視網膜炎與老年性黃斑病變為現代常見的眼睛疾病，其發生原因乃是因為視網膜上的感光細胞因為疾病或遺傳而導致受損或退化，造成病患視力下降、視角萎縮甚至失明。針對上述兩種眼疾患者，在本論文中，我們提出兩種利用脈衝調變技術之低功耗、高解析度影像感測與電流刺激人工視網膜晶片設計，用以取代病患受損的視網膜感光細胞，期許讓病患能恢復原有視力。
第一個提出的設計為一個4096畫素、0.8伏特操作的感測與刺激視網膜晶，每一個畫素主要分為前端用來感測光源的脈衝頻率調變互補式金氧半導體影像感測器以及一個用來刺激細胞的雙相電流刺激器所組成。有別於一般的3T或4T影像感測器，脈衝頻率調變影像感測器可低電壓操作，其可使用之動態範圍也不會因為操作電壓下降而有所限制。為了取代受損的視網膜細胞功能，本設計所出之雙相電流刺激器可將前端所接收的光訊號轉換成可用來刺激細胞的電流訊號。接著透過後製程的方法在晶片中的每個畫素中長出對應的刺激電極，模擬受損感光細胞之能力。此晶片並且提供了三種操作模式可供使用: (1) 測試模式:可將脈衝訊號、電壓訊號及雙相電流訊號依序讀出，將有利於量測晶片規格與特性；(2)可編輯模式: 可將光感測功能關閉，僅保留雙相電流刺激器之功能，並且可依據使用者需求，編輯輸出電流之二維圖形與大小，將有利於晶片測試階段量測使用；(3)植入模式: 用於晶片植入使用，可將輸入輸出腳位縮減至四個訊號，其所需偏壓與時脈都可從內部產生，使其體積最小化，並將手術所需的複雜度降至最低。
第二個設計為一個雙電壓操作且具有脈衝寬度調變技術之感測與刺激視網膜感測器。有別於第一個設計，本晶片採用脈衝寬度調變技術來增強感光電路的表現，此感光電路僅需0.5伏特操作並且具有固定圖形雜訊消除之技術。為了避免刺激電流因為操作電壓下降而隨之衰減，本設計將雙相電流感測器維持在1.8伏特電壓下操作，使其電流能維持足夠能力刺激視網膜細胞。利用本設計提出的時間電壓轉換器電路，可將感光電路之輸出與刺激電路之輸入進行連結並提供較好的抑制雜訊能力。除此之外，為了模仿人眼可自動適應強弱光環境變化的能力，自動動態範圍調變技術也在此設計電路中被提出。本晶片先利用外部電路將訊號進行平均並判斷環境光強度等級，接著針對系統增益進行調變，使輸出電流增益可因外在光強度自動進行調變。

Retinitis pigmentosa (RP) and age-related macular degeneration (AMD) are diseases that notably affect photoreceptors of the retina and cause progressive vision loss. This thesis proposed two pulse modulation CMOS imager with integrated sense-and-stimulus (SAS) techniques, which are used to replace the sensing capability of damaged photoreceptor.
The first work exhibits a 0.8 V CMOS SAS imager with 4096 pixels for retinal prosthesis. The pixel consists of a pulse-frequency modulation (PFM) photon sensor (for sensing) and a balanced current-mode stimulator (for stimulating) to achieve a highly integrated and low-power solution for high-resolution vision recovery. With the PFM CMOS image sensor, an ultra-low-power operation is achieved. Three operation modes (test mode, programming (PG) mode, and implanted (IP) mode) have been implemented for various purposes. In test mode, the internal signals are multiplexed out serially for chip verification. In PG mode, the output pattern of current stimulator array is programmable by external addresses for patterned electrical stimulus experiments of retina. In IP mode, the chip is fully functional with a minimized number of I/O as 4 for in vivo operation.
