Provision of real world and image sensor correspondence points for use in calibration of an imaging system for three dimensional imaging based on light triangulation

A method performed by one or more devices (405;

• 430;
• 434;
• 900), for provision of a pair of real world and image sensor correspondence points for use in calibration of an imaging system (405) for three dimensional imaging based on light triangulation, said imaging system comprising a camera (430;
• 530) with image sensor (431) and a light source (410;
• 510) for providing a light plane (411;
• 511), said light triangulation involving imaging by said camera of reflected light resulting from said light plane (411;
• 511) intersecting with and thereby causing reflections from a surface, said correspondence points being a real world point (514-1;
• 529-1), located in said light plane (411;
• 511), and an image sensor point (544-1;
• 554-1) that corresponds to where said real world point (514-1;
• 529-1) is imaged on the image sensor (431) by the imaging system (405), wherein the method is characterized by:
• providing (801) said real world point (514-1;
• 529-1) as a first virtual intersection between a first real world line (512a;
• 527a) and a second real world line (512b;
• 527b),
• wherein said first real world line (512a;
• 527a) corresponds to a first real intersection between a first real surface (521a;
• 526a) and the light plane (511) and wherein reflected light from said first real intersection is captured by the imaging system (405) in a first image (540a;
• 550a), and
• wherein said second real world line (512b;
• 527b) corresponds to a second real intersection between a second real surface (521b;
• 527b) and the light plane (411;
• 511) and wherein reflected light from said second real intersection is captured by the imaging system (405) in another, second, image (540b;
• 550b);
• and
• providing (802) said image sensor point (544-1;
• 554-1) as a second virtual intersection between a first image line (542a;
• 552a) corresponding to positions of intensity peaks of said captured light in the first image (540a;
• 550a) and a second image line (542b;
• 552b) corresponding to positions of intensity peaks of said captured light in the second image (540b;
• 550b).