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We propose a dynamic range extension method for CMOS imagers with an in-pixel lateral overflow structure, in which one of active and passive readout schemes is selected at each pixel on the basis of the illumination. For a high illumination, the charges stored in both photodiode and area-effective MOS capacitor as an overflow capacitor in a pixel are read with high linearity by a charge amplifier at each column to extend the range of the readable voltage. The column circuit area is suppressed and row-wise pixels are accessed by sharing the pixel control signals and the column amplifier between two readout modes. We also describe an image reproduction scheme that makes use of electric calibration from a pixel-wise mixed-mode image. The signal-to-noise ratio of the scheme is discussed. Preliminary experiments with a 128 x96-pixel prototype imager fabricated in 0.35μm CMOS technology showed an extension of the dynamic range of 18.5 dB (72.8 dB in total) and offline wide-dynamic-range image reproduction. Optimizing of the capacitances in the pixels and the column amplifier and reducing the amount of noise in the column amplifiers will provide a total dynamic range of around 120dB.

We present a technique for in vivo imaging and electrical interface deep inside the mouse brain using a single complementary metal–oxide semiconductor (CMOS) sensor. In this work, we have developed a device which incorporates an imaging array, electrodes, illumination light source and chemical delivery needle. The device encompasses the functionalities for fluorescence imaging and electrophysiological experiments simultaneously. Micro-electro-mechanical systems (MEMS) microfabrication technique is used to post-process the CMOS sensor chip. Integration of light emitting diodes (LEDs) for illumination and formation of on-chip platinum electrodes for electrical interface with neurons complete the packaged device. Using the device, we performed fluorescence imaging and electrophysiological experiments inside the mouse brain. We have successfully induced synaptic response when the Schaffer-collateral pathway of the mouse hippocampus was stimulated using the on-chip Pt electrodes with current intensities from 200 μA to 1 mA. Furthermore, we have verified empirically that this technique has minimal effect on the hippocampus.

The Functionality of a complementary metal oxide semiconductor (CMOS) LSI-based, multichip flexible retinal stimulator was demonstrated in retinal stimulation experiments on rabbits. A 1×4-configured multichip stimulator was fabricated for application to experiments on animals. An experimental procedure including surgical operations was developed, and retinal stimulation was performed with the fabricated multichip stimulator. Neural responses on the visual cortex were successfully evoked by the fabricated stimulator. The stimulator is confirmed to be applicable to acute animal experiments.

A unique fabrication technique of Ge1-xCx nanocrystal (NC) assemblies with high-density (>1011 dots/cm2) and small diameter (

We have developed two CMOS devices to demonstrate the use of CMOS technology for neural imaging and interfacing with the aim of studying the functions of the brain at the molecular level. In this work, we discuss the design, packaging, and implementation of a compact, single device imaging system for imaging inside the mouse brain. We show that the device is capable of imaging and measuring fluorophore concentrations down to 1 mum . The packaged device was tested for in vivo fluorescence imaging by imaging the activity of serine protease in the mouse hippocampus. The result shows imaging of neural activity with spatial resolution close to the pixel size of 7.5 mum and less than 300 ms temporal resolution. A second device was developed to image neuronal network activity and to provide a means for electrical interfacing with neurons. Characterization tests show that the device has comparable performance to current tools used in electrophysiological experiments of the brain. This work paves the way for simultaneous imaging and electrophysiological experiments using a single compact and minimally invasive device in the future.

We present a vision chip architecture with column-level photo-amplification of optical data signals for optical wireless local area networks (LANs) to reduce the pixel area. Based on the architecture, we have fabricated a prototype vision chip in a standard 0.8 μm bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. The device offers position detection of other optical transceivers in the LAN and 4-ch concurrent high-speed optical data acquisition. A data rate of 400 Mbps was demonstrated. The pixel size was 125 μm square, which can be shrunk to smaller than around 60 μm square in 0.35 μm or more advanced BiCMOS or CMOS technologies.