The second work exhibits a dual-supply high dynamic range (HDR) SAS CMOS imager with adaptive gain control for artificial retina applications. When compared with the first work, the 0.5 V operated pulse-width modulation (PWM) based HDR image sensor is adopted to reduce power consumption with dynamic range extension. In this PWM sensor, the proposed threshold-variation cancelling (TVC) scheme is adopted to efficiently eliminate the FPN and achieve a low-noise image quality in the front-end. The 1.8 V operated in-pixel pulse-to-current stimulator provides a biphasic current pulse with sufficient intensity to activate neuron cells for artificial vision recovery applications. The time-to-voltage (T-V) conversion technique with a programmable gain is employed to achieve a reduced fixed-pattern-noise (FPN) and an adaptive sensitivity. The cellular mechanism in the retina varies its sensitivity at different intensity of light. An adaptive gain control system is also proposed to modulate a suitable response for mimicking the mechanism of retinal cells.

[1] D. T. Hartong, E. L. Berson, and T. P. Dryja, “Retinitis pigmentosa,” Lancet, vol. 368, pp. 1795–1809, Nov. 2006.
[2] L. M. Gehrs, J. R. Jackson, E. N. Brown, R. Allikmets, and G. S. Hageman, “Complement, age-related macular degeneration and a vision of the future,” Arch. Ophthalmol., vol. 128, no. 3, pp. 349–358, Mar. 2010.
[3] K. Chen, Z. Yang, L. Hoang, J. Weiland, M. Humayun, and W. Liu “An Integrated 256-Channel Epiretinal Prosthesis,” IEEE J. Solid-State Circuits, vol. 45, no. 9, pp. 1946-1956, Sep. 2010.
[4] A. Rothermel, L. Liu, N. P. Aryan, M. Fischer, J. Wuenschmann, S. Kibbel, and A. Harscher, “A CMOS Chip with Active Pixel Array and Specific Test Features for Subretinal Implantation,” IEEE J. Solid-State Circuits, vol. 44, no. 1, pp. 290-300, Jan. 2009.
[5] L.J. Lin, C.Y. Wu, F. Werblin, D. Balya, and T. Roska, “A Neuromorphic Chip That Imitates the ON Brisk Transient Ganglion Cell Set in the Retinas of Rabbits,” IEEE Sensors Journal, vol. 7, no. 9, pp. 1248-1261, Sep. 2007.
[6] L. Theogarajan, “A Low-Power Fully Implantable 15-Channel Retinal Stimulator Chip,” IEEE J. Solid-State Circuits, vol. 43, no. 10, pp. 2322-2337, Oct. 2008.
[7] T. Tokuda, K. Hiyama, S. Sawamura, K. Sasagawa, Y. Terasawa, K. Nishida, Y. Kitaguchi, T. Fujikado, Y. Tano, and J. Ohta, “CMOS-Based Multichip Networked Flexible Retinal Stimulator Designed for Image-Based Retinal Prosthesis” IEEE Trans. Electron Devices, vol. 56, no. 11, pp.2577-2585, Nov. 2009.
[8] J.G. Linvill, and J.C. Bliss, “A direct translation reading aid for the blind,” Proc. IEEE, 54(1):40-51, Jan. 1966.
[9] W. Liu, and M.S. Humayun, “Retinal Prosthesis,” in IEEE Int. Solid-State Circuits Conf., pp. 218-219, 2004.
[10] J.N. Burghartz, T. Engelhardt, H.G. Graf, C. Harendt, H. Richter, C. Scherjon, and K. Warkentin, “CMOS Imager Technologies for Biomedical Applications,” in IEEE Int. Solid-State Circuits Conf., pp. 142-143, 2008.
[11] E. Noorsal, K. Sooksood, H. Xu, R. Hornig, J. Becker, and M. Ortmanns,“A neural stimulator frontend with high-voltage compliance and programmable pulse shape for epiretinal implants,” IEEE J. Solid-State Circuits, vol. 47, no. 1, pp. 244–256, 2012
[12] H. Chun, Y. Yang, and T. Lehmann, “Safety Ensuring Retinal Prosthesis with Precise Charge Balance and Low Power Consumption” IEEE Trans. Biomed. Circuits Syst., vol. 8, no. 1, pp. 108–118, 2014.
[13] N. Tran, S. Bai, J. Yang, H. Chun, O. Kavehei, Y. Yang, V. Muktamath, D. Ng, H. Meffin, M. Halpern, and E. Fkafidas “A Complete 256-Electrode Retinal Prosthesis Chip,” IEEE J. Solid-State Circuits, vol. 49, no. 3, pp. 751-765, Mar. 2014.
