Active pixel sensor with current mode readout

Details Active pixel sensor with current mode readout Active pixel sensor with current mode readout

1999-03-10

2001-02-27

Mack, Ricky (Department: 2873)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C348S294000, C348S300000, C348S308000, C348S309000

Reexamination Certificate

active

06194696

ABSTRACT:

BACKGROUND
Active pixel sensors often are arranged in arrays of pixels. Each pixel represents one part of the image. The pixels are read out in groups, e.g., one column at a time. It is desirable that these columns be read out at high speed. It is also desirable that the active pixel sensors have as much resolution as possible. This requires a larger array—that means a larger number of columns and a larger number of elements in the columns. Each device in each column is in parallel with a switch controlling when the device is turned on. Therefore, adding more devices puts more devices in parallel.
An exemplary device is shown in FIG.
1
. Each column
100
may have a large number of devices in the column. The source follower
102
drives the entire column, and hence drives the entire analog bus capacitance of the column. A column select switch
104
selects the column. A larger column requires a more powerful column select switch and a more powerful column source follower in order to drive the entire analog bus capacitance. The more powerful switch typically requires a larger transistor, with a longer channel. This itself makes a higher total bus capacitance, and makes it even harder to drive the bus. The stray capacitance
112
of the bus therefore increases. Therefore, the transistor size increases, causes the capacitance to increase, and therefore to require an even larger transistor to drive the capacitance. Eventually the system reaches a point of diminishing returns.
SUMMARY OF THE INVENTION
The present system describes an alternative technique which allows certain of these issues to be obviated.
A first technique operates the system in a current mode.
According to a preferred mode, the current mode readout allows the entire sensor output to keep different parts of the readout bus at virtual zero potential, or at constant potential, so that the stray capacitance does not require a charge.
Accordingly, the system of the present disclosure produces a number of advantages which are described in the following


REFERENCES:
patent: 5097305 (1992-03-01), Mead et al.
patent: 5324958 (1994-06-01), Mead et al.
patent: 5410348 (1995-04-01), Hamasaki
patent: 5436442 (1995-07-01), Michon et al.
patent: 5512750 (1996-04-01), Yanka et al.
patent: 5793322 (1998-08-01), Fossum et al.
patent: 5841126 (1998-11-01), Fossum et al.
Krymski, Charge-Domain Analog Readout for and Image Sensor, Sep. 16, 1999, PCT WO 99/46929.

Affiliated with

Also associated with

Rating

Active pixel sensor with current mode readout does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Active pixel sensor with current mode readout, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active pixel sensor with current mode readout will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2608108