no absolute assignment of an example, bright pixel in an image of the first image pickup device is assigned to one of these stripes. Therefore, a so-called Graycode method is used to enable unambiguous assignment. In this case, for example, initially only a light and a dark strip is projected onto the face, in a second step, each of these strips is again divided into a light and a dark stripe, so that a total of four stripes are present, in a next step is again a subdivision , so that there are eight stripes, etc. The subdivision takes place until finally the desired stripe width or resolution is present. If an image of the object is now taken at each stripe resolution, it is possible by means of the light / dark change to unambiguously associate with each pixel a strip of the last-mentioned stripe grating with the desired resolution. [0010] A further refinement of a fringe pattern method may be a phase shift method that allows for resolution in a subpixel area. In this case, a sinusoidal brightness profile is modulated onto the strip pattern which is rectangular in terms of its brightness values. Then, a first image acquisition is made, then the phase of the modulated wave is shifted by π / 2 transversely to the beam direction. It is a new recording and a new shift until a total of at least four pictures were taken. From the four brightness values of the pixel in the four shots, it is possible to deduce its phase position within the modulated signal. Thus, the exact position of the pixel within a strip can be determined.

Further strip pattern methods are shown approximately in the publications DE 10 2008 041 343 A1 and EP 2 327 956 A1.

Frequently, however, the known methods and devices can only be used for a specific application because they require a high level of prior knowledge of the surface to be inspected. In addition, in addition to reliable inspection of surfaces, industrial conditions such as cycle time compliance, which are relevant for integration into industrial manufacturing, the ability to perform surface inspection in a shop floor, and / or the ability to perform surface inspection simply and quickly to adapt to changing products.

The fringe pattern method and the deflectometry method have in common that they strip patterns with different strip geometries in relation to strip width, gap width, duty cycle of the strip and gap, direction or

Orientation and phase position can be used.

In use, a stripe image process is particularly sensitive to inclinations in a surface of the object and is thus particularly well suited for detecting topographies. By contrast, a deflectometry method is particularly suitable for detecting dents and defects in a surface. Deflectometry systems have in the Application Benefits for very smooth, well-reflective to reflective surfaces. For a surface that is rather rough and less reflective of incident light, that is more likely to be scattering or absorbing, the use of a fringe projection method is usually advantageous.

Against the technical background, it is therefore an object of the present invention to provide an apparatus for inspecting an object and a method which eliminate the disadvantages described and to allow a more variable inspection, in particular of changing objects.

According to a first aspect of the invention, it is therefore proposed to further develop the device mentioned above in that the imaging optics is adjustable in at least a first working distance and a second working distance, and the device further comprises a scattering unit, which is between an active state, in which the scattering unit is influencing the light beam path in front of the pattern generation unit, in particular between the pattern generation unit and the object, and an inactive state in which the scattering unit does not influence the light beam path is changeable.

It has been recognized that the similarities of deflectometry and fringe patterning techniques can be used to provide a device that permits inspection of an object on both rough, more scattering surfaces and smooth, more reflective surfaces. In a fringe projection method, however, the measurement pattern is projected onto the object. In a deflectometry method, on the other hand, the measurement pattern is observed directly at the place of its origin over the object. In a deflectometry method, the object is thus part of the light beam path emanating from the pattern generation unit and imaged on the image recording unit.

The "measurement pattern" may be a stripe pattern or a one-dimensional pattern, but the measurement pattern may also be a two-dimensional pattern, both the one-dimensional pattern and the two-dimensional pattern can be spatially coded or uncoded. Examples of this can be found, for example, in document EP 2442 067 A1.

[0019] As a pattern generation unit, both in a deflectometry method and in a strip pattern method, for example, a digital projector or a pattern generator in a known projector technology is suitable. Slide projectors can also be used. Furthermore, structured light sources are also possible, which have LEDs (light emitting diodes), OLEDs (organic light emitting diodes) and / or LASER (light amplification through stimulated emission of radiation). The pattern generation unit generates a variably adjustable measurement pattern.

In the context of the present application, "working distance" can be understood as meaning an optical working distance or a mechanical working distance The "mechanical working distance" is the clear distance between a first, object-side interference contour of the objective and the object to be measured. The "optical working distance" is the clear distance between a first, object-side interference contour of the objective and a focal plane of the objective, in other words, the optical working distance is the object-side cutting distance of the imaging optics. that is to say, the lens arranged furthest on the object side, the imaging optics, their mount or a cover glass of the imaging optics.

In the proposed device, the mechanical working distance and / or the optical working distance can be adjustable. The device can thus be adjustable at least either in a first mechanical working distance and a second mechanical working distance or in a first optical working distance and a second optical working distance. In particular, the device can also be adjustable both in a first mechanical working distance and a second mechanical working distance as well as in a first optical working distance and a second optical working distance.