[14] M. Ortmanns, A. Rocke, M. Gehrke, and H.J. Tiedtke, “A 232-Channel Epiretinal Stimulator ASIC” IEEE J. Solid-State Circuits, vol. 42, no. 12, pp. 2946-2959, Dec. 2007.
[15] M. Monge, M. Raj, M.Honarvar-Nazari, H.-C. Chang,Y. Zhao, J.Weiland, M. Humayun, Y.-C. Tai, and A. Emami-Neyestanak, “A fully intraocular 0.0169 mm /pixel 512-channel self-calibrating epiretinal prosthesis in 65 nm CMOS,” in IEEE Int. Solid-State Circuits Conf., ISSCC 2013, 2013, pp. 296–297.
[16] L. Da Cruz, B. F. Coley, J. D. Dorn, F. Merlini, E. Filley, P. Christopher, F. K. Chen, F. Wuyyuru, J. A. Sahel, P. E. Stanga, M. S. Humayun, R. J. Greenberg, and G. Dagnelie, “The Argus II epiretinal prosthesis system allows letter and word reading and long-term function in patients with profound vision loss,” Brit. J. Ophthalmol., vol. 97, no. 5, pp. 632–636, May 2013.
[17] M. Barbaro, P. T. Burgi, A. Mortara, P. Nussbaum, and F. Heitger“A 100x100 Pixel Silicon Retina for Gradient Extraction With Steering Filter Capabilities and Temporal Output Coding,” IEEE J. Solid-State Circuits, vol. 37, no. 2, pp. 160–172, Feb. 2002.
[18] Y. Miura, T. Hachida, and M. Kimura, “Artificial Retina Using Thin-Film Transistors Driven by Wireless Power Supply,” IEEE Sensors Journal, vol. 11, no. 7, pp. 1564-1567, Jun. 2011.
[19] C. L. Lee, and C.C. Hsieh, “A 0.6V CMOS Image Sensor with In-Pixel Biphasic Current Driver for Biomedical Application,” IEEE Int. Symp. Circuits and System Conf. Dig., pp. 1455-1458, 2011.
[20] C. L. Lee, and C.C. Hsieh, “A 0.8 V 4096 Pixels CMOS Sense-and -Stimulus Imager for Retinal Prosthesis,” IEEE Trans. Electron Devices, vol. 60, no. 3, pp.1162-1168, Mar. 2013.
[21] D.G. Birch, J.L. Anderson, and G.E. Fish, “Yearly Rates of Rod and Cone Functional Loss in Retinitis Pigmentosa and Cone-Rod Dystrophy,” Ophthalmology, 106, 258-68, 1999.
[22] A.M. Geller, and P.A. Sieving, “Assessment of Foveal Cone Photoreceptors in Stargardt’s Macular Dystrophy Using a Small Dog Detection Task,” Vision Res, 33, 1509-1524, 1993.
[23] Eyewiki Website, “Retinitis Pigmentosa,” [Online]
http://eyewiki.aao.org/Retinitis_Pigmentosa
[24] R. Klein, “Overview of Progress in the Epidemiology of Age-Related Macular Degeneration,” Ophthalmic Epidemiol, 14(4), 184-187, 2007.
[25] R.D. Jager, W.F. Mieler, and J.W. Miller, “Age-Related Macular Degeneration,” N Engl J Med, 358(24), 2606-2617, 2008.
[26] M.B. Gorin, “A Clinician’s View of the Molecular Genetics of Age-Related Maculopathy,” Arch Ophthalmol, 125(1), 21-29, 2007.
[27] Macular Network Website, “Macular Degeneration (AMD or ARMD) – An Overview,” [Online] http://macular.net/macular-degeneration/
[28] Wikipedia Website, “Macular degeneration,” [Online]
http://en.wikipedia.org/wiki/Macular_degeneration
[29] J.G. Linvill, and J.C. Bliss, “A Direct Translation Reading Aid for the Blind,” Proc. IEEE, 54(1):40–51, January 1966.
[30] J. Wyatt, and J.F. Rizzo, “Ocular Implants for the Blind,” IEEE Spectrum, 33, 1996.
[31] R. Eckmiller, “Learning Retinal Implants with Epiretinal Contacts,” Ophthalmic Res., 29:281–289, 1997.
