Peripheral Imaging Corporation

Pheng Tan

Satoru C Tanaka

Hsin-Fu Tseng

Hsin Fu Tseng

A dynamic threshold two-level A/D converter, also termed a tracking digitizer circuit. The module circuitry includes a comparator circuit and a tracking low-pass filter circuit. The dynamic thresholding module takes the output signals from a CIS module and develops a tracking (variable) background signal. The tracking background signal is then compared to the output signals from the CIS in a comparator. The comparator outputs a two-level (binary) output digital signal. The circuit is designed to be used in conjunction with a scanning device, particularly a CIS system. The circuit can be used in a wide variety of applications that require pre-processed digitized video signals. The dynamic thresholding module's circuitry can be implemented quite simply. Moreover, the circuit provides a very low cost and a low parts density module that can easily be incorporated with existing CIS modules without substantially increasing the size of the CIS module or the cost to manufacture the unit. The circuit requires roughly half the space required by existing digital circuits that accomplish similar ends. An IR LED is used in the CIS module to increase the discrimination ability of the device when scanning material with a colored background.

Dynamic thresholding module with IR LED light source for a contact image sensor

A dynamic threshold two-level A/D converter, also termed a tracking digitizer circuit. The module circuitry includes a comparator circuit and a tracking low-pass filter circuit. The dynamic thresholding module takes the output signals from a CIS module and develops a tracking (variable) background signal. The tracking background signal is then compared to the output signals from the CIS in a comparator. The comparator outputs a two-level (binary) output digital signal. The circuit is designed to be used in conjunction with a scanning device, particularly a CIS system. The circuit can be used in a wide variety of applications that require pre-processed digitized video signals. The dynamic thresholding module's circuitry can be implemented quite simply. Moreover, the circuit provides a very low cost and a low parts density module that can easily be incorporated with existing CIS modules without substantially increasing the size of the CIS module or the cost to manufacture the unit. The circuit requires roughly half the space required by existing digital circuits that accomplish similar ends.

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Pheng Tan