DE102005013614A1 - Optical measuring device e.g. for shapes of objects and surfaces, has camera, objective, diffuser, and two light sources with diffuser is nontransparent and light sources are placed inside diffuser for illuminating inside of it - Google Patents

Abstract

The device has a camera, an objective, a diffuser, and two light sources. The diffuser is nontransparent and the light sources are placed inside the diffuser for illuminating the inside of it. Either only two light sources are used, which are situated opposite one another on an imaginary diameter line, or the light sources are placed at the corners of an equilateral triangle or of a cross.

Description

• • Vorrichtungen der Bildverarbeitung, insbesondere der industriellen Bildverarbeitung. Diese Verfahren zeichnen sich dadurch aus, dass innerhalb kürzester Zeit ein oder mehrere Bilder des Gegenstandes aufgenommen werden und dieses anschließend automatisch durch eine elektronische Recheneinheit beurteilt und geprüft wird. Hierfür sind Zeiten von Bruchteilen einer Sekunde für Bildaufnahme inklusive Beurteilung üblich. Die Vermessung von zweidimensionalen (2D) Merkmalen in der Bildebene wie Längen, Winkel, Flächen etc. sind Stand der Technik. Die Vermessung und Prüfung dreidimensionaler Merkmale bereitet Schwierigkeiten, da die aufgenommenen Bilder die dritte Dimension senkrecht zur Bildebene nur unzureichend wiedergeben.
• • Demgegenüber sind Vorrichtungen der optischen 3D-Messtechnik darauf spezialisiert, neben den Merkmalen in der Bildebene auch Merkmale der dritten Dimension senkrecht zur Bildebene zu vermessen. Nachteilig ist dabei, dass diese Verfahren sehr viel mehr Zeit in Anspruch nehmen als die der Bildverarbeitung. Hier sind Zeiten von einer bis zu mehreren Sekunden und Minuten üblich. Auch eine automatische Bewertung der Messergebnisse ist in vielen Fällen nicht üblich.

The invention relates to a device for optical shape detection and / or assessment of objects and surfaces. Most methods and devices for optical shape detection and / or assessment of objects and surfaces fall into two categories:

• • Image processing devices, in particular industrial image processing. These methods are characterized in that within a very short time one or more images of the object are taken and this is then automatically assessed and checked by an electronic processing unit. For this, times of fractions of a second are common for image acquisition and evaluation. The measurement of two-dimensional (2D) features in the image plane such as lengths, angles, surfaces, etc. are state of the art. The measurement and testing of three-dimensional features presents difficulties because the recorded images only insufficiently reproduce the third dimension perpendicular to the image plane.
• On the other hand, devices of optical 3D metrology specialize in measuring not only the features in the image plane but also features of the third dimension perpendicular to the image plane. The disadvantage here is that these methods take much more time than the image processing. Times of one to several seconds and minutes are common here. An automatic evaluation of the measurement results is not common in many cases.

aim is to combine the advantages of both categories and the disadvantages to eliminate. With that you can both two-dimensional and three-dimensional features within short Time checked, measured and assessed automatically. This will be a bridge between the areas of image processing and 3D optical metrology.

in this connection are especially shiny objects and surfaces made of metal, plastic, etc., the very common can be found in the technical area. These surfaces prepare both in the image processing as well as in the optical 3D metrology great difficulties due to directed light reflection. But they are the same diffuse scattering objects considered, which in general do not cause any difficulties.

The exam and / or measurement of 2D and / or 3D features as well as optional An automatic evaluation can be carried out according to the method described in WO 2004/051186 Procedures are performed. In this method, called photometric deflectometry Become a photometric stereo method, be a deflectometric Method and a scattering body (S) combined so that the locations on the scattering body surface are encoded surface.

An apparatus for carrying out this known method is constructed, for example, as follows. A camera K with a lens Obj is aligned with the object G. The object is illuminated by a scattering body S, which in turn comprises at least one, preferably a plurality of, separately switchable light sources or groups of light sources 1 . 2 . 3 , ... is illuminated ( 1 ).

