The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 20, 2021
Filed:
May. 16, 2019
Mitutoyo Corporation, Kanagawa, JP;
Hiroshi Sakai, Kanagawa, JP;
Yutaka Watanabe, Kanagawa, JP;
MITUTOYO CORPORATION, Kanagawa, JP;
Abstract
A calibration method of a variable-focal-length lens including a liquid lens unit whose focal-length is periodically varied in response to a periodic drive-signal includes: using a calibration tool having a plurality of height-different parts on a surface; preparing a calibration table by repeating outputting a drive-signal having a predetermined voltage to the variable-focal-length lens, detecting a surface image of the calibration tool using an image detector, detecting two points having maximum image contrast in the surface image, calculating a focal-depth from a difference in a focal-length between the two points; and recording the focal-depth and the voltage of the drive-signal in a corresponding combination, and retrieving a value of the voltage corresponding to a desired focal-depth from the calibration table to set the variable-focal-length lens at the desired focal-depth, and adjusting the voltage of the drive-signal outputted to the variable-focal-length lens based on the retrieved value.