| 摘要 |
<p>PURPOSE: To accurately calculate a position by taking out an error signal from a first signal to be generated in response to the relative positions of first and second members in first direction and a second signal to be generated in response to a vertical direction for correction. CONSTITUTION: A table has a first converter 16 and a second converter 20. The converter 20 is in the same structure as the converter 16 and consists of a glass piece 21 with a code mark and an electronic optical sensor 22. When a reference point 23 is accurately located at a middle point between the converters 16 and 20, an error for indicating the dislocation of a product by the converter 16 regarding the reference point 23 for the rotary component force of the movement of a table is the same and has a sign that is opposite to that indicating the dislocation obtained by the converter 20. The error of dislocation display due to the converter 16 is corrected by inputting an electrical signal from both converters 16 and 20 to a correction circuit 24, the circuit 24 compares electrical signals from the converters 16 and 20, compare them with a position indicated by the converter 16, and outputs a net error signal that indicates the difference of the actual position of a product. The net error signal is added to a signal from the converter 16 and is displayed on a display 25.</p> |
