Arrangement for optical measurements and related method
An arrangement for optically measuring the surface, such as surface shape and/or associated surface defects, of an optionally glossy target object, comprising: a diffusive, semi-transparent illumination structure defining a hollow, preferably curved, elongated surface shape, constituting a tunnel shape, configured to surround at least one target object at least partially, a number of LED (light-emitting diode) light sources optically coupled to the illumination structure for illuminating at least one target object via the surface of the illumination structure, wherein the light sources are situated at a distance from the surface of the illumination structure, wherein the LED light sources are arranged in a matrix array along the curvilinear cross-section of the illumination structure and along the length of the tunnel shape of the illumination structure, at least one imaging device, configured to image the target object.
1 . An arrangement for optically measuring surfaces of target objects, the arrangement comprising:
a diffusive, semi-transparent illumination structure defining a hollow, elongated surface shape, constituting a tunnel shape, configured to surround at least a first target object at least partially,
a number of LED (light-emitting diode) light sources optically coupled to the illumination structure for illuminating at least the first target object via the surface of the illumination structure, wherein the light sources are situated at a distance from the surface of the illumination structure, wherein the LED light sources are arranged in a matrix array along a curvilinear first cross-section of the illumination structure and along the length of the tunnel shape of the illumination structure, wherein the individual LED light sources have a beam opening angle and are spaced with a distance from one another,
at least one imaging device, configured to image the target object through at least one apertures, in the illumination structure or from an open position on a side of the illumination structure, such that the illumination structure is not in between the imaging device and target object, and
a control entity configured to instruct said LED light sources to form an image sequence of predetermined illumination patterns on the surface of the illumination structure to illuminate the target object with said patterns projected via said surface, to instruct the at least one imaging device to obtain one or more images of the target object relative to each illumination pattern, and to derive, through the utilization of said patterns utilized and images obtained, a predetermined surface-related property of the target object,
wherein the illumination structure is a light-shaping diffusor having a substantially rough outer surface that refracts light rays in different directions due to altering refraction angles, the bulk material of the diffusor otherwise being clear, wherein the distance from the surface of the illumination structure the LED light sources are situated at is a distance that allows the LED light to spread and cover the diffusor uniformly, said distance depending at least on the beam opening angle, on the spacing of the LED light sources, and on a thickness of the light-shaping diffusor.
2 . The arrangement of claim 1 , wherein the tunnel shape comprises a second cross-section of a full circle, oval or such curvilinear shape.
3 . The arrangement of claim 1 , wherein the tunnel shape comprises a second cross-section of a quadrilateral shape.
4 . The arrangement of claim 1 , further comprising at least one mirror at either end or at both ends of the illumination structure.
5 . The arrangement of claim 1 , further comprising at least one mirror at an angle in relation the illumination structure.
6 . The arrangement of claim 5 , wherein narrow rigid PCBs (printed circuit boards), each comprising an array of LED light sources, are arranged adjacent and in an angle to each other along a curvilinear path over the illumination structure.
7 . The arrangement of claim 1 , wherein the LED light sources are arranged on narrow PCBs (printed circuit boards) such that LED light sources are arranged in a row adjacent to each other.
8 . The arrangement of claim 7 , wherein the narrow PCBs are narrow rigid PCBs.
9 . The arrangement of claim 1 , wherein LED light sources are arranged into rows of 1 to 20 LEDs.
10 . The arrangement of claim 1 , wherein LED light sources are arranged into rows of 1 to 10 LEDs.
11 . The arrangement of claim 1 , comprising an air gap between the LED light sources and the illumination structure surface.
12 . The arrangement of claim 1 , comprising an optically clear material structure between the light sources and the illumination structure surface.
13 . The arrangement of claim 1 , wherein the individual LED light sources are spaced with a distance of 1-20 millimeters.
14 . The arrangement of claim 1 , wherein at least one imaging device includes a CMOS (complementary metal oxide semiconductor) or CCD (charge-coupled device) technology-based camera.
15 . The arrangement of claim 1 , wherein at least one of said apertures is associated with a lens arrangement comprising a number of lenses.