In 1 are three light sources 1 . 2 and 3 shown. These are preferably in a plane perpendicular to the image plane of 1 runs. But they are not all in the picture plane of 1 , For example, the middle one is the light source 3 , backwards out of the picture plane of 3 added.

• 1. An welchem Ort sind die Lichtquellen 1, 2, 3... zu platzieren, damit die bestmöglichen Mess- und Prüfergebnisse erreicht werden?
• 2. Wie ist eine helle Ausleuchtung des Gegenstandes zu erreichen?
• 3. Ist es vorteilhaft, den Strahl der Lichtquelle durch eine Optik auf den Gegenstand zu bündeln?
• 4. An welchem Ort ist die Kamera K günstig zu platzieren?
• 5. Welche Abmessungen der Sichtöffnung im Streukörper S sind vorteilhaft?
• 6. Aus welchem Material lässt sich der Streukörper vorteilhaft fertigen und wie muss seine Oberfläche beschaffen sein?
• 7. Wie kann man Verschmutzung und mechanische Beschädigungen des Streukörpers und damit schlechte Ergebnisse vermeiden?

In the realization of such a device, a number of questions arise for the person skilled in the art:

• 1. Where are the light sources? 1 . 2 . 3 ... to be placed so that the best possible measurement and test results are achieved?
• 2. How is a bright illumination of the object achieved?
• 3. Is it advantageous to focus the beam of the light source on the object by optics?
• 4. At what place is the camera K cheap to place?
• 5. Which dimensions of the viewing opening in the diffuser S are advantageous?
• 6. From which material can the litter be produced in an advantageous manner and how must its surface be?
• 7. How can you avoid contamination and mechanical damage of the diffuser and thus poor results?

The particular difficulty is to provide a technical solution find that meets all questions equally.

This This is especially difficult because the answers to the questions are conflicting activities are necessary.

If, for example, one attaches particular importance to research question 1, then the light sources are to be placed at a sufficient distance from the scattering body ( 2 ). This results from every point of Light source approximately the same distance to the diffuser and a nearly parallel illumination. For this case, according to the method described in WO 2004/051186, computationally well-controllable conditions are present, since both the direction and the distance of the light source can be regarded as constant. This is particularly important since the surface coding of the scattering body surface arises from the interplay of the scattering element inclination and the direction of illumination. Vertical incidence of the illumination on the respective surface piece of the diffuser causes a coding with high brightness, grazing incidence with minimal brightness. Of great importance is also from which direction the light sources illuminate the scattering body. If these directions are close to each other, the differences in coding are small (low sensitivity of the measuring device to the slope to be measured), they are far apart they are large (high sensitivity). The device then responds very well to slight variations in local object tilt. However, then large areas of the scatterer can not be illuminated.

For question 2 affects a big one Distance of the light sources, however, negative. When doubling Of the distance one must expect that the illuminance of the scattering body and thus the object is reduced by a factor of 4.

This leads to Question 3, whether the light can be bundled advantageous. The illuminance can be then maintained even at greater distances. On the other hand, it speaks again that the optical Equipment and reflectors usually not so uniform illumination enable, as it is possible without them.

In this case, also the question 4 is to be considered. The position of the camera is to be chosen such that it does not produce a shadow on the scattering body. This is especially the case when the camera is positioned close to the diffuser ( 3 ). On the other hand, it is desirable to place the camera as close as possible to the scattering body and the object in order to achieve a good resolution of the object.

The solution to this question is coupled with the question 5. At a small distance of the camera, the viewing aperture in the diffuser can be chosen small, with a larger distance it must be chosen larger, so that all areas of the object can be detected. As a result, however, the scattering body is interrupted in many areas. These areas will not be available to illuminate the item. If the surface of the object is inclined so that only light from these defects of the scattering body can be reflected into the camera, then the device is blind to all affected inclinations ( 4 ).

