Projector and projection system

A projector comprising:

• a discharge lamp configured to emit light;
• a discharge-lamp driving unit configured to supply a driving current for driving the discharge lamp to the discharge lamp;
• a control unit configured to control the discharge-lamp driving unit;
• a light modulating element configured to modulate, according to a video signal, the light emitted from the discharge lamp;
• and
• a projection optical system configured to project the light modulated by the light modulating element on a projection surface, wherein
• the control unit is a control waveform unit configured to alternately repeat a high luminance period in which the driving current having a relatively large absolute value is supplied to the discharge lamp and a low luminance period in which the driving current having a relatively small absolute value is supplied to the discharge lamp, the control unit controlling the discharge-lamp driving unit according to a driving current waveform formed by the control waveform unit including a direct-current waveform pattern in which the driving current in a first high luminance period, the driving current in a first low luminance period immediately after the first high luminance period, and the driving current in a second high luminance period immediately after the first low luminance period have the same first polarity.