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Shizuoka-shi, Japan

Watanabe T.,Brookman Technology Inc. | Park J.-H.,Brookman Technology Inc. | Aoyama S.,Brookman Technology Inc. | Isobe K.,Brookman Technology Inc. | Kawahito S.,University of Shizuoka
IEEE Transactions on Electron Devices | Year: 2010

A negative-bias operation of the transfer gate has revealed a major origin of dark current defects of CMOS image sensors. Charge injection from the photodiode to the substrate at the negative-bias operation has been avoided by an improved well structure. A strong visible light has been observed to cause damage with an increase in the dark current under the normal operating condition, and the damage has been annealed in the power-off mode. This indicates that the strong light possibly causes a threshold voltage shift, which is explained by the photon-assisted tunneling or emission mechanisms. Multiple stress-and-anneal cycles have been found to cause an optical hardening effect, which can be explained by immobile trapped holes. © 2006 IEEE. Source


Han S.-M.,University of Shizuoka | Takasawa T.,University of Shizuoka | Yasutomi K.,University of Shizuoka | Aoyama S.,Brookman Technology Inc. | And 2 more authors.
IEEE Journal of the Electron Devices Society | Year: 2015

This paper presents a CMOS time-of-flight (ToF) range image sensor using high-speed lock-in pixels with background light canceling capability. The proposed lock-in pixel uses MOS gate-induced lateral electric field control of depleted potential of pinned photodiode for implementing a multiple-tap charge modulator while achieving a high-speed charge transfer for high-time resolution. A TOF image sensor with 320 x 240 effective pixels is implemented using a 0.11-\mu \text{m CMOS image sensor process. The TOF sensor has a range resolution of less than 12 mm without background light and 20 mm under background line for the range from 0.8 to 1.8 m and integration time of 50 ms. The effectiveness of in-pixel background light canceling with a three-tap output pixel is demonstrated. © 2013 IEEE. Source


Suh S.,University of Shizuoka | Itoh S.,University of Shizuoka | Aoyama S.,Brookman Technology Inc. | Kawahito S.,University of Shizuoka
Sensors (Switzerland) | Year: 2010

For low-noise complementary metal-oxide-semiconductor (CMOS) image sensors, the reduction of pixel source follower noises is becoming very important. Column-parallel high-gain readout circuits are useful for low-noise CMOS image sensors. This paper presents column-parallel high-gain signal readout circuits, correlated multiple sampling (CMS) circuits and their noise reduction effects. In the CMS, the gain of the noise cancelling is controlled by the number of samplings. It has a similar effect to that of an amplified CDS for the thermal noise but is a little more effective for 1/f and RTS noises. Two types of the CMS with simple integration and folding integration are proposed. In the folding integration, the output signal swing is suppressed by a negative feedback using a comparator and one-bit D-to-A converter. The CMS circuit using the folding integration technique allows to realize a very low-noise level while maintaining a wide dynamic range. The noise reduction effects of their circuits have been investigated with a noise analysis and an implementation of a 1Mpixel pinned photodiode CMOS image sensor. Using 16 samplings, dynamic range of 59.4 dB and noise level of 1.9 e- for the simple integration CMS and 75 dB and 2.2 e- for the folding integration CMS, respectively, are obtained. © 2010 by the authors. Source


Watabe T.,NHK Science and Technical Research Laboratories | Kitamura K.,NHK Science and Technical Research Laboratories | Sawamoto T.,University of Shizuoka | Kosugi T.,Brookman Technology Inc. | And 10 more authors.
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2012

There has been increasing demand for high-reality video systems. Thus, there has been research and development into ultra-high-definition television (UDTV) schemes for the next-generation television broadcasting system called "Super Hi-Vision" (SHV). This system aims to improve viewing experience using higher-resolution pictures. A pixel count of 7680x4320 and frame rate of 120fps are defined as full-spec parameter values for the SHV video signal. The total pixel data output rate of full-spec SHV image sensors will be 48Gb/s or greater. Several image sensors have been developed for UDTV or digital cinema applications [1-4], but they still do not fulfill SHV specifications. © 2012 IEEE. Source


Han S.-M.,University of Shizuoka | Takasawa T.,University of Shizuoka | Akahori T.,Brookman Technology Inc. | Yasutomi K.,University of Shizuoka | And 3 more authors.
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2014

Time-of-Flight (ToF) range imagers have a wide range of applications, such as 3D mice, gesture-based remote controllers, amusement, robots, security systems, and automobiles. Numerous ToF range imager developments have been reported [1-4]. Recent developments are often based on CMOS image sensor technology with pinned photodiode options [5-7], which are suitable for cost-effective mass production. Reported CMOS ToF range imagers use single-tap or two-tap lock-in pixels; to cancel the influence of background light, two or four sub-frames are used to produce a background-canceled range image. These architectures, however, have difficulty with precise range measurements of moving objects, because background light cancelation is not guaranteed for moving objects. Lock-in pixels without any charge-draining gate suffer from background light during the readout time of the operation. Another important issue with CMOS ToF range imagers for high range resolution is the speed of lock-in pixels, which must be improved to use high-modulation-frequency light or short-duration light pulses. © 2014 IEEE. Source

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