In this paper, a binary complementary metal oxide semiconductor (CMOS) image sensor with a gate/body-tied (GBT) metal oxide semiconductor field effect transistor (MOSFET)-type photodetector is presented. The sensitivity of the GBT MOSFET-type photodetector, which was fabricated using the standard CMOS 0.35-μm process, is higher than the sensitivity of the p-n junction photodiode, because the output signal of the photodetector is amplified by the MOSFET. A binary image sensor becomes more efficient when using this photodetector. Lower power consumptions and higher speeds of operation are possible, compared to the conventional image sensors using multi-bit analog to digital converters (ADCs). The frame rate of the proposed image sensor is over 2000 frames per second, which is higher than those of the conventional CMOS image sensors. The output signal of an active pixel sensor is applied to a comparator and compared with a reference level. The 1-bit output data of the binary process is determined by this level. To obtain a video signal, the 1-bit output data is stored in the memory and is read out by horizontal scanning. The proposed chip is composed of a GBT pixel array (144 × 100), binary-process circuit, vertical scanner, horizontal scanner, and readout circuit. The operation mode can be selected from between binary mode and multi-bit mode.
A novel high-sensitivity active pixel sensor (APS) with a variable threshold photodetector has been presented and for the first time, a simple SPICE model for the variable threshold photodetector is presented. Its SPICE model is in good agreement with measurements and is more simpler than the conventional model. The proposed APS has a gate/body-tied PMOSFET-type photodetector with an overlapping control gate that makes it possible to control the sensitivity of the proposed APS. It is a hybrid device composed of a metal-oxide-semiconductor field-effect transistor (MOSFET), a lateral bipolar junction transistor (BJT) and a vertical BJT. Using sufficient overlapping control gate bias to operate the MOSFET in inversion mode, the variable threshold photodetector allows for increasing the photocurrent gain by 105 at low light intensities when the control gate bias is -3 V. Thus, the proposed APS with a variable threshold photodetector has better low-light-level sensitivity than the conventional APS operating mode, and it has a variable sensitivity which is determined by the control gate bias. The proposed sensor has been fabricated by using 0.35 μm 2-poly 4-metal standard complementary MOS (CMOS) process and its characteristics have been evaluated.
In recent times, much research in the field of complementary metal oxide semiconductor (CMOS) image sensors (CISs) regarding plasmonic color filters (PCFs) has been reported. In this paper, we investigated the influence of vertically asymmetrical metallic apertures on the extraordinary optical transmission of PCFs. We designed a structural model of the asymmetric cylindrical aperture. In addition, we simulated the spectral variation in the wavelength transmission. For the simulation, we used a commercial computer simulation tool utilizing the FDTD method. SiO2 was used as the substrate insulator, top-side insulator, and the fill material in the cylindrical aperture. We applied Au as the metal layer; dispersion information for Au was derived from the Lorentz–Drude model. We also presented the electric field distribution under several different conditions at the peak wavelength of the calculated transmission spectrum. Furthermore, we determined the transmittance spectral characteristics and the peak transmittance under several different conditions.
In this paper, a complementary metal oxide semiconductor (CMOS) binary image sensor based on a gate/body-tied
(GBT) MOSFET-type photodetector is proposed. The proposed CMOS binary image sensor was simulated and measured
using a standard CMOS 0.18-μm process. The GBT MOSFET-type photodetector is composed of a floating gate (n+-
polysilicon) tied to the body (n-well) of the p-type MOSFET. The size of the active pixel sensor (APS) using GBT
photodetector is smaller than that of APS using the photodiode. This means that the resolution of the image can be
increased. The high-gain GBT photodetector has a higher photosensitivity compared to the p-n junction photodiode that
is used in a conventional APS. Because GBT has a high sensitivity, fast operation of the binary processing is possible. A
CMOS image sensor with the binary processing can be designed with simple circuits composed of a comparator and a Dflip-
flop while a complex analog to digital converter (ADC) is not required. In addition, the binary image sensor has low
power consumption and high speed operation with the ability to switch back and forth between a binary mode and an
analog mode.
