A high-sensitivity 3D shape measurement method using a microscope

Abstract

Optical microscopes generally have magnifications ranging from several tens to several thousands and they are often used to observe micro-specimens. Three-dimensional (3D) shape measurements of specimen surfaces are used in a wide range of fields including medicine, pharmacy, life science, and materials science. Conventional methods invariably employ 3D measurement techniques that involve adjusting the focal length of a microscope, which requires a complex automatic adjustment mechanism. Furthermore, since the depth is determined by controlling the focal length, 3D measurements have a low sensitivity. To realize a 3D measurement system with a simple configuration and a high measurement accuracy, we propose a high-sensitivity 3D shape measurement method that employs a microscope and is based on a pattern projection technique. The measurement system consists simply of a conventional optical microscope, a line laser, and a computer. The 3D measurement method employs slit pattern projection. A slit pattern produced by the line laser beam is projected onto the target surface and a reflected image is obtained using a camera installed on the microscope. 3D shape information of the target is obtained using image processing based on the triangulation method. We obtain 3D shape information of the target surface by scanning the slit projection pattern across most of the target surfaces by translating the stage on which the specimen is mounted. The experimental results demonstrate the effectiveness of the proposed method.