In Questions 6 and 7 are concerned with the material of the scattering body whose Texture of the surface, Pollution and possible mechanical damage. It is conceivable z. B. a roughened, transparent plastic (surface spreader) or a milky translucent plastic (volume spreader). A cheap, uniform dispersion in all directions is achieved with the volume spreader, however a lot of light remains unused. In addition, arises at the smooth surface an unwanted one Light reflex. A surface spreader again deflects the path of light to a lesser extent, so that more light can be used. On the other hand speaks that no even radiation is reached in all directions and a rough surface for Pollution by dust and fingerprints tends and only very hard to clean. Chooses one for one the scattering body instead of plastic glass, you can get better properties in terms of mechanical resistance and re reach the cleaning. On the other hand, the precise production of a dimensionally accurate Scattering body at Glass much more expensive than plastic. Added to this is the risk of breakage at glass.

All these questions are solved according to the invention as follows: Instead of the translucent diffuser an opaque scatterer is used, also the light sources are arranged inside. This solution is far from obvious, especially with regard to the particularly important question 1. The closer a light source is to the scattering body, in other words even within the scattering body, in the extreme case, the less one can assume that the scattering body is illuminated by a parallel bundle of rays. Instead, it can be assumed that the light sources emit, for example, into the entire hemisphere ( 5 ). Depending on the light source and radiation characteristic with respect to the direction results in a different illumination distribution on the scattering body. The entire arithmetical evaluation - as it results from WO 2004/051186 - would be useless hereby. Also, the distance of the light sources to each point of the diffuser varies widely depending on the position of the light source. Placing the light sources in the center of a spherical diffuser is eliminated because the center and its surroundings are reserved for the object.

According to the invention, this problem is solved in that the complex influencing factors, for example the direction of illumination on the scattering body, the respective distance of the scattering body and its illuminated surface from the light source and the spatial radiation characteristic of the light source can be skillfully compensated in such a way that an illumination distribution is mimicked, as in the case of illumination from outside with parallel light radiation ( 2 ). This project seems almost hopeless due to the large number of interdependent parameters. For a specific combination of parameters, a solution could be found according to the invention. Due to the computationally complex relationships, a solution was determined by means of a simulation and here only the result is shown.

When Lighting device is designed as a Lambertstrahler Light source preferred. This means that the radiance with the Cosine of the emission angle varies. This distribution is common illuminated bodies, but not found in self-luminous bodies and light sources. At the common you will find a constant radiation in all spatial directions (e.g. Lightbulbs, Gas discharge lamps) or strongly directed radiation Lasers and LEDs. Nevertheless, the special case of lambert-shaped radiation can with special for it designed LEDs can be achieved.

The shape of the scattering body is preferably carried out in the form of a sphere, hemisphere or parts thereof. As the material preferably metal, opaque plastic or other materials are selected, which are well manageable in terms of manufacturing technology. The critical question is to choose the location and orientation of the light sources correctly. For orientation on the surface of a hemispherical scattering body, the terms North Pole for the side of the hemisphere and the equator for the end of the hemisphere are used. The light sources are preferably to be placed in a plane near the equatorial plane. Your main beam is to be aligned perpendicular to this plane upwards. There are several, but preferably four light sources used, which are preferably arranged in the form of a cross, for example a "+" or "X". The center of the cross is preferably on a line that is perpendicular to the equatorial plane and passes through the center. The light sources are to be arranged at a certain distance from the center of the sphere, for example at 20% to 80%, preferably at 30% to 70% of the spherical radius. Particularly favorable conditions are in the vicinity of 50% of the spherical radius ( 6 ).

To the representation of the light sources 1 . 2 . 3 , etc. is also noted here: Preferably, four light sources are provided, which are arranged in a plane. It is conceivable to arrange the light sources in the equatorial plane of the scattering body S or slightly above or below it. In 6 the light sources are only apparently arranged in a row. In fact, for example, the light sources 1 and 2 on a diameter line of the equatorial plane. The light source 3 is opposite the image plane of 6 offset to the rear and in turn preferably arranged on a diameter line, together with a light source, not shown here 4 ,

considered one the light sources vertically from above, for example from the View of the camera K, one sees that they are at a distance to the through a cross marked center of the scattering body in a level are arranged and, for example, on the corners of a preferably equilateral triangle or at the ends of a cross, which preferably has the shape of a "+" or an "X".

