Conventional Image Sensors Research Articles

A new readout circuit for an ultrahigh sensitivity CMOS image sensor

We have developed a new readout circuit for highly sensitive CMOS image sensors. The circuit makes it possible to obtain a high signal-to-noise ratio by effectively transferring signal charges accumulated in the photodiode to a small capacitance. We fabricated and tested a CMOS image sensor with the readout circuit, and confirmed that it has higher sensitivity than conventional passive-pixel CMOS image sensors.

A high-sensitivity CCD image sensor using source follower circuit with actively controlled gain characteristics

A high-sensitivity charge coupled device (CCD) image sensor that utilizes a new output structure has been developed. The structure utilizes an enhancement inverter, a coupling capacitor, and resistors in addition to the conventional source follower. The output of the source follower is inverted and ac component of that signal is fed back to the gate of the load transistor of source follower to modulate the impedance. The overall gain improvement can be estimated from simple small-signal analysis and the results match well to the circuit simulation. A 1/4 in. 250,000 pixels color CCD image sensor was fabricated employing the new output circuit. The fabrication process is same to that for conventional CCD image sensors since the inverter in this circuit consists of enhancement mode transistors. It is observed that 14% of sensitivity improvement in the CCD image sensor is achieved by the new structure and the linearity shows no distortion compared to conventional image sensors in the full range of imaging illumination.

高解像度純電子式手振れ補正システム

A high-resolution image-stabilizing system by using only digital processing was developed for camcorders. In this system, a CCD image sensor that has more pixels than a conventional CCD image sensor was adopted to get a large margin for image stabilization and to abolish electronic zooming processing that spoiled picture resolution in a conventional system. The image-stabilizing procedure was divided to two parts : compensation for low frequency image fluctuation and that for remained image fluctuation. The compensation for low frequency image fluctuation was achieved by a readout control of the CCD image sensor according to a motion prediction. On the other hand the compensation for remained image fluctuation was achieved by a readout control of an image memory according to a detected motion vector from images read out from the CCD image sensor. As a result, high image-stabilizing equal to that of a conventional system and maintenance of picture resolution were achieved.

Fast Square-area Detection Algorithm using Automata for VLSI Implementation.

Conventional image sensors, including CCD sensors and smart sensors are considered for just acquiring the image as the matrix of dots, not for recognizing the meaning of image.In this paper, we propose a novel real-time algorithm to detect the square area in an object using the structure of node automata, and discuss its implementation as a CMOS image sensor, where the pixels and the node automata are integrated in one chip. We also discuss the search algorithm of their position in the pixel plain using area dividing methodology.

An Artificial Retina Chip with Pixel-wise Self-Adjusting Intensity Response

A human retina like, wide operating-range CMOS image sensor with pixels that shift their intensity-response curves according to the intensity of light has been constructed. The chip realizes an operating range 28dB wider than that of conventional CMOS image sensor. The chip integrates 128×128 pixels whose size is 24×24μm2 with 0.8μm single poly-Si and double metal CMOS technology. The chip size is 6.0×4.6mm2.

高感度ＣＭＯＳイメージセンサの開発

CMOS image sensors with low power consumption and signal-processing circuits are widely used for mobile products and digital still cameras. A conventional MOS image sensor has high fixed pattern noise, up to the 30 mVp-p level, caused by the subthreshold voltage fluctuations of the cell-amplifier transistor and high random noises both the low-frequency cell-source follower circuits and the high-frequency output amplifier circuit. We developed and evaluated new circuit technologies to suppress both the fixed pattern noise in the pixels and the random noise in the cell-source follower and output amplifier. Using three kinds of analog circuit technologies, we developed an amplified 1/2-inch 1.3 M-pixel CMOS image sensor with low power consumption (60 mW) and high signal-to-noise ratio (50 dB).