The mechanical working distance can be adjustable by, for example, the imaging optics and the slide are movable relative to each other. On This way, for example, by mechanically moving the imaging optics, the mechanical working distance can be set.

The optical working distance can be adjustable by a focal length of the imaging optics is adjustable. In this way, the imaging optics are capable of operating with a shorter working distance in a fringe pattern process and with a longer working distance in a deflectometry process. Since the resolution of the image acquisition decreases with larger working distances, such a sequence is also suitable for the respective applications. In stripe projection, the survey of a topography is usually in the foreground. In the context of a deflectometry method, however, a purely qualitative check for surface damage is generally the main issue, which requires less accuracy.

In the proposed device, the optical working distance and the mechanical working distance may be alternatively or cumulatively adjustable. If both the optical working distance and the mechanical working distance of the device is adjustable, it is thus also possible for the working distance of the device to be adjusted in part by varying the mechanical working distance and partly by varying the optical working distance, ie by a mixing mold.

In particular, the device is in a first operating mode in which the optical working distance corresponds to the mechanical working distance, and in a second operating mode in which the optical working distance is greater than the mechanical working distance, adjustable. In the first mode of operation, a strip pattern method may then be performed, and in the second mode of operation, a deflectometry method may then be performed.

The measurement pattern is projected onto the object by the pattern generation unit in the stripe image process. In the deflectometry method, the measurement pattern is scattered by the scattering disk element and imaged onto the image acquisition unit via the object and the imaging optics. Thus, in the fringe pattern method, the scattering unit is not needed, whereas it is necessary in the deflectometry method. An "active state" is thus understood to mean that the scattering unit influences a light beam path of the light emitted by the pattern generation unit. An "inactive state" is understood to mean that the scattering unit does not influence the light beam path of the light emitted by the pattern generation unit. An active state can be achieved, for example, by moving the scattering unit so that it is no longer in the light beam path. But it can also be provided that the scattering unit is electrically controlled and optionally active or inactive switchable.

It can also be designed as a volume scattering unit, but scattering can take place on one or both surfaces of the scattering unit or else in a scattering volume.

The proposed combined and variable in their working distance device is capable of adapted to the properties of the object, such as the surface quality, gloss level or absorption behavior, either for the measurement task topography / 3d geometry with the strip pattern method or for the measurement task Quality / visual inspection to be used with the Deflektometrieverfahren.

In the context of the present invention, "light" is understood to mean any electromagnetic wave, in particular regardless of whether it lies in a spectral range which is visible to the human eye or in an ultraviolet or infrared spectral range From monochromatic light to broadband white light, all kinds of lighting are conceivable.

The device is particularly suitable for use in coordinate measuring machines. However, it can also be used in all other measuring systems, such as multi-sensor measuring systems, but also in material microscopes or production machines. According to a second aspect of the invention, therefore, a method for changing an operating mode of an apparatus for optically inspecting an object is proposed, wherein the apparatus comprises a slide for carrying the object, a pattern generating unit for illuminating the object with a measuring pattern, an image recording unit for recording a number of images of the object, an imaging optics for influencing a light beam path between the object and the image recording unit wherein the device is adjustable at least a first working distance and a second working distance, a data processing unit which is adapted to at least one property of the object based on the number of images and to control the device, and a scattering unit that changes between an active state in which the scattering unit affects a light beam path in front of the pattern generating unit and an inactive state bar, in which the scattering unit does not affect the light beam path in front of the pattern generation unit, with the following steps:

Assigning the first working distance and the inactive state to a first operating mode,

Assigning one of the second working distance, which is greater than the first working distance, and the active state, to a second operating mode,

Switching between the first operating mode and the second operating mode by changing the working distance of the imaging optics between the first working distance and the second working distance and changing the scattering unit from the active to the inactive state.

The method thus provides the same advantages as the device according to the first aspect of the invention.

The object initially posed is therefore completely solved. According to one embodiment of the device according to the first aspect, it is proposed that the scattering unit for changing between the active and the inactive state can be moved by the data processing unit by means of an actuator optionally into a light beam path in front of the pattern generation unit.

Thereby, the change between the active and the inactive state constructively relatively simply in a mechanical manner, i. E. by moving the scattering unit.

According to a further embodiment of the device according to the first aspect, it is proposed that the scattering unit is an etched substrate or a diffractive optical element or a holographic optical element.

In this way, the scattering unit can be provided in a favorable manner for the particular application. Examples of etched lenses are found for example in the document DE 102 20 045 A1.

According to a further embodiment of the device according to the first aspect, it is proposed that the scattering unit is an electrically controllable scattering unit which can be switched by the data processing unit between at least one scattering setting and a non-scattering setting.

