Showing papers by "Takashi Tokuda published in 2004"
TL;DR: A new architecture for pixel-level parallel image processing in the pulse domain for CMOS vision chips has been developed and step responses of the prototype vision chip for fundamental image processing operations show good agreement with those expected by correlation-based spatial filtering.
Abstract: A new architecture for pixel-level parallel image processing in the pulse domain for CMOS vision chips has been developed. Image processing such as edge enhancement, edge detection, and blurring are realized based on suppression and promotion of digital pulses; the pixel value is represented by the frequency of digital pulses by use of a pulse-frequency modulation (PFM) photosensor or that with an in-pixel 1-bit analog-to-digital converter. The proposed architecture is suitable for low-voltage operation in deep-submicrometer technologies because the image processing is implemented by 1-bit fully digital circuits with a small number of logic gates. The principles of the image processing are addressed. We have fabricated a 16 /spl times/ 16-pixel prototype vision chip. The relationship between illumination and the output pulse frequency is characterized. Step responses of the prototype vision chip for fundamental image processing operations show good agreement with those expected by correlation-based spatial filtering. A simple image binarization method specific to our architecture is also presented. The histograms of the intervals of the output pulses after image processing show multiple peaks, which indicates that averaging of the intervals is required for longer periods to achieve higher image-processing quality. To improve the linearity of pulse frequency dependence on illumination, usage of random clocks is discussed.
31 citations
TL;DR: In this article, a micro-origami structure with SiGe/Si heteroepitaxial layer on a silicon-on-insulator (SOI) substrate has been successfully fabricated.
Abstract: A micromirror structure with SiGe/Si heteroepitaxial layer on a silicon-on-insulator (SOI) substrate using a ‘Micro-origami’ technique has been successfully fabricated. The micromirror is supported by two curved hinge structures. The device is driven by application of a current, and net angular displacements larger than 10° (static) and 30° (in resonance) were obtained. These values are comparable with or even larger than the reported values for other MEMS optical switches or beam scanning devices. The experimental results suggest that the movement is evoked by a thermal effect. The Micro-origami device has advantages of low operation voltage smaller than 2 V, and structural compatibility with the Si or SiGe LSIs.
12 citations
TL;DR: The high-sensitive PFM photosensor is proposed and demonstrated, whose output frequency is proportionate to the incident light intensity, that utilizes MOS interface-trap charge pumping (ITCP) as a frequency-controlled ultra-low current.
Abstract: A high-sensitive CMOS photosensor based on a pulse frequency modulation (PFM) scheme is presented. We propose and demonstrate the high-sensitive PFM photosensor, whose output frequency is proportionate to the incident light intensity, that utilizes MOS interface-trap charge pumping (ITCP) as a frequency-controlled ultra-low current. The proposed pixel sensor consists of only 4 transistors: a transistor as an ultra-low current source; a sense amplifier transistor; a selection transistor; and, a reset transistor. The prototype device is fabricated using 0.6-µm standard CMOS technology. High sensitivity 4.0 × 105Hz/(W·m-2), which is larger than two orders of magnitude compared to previous works, was obtained.
11 citations
TL;DR: In this paper, a simple model of the pulse-frequency-modulation (PFM) photosensor is presented, which provides explicit relationships between circuit parameters and output characteristics, and treats the PFM photosensor with a feedback loop as an open loop circuit.
Abstract: We present a simple model of the pulse-frequency-modulation (PFM) photosensor that provides explicit relationships between circuit parameters and output characteristics. The model treats the PFM photosensor with a feedback loop as an open loop circuit. Several characteristics such as output pulse frequency for light intensity and photosensitivity are expressed by device parameters of a photodiode, reset transistor, and chain of inverters. The relationships derived from the proposed model help us to comprehend the results by simulation program with integrated circuit emphasis (SPICE) or experiments. We design and fabricate a 128 x 128-pixel PFM image sensor with photosensitivity of 0.15 Hz/lux. As a demonstration, a figure of a dinosaur is captured using the fabricated image sensor to discuss its operation. Characteristics of a normal pixel and white and black defect pixels are measured and discussed based on the results of formulations.
6 citations
01 Jan 2004
TL;DR: In this paper, a 64/spl times/64-pixel image sensor with a pulse modulation photoensor was designed for on-chip imaging of a mouse hippocampus and demonstrated the feasibility of the pulse modulation measurement scheme for biosensing applications.
Abstract: Image sensors with a pulse modulation measurement scheme are fabricated for bioimaging and biosensing applications. We designed pulse modulation photosensors and a 64/spl times/64-pixel image sensor. We demonstrated the feasibility of the pulse modulation measurement scheme for biosensing applications. We obtained a dynamic range of 120 dB and minimum sensing intensity level of 2 nW/cm/sup 2/. We also confirmed that 0.2% of intensity change is detectable at the minimum intensity region. An in-vitro, on-chip imaging of a mouse hippocampus was successfully demonstrated.
