Dynamic thresholding module
First Claim
1. A dynamic thresholding module in combination with a contact image sensing module comprising:
- a comparator and a tracking low-pass filter comprising an analog circuit, said analog circuit processes an analog input video signal from said contact image sensing module and produces a two-level digital output, said dynamic thresholding module digitizes said input video signal by establishing a variable average background level for said input video signal, comparing said input video signal to said average background level in said comparator, and then generating an output signal that is of value one when said input video signal is from a light area of a scanned image, and said output signal is of value zero when said input video signal is from a dark area of a scanned image.
10 Assignments
0 Petitions
Accused Products
Abstract
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.
6 Citations
16 Claims
-
1. A dynamic thresholding module in combination with a contact image sensing module comprising:
-
a comparator and a tracking low-pass filter comprising an analog circuit, said analog circuit processes an analog input video signal from said contact image sensing module and produces a two-level digital output, said dynamic thresholding module digitizes said input video signal by establishing a variable average background level for said input video signal, comparing said input video signal to said average background level in said comparator, and then generating an output signal that is of value one when said input video signal is from a light area of a scanned image, and said output signal is of value zero when said input video signal is from a dark area of a scanned image. - View Dependent Claims (2, 3, 4, 5, 6)
said tracking low-pass filter comprises a buffer amplifier and an initial threshold bias circuit.
-
-
3. The dynamic thresholding module in combination with a contact image sensing module as defined in claim 2 wherein:
said tracking low-pass filter further comprises a resistor and a capacitor.
-
4. The dynamic thresholding module in combination with a contact image sensing module as defined in claim 2 wherein:
said initial threshold bias circuit comprises a first resistor, a second resistor, and a third resistor.
-
5. The dynamic thresholding module in combination with a contact image sensing module as defined in claim 1 wherein:
a discrimination level for said average background level is determined by a time constant of said low-pass filter portion and an initial threshold bias voltage setting.
-
6. The dynamic thresholding module in combination with a contact image sensing module as defined in claim 1 wherein:
-
said input video signal is averaged and summed with a voltage level of an initial threshold bias circuit to generate a reference background signal, said reference background signal is buffered by a buffer amplifier so that said reference background signal is isolated from said input video signal, said reference background signal is then applied to a first input pin of a comparator, and said input video signal is applied directly to a second input pin of said comparator, said comparator thereby generating said output signal.
-
-
7. A dynamic thresholding module in combination with a contact image sensing module comprising:
-
a tracking low-pass filter comprising a buffer amplifier and an initial threshold bias circuit and a comparator circuit, said comparator circuit and said tracking low-pass filter comprise an analog circuit;
whereinan input video signal from said contact image sensing module is averaged and summed in said tracking low-pass filter with a voltage level of an initial threshold bias circuit to generate a reference background signal, said reference background signal is buffered by a buffer amplifier so that said reference background signal is isolated from said input video signal, said reference background signal is then applied to a first input pin of said comparator, and said input video signal is applied directly to a second input pin of said comparator, said comparator thereby generating an output signal that is of value one when said input video signal is from a light area of a scanned image, and said output signal is of value zero when said input video signal is from a dark area of a scanned image. - View Dependent Claims (8)
a discrimination level for said average background level is determined by a time constant of said low-pass filter portion and an initial threshold bias voltage setting.
-
-
9. A dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array comprising:
-
a comparator and a tracking low-pass filter comprising an analog circuit, said analog circuit processes an analog input video signal from said image sensing module and produces a two-level digital output, said dynamic thresholding module digitizes said input video signal by establishing a variable average background level for said input video signal, comparing said input video signal to said average background level in said comparator, and then generating an output signal that is of value one when said input video signal is from a light area of a scanned image, and said output signal is of value zero when said input video signal is from a dark area of a scanned image. - View Dependent Claims (10, 11, 12, 13, 14)
said tracking low-pass filter comprises a buffer amplifier and an initial threshold bias circuit.
-
-
11. The dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array as defined in claim 10 wherein:
said tracking low-pass filter further comprises a resistor and a capacitor.
-
12. The dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array as defined in claim 10 wherein:
said initial threshold bias circuit comprises a first resistor, a second resistor, and a third resistor.
-
13. The dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array as defined in claim 9 wherein:
a discrimination level for said average background level is determined by a time constant of said low-pass filter portion and an initial threshold bias voltage setting.
-
14. The dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array as defined in claim 9 wherein:
-
said input video signal is averaged and summed with a voltage level of an initial threshold bias circuit to generate a reference background signal, said reference background signal is buffered by a buffer amplifier so that said reference background signal is isolated from said input video signal, said reference background signal is then applied to a first input pin of a comparator, and said input video signal is applied directly to a second input pin of said comparator, said comparator thereby generating said output signal.
-
-
15. A dynamic thresholding module in combination with an image sensing module using a CCD array, a photodiode array, or an active pixel array comprising:
-
a tracking low-pass filter comprising a buffer amplifier and an initial threshold bias circuit and a comparator circuit, said comparator circuit and said tracking low-pass filter comprise an analog circuit;
whereinan input video signal from said image sensing module is averaged and summed in said tracking low-pass filter with a voltage level of an initial threshold bias circuit to generate a reference background signal, said reference background signal is buffered by a buffer amplifier so that said reference background signal is isolated from said input video signal, said reference background signal is then applied to a first input pin of said comparator, and said input video signal is applied directly to a second input pin of said comparator, said comparator thereby generating an output signal that is of value one when said input video signal is from a light area of a scanned image, and said output signal is of value zero when said input video signal is from a dark area of a scanned image. - View Dependent Claims (16)
a discrimination level for said average background level is determined by a time constant of said low-pass filter portion and an initial threshold bias voltage setting.
-
Specification