We propose an optical sensing device to obtain both tactile and proximity information with high spatial resolution that is necessary while grasping small and intricately-shaped objects using a robot hand. In our proposed device, tactile information is obtained through a light conductive plate, which allows the capture of a tactile image of high spatial resolution using a camera. Proximity information is detected on the basis of stereo matching of a pair of images obtained by two cameras through the transparent light conductive plate. In order to realize this concept in a small device, a compound-eye camera which is composed of a single image sensor and an array of nine micro lenses is introduced. A prototype device provides three visible light and three infrared images for proximity and tactile information, respectively. The performance of the prototype is evaluated through an experiment and the factors affecting its performance are discussed.
We have demonstrated effectiveness of the selective averaging with a multi-aperture camera for reducing image sensor noise such as random telegraph signal (RTS) noise and large dark current shot noise. In this paper, noise reduction capability in color reproduction with the proposed method is studied by simulation, where we assume an ultra-high-sensitivity 2 x 2-aperture color camera. In the prototype camera, which is being developed, low-noise Bayer color-filter 0.18um CMOS image sensors based on the folding-integration and cyclic column ADCs with 1280 x 1024 effective pixels are utilized. The synthetic F-number is 0.6. Simulation shows that the effective noise in terms of the peak of noise in histogram is reduced from 1.44 electrons to 0.74 electrons, and RTS noise and large dark current shot noise are successfully removed. Color reproduction errors are quantitatively evaluated. The root-mean-square errors of blue, green, red, and white in the CIE-xy color space becomes approximately a half after the selective averaging.
The image-capturing method with higher temporal sampling rate than frame rate of the image sensor using rolling shutter and compound eye imaging system is proposed. Although the pixel resolution of each images captured compound-eye image capturing system are decreased, it is possible to retrieve the spatial resolution from multiple low-resolution images on the basis of super-resolution processing. Appropriate spatial resolution and temporal resolution adaptable for movement in the scene can be provide by segmenting static regions and dynamic regions. The validity of the proposed method is confirmed by experiments of enhancement of temporal resolution and restoration of spatial resolution based on super-resolution technique using a prototype of the compound-eye imaging system.
In our previous work, we proposed a biometric authentication method using a secure imaging system that was based on compressed sensing. In this approach, although we can acquire an encrypted vein image, the verification process requires the restoration of the raw finger-vein image. To address this issue, we propose an improved authentication method that we can verify alternate biometric features from which it is difficult to restore the original finger-vein image by introducing the permutation matrix for randomizing the object signal. Numerical simulations show that our method has favorable accuracy, although it exhibits a slightly degraded accuracy in comparison with that of the conventional method that uses a raw finger-vein image.
We propose a bit-depth expansion (BDE) method targeting natural images. In the analog part of an imaging system, signal intensity fluctuations occur due to noise (e.g. thermal noise in the image sensor). After that, in the digital part, the intensities are rounded off to limited levels. The latter process, which is quantization, increases the intensity of fluctuation errors caused by stochastic resonance. These errors are viewed as false contour artifacts in the gradation region. Our goal was to obtain the original signal from the quantized noisy signal. We formulated a probabilistic model based on this quantization process, and successfully reconstructed smooth gradations from noisy contours. Subjective evaluation by voting clarified that the output image has higher quality.
A low noise high sensitivity CMOS image sensor (CIS) is developed for low-light levels. The prototype sensor contains the optimized 1-Mpixel with the noise robust column-parallel readout circuits. The measured maximum quantum efficiency is approximately 60% at 660nm, and the long-wavelength sensitivity is also enhanced by a large sensing area and an optimized process. In addition, a low dark current of 0.96pA/cm2 at 292 K, a low temporal random noise in a readout circuitry of 1.17e-rms, and a high pixel conversion gain of 124 μV/e- are achieved. The implemented CMOS imager using 0.11 μm CIS technology with a pinned photodiode has a very high sensitivity of 87V/lx·sec that is suitable for the scientific applications such as medical imaging, bioimaging, surveillance cameras, and so on.
The conventional image systems have been developed in order to enhance the quality of the image representation. Jaggy appearing at the edge of a slant line are, however, easily perceived by human eyes, which often severely defect the ‘perceived’ image quality, because of the spatial perceive characteristics of our eye system. Although the size of the jaggy can be reduced by reducing the pixel size, it is hard to completely eliminate the perceived jaggy by using the conventional lattice pixel placement, since our eye system is sensitive enough to perceive such jaggy. In this paper, we describe the basic concept of the pseudorandom pixel placement to reduce the jaggy effect, and discuss the relation of jaggy reduction effect and the pixel structure characteristics, in terms of the fill factor and the number of pixel types.
Antenna diversity is one of the solutions to multipath fading but with the cost of additional hardware for every RF chain. In mobile reception application, it is difficult to install the additional antennas and cables to the vehicle due to limitations in installation cost and features. In this paper, we propose an Integrated Services Digital Broadcasting - Terrestrial (ISDB-T) diversity receiver using a 4-element electronically steerable passive array radiator (ESPAR) antenna with periodically alternating directivity. The proposed receiver obtains diversity gain requiring only a single-RF front-end and cable, thus reducing the hardware complexity compared to conventional antenna diversity receivers. The receiver utilizes compressed sensing-based channel estimation that recovers the channel state information (CSI) with good accuracy. The simulation results show that with perfect CSI, the proposed ISDB-T receiver is capable of obtaining a diversity gain of about 15 dB for a bit error rate of 10-3.
This paper proposes a system that provides the sensation of touching virtual objects in a mobile touch panel using a retractable stylus and the mobile touch panel. The proposed system provides a sensation like the stylus is being inserted into the monitor, and that the user is actually touching the object in the screen when the user pushes a retractable stylus downward on the display. A DC motor is mounted in the retractable stylus, and this motor shrinks the length of the stylus based on feedback from a pressure sensor in the tip of the stylus. When the tip of the virtual stylus touches a virtual object, a voice coil motor in the stylus oscillates according to the surface of the virtual object. So the user experiences a sensation like touching the object on the monitor by using the proposed system.