| 摘要 |
PURPOSE:To detect the displacement of a magnetic head by a resolution being twice of the accuracy of an interval of marks by obtaining the relative movement of other straight line part of a belt wound as an ellipse onto which a head carriage is in contact with respect to the one straight line part. CONSTITUTION:The head carriage 34 is in contact onto one straight line part of a steel belt 42 wound as an ellipse, in driving a pulley 46 by a motor 56, the belt 42 is reciprocated to move the head carriage 34 and a magnetic head 40. Slits 47 are provided regularly as marks to the opposite straight light part and a detection section 48 is fixed to the head carriage 34. The deection section 48 consists of a light emitting element 49, a fixed slit plate 50 on which slits 50A, 50B whose phase is deviated by 1/4 are provided and photodetectors 51, 52. The change in the transmission luminous quantity attended with the movement of the carriage 34 is detected by the photodetectors 51, 52 to recognize the relative movement and the moving direction of the head carriage 34.
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