WO2002066924A1

WO2002066924A1 - Method and device for optically capturing an object

Info

Publication number: WO2002066924A1
Application number: PCT/EP2001/012616
Authority: WO
Inventors: Charalambos Tassakos
Original assignee: Charalambos Tassakos
Priority date: 2001-02-21
Filing date: 2001-10-31
Publication date: 2002-08-29
Also published as: DE10108221A1

Abstract

The invention relates to a method and a device (10) for optically capturing an object (11). The aim of the invention is to enable an object (11) consisting of a light-permeable material, or having a highly light-absorbent or fully light-reflecting surface, to be safely and reliably captured in an optical manner. To this end, measures are taken before or after the optical capture, by which means a deposit is at least partially provided on the object (11), during the optical capture, in order to produce a diffusely reflecting surface. A unit (15) at least partially dampens the surface of the object (11) with extremely small drops of humidity, the object (11) is then optically captured in a unit (17), and the damp deposit is removed in another unit (20) from the surface of the object (11), for example, by means of heat. Following the optical capture, the damp deposit preferably removes itself and is especially embodied as condensed water vapour.

Description

Method and device for optically detecting an object

description

The present invention relates to a method and a device for optical detection, including the measurement of an object.

A digital or analog video camera with a subsequent evaluation of the recorded images can be used, for example, for the optical detection of an object. It is known from the prior art to determine the position and / or orientation of an object either absolutely or relative to a coordinate system or another object. In order to determine the distance between two objects or the distance between two edges of the objects to one another, it is known to illuminate the objects in the region of the edges in such a way that large-area reflections result on the surfaces of the objects. When optically recorded, the surfaces in the area of the edges appear as bright areas; the gap between the edges as a dark area. By evaluating the light / dark transitions, the edges can be detected and the distance between the edges can be determined.

From DE 199 10 699 AI it is known to determine the distance and the offset between two objects or between two edges of the objects by generating line-shaped reflections along the edges of the objects by means of suitable illumination, which are detected and evaluated become. With this method, the edges are thus detected by evaluating the dark / light / dark transitions.

It is also known from the prior art to detect a three-dimensional surface course of the surface of an object in different ways. For example, a two-dimensional projection pattern (eg a grid structure) and the image can be projected onto the surface of the object of the pattern on the surface of the object can be detected and evaluated from at least two angles. In this way, a three-dimensional surface course of the projection pattern on the surface can be determined.

These methods known from the prior art work with light beams, by means of which a reflection or an image is to be generated on the surface of an object to be detected. A prerequisite for the known methods for the optical detection of an object is therefore a diffuse reflection of the light rays or a good image of a projection pattern on the surfaces of the object to be detected. The known methods in particular do not work for objects made of a translucent material or with a highly light-absorbing or a totally reflecting surface. Translucent materials are in particular glass, transparent plastic or, transparent resins. Light-absorbing surfaces are, for example, matt and / or very dark, especially black. For example, totally reflecting surfaces are mirrors or consist of polished aluminum or chrome.

It is known from the prior art not to project the two-dimensional projection pattern onto the surface of such objects for determining the three-dimensional surface course of the surface, but rather to apply it in another way, for example by applying paint or by gluing the pattern. However, this has the disadvantage that the pattern can only be removed again with great effort and time after the optical detection.

It is therefore the object of the present invention to provide a possibility for a safe and reliable optical detection of the object even in the case of an object which consists of a translucent material or has a highly light-absorbing or totally reflecting surface. To achieve this object, the invention proposes, based on the method of the type mentioned at the outset, that measures are taken before or during the optical detection by means of which precipitation is at least partially present on the object during the optical detection to produce a diffusely reflecting surface.

The precipitate applied to the surface of the object according to the invention consists of the finest particles of a liquid or a solid. It preferably consists of the finest droplets of moisture or ice crystals. The precipitation is so fine that the dimensions of the object change only insignificantly when the precipitation is applied to the surface. Alternatively, the effects of precipitation on the dimensions of the object can be taken into account when capturing the object. In any case, the position and / or orientation or a three-dimensional surface course of the object can still be detected with a high degree of accuracy.

Due to the precipitation applied to the surface of the object, the translucency of an object made of a translucent material is severely restricted. In the case of an object with a highly light-absorbing surface, the reflection properties of the surface are significantly increased and improved by the precipitation. In the case of an object with a totally reflecting surface, however, the reflection properties are reduced. Altogether, by the application of the precipitation to the surface, incident light (direct lighting, daylight) or a pattern projected onto it is diffusely reflected by the surface. Thus, if the surface of any object is wetted with the precipitate according to the invention, the methods known per se from the prior art for optically detecting an object can also be used for objects made of a translucent material or with a highly light-absorbing or totally reflecting surface be used.

