Title:
APPARATUS FOR MEASURING THICKNESS OF LIGHT TRANSMITTING MEMBER
Document Type and Number:
Japanese Patent JPH03167409
Kind Code:
A
Abstract:
PURPOSE:To perform highly accurate measurement by obtaining the thickness of a member to be measured based on the thickness of a reference-thickness member when optical intensities which are detected with a plurality of light detecting means indicate maximum intensities in agreement. CONSTITUTION:Under the state wherein a member to be measured 5 and a reference thickness member 6 are removed, the laser light beams emitted from a first and second laser devices 1 and 2 are split through a first beam splitter (BS) 3 and joined again through a third beam splitter BS 8. An optical system is adjusted so that the difference between light paths become zero at this period. Then, the members 5 and 6 are set in the optical system. A thickness (t) of the member 6 through which one light beam is transmitted is changed, and the light intensities which are detected with photodetectors 9 and 10 are observed. A thickness t0 of the member 6 when these light intensities agree and indicate the maximum intensity is obtained. At this time, the optical path length when the light passes through the member 6 having the thick ness t0 is equal to the optical path length when the light passes through the member 5 having the thickness (d). Therefore, when the same material is selected for the members 5 and 6, the thickness (d) of the member 5 can be obtained as d = t0.
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Inventors:
HIRANO MASAO
Application Number:
JP30715289A
Publication Date:
July 19, 1991
Filing Date:
November 27, 1989
Export Citation:
Assignee:
HOYA CORP
International Classes:
G01B11/06; (IPC1-7): G01B11/06
Attorney, Agent or Firm:
Setsuo Aniya (1 person outside)