A complementary metal oxide semiconductor (CMOS) multichip neural stimulator was fabricated and characterized. The device was designed specifically for retinal prosthesis. In this work, to achieve required performances for in vivo experiments, a new CMOS unit chip was designed with a power-on-reset mechanism and a low series resistance. We have developed a fabrication process for the proposed device focusing on the tight-seal performance of the device against saline solution to achieve a reliable long term operation. The proposed packaging technology is based on a flip-chip technique and has a feature of embedded Pt bulk electrodes. The basic functionality of the fabricated CMOS chip and packaged stimulator was confirmed. The device passed a 10-day endurance test in saline solution.

A new scheme to image on-chip DNA spots using an optical/potential dual-image complementary metal oxide semiconductor (CMOS) sensor was proposed and demonstrated. Dry DNA spots have been successfully imaged without using an off-chip reference electrode. The structure of our dual-image sensor plays an essential role in the measurement method. The sensor was revealed to be capable of sensing the dielectric properties of materials placed on the sensor surface. The present measurement scheme is expected to be a powerful method for sensing dry on-chip biomolecular spots, with better compatibility with conventional slide-glass-based microarray technologies.

In our previous work, we demonstrated the potential of a complementary metal–oxide–semiconductor (CMOS) imaging device for use in imaging of the mouse brain. We showed that the device is capable of detecting fluorescence signal inside the mouse brain and successfully imaged real-time protease activity inside the hippocampus. In this work, we have improved the imaging device by integrating an excitation light source in the form of an ultraviolet light-emitting diode chip and an injection needle onto the sensor chip. This results in a compact single device imaging system for minimal invasive imaging inside the mouse brain. Also experimental repeatability is improved which enabled us to successful perform calibration of fluorophore concentration using the device. Fluorescence imaging experiments inside the brain phantom as well as in the mouse brain show that the device is capable of real time fluorescence detection. Using the device, we found that diffusion rate of chemical injected into the brain is smaller than 10 pmol/min. This work is expected to lead to the successful use of a CMOS imaging device for the study of the functions of the brain.

A CMOS image sensor, which can sense optical images and 2D arrayed electrochemical profiles, was designed and fabricated. Target applications of the sensor include biomolecular microarray technology. An 8 × 8-pixel arrayed electrochemical sensor was successfully implemented into a 128 × 128-pixel APS CMOS image sensor. A current-sensing voltage follower was used as the column amplifier unit for electrochemical measurements. Eight column amplifier units were connected to electrochemical sensing pixels in each column one by one, and they function as on-chip potentiostats. The sensor can measure 2D arrayed voltammetry in an on-chip configuration. The basic properties and functions of the fabricated sensor were characterized. It was confirmed that optical and electrochemical imaging functions can be operated simultaneously and independently. The current range of the electrochemical measurement function was measured to be approximately 10 nA and 100 μA. A 2D arrayed cyclic voltammetry measurement was successfully demonstrated.

We propose a new pixel structure of pulse-width-modulation (PWM) CMOS active pixel sensor with a small pixel size performing a pixel-level single-slope A/D conversion to realize a low and single power supply operation. The pixel is composed of only three transistors without pixel-circuit sharing, and has a gate-common amplifier that compares a photodiode voltage on the gate node with a ramp signal on the source for A/D conversion. We have fabricated a 128×96-pixel prototype imager with an on-chip ramp generator and bootstrap circuits in a 0.35-µm CMOS technology, and successfully demonstrated image acquisition with a 1.4-1.8-V single power supply.

We have developed an on-chip biofluorescence imaging device by packaging a dedicated CMOS image sensor using a simple technique. By using on-chip imaging configuration, we have verified in vivo fluorescence imaging inside a specially developed brain tissue phantom that closely resembles the mammalian brain. In order to implement on-chip imaging, an excitation light filter is applied onto the chip. A transmittance of −44 dB is achieved by multiple coating of the filter. On-chip measurement of the AMC fluorophore shows that detection of concentration of 1 μM is possible. The phantom medium has mechanical rigidity and optical property similar to the mouse brain. Feasibility of imaging the released fluorophore inside the phantom sample is demonstrated. It is shown that light scattering in the phantom medium does not reduce the image resolution considerably, if the imaging depth is kept below 500 μm. The fully packaged chip, specially designed with this technique is about 350 μm thick and 2.7 mm wide. The image sensor pixel size of 7.5 μm × 7.5 μm is close to the size of a single neuron cell. Although the device is designed specially for in vivo imaging of the mouse hippocampus to study its neuronal activity, a wide range of applications are foreseen in the biomedical and pharmaceutical field.