In this paper, we proposed the plasmonic color filters to decrease ambient light errors on active type dual band infrared image sensors for a large-area multi-touch display system. Although the strong point of the touch display system in the area of education and exhibition there are some limits of the ambient light. When an unexpected ambient light incidents into the display the touch recognition system can make errors classifying the touch point in the unexpected ambient light area. We proposed a new touch recognition image sensor system to decrease the ambient light error and investigated the optical transmission properties of plasmonic color filters for IR image sensor. To find a proper structure of the plasmonic color filters we used a commercial computer simulation tool utilizing finite-difference time-domain (FDTD) method as several thicknesses and whit the cover passivation layer or not. Gold (Au) applied for the metal film and the dispersion information associated with was derived from the Lorentz-Drude model. We also described the mechanism applied the double band filter on the IR image sensors.
This paper presents a novel high-sensitivity and wide dynamic range complementary metal oxide semiconductor
(CMOS) active pixel sensor (APS) with an overlapping control gate. The proposed APS has a high-sensitivity gate/bodytied
(GBT) photodetector with an overlapping control gate that makes it possible to control the sensitivity of the
proposed APS. The floating gate of the GBT photodetector is connected to the n-well and the overlapping control gate is
placed on top of the floating gate for varying the sensitivity of the proposed APS. Dynamic range of the proposed APS is
significantly increased due to the output voltage feedback structure. Maximum sensitivity of the proposed APS is 50
V/lux•s in the low illumination range and dynamic range is greater than 110 dB. The proposed sensor has been fabricated
by using 2-poly 4-metal 0.35 μm standard CMOS process and its characteristics have been evaluated.
We investigated optical properties of subwavelength patterned metal gratings for photonic device application. It was known that optical transmittance of metal films with subwavelength periodic hole arrays can be controlled by applying a dielectric overlay to the film and the films can act as wavelength or frequency selective filters. Following advancement in lithography technology it could be applied up to complementary metal oxide semiconductor (CMOS) image sensors (CIS) by patterning metal layers placed on each pixel’s photo detective device. However it is not easy to replace organic color filters applied on CIS up to date because the standard CIS structure has multi-metal layers, thick dielectric layers, and too thick metal layers. In this work, we explore possibility to integrate the metal film into a CIS chip and present an alternative proposal by computer simulation utilizing finite-difference time-domain (FDTD) method. We applied aluminum (Al) for the metal film and the dispersion information associated with Al was derived from the Lorentz-Drude model. We expect that this work could contribute to search to apply subwavelength patterned metal gratings to photonic devices.
Various approaches have been utilized to extend the dynamic range of the CMOS image sensor, which are based on a
linear-logarithmic CIS, overflow integration capacitor and multiple sampling or individual pixel resetting. These
approaches, however, suffer from noise, nonlinearity, lower sensitivity, reduced operating speed and lower resolution. In
order to overcome these problems, we have previously proposed a dynamic range extension method by combining output
signals from two photodiodes with different sensitivities, such as a high-sensitivity photodiode and a low-sensitivity
photodiode. The proposed active pixel sensor has been fabricated by using 2-poly 4-metal standard CMOS process and
its characteristics have been measured. It is found that charges in the high- and low-sensitivity photodiodes could be
mixed each other and the lost image information of the high-sensitivity photodiode could be regenerated using the
charges in the low-sensitivity photodiode, as shown by simulation results. Dynamic range extension of the proposed
active pixel sensor has been experimentally verified.
A dynamic range (DR) extension technique based on a 3-transistor (3-Tr.) active pixel sensor (APS) and dual image
sampling has been proposed. The feature of the proposed APS was that the APS used two photodiodes with different
sensitivities, a high-sensitivity photodiode and a low-sensitivity photodiode. Operation of the proposed APS was
simulated by using a 128×128 pixel array. Compared with previously proposed wide DR (WDR) APS, the proposed
approach has several advantages; no-external equipments or signal processing for combining images, no-additional timerequirement
for additional charge accumulation, adjustable DR extension and no temporal disparity.
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