1. A surface pressure input panel for detecting surface irregularities in an object comprising: a pressure sensitive sheet having first and second groups of electrode lines formed thereon and intersecting with each other to form intersection portions; and an element coupled to the sheet for vibrating the sheet at a given reference frequency, the sheet vibrating locally at frequencies that differ from the reference frequency when the surface irregularities of the object are pressed against corresponding portions of the sheet, the sheet being adapted to generate electric signals that represent the local vibration frequencies and to apply the electrical signals to the first and second groups of electrode lines so that a relative location of each generated electrical signal can be determined.