[32] M. Schwarz, R. Hauschild, B.J. Hosticka, J. Huppertz, T. Kneip, S. Kolnsberg, L. Ewe, and H.K. Trieu, “Single-Chip CMOS Image Sensors for a Retina Implant System,” IEEE Trans. Circuits & Systems II, 46(7):870–877, July,1999.
[33] M.S. Humayun, J.D.Weiland, G.Y. Fujii, R. Greenberg, R.Williamson, J. Little, B. Mech, V. Cimmarusti, G.V. Boeme, G. Dagnelie, and E.de Juan Jr, “Visual Perception in a Blind Subject with a Chronic Microelectronic Retinal Prosthesis,” Vision Research, 43:2573–2581, 2003.
[34] W. Liu and M.S. Humayun, “Retinal Prosthesis,” In Dig. Tech. Papers Int’l Solid-State Circuits Conf. (ISSCC), pages 218–219, San Francisco, CA, February 2004.
[35] J.F. Rizzo III, J. Wyatt, J. Loewenstein, S. Kelly, and D. Shire, “Methods and Perceptual Thresholds for Short-Term Electrical Stimulation of Human Retina with Microelectrode Arrays,” Invest. Ophthalmology & Visual Sci., 44(12):5355–5361, December 2003.
[36] R. Hornig, T. Laube, P. Walter, M. Velikay-Parel, N. Bornfeld, M. Feucht, H. Akguel, G. R‥ossler, N. Alteheld, D. L. Notarp, J. Wyatt, and G. Richard, “A Method and Technical Equipment for an Acute Human Trial to Evaluate Retinal Implant Technology,” J. Neural Eng., 2(1):S129–S134, 2005.
[37] A. Y. Chow,M. T. Pardue, V. Y. Chow, G. A. Peyman, C. Liang, J. I. Perlman, and N. S. Peachey, “Implantation of Silicon Chip Microphotodiode Arrays into the Cat Subretinal Space,” IEEE Trans. Neural Syst. Rehab. Eng., 9:86–95, 2001.
[38] A.Y. Chow, V.Y. Chow, K. Packo, J. Pollack, G. Peyman, and R. Schuchard, “The Artificial Silicon Retina Microchip for the Treatment of Vision Loss from Retinitis Pigmentosa,” Arch. Ophthalmol., 122(4):460–469, 2004.
[39] E. Zrenner, “Will Retinal Implants Restore Vision?” Science, 295:1022–1025, February 2002.
[40] E. Zrenner, D. Besch, K.U. Bartz-Schmidt, F. Gekeler, V.P. Gabel, C. Kuttenkeuler, H. Sachs, H. Sailer, B. Wilhelm, and R. Wilke. Subretinal Chronic, “Multi-Electrode Arrays Implanted in Blind Patients. Invest,” Ophthalmology & Visual Sci., 47:E–Abstract 1538, 2006.
[41] D. Palanker, P. Huie, A. Vankov, R. Aramant,M. Seiler, H. Fishman, M. Marmor, and M. Blumenkranz, “Migration of Retinal Cells through a Perforated Membrane: Implications for a High-Resolution Prosthesis,” Invest. Ophthalmology & Visual Sci., 45(9):3266–3270, September 2004.
[42] D. Palanker, A. Vankov, P. Huie, and S. Baccus, “Design of a High-Resolution Optoelectronic Retinal Prosthesis,” J. Neural Eng., 2:S105–S120, 2005.
[43] D. Palanker, P. Huie, A. Vankov, A. Asher, and S. Baccus, “Towards High- Resolution Optoelectronic Retinal Prosthesis,” BIOS, 5688A, 2005.
[44] H. Sakaguchi, T. Fujikado1, X. Fang, H. Kanda, M. Osanai, K. Nakauchi, Y. Ikuno, M. Kamei, T. Yagi, S. Nishimura, M. Ohji, T. Yagi, and Yasuo Tano, “Transretinal Electrical Stimulation with a Suprachoroidal Multichannel Electrode in Rabbit Eyes,” Jpn. J. Ophthalmol., 48(3):256–261, 2004.
