Length measuring instrument, code, and code conversion method

A code conversion method for converting a first ternary gray code into a second ternary gray code, the code conversion method comprising:

• reading by a length measuring instrument a conversion target by emitting light onto the conversion target and receiving light reflected by the conversion target;
• setting, by the length measuring instrument, a digit of the conversion target, starting from the lowest-order digit of the first ternary gray code;
• when a sum of numerical values at digits higher than the digit of the conversion target is 0 or an even number, or when the sum of the numerical values at digits higher than the digit of the conversion target is an odd number while a numerical value at the digit of the conversion target is 1, maintaining, by the length measuring instrument, the numerical value at the digit of the conversion target;
• when the sum of the numerical values at digits higher than the digit of the conversion target is an odd number while the numerical value at the digit of the conversion target is 0, converting, by the length measuring instrument, the numerical value at the digit of the conversion target to 2;
• when the sum of the numerical values at digits higher than the digit of the conversion target is an odd number while the numerical value at the digit of the conversion target is 2, converting, by the length measuring instrument, the numerical value at the digit of the conversion target to 0;
• converting, by the length measuring instrument, the first ternary gray code into the second ternary gray code based on the maintained numerical value or the converted numerical value at the digit of the conversion target;
• and
• transmitting, by the length measuring instrument, data corresponding to the second ternary gray code to an external device.