Optical touch display

A method in an interactive display device, comprising:

• providing a user with user perceivable visual content on an image layer, wherein a touching surface covers the image layer or formed by the image layer, the touching surface comprising a plurality of sub-regions that comprise at least a first sub-region and a second sub-region;
• alternatingly illuminating different sub-regions of the touching surface with a plurality of invisible light sources, wherein the first sub-region being illuminated by a first light source of the plurality of invisible light sources, and the second sub-region being illuminated by a second light source of the plurality of invisible light sources;
• capturing an image of the first illuminated sub-region with a first touch detection unit, when the first sub-region is illuminated by the first light source, and when the second light source operates at sufficiently reduced illumination level to reduce undesired reflections of invisible light from non-contacting objects in the vicinity of the touching surface;
• capturing an image of the second illuminated sub-region with a second touch detection unit, when the second sub-region is illuminated by the second light source, and when the first light source operates at sufficiently reduced illumination level to reduce undesired reflections of invisible light from non-contacting objects in the vicinity of the touching surface;
• and,
• detecting from the captured images contact areas where a pointing object contacts the touching surface and thus causes correspondingly one or more marks in the captured images.

A computer program product comprising a non-transitory computer readable medium having computer executable program code stored thereon, which when executed by at least one processor causes an apparatus at least to perform:

• providing a user with user perceivable visual content on an image layer, wherein there is a touching surface covering the image layer or formed by the image layer, the touching surface comprising a plurality of sub-regions that comprise at least a first sub-region and a second sub-region;
• alternatingly illuminating different sub-regions of the touching surface with a plurality of invisible light sources, wherein the first sub-region being illuminated by a first light source of the plurality of invisible light sources, and the second sub-region being illuminated by a second light source of the plurality of invisible light sources;
• capturing an image of the first illuminated sub-region with a first touch detection unit, when the first sub-region is illuminated by the first light source, and when the second light source operates at sufficiently reduced illumination level to reduce undesired reflections of invisible light from non-contacting objects in the vicinity of the touching surface;
• capturing an image of the second illuminated sub-region with a second touch detection unit, when the second sub-region is illuminated by the second light source, and when the first light source operates at sufficiently reduced illumination level to reduce undesired reflections of invisible light from non-contacting objects in the vicinity of the touching surface;
• and,
• detecting from the captured images contact areas where a pointing object contacts the touching surface and thus causes correspondingly one or more marks in the captured images.