[45] K. Nakauchi, T. Fujikado, H. Kanda, T. Morimoto, J.S. Choi, Y. Ikuno, H. Sakaguchi, M. Kamei, M. Ohji, T. Yagi, S. Nishimura, H. Sawai, Y. Fukuda, and Y. Tano, “Transretinal Electrical Stimulation by an Intrascleral Multichannel Electrode Array in Rabbit Eyes,” Graefe’s Arch. Clin. Exp. Ophthalmol., 243:169–174, 2005.
[46] M. Kamei, T. Fujikado, H. Kanda, T. Morimoto, K. Nakauchi, H. Sakaguchi, Y. Ikuno, M. Ozawa, S. Kusaka, and Y. Tano, “Suprachoroidal-Transretinal Stimulation (STS) Artificial Vision System for Patients with Retinitis Pigmentosa,” Invest. Ophthalmology & Visual Sci., 47:E–Abstract 1537, 2006.
[47] J. Ohta, “Smart CMOS Image Sensor and Applications,” CRC Press, Boca Raton, FL, 2007.
[48] G.F. Poggio, F. Gonzalez, and F. Krause, “Stereoscopic Mechanisms in Monkey Visual Cortex: Binocular Correlation and Disparity Selectivity,” J. Neurosci., 8(12):4531–4550, December 1988.
[49] H.G. Sachs, T. Schanze, M. Wilms, A. Rentzos, U. Brunner, F. Gekeler, and L. Hesse, “Subretinal Implantation and Testing of Polyimide Film Electrodes in Cats,” Graefe’s Arch. Clin. Exp. Ophthalmol. 2005, 243, 464-468.
[50] H. Kanda, T. Morimoto, T. Fujikado, Y. Tano, Y. Fukuda, and H. Sawai, “Electrophysiological Studies of the Feasibility of Suprachoroidal-Transretinal Stimulation for Artificial Vision in Normal and RCS rats. Invest. Ophthal. Vis. Sci. 45, 560-566. 2004.
[51] D. Y. Yanai, J. D. Weiland, M. Mahadevappa, R. J. Greenberg, I. Fine, G. Y. Fujii, and M. S. Humayun, “Visual Performance Using a Retinal Prosthesis in Three Subjects with Retinitis Pigmentosa,” Am. J.Ophthalmol., vol. 143, no. 5, pp. 820–827, May 2007.
[52] M. S. Humayun, J. D. Dorn, L. Da Cruz, G Dagnelie, J. A. Sahel, P. E. Stanga, A. V. Cideciyan, J. L. Duncan, D. Eliott, E. Filley, A. C. Ho, A. Santos, A. B. Safran, A. Arditi, L. V. Del Priore, and R. J. Greenberg, “Interim results from the international trial of second sight’s visual prosthesis,” Ophthalmology, vol. 119, no. 4, pp. 779–788, Apr. 2012.
[53] Second Sight Website, “Argus II,” [Online]
http://www.2-sight.eu/images/stories/2-sight/pdf/product-info-brochure-ee.pdf
[54] D.B. Shire, S.K. Kelly, J. Chen, P. Doyle, M.D. Gingerich, S.F. Cogan, W.A. Drohan, O. Mendoza, L. Theogarajan, J.L. Wyatt, and J.F. Rizzo, “Development and Implantation of a Minimally Invasive Wireless Subretinal Neurostimulator,” IEEE Trans Biomed Eng. 56:2502–2511, 2009.
[55] J. Chen, H.A. Shah, C. Herbert, J.I. Loewenstein, and Rizzo JF III, “Extraction of a Chronically Implanted, Microfabricated, Subretinal Electrode Array,” Ophthalmic Res. 42: 128–137, 2009.
[56] J. Chen, “Surgical Methods for Large Sub-Retinal Prosthetic Implantation,” Fort Lauderdale, FL: ARVO, 2007.
[57] S.R. Montezuma, J. Loewenstein, C. Scholz, and J. Rizzo III, “Biocompatibility of Materials Implanted into the Subretinal Space of Yucatan pigs,” Invest Ophthalmol Vis Sci. 47: 3514–3522, 2006.
[58] J.F. Rizzo III, “Update on Retinal Prosthetic Research: The Boston Retinal Implant Project,” J Neuro-Ophthalmol, 31: 160-168, 2011.