16 . The arrangement of claim 15 , wherein the lens arrangement comprises a plurality of lenses arranged in series and a lens of said plurality disposed prior to at least one other lens of said plurality in the optical path has a diameter smaller than the other lens.
17 . The arrangement of claim 15 , wherein the lens arrangement comprises a body portion facing the aperture with a beveled edge to reduce the shadowing effect of the lens arrangement relative to the illumination structure.
18 . The arrangement of claim 1 , wherein the illumination structure comprises a rough outer surface that refracts light rays in different directions due to altering refraction angles.
19 . The arrangement of claim 1 , wherein the illumination structure contains or substantially consists of plastic or glass material.
20 . The arrangement of claim 1 , wherein the individual LED light sources are spaced with a distance of 1 to 20 millimeters, and the distance between the light sources and the illumination structure surface is 1 to 10 millimeters.
21 . A method for optically measuring a surface of a target object, comprising:
obtaining a diffusive, semi-transparent illumination structure defining a hollow, elongated surface shape, constituting a tunnel shape, configured to surround the target object at least partially, wherein a number of LED (light-emitting diode) light sources are optically coupled to the illumination structure for illuminating the target object via the surface of the illumination structure, wherein the light sources are situated at a distance from the surface of the illumination structure, wherein the LED light sources are arranged in a matrix array along a curvilinear cross-section of the illumination structure and along the length of the tunnel shape of the illumination structure, wherein the individual LED light sources have a beam opening angle and are spaced with a distance from one another,
obtaining at least one imaging device, configured to image the target object through at least one apertures, in the illumination structure or from an open position on a side of the illumination structure, such that the illumination structure is not in between the imaging device and target object,
controlling the LED (light-emitting diode) light sources to form an image sequence of predetermined illumination patterns on the surface of the illumination structure to illuminate the target object with said patterns projected via said surface and instructing said at least one imaging device to obtain one or more images of the target object relative to each illumination pattern, and
deriving, through the utilization of said patterns utilized and images obtained, a predetermined surface-related property of the target object or at least part thereof,
wherein the illumination structure is a light-shaping diffusor having a substantially rough outer surface that refracts light rays in different directions due to altering refraction angles, the bulk material of the diffusor otherwise being clear, wherein the distance from the surface of the illumination structure the LED light sources are situated at is a distance that allows the LED light to spread and cover the diffusor uniformly, said distance depending at least on the beam opening angle, on the spacing of the LED light sources, and on a thickness of the light-shaping diffusor.
22 . An arrangement for optically determining defects of a surface of a target object, the surface having glossy and matte portions, the arrangement comprising:
a diffusive, semi-transparent illumination structure defining a tunnel shape, configured to surround the target object at least partially,
a number of LED (light-emitting diode) light sources optically coupled to the illumination structure for illuminating the glossy and matte portions of the surface of the target object via the surface of the illumination structure, wherein the light sources are situated at a distance from the surface of the illumination structure, wherein the LED light sources are arranged in a matrix array along a first curvilinear cross-section of the illumination structure and along the length of the tunnel shape of the illumination structure,
at least one camera, configured to image the target object through at least one lens-provided aperture, in the illumination structure or from an open position on a side of the illumination structure, such that the illumination structure is not between the imaging device and the target object, and
a control entity that is configured:
to instruct the LED light sources to form a first image sequence of predetermined illumination patterns on the surface of the illumination structure to illuminate the glossy and matte portions with said patterns projected via said surface,
to instruct the at least one camera to obtain one or more first images of the target object relative to each illumination pattern of the first image sequence,
to instruct the LED light sources to change intensity and wavelength according to at least a subset of the one or more first obtained images, to form one or more further image sequences of predetermined illumination patterns on the surface of the illumination structure to illuminate the glossy and matte portions with said patterns projected via said surface,
to instruct the at least one camera to obtain one or more further images of the target object relative to the illumination patterns of the one or more further image sequences,
to determine, based on the one or more further images, one or more best combinations of patterns, intensity and wavelength, for determining defects on the glossy portion and for determining defects on the matte portion, and
to determine, using the one or more best combinations of patterns, intensity and wavelength utilized and the images obtained, one or more defects of the surface of the target object.