| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problems: facilities and much time are required in a method for observing the light to be modulated by driving liquid crystals actually by a light receiver and setting amount of modulation to become the same amount when using positive voltage and negative voltage, thereby being disadvantageous to production; and a light receiving function is separately required to automate the adjustment in a completed projection system. SOLUTION: A voltage source 16 applies a sweep voltage increasing in the positive direction from a first negative value gradually and reducing its value in the negative direction gradually after reaching the maximum positive value to become a first negative value to a common electrode 12. A common current flowing in resistance R at this time is detected. Amount of common voltage is corrected based on a positive common voltage value and a negative common voltage value at the sweep voltage when a value of the detected common current indicates a fixed amount of increase to apply voltage to the liquid crystals 11 symmetrically when driving them actually. Consequently, the adjustment with higher precision becomes possible than the adjustment performed optically in principle by a light receiving device. COPYRIGHT: (C)2009,JPO&INPIT
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