Thereby, the switching of the scattering unit between the active and the inactive state becomes quickly possible. Also, a movement of the scattering unit can be avoided. Examples are LCD screens, in which the liquid crystals can optionally be activated by scattering or, in an inactive state, only have a transmissive effect. For example, reference is made to the document DE 10 2009 025 362 A1.

According to a further embodiment of the device according to the first aspect, it is proposed that the pattern generation unit has a pattern generator for generating a measurement pattern and an imaging device for imaging the measurement pattern on the object. It can thereby be ensured that the measurement pattern is imaged sharply onto the object by means of the imaging device.

According to a further embodiment of the device according to the first aspect, it is proposed that the imaging optics be an object-side or two-sided telecentric objective in the first optical working distance.

A two-sided telecentric lens is characterized in particular by the fact that theoretically no geometric aberrations occur. For example, a double-sided telecentric lens has no distortion. Also, a change of the focus without changing the magnification is possible.

According to a further embodiment of the device according to the first aspect, it is proposed that the imaging optics is further a zoom lens.

For the variable selection of the system magnification suitable for the requirements of the measurement features, a zoom range of at least 10 times can be provided, a maximum of about 20 times, preferably the zoom range should be about 12 times. Even if only a zoom of about 12 times is needed in the field, it is possible to work with measuring devices with different measuring ranges and dimensions by multiple use of the components with a high degree of uniformity in production. Limiting the zoom range typically shortens the length of the system, saving size and weight. This feature is particularly important when it comes to building small compact systems. In this way, for example, a compact system can be created, that also pivoting joints can be used. The design can be carried out for a magnification range of 0.5x to 6x, ie a 12x zoom range.

According to a further embodiment of the device according to the first aspect, it is proposed that the imaging optics can be set to a first optical working distance, a second optical working distance and a third optical working distance. In particular, for the telecentric operation, the optical system should have a certain standard working distance. Since in industrial metrology, but also objects are examined, which are not only flat, it may be necessary to allow other working distances. For example, for observations of deep wells or within larger three-dimensional bodies, it may happen that the standard working distance is insufficient to focus on the desired observation plane. Also for the Deflektometrieverfahren and the stripe bildverfahren different working distances are needed.

Therefore, it is proposed to support one or more larger or smaller optical working distances with the imaging optics. Since the optics can not be optimally designed for several working distances at the same time, smears in the imaging quality are tolerated with an increased working distance.

Due to the increase in the working distance, it inevitably leads to a reduced numerical aperture and thus to a poorer optical resolution in the image. Also, effects of distortion and chromatic aberrations can be accepted within certain limits with an increased or decreased working distance.

On the other hand, for a higher resolution of one kind, macrofunction can be very helpful. In this case, it makes sense to have a setting of the imaging optics, which has a significantly reduced working distance with high imaging quality. Since this is the highest resolution, this operating mode can only be combined sensibly with high magnifications. It may be useful to use a higher magnification in macro mode than is available in the standard working distance.

According to a further embodiment of the device according to the first aspect, it is proposed that the data processing unit is designed to regulate the state of the scattering unit and the working distance of the device. In particular, it may further be provided that the data processing unit is further configured to control an enlargement or a magnification of the imaging optics. In particular, it may be provided according to a further embodiment of the device according to the first aspect that the device is set up such that set in a first operating mode, the first working distance and the inactive state is selected, and that in a second operating mode of the second Working distance, in particular, is greater than the first working distance, and the active state is selected.

In this way, it becomes possible to have the measuring method to be set automatically by means of the data processing unit. All components can be adjusted by the data processing unit based on the selected measurement method.

According to a further embodiment of the device according to the first aspect, it is proposed that the second optical working distance is twice to two and a half times as large as the first optical working distance.

In particular, according to a further embodiment of the device according to the first aspect, it is proposed that the first optical working distance is 80 mm and the second optical working distance is 200 mm, or that the first optical working distance is 40 mm and the second optical working distance is 80 mm is.

In this way, the requirements for a standard working distance of 80 mm, an increased working distance of 200 mm and a macro-working distance of 40 mm explained above can be used with reasonable and proven values in practice. In the standard working distance can be done on both sides telecentric imaging. In the increased working distance, an image with reduced optical imaging quality at the adjusted magnification and with a limited numerical aperture can take place. The macro working distance makes sense for high magnifications and forms telecentric if possible on both sides.

According to a further embodiment of the device according to the first aspect, it is proposed that the data processing unit is designed to be the first Operation mode, a strip pattern method and perform as a second mode of operation a deflectometry method for optically inspecting the object.

Also, according to an embodiment of the apparatus according to the second aspect, it is proposed that the first mode of operation is a strip pattern method and the second mode of operation is a deflectometry method.