In the case of optical detection, the determination of the position and / or the orientation of an object by edge detection is particularly intended. A light / dark or a dark / light / dark transition on the surface can be determined for edge detection. In the case of optical detection, the projection of one or more one- or two-dimensional projection patterns, for example a lattice structure, onto the surface of an object is also considered.

The precipitate can also be applied to the surface of an object with little effort. Various possibilities are conceivable for this, which are explained in more detail below. It is also possible to remove the precipitate from the surface after the object has been optically detected. In particular, it is thought that the precipitation can be removed automatically. After the optical detection of the object, the precipitation preferably removes on its own. The precipitate can, for example, be wiped off the surface or removed by evaporation (heat and / or air supply) or removed. Advantageously, the precipitate is removed after the optical detection has ended or removes itself after the optical detection has ended.

The precipitation preferably consists of the finest water droplets. Water can be used to create diffuse reflection properties of the surface of an object to be detected. Any additives can be added to the water, e.g. to increase the reflectivity (e.g. through silver or gold color additives), to reduce the size of the moisture droplets, to improve the adhesion of the moisture deposit on the surface of the object, to remove the moisture deposit from the surface To facilitate the surface (for example, by evaporation-promoting substances) or around the surface or Protect the object (e.g. by means of corrosion-inhibiting substances). However, the water droplets and the additives should be easily removed from the surface or removed by themselves after the object has been detected.

According to an advantageous development of the present invention, it is proposed that a one- or two-dimensional projection pattern is projected onto the surface of the object provided with the precipitate and the course of the projection pattern on the surface is optically recorded and evaluated. In this way, the three-dimensional surface course of an object made of any material and with any reflection properties can be recorded using methods known per se.

According to a preferred embodiment of the present invention, it is proposed that the surface of the object provided with the precipitate is illuminated so that diffuse light reflections form on the surface, the course of which is optically recorded and evaluated. The reflections can be extensive, so that there is a light / dark transition at the edges of the object, or extend linearly along the edges so that there is a dark / light / dark transition along the edges.

For simple wetting of the surface of the object with a precipitation of moisture, it is proposed that the object is at least partially cooled before the optical detection, so that moisture contained in the ambient air condenses or ices on the surface of the cooled area of the object. The higher the ambient temperature, the more moisture can be stored in the ambient air. If the temperature of the ambient air decreases in the area of the cooled area, the moisture storage capacity of the ambient air also decreases. Excess moisture is released from the ambient air and is stored on the cooled areas of the Surface. Depending on the temperature of the surface, the moisture is deposited as very fine droplets or as ice crystals. The ice crystals change into a liquid state of their own by heating or at ambient temperature. The moisture droplets can be removed by heating or remove themselves at ambient temperature.

Advantageously, a liquid is applied to the object, which evaporates after the application and generates evaporative cooling, by means of which the object is at least partially cooled.

Furthermore, it is proposed that the object is at least partially deliberately sprayed with supersaturated moisture vapor before the optical detection and that moisture contained in the moisture vapor condenses on the surface of the sprayed area of the object. This method too is based on a temperature difference between the surface and the ambient air that is locally limited to the area of the surface to be wetted. This temperature difference can be achieved, for example, by lowering the temperature of the surface to be wetted or by increasing the temperature of the ambient air. Due to the lower temperature of the surface to be wetted relative to the ambient air, the ambient air is locally cooled to a region around the surface. This reduces the moisture storage capacity of the ambient air in the area of the surface and causes excess moisture to be deposited on the surface.

The moisture vapor is, for example, water vapor, which is supplied to the surface of the object to be wetted via a feed line. In the immediate vicinity of the surface, the moisture vapor emerges from the supply line and condenses. The moisture vapor can be brought specifically to the surface to be wetted, so that it is only there and not condensed elsewhere, for example on the lens of means for optically detecting the object.

For particularly simple wetting of the surface of the object with a moisture deposit, it is proposed that the object be at least partially sprayed with the finest moisture droplets before the optical detection. These finest droplets of moisture can be applied to the surface of the object, for example using an atomizer. The size of the moisture droplets can be reduced by suitable additives, for example to reduce the surface tension of the moisture.

The wetting of the object with the precipitation can also be achieved by a static charge on the surface of the object to be wetted and / or the particles of the precipitation. This can ensure that the particles really only reach the desired surface of the object and not the means for optically detecting the object, so that the optical detection of the object is not impaired.