The aim of the present study is to demonstrate the application of complementary metal-oxide semiconductor (CMOS) imaging technology for studying the mouse brain. By using a dedicated CMOS image sensor, we have successfully imaged and measured brain serine protease activity in vivo, in real-time, and for an extended period of time. We have developed a biofluorescence imaging device by packaging the CMOS image sensor which enabled on-chip imaging configuration. In this configuration, no optics are required whereby an excitation filter is applied onto the sensor to replace the filter cube block found in conventional fluorescence microscopes. The fully packaged device measures 350 microm thick x 2.7 mm wide, consists of an array of 176 x 144 pixels, and is small enough for measurement inside a single hemisphere of the mouse brain, while still providing sufficient imaging resolution. In the experiment, intraperitoneally injected kainic acid induced upregulation of serine protease activity in the brain. These events were captured in real time by imaging and measuring the fluorescence from a fluorogenic substrate that detected this activity. The entire device, which weighs less than 1% of the body weight of the mouse, holds promise for studying freely moving animals.

We have designed and fabricated a 16 × 16 pixel pulse frequency modulation (PFM) image sensor for retinal prosthesis. This sensor is a prototype for demonstrating application 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 image sensor for retinal prosthesis by in vitro electrophysiological experiments using the detached frog retina, and confirmed that it can electrically stimulate the retinal cells effectively.

We have developed a CMOS image sensor based on pulse frequency modulation for subretinal implantation. The sensor chip forms part of the proposed intraocular retinal prosthesis system where data and power transmission are provided wirelessly from an extraocular unit. Image sensing and electrical stimulus are integrated onto the same chip. Image of sufficient resolution has been demonstrated using 16times16 pixels. Biphasic current stimulus pulses at above threshold levels of the human retina (500 muA) at varying frame rates (4 Hz to 8 kHz) have been achieved. The implant chip was fabricated using standard CMOS technology

This paper describes the development of a complementary metal–oxide–semiconductor (CMOS) image sensor for in vitro and in vivo imaging of the hippocampus. The 176×144 pixel array image sensor is designed based on a modified three-transistor active pixel sensor circuit. Flexibility in readout for real-time imaging and wide dynamic range measurement is implemented using analog and digital output. A minimum light intensity detection level of 50 nW/cm2 has been measured using the image sensor. A novel packaging method is developed to enable both in vitro and in vivo imaging. In this method, a color filter is applied onto the image sensor that selectively blocks excitation light transmittance to below -44 dB. The packaged device thickness measuring 350 µm, limits tissue damage during invasive imaging. Using the device, static images of the mouse brain slice and real time imaging of the hippocampus of a mouse are successfully demonstrated for the first time.

A complementary metal oxide semiconductor (CMOS) image sensor for the detection of modulated light under background illumination has been developed. When an object is illuminated by a modulated light source under background illumination the sensor enables the object alone to be captured. This paper describes improvements in pixel architecture for reducing fixed pattern noise (FPN) and improving the sensitivity of the image sensor. The improved 128 × 128 pixel CMOS image sensor with a column parallel analog-to-digital converter (ADC) circuit was fabricated using 0.35-mm CMOS technology. The resulting captured images are shown and the properties of improved pixel architecture are described. The image sensor has FPN of 1/28 that of the previous image sensor and an improved pixel architecture comprising a common in-pixel amp and a correlated double sampling (CDS) circuit. The use of a split photogate increases the sensitivity of the image sensor to 1.3 times that of the previous image sensor.

