Apparatus for investigating surface texture

Claim 1

IN APPARATUS FOR INVESTIGATING SURFACE TEXTURE HAVING A STYLUS FOR ENGAGEMENT WITH THE SURFACE UNDER TEST, MEANS FOR TRAVERSING THE STYLUS ALONG THE TEST SURFACE AND MEANS FOR GENERATING AMPLIFIED ELECTRICAL SIGNALS REPRESENTATIVE OF THE PROFILE OF THE TEST SURFACE IN ACCORDANCE WITH THE WORKING MOVEMENTS OF THE STYLUS APPROXIMATELY NORMAL TO THE TEST SURFACE DURING TRAVERSING, MEANS FOR THE INVESTIGATION OF SURFACE HIGH SPOTS OR VALLEYS, COMPRISING MEANS FOR RECEIVING THE AMPLIFIED PROFILE-REPRESENTATIVE SIGNALS DURING A PRELIMINARY TRAVERSING MOVEMENT OF THE STYLUS, AN ADJUSTABLE GAIN DEVICE WHICH IS OPERATED, IN PREPARATION FOR A SECOND TRAVERSING MOVEMENT OF THE STYLUS ALONG THE TEST SURFACE, IN ACCORDANCE WITH THE VALUE OF A CHARACTERISTIC MAGNITUDE OF THE AMPLIFIED PROFILE-REPRESENTATIVE SIGNALS FED TO THE RECEIVING MEANS DURING THE PRELIMINARY TRAVERSING MOVEMENT, SO THAT THE PROFILE-REPRESENTATIVE SIGNALS GENERATED DURING SUCH SECOND TRAVERSING MOVEMENT ARE AMPLIFIED AT A GAIN SUCH THAT THE VALUE OF THE SAID CHARACTERISTIC MAGNITUDE CORRESPONDS TO A PRE-SELECTED VALUE, A TRIGGER CIRCUIT FOR RECEIVING THE AMPLIFIED PROFILEREPRESENTATIVE SIGNALS AT THE ADJUSTED GAIN DURING THE SECOND TRAVERSING MOVEMENT OF THE STYLUS, MEANS FOR ADJUSTING THE LEVEL AT WHICH THE TRIGGER CIRCUIT IS ACTUATED, WHEREBY ONLY SELECTED OF THE AMPLIFIED PROFILE-REPRESENTATIVE SIGNALS GIVE RISE TO OUTPUT PULSES FROM THE TRIGGER CIRCUIT, AND MEANS FED WITH THE OUTPUT PULSES OF THE TRIGGER CIRCUIT FOR PROVIDING A MEASUREMENT OR INDICATION RELATING TO SURFACE HIGH SPOTS OR VALLEYS IN ACCORDANCE WITH THE SETTING OF THE LEVEL-ACTUATING ADJUSTING MEANS.