A percussion musical instrumcnt that has two elongated cylindrical pieces of wood connected together adjacent one of their adjacent ends with a hinge type structure. Related methods and apparatus are also included. A primary laser beam is passed through or over a beam splitter or a diffraction grating and formed into a plurality of secondary beams which produce on the target surface a pattern which identifies the zone investigated with the radiometer. When the display panel displays at least one two-dimensional region and at least one three-dimensional region according to an image signal, the processor determines positions of the at least one two-dimensional region and the at least one three-dimensional region on the display panel according to the image signal.