[59] E. Zrenner, K. U. Bartz-Schmidt, H. Benav, D. Besch, A. Bruckmann, V. P. Gabel, F. Gekeler, U. Greppmaier, A. Harscher, S. Kibbel, J. Koch, A. Kusnyerik, T. Peters, K. Stingl, H. Sachs, A. Stett, P. Szurman, B. Wilhelm, and R. Wilke, “Subretinal Electronic Chips Allow Blind Patients to Read Letters and Combine Them to Words,” Proc. Biol. Sci., vol. 278, no. 1711, pp. 1489–1497, May 2011.
[60] R.Wilke, V. P. Gabel, H. Sachs, K. U. Bartz Schmidt, F.Gekeler, D.Besch, P. Szurman, A. Stett, B. Wilhelm, T. Peters, A. Harscher, U. Greppmaier, S. Kibbel, H. Benav, A. Bruckmann, K. Stingl, A. Kusnyerik, and E. Zrenner, “Spatial Resolution and Perception of Patterns Mediated by a Subretinal 16-Electrode Array in Patients Blinded by Hereditary Retinal Dystrophies,” Invest. Ophthalmol. Vis. Sci., vol. 52, no. 8, pp. 5995–6003, Aug. 2011.
[61] K. Stingl, K. U. Bartz Schmidt, D. Besch, A. Braun, A. Bruckmann, F. Gekeler, U. Greppmaier, S. Hipp, G. H¨ortd¨orfer, C. Kernstock, A. Kusnyerik, A. Schatz, K. T. Stingl, T. Peters, B. Wilhelm, and E. Zrenner, “Artificial Vision with Wirelessly Powered Subretinal Electronic Implant Alpha-IMS,” Proc. Royal Soc. B: Biol. Sci., vol. 280, no. 1757, pp. 1–8, Apr. 2013.
[62] K. Stingl, K. U. Bartz Schmidt, D. Besch, A. Braun, A. Bruckmann, F. Gekeler, U. Greppmaier, S. Hipp, G. H¨ortd¨orfer, C. Kernstock, A. Kusnyerik, A. Schatz, K. T. Stingl, T. Peters, B. Wilhelm, and E. Zrenner, “Details on the Patient Cohort and the Subretinal Implant Alpha IMS (Retina Implant AG, Reutlingen) in the First Module of a Multicenter Clinical Trial and Video Material of Patient Reports,” Proc. Royal Soc. B, vol. 280, no. 1757, pp. 1–8, Apr. 2013.
[63] Retina Implant Website, “Subretinal Implant Technology,” [Online] http://retina-implant.de/en/patients/technology/default.aspx
[64] T. Fujikado, T. Morimoto, H. Kanda, S. Kusaka, K. Nakauchi, M. Ozawa, K. Matsushita, H. Sakaguchi, Y. Ikuno, M. Kamei, and Y. Tano, “Clinical Trial of Chronic Implantation of Suprachoroidal-Transretinal Stimulation System for Retinal Prosthesis,” Sensors Mater., vol. 24, no. 4, pp. 181–187, Apr. 2012.
[65] P. Denyer, D. Renshaw, G. Wang, M. Lu, and S. Anderson, “On-chip CMOS sensors for VLSI imaging systems,” in Proc. VLSI-91, 1991, pp. 157–166.
[66] B. Fowler, A. El Gamal, and H. Tian, "Analysis of temporal noise in CMOS photodiode active pixel sensor", IEEE J. Solid-State Circuits, vol. 36, pp.92 -101 2001.
[67] E. R. Fossum and D. B. Hondongwa, "A Review of the Pinned Photodiode for CCD and CMOS Image Sensors," IEEE J. Electron Devices Society, vol. 2, pp. 33-43, 2014.
[68] M.L. Simpson, G.S. Sayler, G. Patterson, D.E. Nivens, E.K. Bolton, J.M. Rochelle, and J.C. Arnott, “An Integrated CMOS Microluminometer for Low Level Luminescence Sensing in the Bioluminescent Bioreporter Integrated Circuit,” Sensors & Actuators B, 72:134–140, 2001.
[69] E.K. Bolton, G.S. Sayler, D.E. Nivens, J.M. Rochelle, S. Ripp, and M.L. Simpson, “Integratged CMOS Photodetectors and Signal Processing for Very Low Level Chemical Sensing with the Bioluminescent Bioreporter Integrated Circuits,” Sensors & Actuators B, 85:179–185, 2002.