In 6 are in the beam path between the light sources 1 and 2 On the one hand and the object G on the other hand shading A provided that prevent direct illumination of the subject. In 6 is that of the light source 3 associated shading not shown for the sake of simplicity.

The Arrangement of the illustrated here and in other embodiments provided shading A is arbitrary. Crucial is the point of view a direct illumination of the object by the light sources to avoid. So it's possible the shading on the holder of a light source or on attach the holder of the object. Finally, can also a separate holder for the shadowing be provided.

With This choice of parameters ensures that all points of the scatterer are surface coded. The type of coding and the illumination distribution corresponds largely a lighting from the outside from a great distance, although the light sources in reality, illuminate the scattered body from within the smallest possible distance.

In order to is calculation of the slope according to the already from WO 2004/051186 known method possible.

alternative can the light sources but also be placed near the equator and the opposite Side of the scatterer on the equator spotlighting. In this case, you can the source distant points of the scattered body illuminated brighter be as the source near.

In addition, for objects with a predominantly scattering surface and / or a combination of shiny and scattering surface, direct illumination of the object also makes sense be. For this purpose, light sources can for example be mounted on the inside of the scattering body or project through openings in the interior, preferably with the light direction to the object.

It may be advantageous in all the cases mentioned to slidably attach the light sources in order to be able to vary the position depending on the application ( 6 ).

In With reference to question 2, a very good illumination is achieved because the light everywhere the inside of the scatterer can reach. An optic for bundling the light is not necessary (Question 3).

The Camera can advantageously be placed directly outside the scattering body there is no shadowing (question 4).

The view port can therefore be kept to a minimum (question 5).

When All materials are available non-translucent materials available, such as metal, Plastic etc. (question 6).

A Cleaning is generally not necessary as the interior of the diffuser from dirt and touch protected is. Damage is also largely excluded (question 7).

Furthermore This arrangement of the light sources offers further advantages. One can Make sure the user of the device is not from a light source blinded. This is especially true for high power light sources such as B. powerful LEDs of importance, for which may already Laser protection regulations apply. In addition, a falsification the measurement is avoided by ambient light.

Farther the device is as preferred constructed as follows.

Camera:

When Camera is preferably an electronically operating camera, in particular a CCD or CMOS camera is used. Their pictures can be used for Further processing transmitted to an electronic processing unit or within a so called smart camera itself are processed.

Lens:

The Lens is preferably designed as a macro lens since the object is preferably at a short working distance from Lens is located. Likewise several cameras with multiple lenses are used. Conceivable are also micro-lenses, if very high magnifications are required.

Diffuser:

This scattering body is preferably in the form of a hemisphere, sphere, ellipsoid or parts thereof ( 6 ).

The scattering body of known devices can, when illuminated from outside, consist of transparent material, such as matt glass, matt translucent plastic, etc. ( 7 ). According to the invention, however, an opaque material such as metal, opaque plastic, etc. is used ( 6 ). The scattering body can be uncoated, for example, with a rough and thus diffusely scattering surface. Preferably, however, it is coated with a diffusely reflecting paint which scatters incident light in an undirected manner. The preferred color is white, but other colors are also possible. It is particularly advantageous if the color has fluorescent or phosphorescent properties. Also, the material of the scattering body itself can show this property, in this case, a coating is not absolutely necessary. As a result, light of preferably short wavelength such. B. blue or ultraviolet light in longer-wave light, but in particular also white light to be converted. It is also particularly advantageous to equip the camera or the objective with a blocking filter for specific wavelengths, preferably for small wavelengths. This prevents direct light from entering the camera into the camera, but allows the light scattered by fluorescence and / or phosphorescence to pass through.