In particular, so at a working distance of 80 mm, the strip projection method and perform at a working distance of 200 mm, the Deflektometrieverfahren. Alternatively, however, the strip projection method can also be carried out at a working distance of 40 mm and the deflectometry method at a working distance of 200 mm. In a further alternative, the strip projection method can be carried out at a working distance of 40 mm and the deflectometry method at a working distance of 80 mm.

It is understood that the features mentioned above and those yet to be explained not only in the particular combination given, but also in other combinations or alone, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

Fig. 1 is a schematic view of an embodiment of a device according to the first aspect;

FIG. 2 shows a schematic view of the device in FIG. 1 in an operating mode for carrying out a deflectometry method; FIG.

Fig. 3 is a schematic view of the apparatus of Fig. 1 in an operating mode for performing a stripe image process; 4 shows an isometric view of a coordinate measuring machine with a further embodiment of a device for inspecting an object;

5 shows a schematic illustration of the further embodiment of a device according to the first aspect; and

6 is a schematic flow diagram of an embodiment of a method according to the second aspect.

FIG. 1 shows a device 10 for inspecting an object 12. The object 12 is arranged on a slide 14. For example, the slide 14 may be an XY table, a turntable, or even just a base plate.

For simple measurement of a topography of an object 12 within a field of view of a camera, the fringe projection method has established itself. In this case, a measurement pattern is projected onto the object 12 and this image object with the illuminated stripes is recorded by a camera. If several images with different measurement patterns are taken, the topography of the object 12 can be recalculated from the image sequence together with the knowledge of the measurement pattern used. Such a method works especially with matt or slightly scattering objects. With glossy objects, it increasingly happens that a large portion of the intensity of the illumination is deflected by reflection on the glossy object 12 in such a way that it is no longer captured and imaged by the camera. The illumination of the object is thus carried out in the strip projection method with a measurement pattern. Thus, an interface to provide a lighting to which a compact strip projector can be connected. The strip projector must be supplied with the electrical power for driving the light source, such as an LED, or for the operation of a pattern generator. To control the pattern generator, a corresponding line must also be available for control. Further, it is advantageous if the operation of the pattern generator is synchronized with the timing of the camera for the image recording, thus each a pattern is available during an image capture. In addition, the illumination pattern must be modified between the different image recordings.

On the other hand, the deflectometry method can be used to inspect the object 12. In a deflectometry method, the strips of the measuring pattern are no longer projected or projected onto the object 12, but instead a camera picks up the measuring pattern onto a lighting screen via a shiny and reflective surface of the object 12. As a result, the surface of the object 12 becomes part of the optical path or of the light beam path. Here as well, an overlay of a measurement pattern and the surface of the object is created. If the measurement patterns are also varied between the image recordings, the topography of the object 12 can be recalculated as in the fringe projection. In particular, it is also possible to perceive purely qualitative unevenness or damage to a surface of the object 12.

The difference between the methods is thus that, in the case of a strip projection method, the measurement pattern is projected onto the object 12, while in the case of a deflectometry method the measurement pattern is viewed and recorded by a corresponding screen from the camera across the object. By means of the device 10 explained below, the conversion from a strip projection method to a deflectometry method can be carried out simply by inserting, for example, a ground glass, generally a scattering unit, optionally in the light beam path, in particular in front of the strip projector.

In order to provide the device 10 with such flexibility with regard to the measuring method to be used, the device 10 has a pattern generation unit 16. The pattern generation unit 16 is provided to generate and imitate a measurement pattern. The measurement pattern can be varied over time. The variation may relate, for example, the number or the width of the strips and gaps between the strips. The strips can also be provided with a sinusoidal or rectangular intensity profile. Furthermore, the device 10 has an image recording unit 18. The image acquisition unit 18 can be, for example, a camera or a video camera that is capable of, for example, recording and storing images of the object 12 in connection with the generation of the patterns in the pattern generation unit 16. Furthermore, an imaging optics 20 is provided. The imaging optics 20 serves to image the object 12 in a suitable manner onto the image recording unit 18. In particular, the imaging optics 20 is a two-sided telecentric lens.

A light beam path is designated by the reference numeral 22. In the context of the present application, "light" is understood to mean any electromagnetic wave, in particular also light in a wavelength range not visible to the human eye, for example infrared radiation. The light emitted by the pattern generating unit 16 thus falls on the object 12 and then further through the imaging optics 20 onto the image pickup unit 18.

