Method and apparatus for optically inspecting a test specimen having an at least partly reflective surface
An apparatus for optically inspecting a test specimen has an at least partly reflective surface including a camera having a number of pixels and an illumination device having a multiplicity of spatially distributed light sources. A workpiece receptacle serves for positioning the test specimen relative to the illumination device and the camera, such that light from the light sources is reflected by the surface to the camera. An evaluation and control unit generates a series of different illumination patterns on the surface, wherein in the course of the series different light sources are switched on. An individual light origin region is determined on the basis of the images recorded by the camera for at least one pixel, whereby the region represents a spatial distribution of individual light contributions generated by the light sources via the surface on the at least one pixel.
1. A method for optically inspecting a test specimen having an at least partly reflective surface, the method comprising:
providing a camera having a number of pixels;
providing an illumination device having a multiplicity of spatially distributed light sources;
positioning the test specimen relative to the illumination device and the camera, such that light from the light sources is reflected via the surface to the camera when the light source is switched on;
generating a series of two or more mutually different illumination patterns on the surface, wherein two or more light sources are switched on in the course of generating the series,
recording a series of images of the surface with respective ones of the illumination patterns, and
determining properties of the test specimen in a manner dependent on the images;
wherein an individual light origin region is determined on the basis of the images recorded by the camera for at least one pixel, the region representing a spatial distribution of individual light contributions generated by the light sources via the surface on the at least one pixel and wherein the properties of the test specimen are determined on the basis of the individual light origin region.
2. The method according to claim 1 , further comprising switching on each light source whose light is reflected via the surface to the camera once.
3. The method according to claim 1 , further comprising switching on each light source whose light is reflected via the surface to the camera individually.
4. The method according to claim 1 , wherein in the course of the generating the series a plurality of light sources are switched on simultaneously to generate a multiplicity of spatially extended illumination patterns and wherein the individual light contributions of the light sources used are calculated on the basis of the multiplicity of spatially extended illumination patterns.
5. The method according to claim 1 , wherein the light sources are each digitally switched on or off in the course of the generating the series.
6. The method according to claim 1 , wherein region properties of the individual light origin region are identified and wherein the properties of the test specimen are determined on the basis of region properties of the individual light origin region.
7. The method according to claim 6 , wherein the identified region properties are selected from the group of region properties consisting of a shape of the individual light origin region, an extent of the individual light origin region, a symmetry of the individual light origin region, an orientation of the individual light origin region, and an intensity distribution within the individual light origin region.
8. The method according to claim 6 , wherein a predetermined number of further illumination patterns for further image recordings are determined in a manner dependent on the region properties of the individual light origin region.
9. The method according to claim 1 , wherein a multiplicity of individual light origin regions are determined for a multiplicity of pixels.
10. The method according to claim 1 , wherein the illumination device comprises a matrix of at least 10×10 light sources.
11. The method according to claim 1 , wherein the light sources of the illumination device form a tunnel-like sheathing surface that surrounds the surface at least partially.
12. The method according to claim 1 , wherein a first and at least one second series of different illumination patterns are generated, wherein the illumination patterns of the first and second series are identical, but are generated at different distances with respect to the surface.
13. An apparatus for optically inspecting a test specimen having an at least partly reflective surface, the apparatus comprising:
a camera having a number of pixels;
an illumination device having a multiplicity of spatially distributed light sources;
a workpiece receptacle for positioning the test specimen relative to the illumination device and the camera so as to cause light from the light sources to be reflected via the surface to the camera when the light source is switched on;
a control unit for generating a series of two or more mutually different illumination patterns on the surface, wherein two or more light sources are switched on in the course of generating the series, and for recording a series of images of the surface with respective ones of the illumination patterns;
an evaluation unit for determining properties of the test specimen in a manner dependent on the images; and,
the evaluation unit being configured to determine an individual light origin region on the basis of the images recorded by the camera for at least one pixel, the region representing a spatial distribution of individual light contributions generated by the light sources via the surface on the at least one pixel and the evaluation unit being further configured to determine properties of the test specimen on the basis of the individual light origin region.