The functioning of a 16 × 16 pixel pulse frequency modulation (PFM) image sensor for retinal prosthesis is verified through in vitro electrophysiological experiments using detached frog retinas. This image sensor is a prototype for demonstrating the application to in vitro electrophysiological experiments. Each pixel of the image sensor consists of a pulse generator (PFM photosensor), a stimulus circuit, and a stimulus electrode (Al bonding pad). The image sensor is fabricated using standard 0.6 μm CMOS technology. For in vitro electrophysiological experiments, a Pt/Au stacked electrode is formed on the Al bonding pad of each pixel and the entire sensor is fixed in epoxy resin. The PFM image sensor is confirmed experimentally to provide electrical stimulus to the retinal cells in a detached frog retina.

We fabricated a low-voltage 32×32-pixel pulse-frequency-modulation vision chip with an image processing function executed in a pulse domain in a standard 0.35-μm CMOS technology. We showed the characteristics and feasibility of our vision chip architecture.

An optical and potential dual imaging CMOS sensor for bioscientific applications was proposed and fabricated. The CMOS image sensor has the capability to simultaneously capture optical and on-chip potential images. The sensor is designed with target applications of on-chip DNA (or protein) microarray analysis and on-chip neural imaging. A potential imaging function was implemented onto a CMOS image sensor with a simple pixel circuitry that is compatible with optical image sensor pixels. The basic properties of the potential-sensing pixel were characterized. By choosing an appropriate operating sequence and off-chip configuration, the sensor can be operated in either a wide-range potential imaging mode (>5 V) or a high-resolution potential imaging mode (1.6 mV). The sensor is applicable for most of the target applications and is capable of detecting a pH change in the solution placed on the surface. Two-dimensional optical and potential dual imaging was successfully demonstrated, and the profile of a potential spot smaller than 50 μm was clearly observed.

An LSI-based cooperative multi-chip neural interface device, for stimulation as well as recording, is proposed and fabricated. The proposed multi-chip device consists of small (600 μm × 600 μm in the present design) intelligent neural interface unit chips. The unit chip has nine neural stimulation/recording electrodes and an individual control circuit. It can work not only as a stand-alone unit, but also in cooperation with other unit chips. One can configure any number of the unit chips as a multi-chip neural interface device. Compared to conventional single-chip architecture, the proposed multi-chip architecture has a number of advantages including thinness, mechanical strength, flexibility, and extendibility. That makes the multi-chip neural interface device more suitable for in vivo applications than conventional single-chip devices. Packaging technology for the multi-chip device was also developed. We developed a thin, flexible packaging technique for the multi-chip neural interface device and LSI-compatible Pt/Au stacked bump electrodes. The functions of the fabricated multi-chip neural interface device were characterized and the feasibility of the device as a random-access, multi-site stimulator was demonstrated.

Nanoscopic characterization of the local ferroelectricity by piezoresponse measurements with scanning probe microscope is performed on a 40 nm-thick (Pb,La)(Zr,Ti)O 3 (PLZT) (8/65/35) thin film prepared on a Nb-SrTiO(001) substrate. The microscopic piezoresponse showed a nearly linear dependence on the DC bias voltage with a slight bistability. The poled structure showed rapid retention. We attribute the bistability observed in the piezoresponse and the vanishing of the poled structure to a phase transition between the relaxor phase and the field-induced ferroelectric phase. The control and imaging of the local domain structure are also performed.

In this paper, we propose a flexible retinal prosthetic device using a distributed sensor network. The novel point of the proposed device is that the flexible stimulator consists of micro-sized CMOS devices linked in a network. In the micro-sized CMOS device single-wire serial interface, a photosensor with a pixel-level analog-to-digital converter (ADC), an image processing circuit, and a current driver circuit are integrated. The device is fabricated using 0.6 μm CMOS technology with a size of 500 μm × 500 μm. We present the results of a successful test of a prototype device.

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.

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.

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.

