| 摘要 |
PURPOSE:To perform automatic focusing securely and speedily by calculating the position of a reference point on a measurement surface by an optical system which takes a measurement with low power and moving an optical system which takes a measurement with high power relatively to the position of the reference point. CONSTITUTION:An optical system 8 for measuring the 2nd measurement surface measures the position of a corner part 11 of a VTR head 5 and then an X-Y table 4 is moved previously so that the corner part 11 of the VTR head 5 coincides with the reference point 23 of an image processor. Further, the position of the corner part 11 of the VTR head 5 is measured again and confirmed, and the position of a magnetic gap is calculated from the measured position. This arithmetic is carried out only by adding deviations 24 and 25 of design from the corner part 11 of the VTR head 5 and the magnetic gap 6. After the position of the magnetic gap 6 is calculated, the X-Y table 4 is moved to a position 26 where the magnetic gap 6 is predetermined as the focus position of the optical system 1 for measuring the 1st measurement surface, coordinates of this point are stored in the image processor 15, and the X-Y table 4 is moved by differences between the stored values and coordinates of the magnetic gap 6 which are found by arithmetic. |