Furthermore, a data processing unit 24 is provided. The data processing unit 24 serves to regulate all elements of the device 10 and - depending on the selected measuring method - to evaluate the images taken by the image recording unit 18 with regard to the desired properties of the object 12. In particular, the data processing unit 24 has the task of making the settings and processes within the device 10 and also to coordinate accordingly in a meaningful sequence. The main tasks of the data processing unit 24 may include setting all the required components in the apparatus 10, coordinating the operations in the apparatus 10 in a technically meaningful order, setting a zoom system of the imaging optics 20 to a desired position, and thereby managing the different operations of the Zooming operation for the various functions, such as magnification, working distance, chromatic image adjustment, etc. Furthermore, an adjustment of an illumination system of the device 10 as well as an automatic optimization of the illumination settings for different objects or measurement methods can be the task of the data processing unit 24. The data processing unit 24 can be used to control all necessary operating parameters of the image acquisition unit 18, such as exposure time, Gain and gamma correction, if necessary, depending on the selected wavelength of light be. Furthermore, the data processing unit 24 can coordinate the communication with a further control unit, for example for positioning a carrier system and / or travel movements during a measurement process.

In Fig. 1, the data processing unit 24 is shown schematically as a block. However, it can also be a matter of several, in particular spatially separated, data processing units which communicate with each other.

The device 10 has at least a first working distance 26 and a second working distance 28. By "working distance" can be understood a mechanical and / or an optical working distance. Preferably, the optical working distance of the device 10 is adjustable. Thus, the imaging optics 20 are focused on the object 12 or the imaging optics 20 are positioned relative to the object 12 in such a way that the focal plane of the imaging optics is positioned in the first working distance 26 20 is located on the object 12. The strips projected onto the object 12 are then considered as part of the stripe image process.

Furthermore, the apparatus 10 has a scattering unit 30 which scatters the measurement patterns generated by the pattern generation unit 16. These are then reflected by the object 12 and imaged by the imaging optics 20 onto the image acquisition unit 18. The image recording unit 18 then views the measurement pattern on the scattering unit 30 via the imaging optics 20 and the object 12. A deflectometry procedure is then carried out. In this case, the focal plane of the imaging optics 20 is then set to the second working distance 28 or the imaging optics 20 is positioned relative to the object 12 such that the focal plane of the imaging optics 20 lies on the scattering unit 30. Consequently, the second optical working distance 28 is greater than the first optical working distance 26. Consequently, when performing a deflectometry method, the optical working distance of the device is greater than the mechanical working distance of the device. When a stripe image process is performed, the optical working distance of the device corresponds to the mechanical working distance of the device. Therefore, in the proposed device, the mechanical and / or the optical working distance can be adjusted. In this way, the ratio between the optical working distance and the mechanical working distance can be adjusted to suit the particular measuring method to be performed.

For example, the first working distance 26 can be 80 mm and the second working distance 28 200 mm. A communication of the data processing unit 24 with the image acquisition unit 18, the imaging optics 20, the pattern generation unit 16 and / or the scattering unit 30 can be done both wired and wireless. The wired communication can be provided for example by means of electrical and / or optical data transmission.

The scattering unit 30 is preferably arranged in the light beam path 22 between the object 12 and the pattern generation unit 16. This means that the scattering unit 30 is arranged in front of the pattern generation unit 16. The scattering unit 30 may be located both in an active state in which it influences the light beam path 22, but it may also be in an inactive state in which it does not influence the light beam path 22.

It is possible that the scattering unit 30 is in the light beam path 22 during each time. In this case, the scattering unit 30 may be electrically controllable, for example, such that its refractive properties can be changed electrically controlled. However, it can of course also be provided that the scattering unit 30 can be moved mechanically, for example by means of an actuator, so that it can be moved selectively into or out of the light beam path 22. In this case, scattering unit 30 may be, for example, an element made by etching, a diffractive optical element or a holographic optical element. The lines 32, 33, 34 and 35 shown for communicating the data processing unit 24 with the imaging optics 20, the image acquisition unit 18, the pattern generation unit 16 and the scattering unit 30 are shown merely to illustrate the communication and control paths. As already stated above, each can optionally be either a wireless, but also a wired communication connection.

Fig. 2 shows the device 10 of Fig. 1 in a setting for performing a Deflektometrieverfahrens.

In detail, the pattern generation unit 16 is shown. In particular, the pattern generation unit 16 may include a pattern generator 36 for generating the measurement pattern. Furthermore, an imaging device 38 can be provided, which is designed to image the measurement patterns appropriately on the object 12, if necessary.

In the deflectometry method, the scattering unit 30 is in an active state. As shown, for example, it may be located in the light beam path 22 and may scatter the measurement pattern generated by the pattern generation unit 16. The image recording unit 18 then looks, as it were, over the object 12 at the scattering unit 30 and the measurement pattern emanating therefrom. The imaging optics 20 is set to the second working distance 28.