The Inside of the scatterer is illuminated by one or more light sources. Preferably the object G is arranged in or near the center of the scattering body. The preferred form of the scatterer is a hemisphere. The simpler name will be here too the terms North Pole for the crest of the hemisphere and the term equator used for the hemisphere edge. Around the object G simply in a movement along the equatorial plane into the center of the scatterer to lead to be able to it is beneficial to the scattering body from the north pole only to an area just north of the equator, at least where the object is to be introduced.

For the camera and the lens, which are preferably located outside of the scattering body, the scattering body can also have an opening B, also referred to as a sighting opening, which provides the view allows the object ( 6 ). The opening B also acts as a diaphragm for the lens. The opening B should be made so large that it allows the undisturbed view of the object to be tested or even parts thereof. A large opening causes a lot of light to reach the camera. This is desirable especially for short exposure times. In addition, the diffraction-limited resolution increases with a wide opening. On the other hand, the opening B should be as small as possible, so that the largest possible part of the scattering surface remains usable. At the same time, the depth of field can be extended at a small opening B, so that even objects G with large height differences everywhere can be sharply mapped. These requirements can be reconciled if the position of the opening B and the position of the entrance pupil EP of the objective are identical. Optionally, it may also be advantageous for technical reasons to place the plane of the opening B only in the vicinity of the entrance pupil EP. This is especially the case when the location of the entrance pupil is physically inaccessible because it is within the objective. The diameter of the viewing aperture is preferably to be selected equal to or smaller than the diameter of the entrance pupil of the objective, so that as little as possible of the scattering body surface remains unused. If the diameter of the viewing opening is smaller than that of the entrance pupil of the objective, the viewing aperture represents the aperture stop of the overall optical system consisting of the objective and the viewing aperture. Thus, the position of the entrance pupil EP of the overall system can be particularly in the case of a wide opening of the camera aperture and a small viewing aperture be forced to the place of viewing.

One further cheaper Effect carries to help make the usable area of the scatterer can be as big as possible. It will be first Assuming the object is very strong and shiny as a level mirror to be considered in the equatorial plane lies. The lens is on the mirror, d. H. the equatorial plane focused. In the mirror, the viewing aperture is out of focus. The question arises, how big is the blur disk. Owing to symmetry considerations one comes to the conclusion that the diameter of the blur disk exactly the diameter of the entrance pupil of the overall optical system corresponds, so the view opening. The edge of the viewing aperture blurs so that to the center of the viewing aperture, so to speak as if the scattering body no opening would have. This Effect is intensified if you go to a level slightly north of the equator focused, the blur disk will be bigger than the sight opening and guaranteed a safe overlap. So far, it was assumed that a mirror as an object, which is a clear Picture delivers. For rougher shiny surfaces the image of the viewing aperture blurs next, for diffuse scattering surfaces completely. It is advantageous if the viewing opening of the scattering body as replaceable insert is executed. Thus, depending on the requirement, a larger or smaller viewing opening can be used become.

alternative to the circular view opening Variants are conceivable that release only a part of the circular area. Examples are one or more circular sectors. Subdivisions are also conceivable in the radial direction, preferably combined with circular sectors. It But other forms are possible such as B. a hole eccentric with respect to the optical axis of the lens to any shapes. This viewing opening is preferably rotatable executed around the optical axis of the lens, for example as a rotatable Calotte, the flush in the scattering body is used. While the exposure of a camera image then the rotating viewing aperture, the entrance pupil of the lens. It is particularly advantageous if the viewing opening is the entrance pupil while an exposure exactly once, twice or with another integer Multiple passes, thus a uniform exposure is reached within the entrance pupil.

Is a transparent object to be checked, eg. B. from clear glass, plastic, etc. so the camera with the lens is preferably arranged looking from the south pole to the north. The camera looks at the scattering body through the body to be tested ( 8th ). In this case, a viewing opening is not absolutely necessary.

