本篇論文以穩態視覺誘發電位(Steady-State Visual Evoked Potential, SSVEP)為基礎，提出了新的編碼設計方式。一般穩態視覺誘發電位之閃光刺激訊號是以頻率編碼為主，使用者須注視以固定頻率持續閃爍之閃光源來誘發出相對應之穩態視覺誘發電位反應；而本論文所提出之編碼方式同時結合了穩態視覺誘發電位之頻率鎖定及時間鎖定特性，其具有特殊的刺激序列結構，將使得閃光源呈現閃爍與熄滅交錯之狀態，如此即可改善一般穩態視覺誘發電位刺激方式容易造成使用者視覺疲勞與不適感之缺點。以此閃光編碼方式所誘發出之穩態視覺誘發電位能量將呈現與刺激序列週期相對應之週期性變化，因此腦電訊號只要經過適當的數位訊號處理即可計算出穩態視覺誘發電位能量變化之週期，並藉此達到辨識閃光選項之目的。最後，本論文已經藉由實驗證實此編碼方式所誘發之穩態視覺誘發電位確實具有上述特性，且可做為大腦人機介面之閃光選項使用。

This study proposes a novel stimulation method for steady state visual evoked potential-based brain computer interfaces (SSVEP-based BCIs). The general SSVEP response is induced by a flicker flashing at a fixed frequency. However, visual fatigue evoked by durative stimuli will reduce the amplitude of SSVEP response and make the user uncomfortable. The new coding approach combined of the frequency-locked and time-locked features of SSVEP can eliminate these disadvantages. The flickers will flash for 1 second and turn off respectively for 0.5, 1 and 1.5 seconds by turns. The cycles of the stimulus sequences may cause the corresponding reaction, and the SSVEP energy may appear as periodic variations. This feature will be used in the classification. Finally, the experiment results demonstrate that the SSVEP induced by the proposed method do have the periodic property and can be used in the BCI system.

[1] G. Schalk, D. J. McFarland, T. Hinterberger, N. Birbaumer, and J. R. Wolpaw, “BCI2000: A General-Purpose Brain-Computer Interface (BCI) System”, IEEE Transactions on Biomedical Engineering, Vol. 51, pp. 1034-1043, No. 6, Jun. 2004.
[2] L. J. Trejo, R. Rosipal, and B. Matthews, “Brain–Computer Interfaces for 1-D and 2-D Cursor: Designs Using Volitional Control of the EEG Spectrum or Steady-State Visual Evoked Potentials”, IEEE Transactions on Neural System and Rehabilitation Engineering, Vol. 14, No. 2, pp. 225-229, Jun. 2006.
[3] M. Cheng, X. R. Gao, S. K. Gao, and D. F. Xu, “Design and Implementation of a Brain-Computer Interface with High Transfer Rates”, IEEE Transactions on Biomedical Engineering, Vol. 49, No. 10, pp. 1181-1186, Oct. 2002.
[4] R. C. Panicker, S. Puthusserypady, and Y. Sun, “An Asynchronous P300 BCI with SSVEP-Based Control State Detection”, IEEE Transactions on Biomedical Engineering, Vol. 58, No. 6, pp. 1781-1788, Jun. 2011.
[5] P. L. Lee, J. J. Sie, Y. J. Liu, C. H. Wu, M. H. Lee, C. H. Shu, P. H. Li, C. W. Sun, and K. K. Shyu, “An SSVEP-Actuated Brain Computer Interface Using Phase-Tagged Flickering Sequences: A Cursor System”, Annals of Biomedical Engineering, Vol. 38, No. 7, pp. 2383-2397, Jul. 2010.
[6] H. Cecotti and A. Graser, “Convolutional Neural Networks for P300 Detection with Application to Brain-Computer Interfaces”, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 33, No. 3, Mar. 2011.
[7] J. Wolpaw, N. Birbaumer, D. J. McFarland, G. Pfurtscheller, T. M. Vaughan, “Brain-Computer Interfaces for Communication and Control”, Clinical Neurophysiology, Vol. 113, pp. 767-791, 2002.
[8] J. V. Odom, M. Bach, M. Brigell, G. E. Holder, D. L. McCulloch, A. P. Tormene, Vaegan, “ISCEV Standard for Clinical Visual Evoked Potentials(2009 update)”, Doc. Ophthalmol., 120, pp. 111-119, 2010.
