Light source device and projection display device

A projection display device comprising:

• a light source device;
• a light modulating section forming an optical image by modulating luminous flux emitted from the light source device according to input image information;
• and
• a projecting section projecting the optical image formed by the light modulating section,
• the light source device including:
• a microwave generating section generating microwaves;
• a central conductor connected to the microwave generating section and emitting the microwaves;
• a discharge lamp connected to the central conductor and emitting light by the microwaves;
• and
• a reflector surrounding the discharge lamp, the reflector which has an opening at one end thereof and is formed of conductor material,
• the light source device in which the relationship between a wavelength λ of the microwaves, an inside surface length D which is an inside diameter of the opening of the reflector or a maximum length of a cross-sectional shape of the opening of the reflector, and a length L from a first end of the discharge lamp opposite to a second end connected to the central conductor to the opening of the reflector is D≦λ/2 and L/D≧0.8.