CMOS image sensors are generally considered as being particularly suited to the harsh space environment, if they can get their performance up to the CCD levels. Recent developments indicate however that this object can be achieved.
This paper presents the current state of the art in CMOS Active Pixel Sensors (APS) for space applications at Fillfactory and also highlights some commercial and industrial development that can be of interest for the space community.
This paper describes a CMOS Active Pixel Image Sensor developed for generic X-ray imaging systems using standard CMOS technology and an active pixel architecture featuring low noise and a high sensitivity. The image sensor has been manufactured in a standard 0.35 μm technology using 8" wafers. The resolution of the sensor is 3360x3348 pixels of 40x40 μm2 each. The diagonal of the sensor measures little over 190 mm. The paper discusses the floor planning, stitching diagram, and the electro-optical performance of the sensor that has been developed.
We will present a 3044 x 4556 pixels CMOS image sensor with a pixel array of 36 x 24 mm2, equal to the size of 35
mm film. Though primarily developed for digital photography, the compatibility of the device with standard optics for
film cameras makes the device also attractive for machine vision applications as well as many scientific and highresolution
applications. The sensor makes use of a standard rolling shutter 3-transistor active pixel in standard 0.35 μm
CMOS technology. On-chip double sampling is used to reduce fixed pattern noise. The pixel is 8 μm large, has 60,000
electrons full well charge and a conversion gain of 18.5 μV/electron. The product of quantum efficiency and fill factor
of the monochrome device is 40%. Temporal noise is 35 electrons, offering a dynamic range of 65.4 dB. Dark current is
4.2 mV/s at 30 degrees C. Fixed pattern noise is less than 1.5 mV RMS over the entire focal plane and less than 1 mV
RMS in local windows of 32 x 32 pixels. The sensor is read out over 4 parallel outputs at 15 MHz each, offering 3.2
images/second. The device runs at 3.3 V and consumes 200 mW.
The paper describes the result of the first phase of the ESPRIT LTR project SVAVISCA. The aim of the project was to add color capabilities to a previously developed monochromatic version of a retina-like CMOS sensor. In such sensor, the photosites are arranged in concentric rings and with a size varying linearly with the distance from the geometric center. Two different technologies were investigated: 1) the use of Ferroelectric Liquid Crystal filters in front of the lens, 2) the deposition of color microfilters on the surface of the chip itself. The main conclusion is that the solution based on microdeposited filters is preferable in terms of both color quality and frame rate. The paper will describe in more detail the design procedures and the test results obtained.
A color CMOS image sensor has been developed which meets the performance of mainstream CCDs. The pixel combines a high fill factor with a low diode capacitance. This yields a high light sensitivity, expressed by the conversion gain of 9 (mu) V/electron and the quantum efficiency fill factor product of 28 percent. The temporal noise is 63 electrons, and the dynamic range is 67 dB. An offset compensation circuit in the column amplifiers limits the peak-to-peak fixed pattern noise to 0.15 percent of the saturation voltage.
In this article we discuss the trade-offs for the design, fabrication and interfacing of fast pixel addressable (random-access) cameras. In order to benefit most from the random addressability, the interface must be optimized for access through a data bus/address bus structure. Measures to correct the camera's inherent non-uniformity must not slow down the interface speed.
The paper presents a low cost, miniature sensor that is able to compute in real time (up to 1000 frames/sec) motion parameters like the degree of translation, expansion or rotation that is present in the observed scene, as well as the so-called time-to-crash (TTC), that is the time required for a moving object to collide with the sensor. The sensing principle is that of computing and analyzing the optical flow projected by the scene on the sensor focal plane, through a novel algorithmic technique, based on sparse sampling of the image and one-dimensional correlation. The hardware implementation of the algorithm is based on two custom VLSI chips: one is a CMOS image sensor, having nonstandard pixel geometry, while the other one is a digital correlator that computes at high speed the optical flow vectors. The high-level control and communication tasks are managed by a microcontroller, thus guaranteeing a high level of flexibility and adaptability of the sensor properties towards different application requirements and/or variable external conditions.
A new image sensor, using CMOS technology, has been designed and fabricated. The pixel distribution of this sensor follows a log-polar mapping, thus the pixel concentration is maximum at the center reducing the number of pixels towards the periphery, having a resolution of 56 rings with 128 pixels per ring. The design of this kind of sensors has special issues regarding the space-variant nature of the pixel distribution. The main topic is the different pixel size that requires scaling mechanisms to achieve the same output independently of the pixel size. This paper presents some study results on the scaling mechanisms of this kind of sensors. A mechanism for current scaling is presented. This mechanism has been studied along with the logarithmic response of these special kind of sensing cells. The chip has been fabricated using standard 0.7 micrometer CMOS technology.
We report on the design, design issues, fabrication and performance of a log-polar CMOS image sensor. The sensor is developed for the use in a videophone system for deaf and hearing impaired people, who are not capable of communicating through a 'normal' telephone. The system allows 15 detailed images per second to be transmitted over existing telephone lines. This framerate is sufficient for conversations by means of sign language or lip reading. The pixel array of the sensor consists of 76 concentric circles with (up to) 128 pixels per circle, in total 8013 pixels. The interior pixels have a pitch of 14 micrometers, up to 250 micrometers at the border. The 8013-pixels image is mapped (log-polar transformation) in a X-Y addressable 76 by 128 array.
Two CMOS image sensor concepts, developed for motion extraction, are proposed. The algorithm implemented in each pixel is either: the calculation of the temporal variation of the difference of the logarithm of intensity in two adjacent pixels; or a more general implementation of the spatial and temporal filtering over the local neighborhood. Temporal differencing yields peak in the response of pixels with changing intensity. The spatial differencing provides high-pass filtering and invariance to time-varying external lighting. We also compare two ways to use this sensor module to compute the velocity of edges moving along the sensor. In one implementation, the sensor is used as an input for a correlation algorithm, calculating the optical flow vector. The other possibility is to detect motion locally in each pixel, and measuring the time of switching between adjacent pixels which detect the motion.