We developed a Time Delay Integration (TDI) CCD image sensor that consists of four multispectral bands (B1-B4 zone)
and one panchromatic band (P zone) in an integrated, compact package. The B zones have a horizontal resolution of 3k
columns, with a pixel size of 28 μm x 28 μm. The P zone has a horizontal resolution of 12k columns, with a pixel size of
7 μm x 7 μm. The large pixel size of B zones provides excellent colour differentiation even under extremely low light
intensity, while the small pixel size and the large pixel number of broad band zone (P zone) provides high resolution
images within a wide spectrum range. By utilizing a particularly designed hybrid optical filter, the sensor is able to
collect blue, green, red, and near infrared images with only negligible optical crosstalk. The sensor uses selectable
outputs and data rate: 2 or 1 outputs running at 16.5 MHz (B1-B4 Zone) per output, and 8 or 4 outputs running at 33
MHz (P Zone) per output. Special design features minimize optical crosstalk between the image zones, and achieve a
low signal noise: ≤ 85 e- in B zone, and ≤ 35 e- in P zone. To acquire spectral reflectance signatures with good fidelity,
the image sensor must be very sensitive to weak light in some spectral bands and cannot be over exposed to light in other
spectral bands. To fulfil this requirement, the sensor is designed to show a balanced responsivity in all the image zones.
Over all, the sensor demonstrates outstanding performance, providing exceptional images that are crucial for remote
sensing applications.
Remote Hyperspectral and Multispectral sensors have been developed using modern CCD and CMOS fabrication
techniques combined with advanced dichroic filters. The resulting sensors are more cost effective while maintaining the
high performance needed in remote sensing applications. A single device can contain multiple imaging areas tailored to
different multispectral bandwidths in a highly cost effective and reliable package. This paper discusses a five band
visible to near IR scanning sensor. By bonding advanced dichroic filters onto the cover glass and directly in the imaging
path a highly efficient multispectral sensor is achieved. Up to 12,000 linear pixel arrays are possible1 with this advanced
filter technology approach. Individual imaging areas on the device are designed to have unique pixel sizes and clocking
to enable tailored imaging performance for the individual spectral bands. Individual elements are also based on high
resolution Time Delay and Integration technology2,3 (TDI) to maximize sensitivity and throughput. Additionally for
hyperspectral imagers, a split frame CCD design is discussed using high sensitivity back side illuminated (BSI)
processes that can achieve high quantum efficiency. As these sensors are used in remote sensing applications, device
robustness and radiation tolerance was required.
We have developed two single-chip CCD sensor architectures for high-speed, 3-channel color imaging. Both are line-scan sensors for Time Delay and Integration (TDI) imaging. One architecture achieves a sub-microsecond TDI register shift time by contacting metal to poly-Si gates through the imaging regions. The other has no metal in the imaging regions and requires a longer shift time. Both sensors are capable of 40 MHz data rate per channel. Line rates for 2048-pixel devices of 16.5 and 18.5 kHz (shift times of 7.5 and 0.7 microsecond(s) /stage) are achieved.
We have developed a linescan sensor suited for high image quality, high-resolution, high-speed imaging. The 6k-pixel sensor has: four corner outputs each operating at 40 MHz for high scanning speed; 7 micrometers pixels for shorter sensor length and simpler optical design; an exposure control and antiblooming structure that does not produce imaging artifacts; 9.5 (mu) V/e charge conversion efficiency at the output for enhanced sensitivity and dynamic range under light-starved conditions; optimized pinned photodiodes for low image lag (< 350 electrons) and enhanced UV response (> 40% QE at 250 nm); 100% fill factor down to the deep UV; a pixel storage structure that suppresses photosite-to- shift-register optical crosstalk; highly linear output structures and amplifiers (< 1% non-linearity); matched 5- V 2-phase clocks that can be driven with off-the-shelf CMOS drivers; output waveform shape that allows 40-MHz CDS; and photoresponse non-uniformity that is < +/- 2% of the signal.
DALSA and Philips Digital Video Systems have developed a high performance pinned-photo-diode CCD linescan sensor for scanning of motion picture film. This application requires a sensor with performance optimized for a high dynamic range optical input, with high speed operation. The sensor is named the IL-P2-2048. It is based on the existing DALSA IL- P1-2048 linescan sensor design with a number of significant changes--the full well has been increased to in excess of 300,000 electrons, with a maximum video swing of more than 1000 mV with two bi-directional outputs operating at > 21 MHz video rate. Of importance is the introduction of pinned- photo diode pixels (10 X 10 micron pitch) which possess extremely low fixed pattern noise, low pixel-response non- uniformity, and low image lag. The sensor also has pixel select gates to enable the user to select the full resolution or a reduced number of pixels for use in different imaging formats; the pixel selection is nevertheless dynamic and can be user selectable. The output circuitry has excellent linearity from a few mV to the full signal swing of 1000 mV. In this paper the authors present the design and test results of the sensor.
Photodiode devices, in which the photosite consists of a reverse biased pn diode, have excellent quantum efficiencies at visible wavelengths and in the UV. However, they display high levels of dark and bright image lag, and high levels of fixed pattern noise (FPN) when operated with electronic shuttering. We have addressed these performance issues by replacing the photodiode photosites with pinned photodiode (PPD) photosites. In the PPD the n+ region of the conventional photodiode is replaced by a n region and a shallow highly doped p region - the surface potential in the photosite is pinned such that the photosite behaves as an ungated buried channel well. The high quantum efficiencies associated with photodiodes are maintained while allowing for large reductions in image lag and fixed pattern noise. We have developed PPD processes for two different photosite architectures. In the first architecture, charge is generated in the PPD and immediately spills to an adjacent gated integration well. In the second architecture, the charge is generated and stored in the PPD. Each of the architectures can be configured to allow for antiblooming/electronic shuttering. Both of the PPD processes and their associated architectures have been characterized, and order of magnitude reductions in image lag have been observed for PPD photosites relative to conventional photodiodes. No degradation in QE, PRNU, or well capacity has been observed. One of the PPD processes has been implemented in a family of high sped, quad output, linear sensors with 200 MHz data rates. Performance results are presented.
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