aspects of the present invention relate to pressure sensitive touch screens and touch surfaces for clarity of exposition throughout the present specification the term u201c touch screen u201d is used as a generic term to refer to touch sensitive surfaces that may or may not include an electronic display as such the term u201c touch screen u201d as used herein includes inter alia a mouse touchpad as included in many laptop computers and the cover of a handheld electronic device the term u201c optical touch screen u201d is used as a generic term to refer to light based touch screens including inter alia screens that detect a touch based on the difference between an expected light intensity and a detected light intensity where the detected light intensity may be greater than or less than the expected light intensity the term u201c screen glass u201d is used as a generic term to refer to a transparent screen surface the screen may be constructed inter alia from glass or from a non glass material including inter alia crystal acrylic and plastic in some embodiments of the present invention the screen allows near infrared light to pass through but is otherwise non transparent for clarity of exposition throughout the present specification the term u201c emitter u201d is used as a generic term to refer to a light emitting element including inter alia a light emitting diode led and the output end of a fiber optic or tubular light guide that outputs light into a lens or reflector that directs the light over a display surface the term u201c receiver u201d is used as a generic term to refer to a light detecting element including inter alia a photo diode pd and the input end of a fiber optic or tubular light guide that.