The method according to the invention can be used in a particularly advantageous manner for detecting the absolute position and / or orientation of an object. It is also advantageous to use the method according to the invention for detecting the position and / or orientation of an object relative to another object. Finally, the method according to the invention can also be used to record a three-dimensional surface course of at least part of the surface of the object.

The method according to the invention is preferably used for optical detection, in particular for positioning, alignment and / or measurement, of an object made of a translucent material or an object with a highly light-absorbing or a totally reflecting surface used. A practical application example is the positioning and alignment of a

Motor vehicle headlights relative to an installation recess of the body of a motor vehicle. The surface of the headlamp under consideration has a cover plate made of transparent glass or plastic. The cover plate can hardly be optically detected using the known methods. However, if, as proposed according to the invention, a precipitate is applied to the cover pane, one or more He11 / dark transitions or a dark / light / dark transition can be produced at an edge at the edge or on a surface of the headlamp with suitable lighting , A light / dark or a dark / light / dark transition can also be created at the edge of the recessed recess. The position and orientation of the edges and thus the position and orientation of the headlight relative to the recessed recess can be determined by optically detecting the transitions. In this way, the correct installation of a headlamp in the body can be checked during the production of a motor vehicle in the assembly line and, if necessary, corrected before the headlamp is attached.

Another practical example is gripping a windshield for a motor vehicle, for example by means of a robot-guided vacuum gripper with vacuum suction units. In order to determine the position of the windshield and to determine a gripping position for the suction units, certain areas of the windshield are provided with precipitation in order to produce a diffuse reflection of light or a diffuse image of a projection pattern. This also enables the spatial position of the windshield to be determined relative to the rest of the body, and thus a controlled installation even in one movement.

As a further solution to the object of the present invention it is proposed, starting from the device of the type mentioned at the outset, that the device has means for applying a precipitate to at least a part of the object for producing a diffusely reflecting surface during the optical detection, the means indirectly or before or during the optical detection apply immediately.

According to a preferred embodiment of the present invention, it is proposed that the device have means for removing the precipitate after the optical detection has ended.

According to an advantageous development of the present invention, it is proposed that the device have means for executing the method according to the invention.

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are shown in the drawing. All of the described or illustrated features, alone or in any combination, form the subject matter of the invention, regardless of their combination with the patent claims or their dependency, and regardless of their wording or representation in the description or in the drawing. Show it:

Figure 1 is a flow chart of an inventive

Method according to a preferred embodiment; and

Figure 2 shows an inventive device according to a preferred embodiment.

1 shows a flowchart of a method according to the invention in accordance with a preferred embodiment shown. The method is used for the optical detection of an object made of a translucent material or with a highly light-absorbing or totally reflecting surface. Objects made of a translucent material are, for example, diffusing screens or transparent cover panes for headlights or panes in general. Objects with a strongly light-absorbing surface are, for example, matt black lacquered objects, objects made of black rubber, for example car tires. Objects with a totally reflecting surface are, for example, polished decorative strips, door handles, operating levers or engine blocks. With such objects, optical detection by means of edge detection or by means of a two-dimensional projection pattern, for example a grid structure, projected onto a surface of the object is not possible according to the prior art or only under difficult conditions, since incident light is either not at all (transparent objects), not enough (light absorbing objects) or far too strongly (totally reflecting objects) is reflected. A diffusely reflecting surface would be ideal for capturing an object.

According to the invention, it is therefore proposed that measures are taken before or during the optical detection by means of which precipitation is at least partially present on the object during the optical detection to produce a diffusely reflecting surface. Precipitation reduces the translucency of an object made of a translucent material, improves the reflective properties of an object with a highly light-absorbing surface, and reduces the reflective properties of an object with a totally reflective surface. In the case of objects that are wetted with a precipitation, optical detection, for example by edge detection or by detecting a one- or two-dimensional projection pattern projected onto the surface, can be carried out without any problems, since due to the precipitation there is a sufficient amount of light is reflected and is thus available for optical detection or a total reflection of the light is prevented.

The method according to the invention begins in a function block 1. In a function block 2, the object to be detected is at least partially wetted with a precipitate. The surface of the object can be wetted in various ways. It is conceivable to cool the object at least partially, so that moisture contained in the ambient air on the surface of the cooled regions of the object condenses or ices better. To cool the object, for example, a cold spray can be used, such as is used to detect faults in electrical circuits or to treat sports injuries. For cooling, a volatile liquid can also be applied to the object, which evaporates and creates an evaporative cold, by means of which the object is cooled. Likewise, the object can be sprayed with moisture vapor at least partially in a targeted manner, so that moisture contained therein condenses on the surface of the object. Furthermore, it is conceivable to at least partially spray the object with the finest droplets of moisture, for example from an atomizer. Finally, the surface can be wetted with the particles by statically charging the surface and / or the particles.