Light sources:

As light sources, for example, incandescent lamps, gas discharge lamps, light sources with optical fiber, flash lamps, laser light sources and semiconductor radiation sources are conceivable. In particular, light emitting diodes (LEDs) are of interest because they have a small size, are fast to switch and have a long life. In particular, high power LEDs with high radiant power are advantageous. The light sources can be switched on independently of each other and create different lighting situations. The light sources or groups of light sources can be switched independently of each other. Depending on which light source or group of light sources is switched on, a different lighting situation arises. The goal is to get the light sources 1 . 2 . 3 ... to be placed so that all locations on the scattering body surface can be coded areally. For example, to encode this area at a point of the equator along the direction to the north pole and further to the opposite point of the equator, a steadily increasing or decreasing illumination along that line is desirable. This is preferably achieved in that the Light source is placed outside the center of the scattering body, preferably in the equatorial plane with the light direction perpendicular thereto. The closer the light source is to the center, the more even the distribution, the farther the edge, the more uneven. For coding, the greatest possible differences in the illumination between one endpoint and the other are desired, but the transition should be as uniform as possible. At the same time the light source is the largest possible area in the center of the scatterer for the object to be tested freilas sen. A good compromise on all of these criteria is achieved when the light source is placed at about 20% to 80%, preferably at about 30% to 70% of the sphere radius. In particular, positions in the range of 50% are favorable ( 6 ).

alternative however, a light source may also be placed near the equator and the opposite Side of the scatterer spotlighting. In this case, the source distant points of the scatterer are brighter be lit up as the source near.

It may be advantageous in all the cases mentioned to slidably attach the light sources in order to be able to vary the position depending on the application ( 6 ). When shifting the light sources, care is taken to ensure that their symmetrical arrangement is maintained.

For items with predominantly scattering surface and / or a combination of shiny and diffusing surface additionally a direct illumination of the object be useful. For this can Light sources, for example, attached to the inside of the scatterer or through openings shine into the interior or protrude into this, preferably with the light direction to the object.

Next the location of the light source and the resulting distance to every place of the scattering body surface goes decisively the respective inclination of the scattering surface for Lighting direction and the radiation characteristic of the light source dependent on the different spatial directions. Advantageously, for example, the spherical Shape of the scatterer, at the inclination of each surface point is different and allows a unique coding. At the same time there is a steady transition of the slope of one Point to a neighboring point instead, so that the illuminance is equal to or can lose weight. An advantageous radiation characteristic of the light source is the Lambertian, here from the equatorial plane be illuminated from, for example, the entire northern hemisphere can. Alternatively, you could also side-emitting light sources are used, for example in the vicinity of the Placed scattered body surface become.

A second light source can with respect the center of the scatterer be arranged symmetrically. With two light sources, the scattering body surface can go along one direction along an imaginary direction from an equator point to the opposite equator point. Thus, only one direction of inclination can be detected.

Become used three light sources, these can preferably arranged at the corners of an equilateral triangle but other arrangements are also possible. With three light sources already can encoded two directions on the scattering surface become. Three light sources thus represent the minimum number of Are sources with which the scattering body surface can be coded area.

For the here addressed light sources, the above applies accordingly: They are arranged in a plane, for example, the equatorial plane a scattering body corresponds or is arranged at a distance to this parallel. The triangle has a center point that lies on a line that the center of the litter body cuts and which is perpendicular to the equatorial plane of the scatterer.

Especially However, it is advantageous to use four light sources, the in the form of an "X" or a "+". In this arrangement, two sources each face each other. you For example, you can activate such a pair, if only one Encoding direction of interest is when both directions are in demand are, the other pair is activated. Also for the supply of the tested objects this arrangement is advantageous because it provides more clearance as for example the symmetrical arrangement of three sources. A larger number from light sources is also possible but not necessary.

at Use of four light sources is basically the same as above: The light sources are arranged in a plane that is the equatorial plane is equal to or parallel to this. The light sources are lying in pairs opposite each other and are preferably arranged symmetrically. In the arrangement in the form of a cross, be it in the form of an "X" or a "+", this is the center of the cross on a line that intersects the midpoint of the equatorial plane and perpendicular to it this one stands.

