WO1998015815A1

WO1998015815A1 - Arrangement for examining mat, flat and/or curved surfaces

Info

Publication number: WO1998015815A1
Application number: PCT/DE1997/002364
Authority: WO
Inventors: Achim Willing
Original assignee: Dr. Ing. Willing Gmbh
Priority date: 1996-10-08
Filing date: 1997-10-07
Publication date: 1998-04-16
Also published as: DE19641349A1; EP0931255A1

Abstract

The invention relates to an arrangement for examining mat flat and/or curved surfaces to detect faults linked with irregularity in the run of the surface, specially to examine mat, non-painted body structures. To this end, a lighting device conducts a strip illumination of the surface. The surface thus illuminated is observed in an reflecting angle. At least one light-dark border (6), that is only bigger in angular range than a limiting angle to the normal to the surface to be examined, is placed almost parallel to the surface and transversely with respect to the main observation direction. The angular range defined between the limiting angle and the normal remains dark. The light-dark border is bigger than the limiting angle in the angular range and is displaceable in relation to the surface (1), whereby the limiting angle amounts to at least 60°.

Description

Arrangement for the inspection of matt flat and / or curved surfaces

The invention relates to an arrangement for the inspection of matt flat and / or curved surfaces according to the preamble of the main claim.

Defective deformations of mat surfaces, for example dents, elevations, which result from gradual or abrupt deviations from the error-free desired course of the curvature of surfaces, are difficult to detect visually according to the prior art. Surfaces with a high proportion of gloss are required to detect such defects. If high-gloss surfaces are used as mirrors to observe a lattice or stripe-shaped lighting structure, errors appear as distortions, islands of light or dark spots and can therefore be easily recognized. For this reason, matt surfaces, for example raw parts of car bodies, provided for inspection with a very shiny coating by special oil. As a result, the reflection properties required to recognize the lighting structure are generated on the surface and visual error detection is made possible. However, this process is complex and therefore uneconomical.

A test room for checking the surface of vehicle bodies for defects is known from DE 38 13 239 AI. In this test room, test lights are provided which have a uniformly illuminated frosted glass pane with an inclined black stripe grid. The test lights are arranged in such a way that this black stripe grid is "completely" reflected in the surface area to be checked. This design of the test lights has the disadvantage that the contrast on the visual task is reduced due to the large number of strips, since they are not effective for the visual task

Streaks of light shine in and thus reduce the contrast. In addition, the many stripes confuse the observer and the oblique arrangement of the stripes only gives a sharp image at certain points.

The invention is therefore based on the object of providing an arrangement for the inspection of matt flat and / or curved surfaces for the detection of faults, which permits clear fault detection on the surfaces.

This object is achieved according to the invention by the characterizing features of the main claim in conjunction with the features of the preamble. Characterized in that at least one light-dark edge is arranged quasi-parallel to the surface and transversely to the main observation direction only in an angular range greater than 60 ° to the normal of the surface to be inspected and the corresponding other angular range remains dark and that the light-dark edge an error in the surface can be clearly recognized without being covered by other lighting structures in the angle range under consideration with respect to the surface. Due to the relative shift between the light-dark edge and the surface to be inspected, a large area can be covered in the direction of observation and the error can be "good" removed. Due to the quasi-parallel arrangement of both flat and uniaxial or biaxial curved surfaces, the light-dark edge can be displayed sharply in the direction transverse to the direction of observation over the entire length and the lighting conditions are similar over the entire length.

The sensitivity can be increased by continuously or abruptly shifting the light-dark edge, preferably a light stripe, since the image of a contrast is stored in the memory of a person looking at it and when switching to another light-dark that is slightly shifted locally Edge can be used for comparison with the newly set light-dark edge. Since no disturbing lighting structures influence the contrast edge, a lower contrast (eg 1:30) can be used. The measures specified in the subclaims make further advantageous developments and improvements possible.

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it:

1 shows a schematic view of the arrangement according to the invention for inspection according to a first exemplary embodiment,

2 shows a schematic perspective view of an arrangement according to FIG. 1 with a curved surface,

3 shows a representation corresponding to FIG. 1 with other beam profiles,

Fig. 4 is a schematic representation of a

Arrangement for inspection in a further exemplary embodiment,

5 is a perspective view of an arrangement corresponding to FIG. 4,

6 is a perspective view of the arrangement according to the invention with vertical surfaces to be observed,

7 shows a schematic illustration of a further exemplary embodiment of the present invention, 8 shows a schematic illustration of another exemplary embodiment of the invention,

9 is a schematic representation of a further embodiment of the invention, and

Fig. 10 is a schematic representation of another embodiment of the invention.