The actual optical detection of the object then takes place in a function block 3 in a manner known per se from the prior art. As part of the optical detection, for example, a one- or two-dimensional projection pattern, for example a lattice structure, is projected onto the surface of the object wetted with moisture, the course of the lattice structure on the surface is optically recorded and evaluated. Likewise, the surface of the object wetted by the moisture deposit can be illuminated for optical detection of the object, so that Diffuse reflections form on the surface, the course of which is optically recorded and evaluated. The reflections can form over a large area on the surface or - with appropriate lighting and corresponding optical detection - can only run along the edges of the object. Depending on the type of reflection, a light / dark transition or a dark / light / dark transition, for example, is recorded and evaluated.

In a function block 4, the moisture deposit is automatically removed or the

Moisture precipitation then by itself from the surface of the object. The precipitation can be removed, for example, by wiping it away or by evaporation due to the supply of heat or air. The method according to the invention is ended in a function block 5.

FIG. 2 shows a device 10 according to the invention in accordance with a preferred embodiment. In this exemplary embodiment, the object to be detected is a motor vehicle headlight or a cover plate 11 of the headlight for a motor vehicle. With the help of the device

10 it is checked whether the headlight is properly fitted into a recess 12 of the motor vehicle body 13. The device 10 is used in the assembly line during the manufacture of the motor vehicle. The body 13 moves continuously in the direction of an arrow 14.

The device 10 according to the invention essentially comprises three units. First, the body 13 passes through a first unit 15 for wetting the surface of the cover plate

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Claims

claims

1. A method for the optical detection of an object (11), characterized in that measures are taken before or during the optical detection, by means of which precipitation is at least partially present on the object (11) during the optical detection in order to produce a diffusely reflecting surface ,

2. The method according to claim 1, characterized in that a deposit consisting of moisture droplets or ice crystals is applied to the object (11) before or during the optical detection.

3. The method according to claim 1 or 2, characterized in that the precipitation after the optical detection of the object is removed by itself.

4. The method according to any one of claims 1 to 3, characterized in that the precipitate is removed after the end of the optical detection or removed by itself.

5. The method according to any one of claims 1 to 4, characterized in that a one- or two-dimensional projection pattern is projected onto the surface of the object (11) provided with the precipitate and the course of the projection pattern on the surface is optically recorded and evaluated.

6. The method according to any one of claims 1 to 5, characterized in that the surface of the object (11) provided with the precipitation is illuminated, so that diffuse light reflections form on the surface, the course of which is optically recorded and evaluated.

Method according to one of claims 1 to 6, characterized in that the object (11) is at least partially cooled before the optical detection, so that moisture contained in the ambient air condenses or freezes on the surface of the cooled region of the object (11).

8. The method according to claim 7, characterized in that a liquid is applied to the object (11), which evaporates after the application and generates an evaporative cold, through which the object (11) is at least partially cooled.

9. The method according to any one of claims 1 to 6, characterized in that the object (11) is at least partially selectively sprayed with supersaturated moisture vapor before the optical detection and condenses on the surface of the sprayed area of the object (11) moisture contained in the moisture vapor ,

10. The method according to any one of claims 1 to 6, characterized in that the object (11) is at least partially sprayed with the finest moisture droplets before the optical detection.

11. Use of a method according to one of claims 1 to 10 for detecting the absolute position and / or orientation of the object (11).

12. Use of a method according to one of claims 1 to 10 for detecting the position and / or orientation of the object (11) relative to another object (12, 13).

13. Use of a method according to one of claims 1 to 10 for detecting a three-dimensional surface course of at least part of the surface of the object (11).

14. Use of a method according to one of claims 1 to 10 for the optical detection of an object (11) made of a translucent material or an object (11! With a highly light-absorbing or a totally reflecting surface.

15. Device (10) for optically detecting an object

(11), characterized in that the device means (15, 16) for applying a precipitate to at least a part of the object (11) for generation. a diffusely reflecting surface during the optical detection, the means (15, .16) applying the precipitation directly or indirectly before or during the optical detection.

16. The device (10) according to claim 15, characterized in that the device (10) means (20) for

Removal of the precipitate after completion of the optical detection.

17. The device (10) according to claim 15 or 16, characterized in that the device has means for performing a method according to one of claims 1 to 9.