[70] K. Kagawa, K. Yasuoka, D. C. Ng, T. Furumiya, T. Tokuda, J. Ohta, and M. Nunoshita, “Pulse-Domain Digital Image Processing for Vision Chips Employing Low-Voltage Operation in Deep-Submicron Technologies,” IEEE Selcted Topic Quantum Electron., 10(4):816–828, July 2004.
[71] K. Kagawa, S. Yamamoto, T. Furumiya, T. Tokuda, M. Nunoshita, and J. Ohta, “A pulse-frequency-modulation vision chip using a capacitive feedback reset with an in-pixel 1-bit image processing,” In Proc. SPIE, volume 6068, pages 60680C–1–60680C–9, San Jose, January 2006.
[72] J. Ohta, N. Yoshida, K. Kagawa, and M. Nunoshita, “Proposal of Application of Pulsed Vision Chip for Retinal Prosthesis,” Jpn. J. Appl. Phys., 41(4B):2322–2325,April 2002.
[73] K. Kagawa, K. Isakari, T. Furumiya, A. Uehara, T. Tokuda, J. Ohta, and M. Nunoshita, “Pixel design of a pulsed CMOS image sensor for retinal prosthesis with digital photosensitivity control,” Electron. Lett., 39(5):419–421, May 2003.
[74] [203] A. Uehara, K. Kagawa, T. Tokuda, J. Ohta, and M. Nunoshita, “Backilluminated pulse-frequency-modulated photosensor using a silicon- onsapphire technology developed for use as an epi-retinal prosthesis device,” Electron. Lett., 39(15):1102–1104, July 2003.
[75] David C. Ng, K. Isakari, A. Uehara, K. Kagawa, T. Tokuda, J. Ohta, and M. Nunoshita, “A study of bending effect on pulsed frequency modulation based photosensor for retinal prosthesis,” Jpn. J. Appl. Phys., 42(12):7621–7624, December 2003.
[76] K. Kagawa, N. Yoshida, T. Tokuda, J. Ohta, and M. Nunoshita, “Building a Simple Model of A Pulse-Frequency-Modulation Photosensor and Demonstration of a 128×128-pixel Pulse-Frequency-Modulation Image Sensor Fabricated in a Standard 0.35-μm Complementary Metal-Oxide Semiconductor Technology,” Opt. Rev., 11(3):176–181, May 2004.
[77] A. Uehara, K. Kagawa, T. Tokuda, J. Ohta, and M. Nunoshita, “A highsensitive digital photosensor using MOS interface-trap charge pumping,” IEICE Electronics Express, 1(18):556–561, December 2004.
[78] T. Furumiya, D. C. Ng, K. Yasuoka, K. Kagawa, T. Tokuda, M. Nunoshita, and J. Ohta, “Functional verification of pulse frequency modulation-based image sensor for retinal prosthesis by in vitro electrophysiological experiments using frog retina,” Biosensors& Bioelectron., 21(7):1059–1068, January 2006.
[79] S. Yamamoto, K. Kagawa, T. Furumiya, T. Tokuda,M. Nunoshita, and J. Ohta, “Prototyping and evaluation of a 32× 32-pixel pulse-frequency-modulation vision chip with capacitive-feedback reset,” J. Inst. Image Information & Television Eng., 60(4):621–626, April 2006.
[80] T. Furumiya, S. Yamamoto, K. Kagawa, T. Tokuda, M. Nunoshita, and J. Ohta, “Optimization of electrical stimulus pulse parameter for low-power operation of a retinal prosthetic device,” Jpn. J. Appl. Phys., 45(19):L505–L507, May 2006.
[81] T. Furumiya, K. Kagawa, A. Uehara, T. Tokuda, J. Ohta, and M. Nunoshita, “32 × 32-pixel pulse-frequency-modulation based image sensor for retinal prosthesis,” J. Inst. Image Information & Television Eng., 58(3):352–361, March 2004. In Japanese.
[82] D. C. Ng, T. Furumiya, K. Yasuoka, A. Uehara, K. Kagawa, T. Tokuda, M. Nunoshita, and J. Ohta, “Pulse Frequency Modulation-based CMOS Image Sensor for Subretinal Stimulation,” IEEE Trans. Circuits & Systems II, 53(6):487–491, June 2006.
