RTS noise impact in CMOS image sensors readout circuit

CMOS image sensors are nowadays widely used in imaging applications even for high end applications. This is really possible thanks to a reduction of noise obtained, among others, by Correlated Double Sampling (CDS) readout. Random Telegraph Signal (RTS) noise has thus become an issue for low light level applications especially in the context of downscaling transistor dimension. This paper describes the analysis of in-pixel source follower transistor RTS noise filtering by CDS circuit. The measurement of a non Gaussian distribution with a positive skew of image sensor output noise is analysed and dimension (W and L) impact of the in-pixel source follower is analysed

Novel readout circuit architecture for CMOS image sensors minimizing RTS noise

This letter presents a novel readout architecture and its associated readout sequence for complementary metal–oxide– semiconductor (CMOS) image sensors (CISs) based on switch biasing techniques in order to reduce noisy pixel numbers induced by in-pixel source-follower transistor random telegraph signal noise. Measurement results done on a test image sensor designed with 0.35-μm CIS technology demonstrate an efficient reduction of noisy pixel numbers without a pixel performance decrease

Low-frequency noise impact on CMOS image sensors

CMOS image sensors are nowadays extensively used in imaging applications even for high-end applications. This is really possible thanks to a reduction of noise obtained, among others, by Correlated Double Sampling (CDS) readout. Random Telegraph Signal (RTS) noise has thus become an issue for low light level applications especially in the context of downscaling transistor size. This paper describes the analysis of in-pixel source follower transistor RTS noise filtering by CDS circuit. The measurement of a non Gaussian distribution with a positive skew of image sensor output noise is analysed. Impact of dimensions (W and L) of the in-pixel source follower is demonstrated. Circuit to circuit pixel output noise dispersion on 12 circuits coming from 3 different wafers is also analysed and weak dispersion is seen

Custom transistor layout design techniques for random telegraph signal noise reduction in CMOS image sensors

Interface and near oxide traps in small gate area MOS transistors (gate area ,1 mm2) lead to RTS noise which implies the emergence of noisy pixels in CMOS image sensors. To reduce this noise, two simple and efficient layout techniques of custom transistors have been imagined. These techniques have been successfully implemented in an image sensor test chip fabricated in a 0.35 mm CMOS image sensor process. Experimental results demonstrate a significant reduction of the noisy pixels for the two different techniques

Overview of CMOS process and design options for image sensor dedicated to space applications

With the growth of huge volume markets (mobile phones, digital cameras…) CMOS technologies for image sensor improve significantly. New process flows appear in order to optimize some parameters such as quantum efficiency, dark current, and conversion gain. Space applications can of course benefit from these improvements. To illustrate this evolution, this paper reports results from three technologies that have been evaluated with test vehicles composed of several sub arrays designed with some space applications as target. These three technologies are CMOS standard, improved and sensor optimized process in 0.35µm generation. Measurements are focussed on quantum efficiency, dark current, conversion gain and noise. Other measurements such as Modulation Transfer Function (MTF) and crosstalk are depicted in [1]. A comparison between results has been done and three categories of CMOS process for image sensors have been listed. Radiation tolerance has been also studied for the CMOS improved process in the way of hardening the imager by design. Results at 4, 15, 25 and 50 krad prove a good ionizing dose radiation tolerance applying specific techniques

Population Synthesis of Normal Radio and Gamma-ray Pulsars Using Markov Chain Monte Carlo Techniques