[9] E. E. Sutter, “The Brain Response Interface: Communication through Visually-Induced Electrical Brain Response”, Journal of Microcomputer Application, Vol. 15, pp. 31-45, Jan. 1992.
[10] P. L. Lee, C. H. Wu, J. C. Hsieh, and Y. T. Wu, “Visual Evoked Potential Actuated Brain Computer Interface: A Brain-Actuated Cursor System”, Electronics Letters, Vol. 4, No. 15, Jul. 2005.
[11] 謝竣傑，「多頻相位編碼之閃光視覺誘發電位驅動大腦人機介面」，國立中央大學電機工程學系，碩士論文，民國九十六年七月。
[12] M. Middendorf, G. McMillan, G. Calhoun, and K.S. Jones, “Brain-Computer Interfaces Based on the Steady-State Visual Evoked Response”, IEEE Transactions on Rehabilitation Engineering, Vol. 8, No. 2, pp. 211-214, Jun. 2000.
[13] C. Jia, X. R. Gao, B. Hong, S. K. Gao, ”Frequency and Phase Mixed Coding in SSVEP-Based Brain-Computer Interface”, IEEE Transactions on Biomedical Engineering, Vol. 58, No. 1, pp. 200-206, Jan. 2011.
[14] E. C. Lalor, S. P. Kelly, C. Finucane, R. Burke, R. Smith, R. B. Reilly, and G. McDarby, “Steady-State VEP-Based Brain-Computer Interface Control in an Immersive 3D Gaming Environment”, EURASIP Journal on Applied Signal Processing, 19, pp. 3156-3164, 2005.
[15] Y. Wang, R. Wang, X. R. Gao, B. Hong and S. K. Gao, “A Practical VEP-Based Brain-Computer Interface”, IEEE Transactions on Neural Systems and Rehabilitation Engineering, Vol. 14, No. 2, pp. 234-239, Jun. 2006.
[16] 梁家銘，「穩態視覺誘發電位於大腦人機介面之刺激頻率及責任週期設計」，國立中央大學電機工程學系，碩士論文，民國一百年六月。
[17] J. Pan, X. R. Gao, F. Duan, Z. Yan, and S. K. Gao, “Enhancing the Classification Accuracy of Steady-State Visual Evoked Potential-Based Brain-Computer Interfaces Using Phase Constrained Canonical Correlation Analysis”, Neural Engineering, Vol. 8, No. 3, May 2011.
[18] 黃進強，「交流耦合平衡增益之腦波量測系統」，國立中央大學電機工程學系，碩士論文，民國九十六年七月。
[19] Analog Devices Inc., “RFI Rectification Concepts”, Tutorial MT-096, Rev. 0, 2009.
[20] C. Kitchin, L. Counts, and M. Gerstenhaber, “Reducing RFI Rectification Errors in In-Amp Circuits”, Application Note AN-671, Analog Devices Inc., Rev. 0, 2003.
[21] Jr. J. W. Clark, M. R. Neuman, W. H. Olson, R. A. Peura, Jr. F. P. Primiano, M. P. Siedband, J. G. Webster (Editor), L. A. Wheeler, Medical Instrumentation Application and Design, 4th Edition, John Wiley & Sons Inc., 2009.
[22] Burr-Brown Corporation, INA128 Datasheet, Oct. 1996.
[23] B. B. Winter and J. G. Webster, “Driven-Right-Leg Circuit Design”, IEEE Transactions on Biomedical Engineering, Vol. BME-30, No. 1, pp.62-66, Jan. 1983.
[24] 盧明智，黃敏祥，「OP AMP應用+實驗模擬」，全華科技圖書股份有限公司，民國八十四年十二月。
[25] Texas Instruments Inc., ISO124 Datasheet, Sep. 2005.
[26] 蒙以正，「數位訊號處理：應用MATLAB」，旗標出版股份有限公司，民國九十七年五月。
[27] A. V. Oppenheim, R.W. Schafer, J. R. Buck, Discrete-Time Signal Processing, 2nd edition, Prentice Hall Inc., 1999.
[28] R. M. Rangayyan, Biomedical Signal Analysis: A Case-Study Approach, John Wiley & Sons Inc., 2002.
[29] L. A. Farwell, E. Donchin, “Talking off the Top of Your Head: A Mental Prosthesis Utilizing Event-Related Brain Potentials”, Electroencephalography and Clinical Neurophysiology, Vol.70, pp. 510-523, Dec. 1988.