[83] J. Ohta, T. Tokuda, K. Kagawa, T. Furumiya, A. Uehara, Y. Terasawa,M. Ozawa, T. Fujikado, and Y. Tano, “Silicon LSI-Based Smart Stimulators for Retinal Prosthesis,” IEEE Eng. Medicine & Biology Magazine, 25(5):47–59, October 2006.
[84] J. Deguchi, T. Watanabe, T. Nakamura, Y. Nakagawa, T. Fukushima, S. Jeoung-Chill, H. Kurino, T. Abe, M. Tamai, and M. Koyanagi, “Three- Dimensionally Stacked Analog Retinal Prosthesis Chip,” Jpn. J. Appl. Phys., 43(4B):1685–1689,April 2004.
[85] D. Ziegler, P. Linderholm, M. Mazza, S. Ferazzutti, D. Bertrand, A.M. Ionescu, and Ph. Renaud, “An active microphotodiode array of oscillating pixels for retinal stimulation,” Sensors & Actuators A, 110:11–17, 2004.
[86] X. Liu and A. El Gamal, “Photocurrent Estimation for a Self-Reset CMOS Image Sensor,” In Proc. SPIE, volume 4669, pages 304–312, San Jose, CA, 2002.
[87] M.T. Chung, C.L. Lee, Y. Chin and C.C. Hsieh, “A 0.5 V PWM CMOS Imager With 82 dB Dynamic Range and 0.055% Fixed-Pattern-Noise,” IEEE J. Solid-State Circuits, vol. 48, no. 10, pp. 2522-2530, Oct. 2013.
[88] S. Hanson, Z.Y. Foo, D. Blaauw, and D. Sylvester, “A 0.5 V Sub-Microwatt CMOS Image Sensor With Pulse-Width Modulation Read-Out,” IEEE J. Solid-State Circuits, vol. 45, no. 4, pp. 759-767, Apr. 2010.
[89] S.U. Ay, “A CMOS Energy Harvesting and Imaging (EHI) Active Pixel Sensor (APS) Imager for Retinal Prosthesis,” IEEE Trans. Biomedical Circuits and Systems, vol. 5, no. 6, pp. 535-545, Dec. 2011.
[90] K. Cho, D. Lee, J. Lee, and G. Han, “Sub-1-V CMOS Image Sensor Using Time-Based Readout Circuit,” IEEE Trans. Electron Devices, vol. 57, no. 1, pp.222-227, Jan. 2010.
[91] D.G. Chen, D. Matolin, A. Bermak, and C. Posch, “Pulse-Modulation Imaging-Review and Performance analysis,” IEEE Trans. Biomedical Circuits and Systems, vol. 5, no. 11, pp. 64-82, Feb. 2011.
[92] N. Tran, J. Tang, S. Bai, E. Skafidas, I. Mareels, D. Ng, and M. Halpern “A Flexible Electrode Driver using 65 nm CMOS Process for 1024-eletrode Epi-retinal Prosthesis” in Future Information Technology Int. conf., pp. 1-5, 2010.
[93] T. Tokuda, Y. Takeuchi, Y. Sagawa, T. Noda, K. Sasagawa, K. Nishida, and J. Ohta, “Development and in vivo Demonstration of CMOS-Based Multichip Retinal Stimulator with Simultaneous Multisite Stimulation Capability,” IEEE Trans. Biomedical Circuits and Systems, vol. 4, no. 6, pp. 445-453, Dec. 2010.
[94] M. Sivaprakasam, W. Liu, G.Wang, J.Weiland, and M. Humayun, “Architecture tradeoffs in high-density microstimulators for retinal prosthesis,” IEEE Trans. Circuits Syst. I, vol. 52, no. 12, pp. 2629–2641, Dec. 2005.
[95] Y. Wong, N. Dommel, P. Preston, L. Hallum, T. Lehmann, N. Lovell, and G. Suaning, “Retinal neurostimulator for a multifocal vision prosthesis,” IEEE Trans. Neural Syst. Rehabil. Eng., vol. 15, no. 3, pp. 425–434, Sep. 2007.
[96] J. Ohta, T. Tokuda, K. Sasagawa, and T. Noda, “Implantable CMOS Biomedical Devices,” Sensors, 9, 9073-9093, 2009