# US 2009/0262103 A1 · Method for adjusting common voltage of liquid crystal display device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0262103 A1 - Document ID: US20090262103A1 - Status: Published application - Kind: A1 - Application number: 12/386,602 - Filed: 2009-04-20 - Published: 2009-10-22 - Earliest claimed: 2008-04-18 - Assignees: Innocom Technology (Shenzhen) Co., Ltd.; Innolux Display Corp. - Inventors: Shun-Ming Huang - Web page: https://patentgrep.com/patent/US20090262103A1 ## CPC - G09G 3/3611: {Control of matrices with row and column drivers} - G09G 3/3614: {Control of polarity reversal in general} - G09G 3/3655: {Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors} - G09G 2320/0247: Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes - G09G 2320/0693: Calibration of display systems - G09G 2360/145: the light originating from the display screen - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A method for adjusting a common voltage of an LCD device includes providing an LCD device and a photodetector, obtaining variable parameters Ya, Yb and Yc, the variable parameters Ya, Yb and Yc respectively denoting flicker intensity of the LCD device when the common voltages are parameters Va, Vb and Vc, Vb exceed Va, and is less than Vc, when Yb exceeds Yc and is less than Ya, increasing the parameters Va, Vb and Vc respectively and repeating the two steps, when Yb exceeds Ya and is less than Yc, decreasing the parameters Va, Vb and Vc respectively and repeating the two steps, and when Yb is less than or equals Ya and is less than or equals Yc, setting an arbitrary value between Va and Vc as an optimum common voltage of the LCD device. ## Claims ### Claim 1 A method for adjusting a common voltage of a liquid crystal display (LCD) device, the method comprising: providing an LCD device and a photodetector; obtaining variable parameters Ya, Yb and Yc, the variable parameters Ya, Yb and Yc respectively denoting flicker intensity of the LCD device when the common voltages are parameters Va, Vb and Vc, Vb exceeding Va, and less than Vc; and when Yb exceeds Yc and is less than Ya, increasing the parameters Va, Vb and Vc respectively and repeating the latter two steps, when Yb exceeds Ya and is less than Yc, decreasing the parameters Va, Vb and Vc respectively and repeating the latter two steps; and when Yb is less than or equals Ya and is less than or equals Yc, setting an arbitrary value between Va and Vc as an optimum common voltage of the LCD device. ### Claim 2 (depends on 1) The method of claim 1, wherein the parameter Va is a predetermined optimum common voltage. ### Claim 3 (depends on 1) The method of claim 1, wherein a difference value between Vb and Va equals that between Vc and Vb. ### Claim 4 (depends on 3) The method of claim 3, further comprising, when Yb exceeds Yc and is less than Ya, adding a parameter A to the parameters Va, Vb and Vc respectively and repeating the latter two steps, and when Yb exceeds Ya and is less than Yc, subtracting the parameter A from the parameters Va, Vb and Vc respectively and repeating the latter two steps. ### Claim 5 (depends on 3) The method of claim 3, wherein when Yb is less than or equals Ya and is less than or equals Yc, setting Vb as the optimum common voltage of the LCD device. ### Claim 6 (depends on 1) The method of claim 1, wherein when Yb is less than or equals Ya and is less than or equals Yc, setting Vb or (Va+Vc)/2 as the optimum common voltage of the LCD device. ### Claim 7 (depends on 1) The method of claim 1, further comprising: detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, an analog-digital converter converting the first electrical signal to a first digital electrical signal, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of a peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Ya denoting flicker intensity of the LCD device when the common voltage is Va. ### Claim 8 (depends on 7) The method of claim 7, further comprising, after conversion of the first electrical signal to the first digital electrical signal, filtering noise from the first digital electrical signal. ### Claim 9 (depends on 7) The method of claim 7, further comprising detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, converting the first electrical signal to a first digital electrical signal through an analog-digital converter, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of a peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Yb denoting flicker intensity of the LCD device when the common voltage is Vb. ### Claim 10 (depends on 9) The method of claim 9, further comprising, after converting the first electrical signal to the first digital electrical signal, filtering noise from the first digital electrical signal. ### Claim 11 (depends on 9) The method of claim 9, further comprising setting the common voltage of the LCD device as the parameter Vc, detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, converting the first electrical signal to a first digital electrical signal through an analog-digital converter, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of the peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Yc denoting flicker intensity of the LCD device when the common voltage is Vc. ### Claim 12 (depends on 11) The method of claim 11, further comprising after converting the first electrical signal to the first digital electrical signal, filtering noise from the first digital electrical signal. ### Claim 13 A method for adjusting a common voltage of a liquid crystal display (LCD) device, the method comprising: providing an LCD device and a photodetector; obtaining variable parameters Ya, Yb and Yc, the variable parameters Ya, Yb and Yc respectively denoting flicker intensity of the LCD device when the common voltages are parameters Va, Vb and Vc, Vb exceeding Va, and less than Vc; and when Yb exceeds Yc and is less than Ya, decreasing the parameters Va, Vb and Vc respectively and repeating the latter two steps, when Yb exceeds Ya and is less than Yc, increasing the parameters Va, Vb and Vc respectively and repeating the latter two steps, and when Yb exceeds or equals Ya and exceeds or equals Yc, setting an arbitrary value between Va and Vc as an optimum common voltage of the LCD device. ### Claim 14 (depends on 13) The method of claim 13, wherein the parameter Va is a predetermined optimum common voltage. ### Claim 15 (depends on 13) The method of claim 13, wherein a difference value between Vb and Va equals that between Vc and Vb. ### Claim 16 (depends on 15) The method of claim 15, wherein when Yb exceeds Yc and is less than Ya, adding a parameter A to the parameters Va, Vb and Vc respectively and repeating the latter two steps, and when Yb exceeds Ya and is less than Yc, subtracting the parameter A from the parameters Va, Vb and Vc respectively and repeating the latter two steps. ### Claim 17 (depends on 13) The method of claim 13, wherein when Yb is less than or equals Ya and is less than or equals Yc, setting Vb or (Va+Vc)/2 as the optimum common voltage of the LCD device. ### Claim 18 (depends on 13) The method of claim 13, further comprising setting the common voltage of the LCD device as the parameter Va, detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, converting the first electrical signal to a first digital electrical signal through an analog-digital converter, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of a peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Ya denoting flicker intensity of the LCD device when the common voltage is Va. ### Claim 19 (depends on 18) The method of claim 18, further comprising: setting the common voltage of the LCD device as the parameter Vb, detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, converting the first electrical signal to a first digital electrical signal through an analog-digital converter, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of a peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Yb denoting flicker intensity of the LCD device when the common voltage is Vb. ### Claim 20 (depends on 19) The method of claim 19, further comprising setting the common voltage of the LCD device as the parameter Vc, detecting an optical signal of the LCD device along with time variation and outputting a corresponding first electrical signal using the photodetector, converting the first electrical signal to a first digital electrical signal through an analog-digital converter, isolating a second electrical signal from the first digital electrical signal, wherein the frequency of the second electrical signal is half of a refresh rate of the LCD device, and calculating an average of an absolute value of a peak-to-peak value of the second electrical signal, wherein the average value is regarded as the variable parameter Yc denoting flicker intensity of the LCD device when the common voltage is Vc.