Conversion device for laser interferometic measuring apparatus

Distance measuring apparatus including a laser interferometic measuring device and a conversion device;

• said laser interferometic measuring device generating out of phase first and second pulses each time a distance being measured changes by a reference distance .lambda./N, where .lambda. is a wavelength of a laser beam employed in said laser interferometic measuring device and N is a positive integer;
• said conversion device receiving said pulses and generating an output signal representing the distance measured by said apparatus, said conversion device comprising:
• (a) first register means for holding a conversion coefficient representing said reference distance in the form of digital data having M-digits, where M is a positive integer and a unit distance in said measuring system of units corresponds to a unit number in an (M+1)-th digit from a least significant digit in said digital data;
• (b) means for converting said first and second pulses into a timing pulse which is generated every time said distance being measured is changed by said reference distance;
• (c) an arithmetic calculator means for receiving a predetermined initial value and for adding said conversion coefficient to said initial value every time said timing pulse is generated, said arithmetic calculator means being operable to generate a carry signal every time a result of calculation exceeds a full range of M-digits;
• and
• (d) means for generating said distance signal every time said carry signal is generated.