Bi-directional, fast-timing, charge coupled device

Details Bi-directional, fast-timing, charge coupled device Bi-directional, fast-timing, charge coupled device

1996-07-10

1997-12-02

Ngo, Ngan V.

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Charge transfer device

257239, 257240, 257241, H01L 27148, H01L 29768

Patent

active

056939680

ABSTRACT:
A fast-timing bi-directional charge coupled device ("CCD") is disclosed. The CCD operates at a much faster overall rate than conventional CCD's, while paradoxically slowing down the readout rate of the pixels. Lower power consumption is required, less heat is generated, thermal noise is lower, and digital noise is lower. The novel CCD is capable of 10-25 .mu.sec timing resolution (or even faster). The configuration entirely eliminates the (formerly) rate-determining step of transferring data "horizontally" from the "top" of the CCD columns. Instead, the charges on columns are transferred either "up" or "down" in an alternating manner. For example, the charges in odd-numbered columns might be transferred one row "up" with each clock cycle, and charges in even-numbered columns might be transferred "down." This alternating charge transfer architecture is termed "bi-directional." There is no "horizontal" transfer of data off the chip; rather, each column outputs to a separate amplifier, preferably located on-chip. There is no need for a shutter in a low flux setting, although a shutter could be used for a high flux application. Without a shutter, the readout from each column is continual, without interruption; i.e., there is no "dead time" when light is not being detected. Assuming that light impinges on adjacent pixels in at least two different columns, the position and time of incoming light is reconstructed from the readouts of adjacent columns. The position of the impinging light is determined as the midpoint of readouts from adjacent columns; and the time of light arrival is proportional to the difference in readout from the adjacent columns. Unlike a conventional CCD, in a fast-timing, bi-directional CCD the clock time equals the time resolution of the overall image. Thus a relatively slow clock time of 10 .mu.sec provides a very fast image time resolution of 10 .mu.sec. In comparison to the 30 msec time resolution that is characteristic of conventional CCD's, the fast-timing bi-directional CCD can have a time resolution at least three orders of magnitude faster. The need for fast horizontal clocking is eliminated, as is the need for cooling. The fastest existing conventional CCD's can have a readout rate of about 10.sup.6 pixels per second. The novel fast-timing CCD's can have a readout rate of 10.sup.7 pixels per second, or even higher. Although the readout architecture of the novel fast-timing bi-directional CCD's is new, no new fabrication technologies are needed to construct the novel CCD's.

REFERENCES:
patent: 4165539 (1979-08-01), Aichelmann, Jr.
patent: 4744057 (1988-05-01), Descure
patent: 5340977 (1994-08-01), Kojima et al.
J. Janesick et al., "History and Advancements of Large Area Array Scientific CCD Imagers," pp. 1-67 in S. Howell (ed.), Astronomical CCD Observing and Reduction Techniques, ASP Conf. Series, vol. 23 (1992).
M. Cherry et al., "Charge Coupled Devices with Fast Timing for Space Physics," pp.261-274 in MASS/AIRWATCH, Huntsville Workshop Report(Huntsville, Alabama Aug. 7-8, 1995).
P.Suni, "Custom Photodetector Arrays Meet Design Challenges," Laser Focus World(Apr. 1994).
Loral CCD442A Specification Sheet (1993).

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