Patent ID: 8246175

Claim:
A lighting device that lights a discharge lamp which contains a pair of electrodes and light emission substance including mercury, comprising: a first terminal connected with the electrode to which the mercury easily adheres as one of the pair of the electrodes; a second terminal connected with the electrode to which mercury is difficult to adhere as the other electrode; a setting unit which sets AC current supplied to the first and second terminals in a starting period from insulation break down of the discharge lamp until start of discharge between the tips of the pair of the electrodes; and a supplying unit which supplies AC current set by the setting unit to the first and second terminals, the setting unit setting AC current such that the half-cycle electric quantity supplied to the first terminal becomes larger than the half-cycle electric quantity supplied to the second terminal in the initial term of the starting period under the condition in which the first terminal initially operates as cathode, and that the half-cycle electricity quantities supplied to the first and second terminals become substantially equal in the final term of the starting period.