4 citations
TL;DR: In this article, a retinal prosthesis with built-in self-test capability is proposed and demonstrated using a prototype stimulus chip with 16/spl times/16 channels using standard 0.6 /spl mu/m CMOS technology, with error of as little as 0.05% in the frequency range of 100 Hz to 100 kHz.
Abstract: A retinal prosthesis device with built-in self-test capability is proposed and demonstrated. The measurement of electrode impedance as a self-test is achieved without increasing the chip area by employing analogue multiplexers to allow the electrodes to be used for both stimulation of retinal cells and measurement of impedance. Measurement is performed using a four-terminal method to ensure good accuracy. A prototype stimulus chip with 16/spl times/16 channels is fabricated using standard 0.6 /spl mu/m CMOS technology, and is demonstrated to provide self-test functionality with error of as little as 0.05% in the frequency range of 100 Hz to 100 kHz.
4 citations
3 citations
01 Jan 2004
TL;DR: A thin, flexible packaging technique was developed for the multi-chip neural stimulation/recording device and LSI-compatible Pt/Au stacked biocompatible bump electrode that made the device more suitable for in vivo applications than conventional single-chip devices.
Abstract: An LSI-based cooperative multi-chip neural stimulation/recording device is proposed and fabricated. The proposed multi-chip device consists of small (600 /spl mu/m /spl times/ 600 /spl mu/m in the present design) intelligent neural stimulation/recording chips (unit chip). The unit chip has a neural stimulation/recording electrode array and individual control circuit. It can work with other unit chips cooperatively. One can configure any number of the unit chips as the multi-chip neural stimulation/recording device. Compared to conventional single-chip architecture, the proposed multi-chip architecture has advantages in thinness, mechanical strength and flexibility, and extendibility. That makes the multi-chip neural stimulation/ recording device more suitable for in vivo applications than conventional single-chip devices. Packaging technology for cooperative multi-chip device is also discussed. We developed a thin, flexible packaging technique for the multi-chip neural stimulation/recording device and LSI-compatible Pt/Au stacked biocompatible bump electrode.
2 citations
17 Jun 2004
TL;DR: This paper proposes a flexible retinal prosthesis device by a distributed sensor network approach that consists of micro-sized CMOS devices linked in network and its function is tested successfully.
Abstract: In this paper, we propose a flexible retinal prosthesis device by a distributed sensor network approach. The novel point of the proposed device is that the flexible stimulator consists of micro-sized CMOS devices linked in network. The micro-sized CMOS device consists of single-wire serial interface, a photo detector with pixel-level ADC, an image processing circuit, a current DAC and a current stimulator. The device is fabricated in a 0.6 /spl mu/m CMOS technology and the device size is 500 /spl mu/m /spl times/ 500 /spl mu/m. The function of the prototype device is tested successfully.
2 citations
01 Jan 2004
TL;DR: The PFM retinal implant chip is evaluated by in-vitro electrophysiological experiments using detached frog retina, and it is confirmed that it can electrically stimulate the retinal cells effectively.
Abstract: We have designed and fabricated a 16/spl times/16-pixel retinal prosthesis device using a pulse-frequency-modulation (PFM) photosensor. This chip is a prototype for demonstrating applications in in-vitro electrophysiological experiments. Each pixel has a bonding pad on which a stimulus electrode is formed by a Pt/Au stacked biocompatible bump electrode. We have evaluated the PFM retinal implant chip by in-vitro electrophysiological experiments using detached frog retina, and confirmed that it can electrically stimulate the retinal cells effectively.
2 citations
TL;DR: A CMOS image sensor using pulse frequency modulation (PFM) for retinal prosthesis using standard 0.6μm CMOS technology is demonstrated and shows that this chip could be used in vitro electro-physiology experiments.
Abstract: We demonstrated a CMOS image sensor using pulse frequency modulation (PFM) for retinal prosthesis. We are fabricated the 32x32 pixel PFM image sensor with standard 0.6μm CMOS technology. We designed this chip for use in in vitro electro-physiology experiments. The image sensor pixel was composed of a PFM-based photosensor with a frequency limiter, a pulse shaper/amplifier, and a stimulus electrode. We measured the image sensor response vs. the illumination level. We further verified the pulse shaper/amplifier characteristics. By using the current output from the stimulus electrode, we successfully demonstrated positive and negative current output of 100μA driving an external electrode placed inside a multi-electrode array immersed in saline. This result shows that this chip could be used in vitro electro-physiology experiments. To observe the output pulse from the sensor, we used the LED display in order to visualize the input scene from each pixel output pulses, and demon-strates the visualization successfully.
27 Jan 2004
TL;DR: In this paper, a retinal prosthetic device using a PFM-based photosensor with a standard CMOS technology and its modification to stimulate retinal cells effectively was described.
Abstract: This paper describes a retinal prosthetic device using a pulse frequency modulation (PFM) based photosensor with a standard CMOS technology and its modification to stimulate retinal cells effectively. A 32x32-pixel PFM photosensor array chip have been fabricated using 0.6 μm CMOS technology and demonstrated the improved functions.