Apparatus and method for testing an active matrix pixel display

A method of testing a condition of a plurality of active element pixels wherein each active element pixel has a column drive electrode, a row drive electrode, and a common electrode, and wherein the method of testing the condition of a plurality of active element pixels comprises the steps of:

• a. driving each column drive electrode in turn with a first periodic signal having a first frequency spectrum with first frequency components;
• b. driving each row drive electrode in turn with a second periodic signal having a second frequency with second frequency components wherein the combination of the first periodic signal and second periodic signal causes a third periodic signal in the common electrode wherein the third periodic signal has a modulated frequency spectrum with modulated frequency components and wherein the second frequency spectrum is selected to provide the modulated frequency spectrum with modulated frequency components positioned between the second frequency components;
• c. filtering in turn the first frequency spectrum from the modulated frequency spectrum to provide a filtered signal with a filtered signal magnitude;
• d. detecting in turn which of the plurality of active element pixels was tested;
• and
• e. relating in turn the filtered signal magnitude to the condition of the active element pixel detected.

An apparatus for testing a condition of an active element pixel wherein the active element pixel has a column drive electrode, a row drive electrode, and a common electrode, and wherein the apparatus for testing the condition of an active element pixel comprises:

• a. means for driving the column drive electrode with a first periodic signal having a first frequency spectrum with first frequency components;
• b. means for driving the row drive electrode with a second periodic signal having a second frequency with second frequency components wherein the combination of the first periodic signal and second periodic signal causes a third periodic signal in the common electrode wherein the third periodic signal has a modulated frequency spectrum with modulated frequency components and wherein the second frequency spectrum is selected to provide the modulated frequency spectrum with modulated frequency components positioned between the second frequency components;
• c. means for filtering the first frequency spectrum from the modulated frequency spectrum to provide a filtered signal with a filtered signal magnitude;
• and
• d. means for relating the filtered signal magnitude to the condition of the active element pixel.

An apparatus for testing a condition of a plurality of active element pixels wherein each active element pixel has a column drive electrode, a row drive electrode, and a common electrode, and wherein the apparatus for testing the condition of a plurality of active element pixels comprises:

• a. means for driving each column drive electrode in turn with a first periodic signal having a first frequency spectrum with first frequency components;
• b. means for driving each row drive electrode in turn with a second periodic signal having a second frequency with second frequency components wherein the combination of the first periodic signal and second periodic signal causes a third periodic signal in the common electrode wherein the third periodic signal has a modulated frequency spectrum with modulated frequency components and wherein the second frequency spectrum is selected to provide the modulated frequency spectrum with modulated frequency components positioned between the second frequency components;
• c. means for filtering in turn the first frequency spectrum from the modulated frequency spectrum to provide a filtered signal with a filtered signal magnitude;
• d. means for detecting which of the plurality of active element pixels was tested;
• and
• e. means for relating the filtered signal magnitude to the condition of the active element pixel detected.

An apparatus for testing a condition of a plurality of active element pixels arranged in rows and columns wherein each active element pixel has a column drive electrode, a row drive electrode, and a common electrode, wherein all column drive electrodes in any particular column are connected to a plurality of column buses, wherein all row drive electrodes in any particular row are connected to a plurality of row buses, wherein all common electrodes in any particular row are connected to a plurality of common buses, and wherein the apparatus for testing the condition of a plurality of active element pixels comprises:

• a. means for driving each column bus in turn with a first periodic signal having a first frequency spectrum with first frequency components;
• b. means for driving every other row bus with a second periodic signal having a second frequency with second frequency components wherein the combination of the first periodic signal and second periodic signal causes a third periodic signal in the common electrode wherein the third periodic signal has a modulated frequency spectrum with modulated frequency components and wherein the second frequency spectrum is selected to provide the modulated frequency spectrum with modulated frequency components positioned between the second frequency components;
• c. a plurality of means for switching between every other common bus in response to a switching signal coordinated with the means for driving every other row bus having a switched common bus output signal;
• d. a plurality of means for filtering the first frequency spectrum from the modulated frequency spectrum to provide a filtered signal with a filtered signal magnitude wherein each means for filtering is connected to the switched common bus output signal;
• e. a plurality of means for detecting which of the plurality of active element pixels was tested wherein each means for detecting is connected to the means for filtering;
• and
• f. means for relating the filtered signal magnitude to the condition of the active element pixel detected.