Moiré deflectometer for measuring distortion in sheet glasses

Saifollah Rasouli; Mohammad Taghi Tavassoly

doi:10.1117/12.666818

9 December 2005 Moire deflectometer for measuring distortion in sheet glasses

Saifollah Rasouli, Mohammad Taghi Tavassoly

Proceedings Volume 6024, ICO20: Optical Devices and Instruments; 60240E (2005) https://doi.org/10.1117/12.666818
Event: ICO20:Optical Devices and Instruments, 2005, Changchun, China

Abstract

In glass casting or shaping processes, some times wavy and distortion defects are developed in glass sheets. Specifying the locations of these defects and measuring the deflections they cause are significant parameters in many applications. There are several techniques for observing and measuring these defects, but the technique we introduce in this work is more simple and flexible and can be easy installed in production line for quality controlling purposes. The presented deflectometer functions in the following way. The imaging system of the device forms an image of large-scale low frequency linear periodical pattern painted on a vertical plane on a transmission grating. The distance between the object grating (painted pattern) and the second grating is so that the frequencies of the image grating and the second (probe) grating are practically the same. There is a small angle between the lines of the latter gratings to form moire fringes. A CCD camera transfers the moire fringes to a PC. By applying phase shifting technique, which is realized by shifting the probe grating in definite steps in its plane in a direction perpendicular to its lines, the phase distribution due to imprecations in optical system and gratings, are specified, At this stage the defected sheet glass is installed between the object grating and the imaging system and the distorted moire pattern is processed as described before. The difference between two-phase distributions is the phase distribution caused by the defects in the glass, which can be easily converted into the required ray deflections. All the processes are carried out automatically in a time less than 30 seconds and the accuracy of the measurement is of the order of 20 arc seconds.

Citation Download Citation

Saifollah Rasouli and Mohammad Taghi Tavassoly "Moire deflectometer for measuring distortion in sheet glasses", Proc. SPIE 6024, ICO20: Optical Devices and Instruments, 60240E (9 December 2005); https://doi.org/10.1117/12.666818

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