In contrast, FIG. 3 shows the setting of the device 10 for carrying out the strip projection method. As can be seen, the scattering unit 30 is now in an inactive state. For example, it may no longer be spatially located in the light beam path 22. Alternatively, however, as already stated above, electronic control of the scattering unit 30 may also be provided. The imaging optics 20 is now set to a first working distance 26 which is smaller than the second working distance 28. Now the object 12 is considered together with the measurement pattern projected on the object 12.

Furthermore, a third working distance 40 is schematically indicated in FIG. 3, which may be smaller than the first working distance 26. In principle, it is also possible to use the third working distance 40 for the fringe projection method and then, for example, the first working distance 26-of course, via the object 12 to the scattering unit 30 -for carrying out a deflectometry method. Of course, as a last alternative, it is also conceivable to use the second working distance 28 together with the third working distance 40. For example, the first working distance 26 may be 80 mm, the second working distance 28 may be 200 mm, and the third working distance 40 may be 40 mm, for example.

The spatial arrangement of the imaging optics 20 relative to the pattern generation unit 16 or the object 12 is to be understood as merely an example. Preferably, for example, an angle of approximately 45 ° should exist between the optical axes of the imaging optics 20 and the imaging device 38. That is, the light beam 22 has an object 12 about a kink of 45 °. In principle, however, other angles or Strahleinkopplungen conceivable, so that may result from this other geometric arrangements.

FIG. 4 shows a coordinate measuring machine 100 which has a device 10.

Coordinate measuring machines are well known in the art. They are used, for example, to check workpieces as part of a quality assurance or to determine the geometry of a workpiece completely in the context of a so-called "reverse engineering". In addition, a variety of other applications are conceivable, such as the additional use for inspecting surfaces. In such coordinate measuring machines, various types of sensors may be used to detect the coordinates of a workpiece to be measured. For example, tactile measuring sensors are known for this purpose, as sold for example by the applicant under the product name "VAST", "VAST XT" or "VAST XXT". Here, the surface of the workpiece to be measured is touched with a stylus whose coordinates are constantly known in the measuring room. Such a stylus can also be moved along the surface of a workpiece, so that in such a measuring process, a plurality of measuring points can be detected at fixed time intervals as part of a so-called "scanning method".

Moreover, it is known to use optical sensors that enable contactless detection of the coordinates of a workpiece. An example of such an optical sensor is the optical sensor sold under the product name "ViScan" by the Applicant.

The sensors can then be used in various types of measurement setups. An example of such a measurement setup is a desk-top multisensor system as shown in FIG. An example of such a table-top multisensor system is the Applicant's "O-INSPECT" product. In such a device, both an optical sensor and a tactile sensor are used to perform various inspection tasks on a machine and ideally with a single setup of a workpiece to be measured. In this way, many test tasks can easily be performed, for example, in medical technology, plastics engineering, electronics and precision mechanics. Of course, various other structures are also conceivable beyond. The proposed device 10 can be provided, for example, as a module of such a coordinate measuring machine 100. Thus, in addition to the normal tactile and / or optical measurement tasks of the coordinate measuring machine 100, a strip pattern method and a deflectometry method can be performed.

Such sensor systems or sensor heads, which carry both tactile and optical sensors, are becoming increasingly important in coordinate metrology. A combination of tactile and optical sensors makes it possible to combine the advantages of the high accuracy of a tactile measuring system with the speed of an optical measuring system in a single coordinate measuring machine. Furthermore, calibration processes are avoided when changing the sensor, as well as a possible re-clamping of a workpiece.

Classically, the sensor head, which may also be referred to as a sensor system, is connected to a carrier system which supports and moves the sensor system. Various support systems are known in the art, such as gantry systems, stand, horizontal arm and arm systems, all types of robotic systems, and ultimately closed CT systems in x-ray sensor systems. Furthermore, the carrier systems can have system components which enable as flexible a positioning of the sensor head as possible. An example of this is the applicant's rotary-pivot joint marketed under the name "RDS". In addition, various adapters may be provided to interconnect the different system components of the carrier system with each other and with the sensor system.

The use of the device 10 and the coordinate measuring machine 100 are thus not limited to the table structure shown in FIG. 4 and the corresponding support system, but can also be used with all other types of support systems. Furthermore, the device 10 can also be used generally in multi-sensor measuring systems or also in a material microscope or production machines.

In addition to the device 10, the coordinate measuring machine 100 on a measuring table 42. On the measuring table 42 is a positioning device 44. This is in particular provided to position the object 12 parallel to an X-axis 46 and to a Y-axis 48. The X-axis 46 and the Y-axis 48 thereby span a measurement plane. For positioning, for example, an X table 50 and a Y table 52 may be provided. The X table 50 is parallel to the X axis 46 and the Y table 52 is movable parallel to the Y axis 48. Both are arranged on a base plate 54. The base plate 54 is supported by a machine frame 56 and 56 ', respectively.

