The classical streak cameras use a vacuum tube making thus fragile, cumbersome and expensive. The FAst MOS Imager
(FAMOSI) project consists in reproducing completely this streak camera functionality with a single CMOS chip. The
advantages of on-chip functionalities lead to a power reduction, a lower cost and miniaturization. In this paper, we show
the capabilities of a prototype fabricated in the AMS 0.35 μm CMOS process. The chip is composed of 64 columns per
64 rows of pixels. The pixels have a size of 20 μm per 20 μm and a fill factor of 47 %. The Chip FAMOSI implements an
electronic shutter and an analog accumulation capability inside the pixel. With this pixel architecture, the sensor can
work in single shot mode when the light pulse power is sufficient and in repetitive mode, i.e. it can measure a recurrent
light pulse and accumulates the successive photo charges into an internal node, for low light pulse detection. This
repetitive mode utilizes an analog accumulation in order to improve the sensitivity and the signal to noise ratio of the
system. Characterizations under static and uniform illumination in single shot mode have been done in order to evaluate
the performances of the detector. The main noises levels have been evaluated and the experiments show that a
conversion gain of 4.8 μV/e- is obtained with a dynamic range of 1.2V. Moreover, the charge transfer characterization in
single shot mode has been realized. It permits to know which potential must be apply to the charge spill transistor to
obtain the whole dynamic of the output with a maximal transfer gain, what is primordial to optimize the analog
accumulation. Finally, the dynamic operation of the sensors is exposed. Measurements show a sample time of 715 ps and
a time resolution better than 2 ns. A 6 ns light pulse has been measured in single shot and in accumulation mode.
High speed cameras use the interesting performances of CMOS imagers which offer advantages in on-chip functionalities, system power reduction, cost and miniaturization. The FAst MOS Imager (FAMOSI) project consists in reproducing the streak camera functionality with a CMOS imager. In this paper, we present a new imager called FAMOSI 2 which implements an electronic shutter and analog accumulation capabilities inside the pixel. With this kind of pixel and the new architecture for controlling the integration, FAMOSI 2 can work in repetitive mode for low light power and in single shot mode for higher light power. This repetitive mode utilizes an analog accumulation to improve the sensitivity of the system with a standard Nwell/Psub photodiode. The prototype has been fabricated in the AMS 0.35 μm CMOS process. The chip is composed of 64 columns per 64 rows of pixels. The pixels have a size of 20 μm per 20 μm and a fill factor of 47 %. Characterizations under static and uniform illumination in single shot mode have been done in order to evaluate the performances of the detector. The main noises levels have been evaluated and the experiments show that a conversion gain of 4.8 μV/e- is obtained with a dynamic range of 1.2 V. Moreover, the charge transfer characterization in single shot mode has been realized. It permits to know which potential must be apply to the charge spill transistor to obtain the whole dynamic of the output with a maximal transfer gain, what is primordial to optimize the analog accumulation.
We designed a camera based on a fast CMOS APS imager for high speed optical detection which produces images simi-larly as a streak camera. This imager produces the intensity information I as function of one spatial dimension and time (I=f(x,t)) from one frame with two spatial dimensions. The time sweeping is obtained by delaying successively the integration phase for each pixel of the same row. For the first FAMOSI (Fast MOs Imager) prototype the start of in-tegration is given by the camera itself. This signal is injected to a laser trigger. This laser emits a 10 nanoseconds light pulse onto the sensor. The temporal evolution of the light pulse is then resolved by the camera with a resolution of 800 ps. In single shot, the maximum dynamic of the camera is estimated to 64 dB and is limited by the readout noise. We decide to work in accumulation mode in order to increase the signal to noise ratio of the camera. But the high laser trigger (about 20 ns rms) does not allow accumulation of several optical events without a large spreading. The camera has been modified in order to be triggered by an external signal delivered by a trigger unit. In this new configuration the laser emit pulses at a repetition rate of 50 Hz. A photodiode detect a part of the laser pulse and generate the trigger signal for FAMOSI. The laser pulse is delayed with an optical fibre before being directed to the camera. The trigger jitter obtained is then less than 100 ps and allows accumulation without significant loss of the temporal resolution. With accumulation the readout noise is attenuated by a √N factor. Then with N = 1000 accumulations, the dynamics approach 93 dB. This allows the camera to work similarly as a synchroscan streak camera and then to observe weak signal.
Nowadays, imagers based on CMOS active pixel sensors (APS) have performances that are competitive with those based on charge-coupled devices (CCD). CMOS imagers offer advantages in on-chip functionalities, system power reduction, cost and miniaturisation. The FAst MOS Imager (FAMOSI) project consists in reproducing the streak camera functionality with a CMOS imager. In this paper, we present the second version of FAMOSI which makes up for the drawbacks of the first one. FAMOSI 2 has a new architecture of pixel which implements an electronic shutter and analogue accumulation capabilities. With this kind of pixel and the new architecture for controlling the integration, FAMOSI 2 can work in the low power repetitive synchroscan mode. The prototype has been fabricated in the AMS 0.35μm CMOS process. The chip is composed of 64 columns per 64 rows of pixels. The pixels have a size of 20μm per 20μm and a fill factor of 47%. The simulation shows that a conversion gain of 3.4μV/e- is obtained with a dynamic range of 1.2V, a time resolution of 400ps and a light pulse repetitive rate of 300kHz.
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