1 schematically shows the arrangement for the inspection of matt flat and / or curved surfaces for the detection of defects, which is provided, for example, in a test room according to the cited prior art. A matt surface 1, which can be, for example, a surface of a bodyshell, is irradiated by a light-dark edge 6 at angles of approximately 60 °, better 75 ° or less to the normal of surface 1.

By slightly changing the observer location 3, the contrast ratios can also be inverted, so that light areas now appear dark and dark areas now appear light. 2, the light-dark edge 6 is supplied by an illumination device 2 which has a luminance structure with a light stripe 5, the other surfaces 4 being dark. 1 and 2, the surface 1 is viewed by an observer 3, who can also be replaced by an image-recording system with corresponding image processing, at the mirror angle corresponding to the light-dark edge 6. The one surrounding an error Surface appears dark to the observer because the mirror angle leads to dark surface 4. Because of the surface curvature at the error F, part of the error appears bright because the respective mirror angle leads to the bright surface 5.

Since the light-dark edge 6 is realized by a light strip-shaped surface 5 between dark surfaces, two light-dark edges arise at the transition from light to dark. The width of the light stripe 5 is to be determined experimentally and is chosen so that the desired detection of the smallest occurring errors is possible. A corresponding representation is shown in FIG. 3, in which an error F appears dark in two places in comparison to FIG. 1, because the error leads to darker areas 4 as well as fewer and more deflected rays.

The light-dark edge 6 is arranged quasi-parallel to the surface 1 and when the one to be inspected

If the surface is a curved surface, such as the roof or the bonnet or trunk lid of a bodyshell, the light-dark edge 6 follows the course of the curvature of the surface 1, as a result of which an observer who views the surface transversely to the curvature in all locations 3.1, 3.2, 3.3 according to FIG. 2 finds the same lighting conditions.

So that a large area in the direction of observation can be inspected, the light-dark edge 6 formed by the light stripe 5 in dark surroundings 4 can be displaced, in FIGS. 1 to 3 in terms of height. This is indicated schematically in Fig. 4, in which the lighting device 2 has an arrangement of several alternating light 5 and dark 4 stripes, whereby the light stripes do not appear at the same time, but are presented one after the other. It can be seen from FIG. 4 that for an observer location 3 different areas of the surface correspond with two light and dark stripes 4, 5 arranged one above the other. For example, the lower light stripe 5 is first switched on and the remaining area is dark, as a result of which the observer

3 can inspect part of the area 1. Subsequently, the lower light stripe 5 is switched off and the upper light stripe 5 is switched on, so that the observer 3 can view another area of the surface 1.

Of course, the light-dark boundary 6 or a light stripe 5 can also be shifted locally other than stepwise or step-wise, for example a light one can be shown in FIG. 4

Stripes are moved continuously from top to bottom or bottom to top. Such a temporal and spatial change in the structure presented causes errors to flash across the entire field of view and become inconspicuous again, thereby creating a dynamic of error detection which on the one hand supports error detection and on the other hand avoids camouflage zones in which errors are not recognized.

The lighting device 2 can be designed in different ways in order to provide the desired light-dark boundary in its luminance structure. For example, a luminous surface provided in the angular range of greater than 60 ° to the normal to surface 1 can be provided can be shielded according to the desired light-dark edge by mechanically movable screens. Furthermore, it is possible to project the luminance pattern onto projection walls, from which the surface 1 is then irradiated. Liquid crystal devices can also be provided, the permeability of which is electronically controlled in accordance with the desired luminous area. FIG. 5 again shows an illumination device with a bright stripe 5 in different local assignment to an arched surface 1, the observer 3 inspecting different surface areas of the surface 1 in accordance with the beam paths shown. The stripes 5 directly lined up are switched to light one after the other in time, the remaining area remaining dark. The observer is preferably equipped, for example, with an infrared control device, so that he can switch on the bright stripes 5 according to his needs. If the surface is more strongly arched transversely to the observation direction, it is advantageous to use an illumination device 2 'with curved light strips 5 which can be switched on. Stripes are sufficient for only slight curvatures.

6 shows an arrangement for the inspection of vertical surfaces 1 ', for example the side walls of a matt body shell. Here, too, the luminous strips 5 are arranged parallel to the inspecting surface 1 'and can be switched on depending on the surface area to be viewed by the observer 3. The glowing stripes on the lights of the fig. 5 and 6 can be Illumination of light-scattering, translucent material can be realized by tubular fluorescent lamps.

In order to visually shade the luminous strips against each other, the fluorescent lamps can be enclosed by box-shaped or channel-shaped reflectors, leaving the light-emitting surface free.

