An energy accumulating capacitor such as an excimer laser is prevented from being overcharged by stored energy in a resonance inductance device. The light source is constituted by a line segment light source extended in a vehicle width direction. In other cases, other optical measurement techniques, such as FTIR and the like, may be applied. The method comprises regenerating a 4:2:0 chroma from a received 4:2:2 chroma using an algorithm.