Determining a transformation between coordinate systems in an ultrasonic haptic device and a visual sensor device

A transformation determiner for determining a transformation between a first coordinate system of an ultrasonic haptic device and a second coordinate system of a visual sensor device, the transformation determiner comprising:

• a processor;
• and
• a memory storing instructions that, when executed by the processor, cause the transformation determiner to:
• trigger generation of an ultrasonic focal point by the ultrasonic haptic device, the position of the ultrasonic focal point being defined in the first coordinate system;
• obtain images captured by the visual sensor device, the images depicting a body part of a user while the ultrasonic focal point is active;
• determine, based on the images, a position of the ultrasonic focal point in the second coordinate system when the body part of the user is, within a margin of error, in the ultrasonic focal point, the determining the position of the ultrasonic focal point including detecting a skin vibration on the body part;
• repeat the instructions to trigger, obtain and determine for at least three additional ultrasonic focal points, each ultrasonic focal point being in a different location compared to the other ultrasonic focal points;
• and
• calculate a first transformation between the first coordinate system and the second coordinate system based on the positions of the ultrasonic focal points in the first coordinate system and the second coordinate system to thereby calibrate a relationship between the ultrasonic haptic device and the visual sensor device.

A computer storage medium storing a computer program for determining a transformation between a first coordinate system of an ultrasonic haptic device and a second coordinate system of a visual sensor device, the computer program comprising computer program code which, when run on a transformation determiner causes the transformation determiner to:

• trigger generation of an ultrasonic focal point by the ultrasonic haptic device, the position of the ultrasonic focal point being defined in the first coordinate system;
• obtain images captured by the visual sensor device, the images depicting a body part of a user while the ultrasonic focal point is active;
• determine, based on the images, a position of the ultrasonic focal point in the second coordinate system when the body part of the user is, within a margin of error, in the ultrasonic focal point, the determining the position of the ultrasonic focal point including detecting a skin vibration on the body part;
• repeat the instructions to trigger, obtain and determine for at least three additional ultrasonic focal points, each ultrasonic focal point being in a different location compared to the other ultrasonic focal points;
• and
• calculate a first transformation between the first coordinate system and the second coordinate system based on the positions of the ultrasonic focal points in the first coordinate system and the second coordinate system to thereby calibrate a relationship between the ultrasonic haptic device and the visual sensor device.