A sufficient contrast is already achieved by the arrangement of the light strips if only the lamps of the strips surrounding the light strips are dimmed down to less than approx. 3%. This dimming has the advantage that the lamps can be switched almost any number of times and thus a long lamp life can be achieved.

Therefore, when the application speaks of "light" and "dark", the definitions relate to each other, i.e. "Dark" is specified in relation to "light" by the desired or necessary contrast.

FIG. 7 shows an illumination device 2 with a luminance structure, which in turn has different strips 7 to be presented one after the other, the individual strips 7 consisting of alternating light and dark fields 8, 9. Because of the complicated structure of the lighting, such an arrangement can be used, in particular, for automatic image acquisition, and the light fields can also be moved continuously. 8 shows an arrangement of a lighting device 2, which is designed as a roller, the Roller is rotatable, as indicated by the arrow, and has an illuminating strip 5, which can repeat along the circumference of the roller. When the roller rotates, the luminous strip, which is aligned parallel to surface 1, changes its position locally and the observer can continuously view the entire surface.

FIG. 9 shows an observation geometry for a cylinder 10 or, analogously, a light strip, the light density structure of which is observed by an observer with the aid of reflector optics 11.

The observer location can be changed with the aid of a deflection of the observer beam path by a deflecting auxiliary mirror 12. This is shown in FIG. 10, wherein an observer 3 observes the light-dark edge 6 reflected in the surface 1 or the light and dark areas 4, 5 via a deflecting mirror 12.

In the exemplary embodiments described above, the light-dark edge 6 or the light stripe was moved in time and place relative to the fixed surface. However, it is also possible that the

Relative movement between the surface and the light-dark edge is achieved by tilting or also pivoting, that is to say by a back and forth movement of the surface 1.

In the exemplary embodiments described above, the luminance structure in the transverse direction to the observation direction should be at least as long as the length of the surface to be viewed. However, it is also conceivable that for large areas a relative movement between the surface and the at least one light-dark edge by shifting the light-dark edge in combination with a transverse shift of the surface, ie a movement in the direction of observation, makes sense.

When the body is moved transversely, the observed field moves over the body. If the light-dark edge 6 is additionally movable, an error can be tracked for a certain time and an adaptation can be made to the curvature of the body.

In the above description, “matt surfaces” are understood to mean those surfaces which have a low proportion of gloss, such as matt metallic surfaces with a fine structure or the like.

Claims

claims

1. Arrangement for the inspection of matt flat and / or curved surfaces for the detection of faults which are associated with a change in the course of the surface, in particular for the inspection of matt, unpainted body-in-white bodies, in which a lighting device illuminates the surface in the form of strips, and thus illuminates the surface Surface is observed at an angle specifying a reflection, characterized in that at least one light-dark edge (6) is arranged quasi-parallel to the surface and transversely to the main observation direction only in an angular range greater than a critical angle to the normal of the surface to be inspected, and the angular range defined between the critical angle and the normal remains dark and the light-dark edge can be displaced in the angular range greater than the critical angle with respect to the surface (1), the critical angle being at least 60 °.

2. Arrangement according to claim 1, characterized in that the critical angle is 75 °.

3. Arrangement according to claim 1 or 2, characterized in that the lighting device (2) has a luminance structure with a strip-shaped field (5) which is delimited by two quasi-parallel light-dark edges (6).

4. Arrangement according to claim 3, characterized in that the strip-shaped field (7) has a plurality of arranged in the direction transverse to the direction of observation, alternating light and dark surface segments (8,9).

5. Arrangement according to one of claims 1 to 4, characterized in that the at least one light-dark edge (6) is curved in accordance with the surface to be inspected (1).

6. Arrangement according to one of claims 1 to 5, characterized in that the at least one light-dark edge (6) is moved continuously.

7. Arrangement according to one of claims 1 to 5, characterized in that the at least one light-dark edge (6) is moved step by step.

8. Arrangement according to one of claims 1 to 7, characterized in that the surface (1) is fixed and the at least one light-dark edge (6) is movable.

9. Arrangement according to one of claims 1 to 7, characterized in that the at least one light-dark edge (6) is fixed and the surface (1) is movable.

10. Arrangement according to one of claims 1 to 9, characterized in that the surface (1) of an observer (3) or an image-taking System with appropriate image processing is inspected.

11. Arrangement according to one of claims 1 to 10, characterized in that the at least one

Light-dark edge (6) is realized by means of a controllable liquid crystal device.

12. Arrangement according to one of claims 1 to 11, characterized in that the movement of the

The light-dark edge (6) can be controlled by means of a control device which can be actuated by the observer.