As a possible position of the light sources was previously called the equatorial plane. For a simple feeding of the test parts but it may make sense be to place the sources in a different plane, for example, further north, to leave the equatorial plane as a measurement level completely free.

Around a direct light incidence of the light sources on the object to be tested to prevent Shades A necessary be, for example, with the holders of the light sources or a holder of the test object are connected. It can also separate mounts for the shadowing A can be provided. The shadings A are so big too choose, that there is no direct light, but at the same time as possible small, so that the object does not cover a part of the scattering body becomes.

Of the diffuser S can be in the area of the opening B outside have a cylindrical approach, which serves as a holder for various Apertures for the realization of different sizes and shapes of the viewing aperture (aperture B) and for the camera can serve.

Stereo System:

In addition to the number of light sources, the number of cameras or lenses can also be varied ( 9 ). If, for example, two cameras are used, a binocular stereo method can also be carried out with the device. Preferably, two viewing openings are provided for the two cameras or lenses, which allow the view from two different positions in the direction of the object to be tested. The disparity of corresponding points in the two camera views provides a statement about the position of object points with respect to the third dimension, ie perpendicular to the equatorial plane. The binocular stereo method is thus a height-measuring method in contrast to the inclination-measuring method of photometric deflectometry. Both methods can be advantageously combined, for example as in US 6,590,669 described. Here, the height-measuring method offers advantages in detecting the global three-dimensional shape of the object, the nei gungsmessende in the detection of the local three-dimensional shape. The number of cameras can be further increased, for example to three or four cameras.

In particular, a device with a larger or equal number of cameras, such as light sources, offers the advantage that a single camera is available for each light source, which can enormously reduce the recording time of the images ( 9 ). In typical electronic cameras (eg CCD and CMOS cameras) there is a big difference between the minimum exposure time and the minimum time for an entire image cycle including reading the image sensor. Exposure time can easily be set to values less than 100 microseconds, while for the entire image cycle, times greater than 10 milliseconds are common. This is because much more time is needed to read the image sensor and transfer the data than for the actual exposure. If a single camera is used, then the time for the image cycle is crucial since the same camera has to take several pictures in succession. If the number of cameras equals the number of light sources, the pure exposure time is decisive. The image acquisition would be started in the rhythm of the lighting with a very short delay, so you can speak of a trigger cascade.

combination with other height-measuring methods.

Alternatively, the device may also be used to combine photometric deflectometry with a height-measuring method other than the binocular stereo method, such as fringe projection, interferometry, white-light interferometry, a time-of-flight method or, preferably, the laser light-section method ( 10 ). For this purpose, a viewing opening is preferably provided in the scattering body for the illuminating laser. Particularly advantageous are semiconductor lasers L, in particular those which have already integrated an optical system for the production of one or more laser lines. Such light sources are very compact and are electronically switchable with extremely little time delay. Conventionally, laser light-section methods employ a mechanism that moves the test object and a single laser line relative to one another, thus sequentially scanning the test specimen section-by-profile for profile sectioning. Each profile section requires a single camera shot, which costs time accordingly. Another disadvantage is that a precise and synchronized to the camera recording displacement unit is needed. It is therefore advantageous if several laser lines are projected simultaneously ( 11 ). Thus, several profile sections of the object to be tested can be detected simultaneously, for example 10 or 20 pieces. In the combination according to the invention with the photometric deflectometry, a single camera image can already be sufficient, so that the displacement unit and the additional time required can be dispensed with. This is possible because the height-measuring method only needs to provide global shape data, but the local shape data is provided by photometric deflectometry.

