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Proceedings Paper

Fine-pitch high-efficiency spatial optical modulator for mobile display applications
Author(s): Jong Hyeong Song; Sang Kyeong Yun; Hee Yeoun Kim; Seungdo An; Heung Woo Park; Yoon Joon Choi; Victor Yurlov; Anatoliy Lapchuk; Chung Mo Yang; Sung Jun Lee; Jae Wook Jang; Ki Un Lee; Ki Suk Woo; El M. Bourim
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Paper Abstract

Diffractive spatial optical modulators (SOM) with fine pitch pixel array were introduced for the mobile applications of laser projection display which requires the small volume, low power consumption and high optical efficiency. Micromechanical designs of piezoelectric (PZT) actuator and mirror ribbon structure were optimized for small volume, but keeping the same level of the other performance. Even though the same design rule and fabrication equipment were used for 10 um pitch SOM and 16 um pitch SOM, the optical efficiency of the fine pitch SOM was 78 % for the 0th order diffraction and is better than that of 16 um pitch SOM (73%). The full on/off contrast ratio has no difference between 10 um pitch and 16 um pitch SOM. All the optical characteristics coincide well with the theoretical estimations. High displacement of 500nm, which is enough to modulate the three Red, Green and Blue colors were achieved by the control of the thicknesses and stresses of constituent structural layers. It was found that the stress of Pt/PZT/Pt actuating layer was the main parameter affecting the initial gap height of the ribbon and also its displacement. For improving the optical properties of the SOM devices, the required ribbon-flatness could be achieved by applying a stress gradient on the SiN layer to compensate for the stress unbalance between Al mirror and SiN supprting layer. The temperature sensitive characteristics of the SOM device, which degrades the image quality, could be minimized by a mechanical compensation method using a thermal expansion effect of Si substrates. This concept could be applied in most of the bridge type MEMS structure. The most critical parameter which limit the SOM device lifetime was found to be the ribbon displacement degradation. By using a temperature accelerating lifetime measurement method based on the displacement degradation the estimated lifetime was more than 4,000 hrs and is of acceptable level in the mobile application. In short, the developed fine pitch SOM device, for making small volume of optical module, has sufficient response time and ribbon displacement for modulating the red, blue and green colors with one SOM chip and is suitable for high quality embedded laser projection displays. Optical module with VGA is successfully demonstrated for its potential applications in mobile laser projection display such as a embed projection cellular phone.

Paper Details

Date Published: 23 February 2009
PDF: 9 pages
Proc. SPIE 7208, MOEMS and Miniaturized Systems VIII, 72080T (23 February 2009); doi: 10.1117/12.808892
Show Author Affiliations
Jong Hyeong Song, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Sang Kyeong Yun, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Hee Yeoun Kim, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Seungdo An, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Heung Woo Park, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Yoon Joon Choi, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Victor Yurlov, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Anatoliy Lapchuk, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Chung Mo Yang, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Sung Jun Lee, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Jae Wook Jang, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Ki Un Lee, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
Ki Suk Woo, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)
El M. Bourim, Samsung Electro-Mechanics Co., Ltd. (Korea, Republic of)


Published in SPIE Proceedings Vol. 7208:
MOEMS and Miniaturized Systems VIII
David L. Dickensheets; Harald Schenk; Wibool Piyawattanametha, Editor(s)

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