The movement of the X-stage 50 and the Y-stage 52 is guided by linear guides in the X direction 58 and in linear guides in the Y direction 60. This structure corresponds to the so-called "table construction". As stated above, other carrier systems are conceivable.

The coordinate measuring apparatus 100 has a measuring head 62. In the measuring head 62, one or more tactile sensors 64 may be arranged. Furthermore, the device 10 is arranged in the measuring head 62. In addition, one or more further optical sensors can also be arranged in the measuring head 62.

The measuring head 62 is held in a Z-carriage, which is guided in a carriage housing 68 parallel to a Z-axis 70. This Z-axis 70 is perpendicular to the X-axis 46 and to the Y-axis 48. The X-axis 46, the Y-axis 48 and the Z-axis 70 thus form a Cartesian coordinate system.

The coordinate measuring machine 100 further has a control panel 72. With the control panel 72, the individual elements of the coordinate measuring machine 100 can be controlled. Furthermore, inputs to the coordinate measuring machine 100 can be specified. In principle, provision may also be made for a display device (not shown) to be arranged in the operating console 72 or elsewhere to direct measured value outputs to a user of the coordinate measuring machine 100. All other elements of the coordinate measuring machine 100 are designated by the same reference numerals as in FIGS. 1 to 3 and will not be explained again below.

Fig. 5 shows schematically a structure of the device 10, as it can be used for example in the coordinate measuring machine 100 in Fig. 4. Same Elements are identified by the same reference numerals and will not be explained again.

In particular, FIG. 5 shows the defined structure of the imaging optics 20. Furthermore, it can be seen that the device 10 can have different illumination units. For example, an inner ring light 74 and an outer ring light 76 may be provided. The ring lights 74, 76 may serve to illuminate the object 12 at different angles of incidence. In principle, other lighting units or types may be provided in addition to the ring lights 74, 76. It can be provided, for example, that a light source of the outer ring light 76 forms the light source of the pattern generation unit 16 and thus the pattern generating unit 16 is provided in the outer ring light 76.

The imaging optics 20 has a front cover 80 to protect the imaging optics 20 from contamination and external influences. Behind it - as seen from the object 12 - is a front lens 82. This is fixed, that is not along an optical axis of the imaging optics 20 movable.

Furthermore, the imaging optics 20 comprises a first lens group 84, a second lens group 86, an aperture stop 88, a third lens group 90 and a fourth lens group 92. The lens group may include one or more lens elements, which in turn may be spaced apart or cemented together. The first lens group 84, the second lens group 86, the aperture stop 88 and also the third lens group 90 are movable along the optical axis of the imaging optics 20. In this way, by means of a single optical design, an imaging optics 20 can be designed which provides the desired different working distances and moreover offers a zooming possibility. In particular, the imaging optics 20 may be designed telecentrically on the object side or on both sides.

Furthermore, a first beam splitter 94 may be provided. A light beam bundle branched off by means of the first beam splitter 94 can then optionally be divided once again by means of a second beam splitter 96. That way it can For example, it may be possible to couple a confocal white-light sensor 98 or, if appropriate, another sensor 102, which has desired measurement properties, concentrically into the imaging optics 20.

In addition, a third beam splitter 104 may be disposed immediately in front of the image pickup unit 18. Further beam splits can be effected in the branched beam by means of a fourth beam splitter 106 and a fifth beam splitter 108. At these points, for example, a light source for incident light 1 10, a focus camera 1 12 and a laser grid network projector 1 14 may be arranged. The focus camera 1 12 and the laser grid adapter 1 14 can be used for example for an autofocus unit.

Under the possibly transparently designed slide 14, a further beam splitter 1 16 may be provided. In this way, an alternative or additional confocal white light sensor 118 can be provided. Furthermore, a light source for transmitted light 120 may be provided.

FIG. 6 shows a schematic flow diagram of a method

130th

The method 130 is intended to change an operating mode of a device 10 for inspecting an object 12. The device 10 can be configured according to the device 10 shown in FIGS. 1 to 3 or FIGS. 4 and 5.

The method then begins in a start step 132. In a step 134, first a first working distance 26 and an inactive state of the scattering unit 30 are assigned to a first operating mode. In this first mode of operation is in particular the strip projection method. In a further step 136, a second working distance, which is greater than the first working distance, and the active state of the scattering unit 30 are associated with a second operating mode, in particular a deflectometry method. During operation of the device 10 or of the coordinate measuring machine 100, a change between the first operating mode and the second operating mode can now take place arbitrarily in a step 138. For this purpose, a change is made between the first working distance 26 and the second working distance 28. This can be done by mechanical movement of the imaging optics 20 and the slide 14 relative to each other and / or by changing the object-side focal length of the imaging optics 20. So by varying the optical and / or the mechanical working distance. When changing the working distance at the same time the scattering unit 30 is changed between the active and the inactive state. In this way, a change of the operating modes is possible. In particular, it becomes possible to switch back and forth between measurements by means of a deflectometry method and a strip projection method.

