Title:
HORIZONTAL DETECTING APPARATUS
Document Type and Number:
Japanese Patent JPH04188012
Kind Code:
A
Abstract:
PURPOSE:To normalize the difference in reflectivity and to perform control so that the vertical attitude is obtained with respect to the optical axis of a projection lens by receiving the reflected light from each block with a photode tector which is divided into a plurality of parts, and obtaining the inclination of above described each block from the light receiving position. CONSTITUTION:A point I on a wafer 3 is illuminated with the approximately parallel light rays outputted from an aperture 9. The light is reflected from the wafer 3. The image is focused on a photodetector 13 through a condensing optical system 12. When the wafer 3 is inclined by a certain angle, the light should be condensed at the center of the photodetector 13 (a point A shown by a solid line) because the light is the parallel light on the axis of the condensing optical system 12. However, the light is cast at an angle switch is twice the slant angle of the wafer 3 with respect to the optical axis. Therefore, the image focusing point is detecting at a deviated point A' shown by a broken line. Since the photodetector 13 is divided into 4 parts, the amount of the light in each light receiving surface is proportional to the output voltage in a detecting circuit 14. The slant angle of the wafer 3 is conversely detected based on the ratio.
Inventors:
AOKI SHINICHIRO
IWAZAWA TOSHIYUKI
SATO TAKEO
IWAZAWA TOSHIYUKI
SATO TAKEO
Application Number:
JP31857990A
Publication Date:
July 06, 1992
Filing Date:
November 22, 1990
Export Citation:
Assignee:
MATSUSHITA ELECTRIC IND CO LTD
International Classes:
G01B11/26; (IPC1-7): G01B11/26
Attorney, Agent or Firm:
Akira Kobiji (2 outside)