H ELECTRICITY
H04 ELECTRIC COMMUNICATION TECHNIQUE
H04N PICTORIAL COMMUNICATION, e.g. TELEVISION
9/00 Details of colour television systems
H04N9/12 Picture reproducers
H04N9/31 Projection devices for colour picture display; , e.g. using electronic spatial light modulators [ESLM]
H04N9/3179 Video signal processing therefor
H04N9/3185 Geometric adjustment, e.g. keystone or convergence