Lithium niobate electro-optic sensor for examining conductive patterns on display panels

Abstract

The fabrication of an electric field detector using an electro- optic LiNbO3 (LN) single crystal is studied for an application to check the electric field of a conductively patterned panel. When this electric field detector moves on the surface of the panel, a constant air gap, which is close enough for the given field intensity and resolution, must be main- tained so as not to damage the surface patterns. For the effective detec- tion of electric field change in this air gap state, an LN single crystal is selected because of its relatively high electro-optic coefficient, transmit- tance, and low dielectric constant. X-cut LN and Z-cut LN structures are selected to estimate the applicability of LN by simulation on the optical intensity variation and electric field distribution of various structures. At an air gap of 10 mm in the Z-cut LN structure, Vp is about 100 to 150 V and optical intensity variation with unit voltage (Q) is 6.7%/V larger than that of the X-cut LN structure. From these characteristics, the Z-cut LN structure proves to be applicable for the electric field detector because the variation of optical intensity (0.8 mW) is sufficient in the ac driving voltage region (620 V) of a real system. © 2003 Society of Photo-Optical