Calibration:

The device according to the invention can be supplemented by a calibration object Kal ( 12 ). He serves the measured inclination using a known reference object to match the true inclination values. This makes it possible to compensate, inter alia, tolerances of the spatial illumination distribution of the light sources, their radiation power, their position and orientation, the shape and position of the scatterer, the emission of its surface or coating and the position and orientation of the camera. As reference objects, objects of known form can be used, in particular those whose surface is reflective and which have a large number of different inclinations. Here, a precisely crafted, shiny metal ball is preferred because all possible inclinations occur here. If dull or partially matt objects are examined, it may be advantageous to provide a matt calibration object, for example a dull or partially dull ball. For this calibration object, the inclination values are measured areally and then compared with the known values. The assignment of measured values to the actual values represents the calibration. In addition, it is possible to monitor the calibration also during the examination of objects, in particular also a possible variation of the radiation power of the light sources. For this purpose, a reference object can be introduced into the field of view of the camera in addition to the test object ( 13 ), for example a flat reflecting surface or a reflecting sphere, a completely or partially matt surface or sphere. Other shapes and surface finishes are possible.

Claims (29)

Device for optical shape measurement and / or testing of objects, with at least one camera, at least one lens, a scattering body and at least two light sources, characterized in that the scattering body is opaque and that the at least two light sources are arranged in the interior of the scattering body and its Illuminate inside, and that either only two light sources are used, which face each other on an imaginary diameter line or that the light sources at the corners of a - preferably equilateral - triangle or a cross are arranged. Device according to claim 1, characterized in that four light sources are arranged in the form of an "x" or a "+". Device according to Claim 1 or 2, characterized the light sources have a Lambert radiation characteristic. Device according to one of the preceding claims, characterized characterized in that the light sources from the center of the scattering body a Spacing, the 20% to 80%, preferably 30% to 70%, in particular about 50% of the distance between the center of the scattering body and its inner surface accounts. Device according to one of the preceding claims, characterized in that the light sources can be activated separately from one another are. Device according to one of the preceding claims, characterized characterized in that the scattering body the shape of a hemisphere, a sphere, an ellipsoid or a Part of this. Device according to one of the preceding claims through several cameras. Device according to one of the preceding claims characterized in that a plurality of cameras are provided, wherein the Number of cameras of the number of independently switchable light sources is equal to or exceeds this. Device according to one of the preceding claims through several viewing openings. Device according to one of the preceding claims by a lighting device for height measurement. Device according to one of the preceding claims by a lighting device that can project at least one line. Device according to one of the preceding claims by a laser light source that project at least one line can. Device according to one of the preceding claims by a laser light source that can simultaneously project multiple lines. Device according to one of the preceding claims by a lighting device for fringe projection. Device according to one of the preceding claims through an interferometric system. Device according to one of the preceding claims characterized in that at least one light sources slidably attached is. Device according to one of the preceding claims, characterized by a light source, which illuminates the object directly and is preferably arranged inside in the scattering body or illuminates or projects through an opening in the scattering body into its interior. Device according to one of the preceding claims, characterized through a scattering body with a viewing opening, which is identical to the entrance pupil of the overall optical system consisting of sight opening and lens. Device according to one of the preceding claims, characterized characterized in that the size of the viewing aperture in diffuser is variable. Device according to one of the preceding claims, characterized in that the shape of the viewing opening in the diffuser is variable is. Device according to one of the preceding claims, characterized characterized in that the sight opening is mobile. Device according to one of the preceding claims through a rotating sight opening. Device according to one of the preceding claims by a calibration device, which is a reference object includes. Device according to one of the preceding claims by a calibration device comprising a sphere as a reference object. Device according to one of the preceding claims by a calibration device, which is a mirror as reference object includes. Device according to one of the preceding claims by a calibration device, which a flat mirror as Reference object comprises. Device according to one of the preceding claims by a fluorescent and / or phosphorescent diffuser and / or a coating with these properties. Device according to one of the preceding claims through a blocking filter for certain wavelengths of the light. Device according to one of the preceding claims through a blocking filter for the wavelengths at least one of the light sources.