All lights dim as turn signal is engage

Has anyone encounter the problem that all the interior lights and head lights blink when you use the turn signal, brake or power in the car? When I use the turn signal, my headlights and speedometer lights also dim as the signal blinking. They also go dim as I apply the break pedal or use the power window. I took my SC 300 to local repair shop and they don't know what the problem is. Does anyone knows what the problem is? It is very annoying when I drive at night. Please advice if anyone encounter this problem.

Bad alternator and possibly a bad battery. Have both checked at a respectable dealer or repair shop.