When the device 10 or the coordinate measuring machine 100 is switched off, the method 130 ends in a stop step 140.

Claims

Patent claims

Device (10) for optically inspecting an object (12), with a microscope slide (14) for carrying the object (12), a pattern generation unit (16) for illuminating the object (12) with a measurement pattern, and an image recording unit (18) for recording of a number of images of the object (12), imaging optics (20) for influencing a light beam path (22) between the object (12) and the image recording unit (18), and a data processing unit (24) which is designed for this purpose, at least to determine a property of the object (12) based on the number of images, characterized in that the device (10) can be adjusted to at least a first working distance (26) and a second working distance (28), and the device is a scattering unit (30) which can be changed between an active state in which the scattering unit (30) influences the light beam path (22) in front of the pattern generation unit (16), and an inactive state in which the scattering unit (30) does not influence the light beam path (22). .

Device according to claim 1, characterized in that the scattering unit (30) for changing between the active and the inactive state of the data processing unit (24) can be moved by means of an actuator into a light beam path (22) in front of the pattern generation unit (16).

Device according to claim 2, characterized in that the scattering unit (30) is an etched substrate or a diffractive optical element or a holographic optical element.

Device according to claim 1, characterized in that the scattering unit (30) is an electrically controllable scattering unit (30) which can be switched by the data processing unit (24) between at least one scattering setting and a non-scattering setting.

5. Device according to one of claims 1 to 4, characterized in that the pattern generation unit (16) has a pattern generator (36) for generating a measurement pattern and an imaging device (38) for imaging the measurement pattern onto the object (12).

6. Device according to one of claims 1 to 5, characterized in that the device (10) can be adjusted to at least a first optical working distance (26) and a second optical working distance (28).

7. Device according to one of claims 1 to 6, characterized in that the device (10) can be adjusted to at least a first mechanical working distance (26) and a second mechanical working distance (28).

8. Device according to claim 6 or 7, characterized in that the imaging optics (20) is a lens that is telecentric on the object side or on both sides at the first optical working distance (26).

9. Device according to claim 8, characterized in that the imaging optics (20) is also a zoom lens.

10. Device according to one of claims 6 to 9, characterized in that the imaging optics (20) can be adjusted to a first optical working distance (26), a second optical working distance (28) and a third optical working distance (40).

1 1 . Device according to one of claims 1 to 10, characterized in that the data processing unit (24) is designed to regulate the state of the scattering unit (30) and the working distance (26, 28, 40) of the imaging optics (20).

12. Device according to one of claims 1 to 1 1, characterized in that the device (10) is set up such that in a first operating mode the first working distance (26) is set and the inactive state is selected, and that the second working distance (28) and the active state are selected in a second operating mode.

13. Device according to one of claims 1 to 12, characterized in that the second optical working distance (28) is twice to two and a half times as large as the first optical working distance (26).

14 Device according to one of claims 1 to 13, characterized in that the first optical working distance (26) is 80 mm and the second optical working distance (28) is 200 mm, or that the first optical working distance (26) is 40 mm and the second optical working distance (28) is 80 mm.

15. Device according to one of claims 1 to 14, characterized in that the data processing unit (24) is designed to carry out a strip image method as the first operating mode and a deflectometry method as the second operating mode for optically inspecting the object (12).

16. Method (130) for changing an operating mode of a device (10) for optically inspecting an object (12), the device having a microscope slide for carrying the object (12), a pattern generation unit (16) for illuminating the object (12). a measurement pattern, an image recording unit (18) for recording a number of images of the object (12), imaging optics (20) for influencing a light beam path (22) between the object (12) and the image recording unit (18), wherein the device (10) can be adjusted to at least a first working distance (26) and a second working distance (28), a data processing unit (24) which is designed to determine at least one property of the object (12) based on the number of images and the Device (10) to regulate, and a scattering unit (30) which can be changed between an active state in which the scattering unit (30) influences a light beam path (22) in front of the pattern generation unit (16), and an inactive state in which the scattering unit (30) does not influence the light beam path (22) in front of the pattern generation unit (16), with the following steps: - Assigning (134) the first working distance (26) and the inactive state to a first operating mode,

- assigning (136) one of the second working distance, which is greater than the first working distance, and the active state to a second operating mode,

- Switching (138) between the first operating mode and the second operating mode by changing the working distance of the imaging optics (20) between the first working distance (26) and the second working distance (28) and the scattering unit (30) from the active to the inactive state is changed.

17. The method according to claim 16, characterized in that the first operating mode is a strip image method and the second operating mode is a deflectometry method.