NUMBER OF REFERENCE PICTURE ELEMENT SETTING METHOD IN IMAGE PROCESSOR FOR LENGTH MEASUREMENT

PURPOSE:To exactly set the number of reference picture element even when the one end of a reference mark for setting a number of reference picture element is located at the middle of the point of the scale photographed on a screen. CONSTITUTION:A scale 3 existing on the same measuring surface S as an object W to be measured is photographed and the point D is displayed on a screen 2. After one end 1a of a reference mark 1 is made in coincidence with a point D0 of the scale 3, the other end side of the reference mark 1 is stretched along the longitudinal direction of the scale 3 and the other end 1b is also made in coincidence with an arbitrary point D3 in the scale 3. In this state, the number of picture element between the both ends 1a and 1b of the reference mark 1 is detected, the length between the points D0 and D3 that the both ends 1a and 1b indicate is read on the screen 2 and this length is inputted as a reference length L0. Based on a number G0 of picture element and the reference length L0, the number of picture element per unit length is calculated, and this number is set as a number M0 of reference picture element.