We present preliminary results of a pulsar population synthesis of normal pulsars from the Galactic disk using a Markov Chain Monte Carlo method to better understand the parameter space of the assumed model. We use the Kuiper test, similar to the Kolmogorov-Smirnov test, to compare the cumulative distributions of chosen observables of detected radio pulsars with those simulated for various parameters. Our code simulates pulsars at birth using Monte Carlo techniques and evolves them to the present assuming initial spatial, kick velocity, magnetic field, and period distributions. Pulsars are spun down to the present, given radio and gamma-ray emission characteristics, filtered through ten selected radio surveys, and a {\it Fermi} all-sky threshold map. Each chain begins with a different random seed and searches a ten-dimensional parameter space for regions of high probability for a total of one thousand different simulations before ending. The code investigates both the "large world" as well as the "small world" of the parameter space. We apply the K-means clustering algorithm to verify if the chains reveal a single or multiple regions of significance. The outcome of the combined set of chains is the weighted average and deviation of each of the ten parameters describing the model. While the model reproduces reasonably well the detected distributions of normal radio pulsars, it does not replicate the predicted detected $\dot P - P$ distribution of {\it Fermi} pulsars. The simulations do not produce sufficient numbers of young, high-$\dot E$ pulsars in the Galactic plane.Comment: 4 pages, 2 figures, The proceedings from the Pulsar Conference: Electromagnetic Radiation from Pulsars and Magnetars will be published in the Astronomical Society of the Pacific Conference Serie

The role of beam geometry in population statistics and pulse profiles of radio and gamma-ray pulsars

We present results of a pulsar population synthesis study that incorporates a number of recent developments and some significant improvements over our previous study. We have included the results of the Parkes multi-beam pulsar survey in our select group of nine radio surveys, doubling our sample of radio pulsars. We adopted with some modifications the radio beam geometry of Arzoumanian, Chernoff & Cordes (2002). For the $\gamma$-ray beam, we have assumed the slot gap geometry described in the work of Muslimov & Harding (2003). To account for the shape of the distribution of radio pulsars in the $\dot P-P$ diagram, we continue to find that decay of the magnetic field on a timescale of 2.8 Myr is needed. With all nine surveys, our model predicts that EGRET should have seen 7 radio-quiet (below the sensitivity of these radio surveys) and 19 radio-loud $\gamma$-ray pulsars. AGILE (nominal sensitivity map) is expected to detect 13 radio-quiet and 37 radio-loud $\gamma$-ray pulsars, while GLAST, with greater sensitivity is expected to detect 276 radio-quiet and 344 radio-loud $\gamma$-ray pulsars. When the Parkes multi-beam pulsar survey is excluded, the ratio of radio-loud to radio-quiet $\gamma$-ray pulsars decreases, especially for GLAST. The decrease for EGRET is 45%, implying that some fraction of EGRET unidentified sources are radio-loud $\gamma$-ray pulsars. In the radio geometry adopted, short period pulsars are core dominated. Unlike the EGRET $\gamma$-ray pulsars, our model predicts that when two $\gamma$-ray peaks appear in the pulse profile, a dominant radio core peak appears in between the $\gamma$-ray peaks. Our findings suggest that further improvements are required in describing both the radio and $\gamma$-ray geometries.Comment: 39 pages, 13 eps figures, accepted for publication in ApJ, April 1, 200

A high dynamic range digital LinLog CMOS image sensor architecture based on Event Readout of pixels and suitable for low voltage operation

Several approaches have been developed to extend the dynamic range of image sensor in order to keep all the information content of natural scenes covering a very broad range of illumination. Digital CMOS image sensor are especially well suited to wide dynamic range imaging by implementing dual sampling, multiple exposure methods using either column or in pixel ADC, or Address Event Representation. A new architecture of digital high dynamic range CMOS image sensor, suitable for low voltage operation, has been developed that implements a built-in dynamic compression function targeted to LinLog behavior, by combining an event based readout of pixels, the use of multiple integrations per frame and the coding of pixel values using the mantissa-exponent principle, to achieve the dynamic range extension

Analysis and Optimization of Noise Response for Low-Noise CMOS Image Sensors

CMOS image sensors are nowadays widely used in imaging applications and particularly in low light flux applications. This is really possible thanks to a reduction of noise obtained, among others, by the use of pinned photodiode associated with a Correlated Double Sampling readout. It reveals new noise sources which become the major contributors. This paper presents noise measurements on low-noise CMOS image sensor. Image sensor noise is analyzed and optimization is done in order to reach an input referred noise of 1 electron rms by column gain amplifier insertion and dark current noise optimization. Pixel array noise histograms are analyzed to determine noise impact of dark current and column gain amplifier insertion. Transfer noise impact, due to the use of pinned photodiode (4T photodiode), is also measured and analyzed by a specific readout sequence