Novel GeC epilayers on Si (001) substrates were grown by using a molecular beam epitaxy (MBE) with a vacuum arc plasma gun as a new-type C source for a first time. To improve crystallinity and obtain a higher substitutional C content x in the Ge1-xCx epilayers, dependence of the growth mode and C incorporation upon the supplied C fraction and growth temperature was investigated systematically by reflection high-energy electron diffraction, X-ray diffraction and Raman spectroscopy analyses. Further, an effect of Ar+ ion irradiation on substitutional C incorporation into the MBE-grown GeC /Si (001) epilayers was clarified. As the result, the maximum value of x= 2.9% was obtained in a singlecrystalline structure. From measuring the optical absorption spectra with FT-IR, it was found out that the Get1-xCx/Si (001) epilayers with 0≤x≤2.0% have an indirect transition-type band structure and a very large bandgap bowing parameter b= 13.4 eV.

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.

An image-sensor-based photo receiver for free-space optical communications, especially, ones employing indoor optical wireless LANs, has been developed. The receiver enables a compact and intelligent optical communication system through its two functional modes : image-sensing and communication. We clarified that the diffusion of photo-generated electrons determines the minimum total transimpedance gain of the amplifier and the maximum intensity of optical communication signals. A 50x50-pixel photo receiver with four independent communication-output channels was designed and fabricated with standard 0. 35 μm CMOS technology. To amplify optical data in the communication mode, it has in-pixel trans-impedance amplifiers and column-parallel main amplifiers. Experiments conducted with it showed that data rates of 50Mbps and 30Mbps were possible for wavelengths of 650nm and 830nm, respectively. Transimpedance gain varied from 660kΩ to 4.9MΩ for the data rate of 10Mbps. We also successfully captured images at a frame rate of 50Hz.

An ion beam-assisted deposition (IBAD) technique has been attempted for molecular beam epitaxy (MBE)-grown Ge 1− x C x /Si(0 0 1) to increase the substitutional C content x and to improve the crystallinity. The GeC epilayers were grown with irradiating Ar + ions by using a differentially pumped Kaufman-type ion gun. The acceleration energy E a of Ar + ions was varied from 0 to 500 eV. The substitutional C content x increased from 2.5% to 3.0% with changing the E a -value from 0 to 200 eV. The increase of x -value in Ge 1− x C x epilayers was attributed to atomic mixing induced by the Ar + ion irradiation. For E a ⩾300 eV, the x -value remarkably decreased with increasing energy E a . The GeC epilayers with better crystallinity were grown by increasing energy E a under the IBAD.

The band structure of GeC epilayers on Si(0 0 1) substrates has been investigated by Fourier transformation infrared spectroscopy, photoreflectance and spectroscopic ellipsometry measurements. The Ge 1− x C x epilayers were grown by molecular beam epitaxy with the substitutional C content x from 0 to 0.025. The absorption coefficient α of these epilayers obeyed a square-root law for the photon energy hν , indicating an indirect band gap semiconductor. The fundamental band gap energy E g and the interband transition-energy E 0 remarkably decreased with increasing x . Large band gap bowing was found out in the GeC epilayers and large bowing parameter of 13.1 eV was evaluated. The modification of the band structure by the incorporation of C atoms was occurred.

Molecular beam epitaxy (MBE) growth of GeC epilayers on Si(0 0 1) substrates was attempted using an arc plasma gun as a novel C source for the first time. In preliminary experiments, the C beam generated by the gun was confirmed to consist mainly of 12 C and to include very few microparticles. In order to improve crystalline quality and obtain a higher substitutional C content x in Ge 1− x C x epilayers, the variation in the growth mode and C incorporation with the supplied C fraction x C and growth temperature T s was investigated systematically by reflection high-energy electron diffraction, X-ray diffraction (XRD) and Raman spectroscopy analyses. At x C =7.3% and T s =400°C, the maximum x value of 2.6% in a single-crystalline structure was obtained from XRD studies. It was clarified that use of the arc plasma gun and enhancement of non-equilibrium growth play important roles in the incorporation of substitutional C and in restraining C-cluster formation in the MBE growth of GeC/Si.

We have fabricated and demonstrated fundamental characteristics of an image sensor integrated with Si-LED using standard S1Ge-B1CMOS process technology Two types of LEDs, avalanche and Zener, were fabricated, in terms of breakdown mode The avalanche type LED was found to have better emission efficiency. We also studied the dependence of the distance between LED and APS on the discharge characteristics of the APS and found that over 500 ii m is required to suppress the effect from the LED