Title:
MEASUREMENT SYSTEM FOR POLYGON MIRROR SURFACE TILT
Document Type and Number:
Japanese Patent JPH02166416
Kind Code:
A
Abstract:
PURPOSE:To accurately measure a surface tilt angle by detecting a difference in time required for a reflected beam to travel between 1st and 2nd detecting means while a polygon mirror rotates. CONSTITUTION:A laser beam 24 is reflected by a mirror 30 which constitutes the polygon mirror 16 to make a scan between A and B by the rotation of the mirror 16. A 1st slit 12 is provided at one end of the scanning section AB perpendicularly to the scanning direction, a 2nd slit 14 is provided at the other end side of the scanning section at a predetermined angle, and photodiodes 13 and 15 are combined individually behind the slits to constituted the 1st and 2nd photodetecting means. Consequently, beams reflected by both mirrors differ in the time when the beam travel between the slits 12 and 14. A computer 19 calculates the counting difference from the counted value sent from a counter 18 and finds the time difference from the counting difference and clock fre quency to find the surface tilt angle. Consequently, the surface tilt angle is accurately measured.
Inventors:
KATO YOSHIMASA
SUGANO TAKAO
SUGANO TAKAO
Application Number:
JP32237088A
Publication Date:
June 27, 1990
Filing Date:
December 20, 1988
Export Citation:
Assignee:
FUJITSU LTD
International Classes:
B41J2/44; G01M11/00; G02B26/12; (IPC1-7): B41J2/44; G01M11/00; G02B26/10
Domestic Patent References:
| JPS62207062A | 1987-09-11 |
Attorney, Agent or Firm:
Sadaichi Igita