Principle and Simulation for Reconstruction of Two-dimensional Image beyond Nyquist Frequency

Principles of the two-dimensional image reproduction including frequency components higher than Nyquist frequency of an image sensor were considered, and resolution progress of an image sensor by digital signal processing was simulated on computer. Simulated imaging device is the two-dimensional (area) image sensor. After the simulation, it is difficult to find the differences between the original and the reproduced image by the naked eye. The reproduced images that have frequency components twice higher than Nyquist frequency were successfully obtained. Using this method, it is possible to enhance the resolution of conventional image sensor twice as high as its inherent resolution without any modification to the image sensor.

論文小特集 リニアセンサ技術 １００ＭＨｚ５ｋビットリニアイメージセンサ

This paper describes a 100-MHz datarate, 5000 element CCD linear image sensor with 20.3μ V/electron amplifier sensitivity. A reset-pulse level-adjustment circuit with a reset gate potential detector, and a self-aligned technique to minimize floating diffusion node capacitance are used to achieve this performance. The reading speed is triple and the photo-sensitivity is twice that of conventional linear image sensors with more than 5000 elements.This sensor is able to scan an 11-inch sheet in 50 μs with 400-dot-per-inch resolution.

Depth profiling of peat deposits with impulse radar

With the growing interest in peat as an energy fuel, the need for better inventories of this resource becomes increasingly important. Although conventional imaging sensors can provide information on the areal extent of peatlands, depth measurements must still be taken in the field in order to estimate the volume of material present. A recently completed program conducted in eastern Newfoundland suggests that impuse radar systems can provide depth information and volume estimates comparable to those obtained with manual measurement techniques. Ground-based data were acquired using 80- and 400-MHz radar systems and airborne data were collected using 80- and 120-MHz systems. For ground-based profiles, peat thickness of up to 8.1 m was clearly measureable. The airborne profile data were generally poorer in quality; however, depths of up to 4.8 m were successfully profiled from an altitude of 1.5 m. No significant seasonal variations were observed. Impulse radar techniques seem to be particularly useful for reconnaissance level surveys. Additional research is needed in order to develop a system suitable for airborne profiling. Key words: impulse radar, peat resources, peatlands, Newfoundland, depth, volume, profiling, airborne profiling, radar propagation.

A CPD image sensor with buried-channel priming couplers

A 398 (H) × 496 (V)-element CPD image sensor with buried-channel charge-priming-transfer (CPT) couplers for ⅔-in format has been developed. The buried-channel CPT structures by use of the external bias change has been adopted based on the theoretical consideration to suppress random noise and to improve vertical transfer efficiency for small signal charge. The vertical transfer efficiency even for small signal charges was improved up from 70 to 95 percent or more by use of the external bias charge in addition to priming charge. It was found that total random noise in the new image sensor corresponds to ∼ 400 electrons, which is about half of that in a conventional CPD image sensor with surface-channel CPT couplers.

Image Sensing: Image sensors feel the squeeze

An 'accordion' solid state image sensor, which has twice as many high sensitivity elements per unit area as earlier sensors but does not need a finer electrode pattern, has been developed at Philips Research Laboratories, Eindhoven. In a conventional solid state image sensor (and also in a charge coupled device shift register) narrow parallel channels of n-type material are located in a layer of p-type silicon; perpendicular to these channels and located on the surface are linear electrodes, insulated from each other and from the silicon surface.

A two-phase drive bipolar linear image sensor using zigzag arrangement of PCD shift register elements

A bipolar linear image sensor composed of a 512-bit photodiode array, two 256-bit switch arrays and two 512-bit plasma-coupled device (PCD) shift registers characterized by zigzag arrangement of conductance transistors has been developed. As compared with a conventional PCD image sensor which needs four-phase or six-phase shift pulses to drive the PCD shift registers, the newly developed sensor requires only two-phase shift pulses and greatly simplifies an external driving circuit. In addition, it can be fabricated by using only four photomasks, providing good cost performance.