Patent ID: 6145214
Filing Date: 2000-11-14
Classification: G01D

Abstract:
A position detection apparatus comprising:a round bar-shaped recording medium having a scale signal of a predetermined recording wavelength recorded over the entire outer circumferential surface of said recording medium and successively repeated in the longitudinal direction, and an origin signal of a greater recording wavelength than said scale signal recorded at a part of the outer circumference at least at one position in the longitudinal direction;scale signal detection head that moves relatively in the longitudinal direction of said recording medium while maintaining a predetermined distance from the outer circumference of said recording medium and detects said scale signal; andan origin signal detection head that moves relatively in the longitudinal direction of said recording medium while maintaining a predetermined distance from the outer circumference which distance is greater than said distance from the outer circumference of said recording medium to said scale signal detection head and that detects said origin signal;wherein said scale signal detection head is located at a position not facing said origin signal and said origin signal detection head is located at a position facing said origin signal recorded on said recording medium.