Light source unit utilizing laser for light source and projector

A light source unit comprising:

• a fluorescent plate on which a fluorescent material layer for emitting light in a predetermined wavelength range when light is shone thereonto is disposed;
• a diffusion plate on which a diffusion layer for emitting light in a diffusing fashion is disposed so as to lie adjacent to the fluorescent material layer;
• a light source for shining the light on to the fluorescent material layer and the diffusion layer;
• a driving device for rotating the fluorescent plate and the diffusion plate together;
• and
• a light cut-off plate which is formed into a size which covers an area on the diffusion plate where the light is to be shone, wherein
• the light cut-off plate is rotatable together with the fluorescent plate and the diffusion plate by being locked by the diffusion plate, and wherein
• when the diffusion plate comes off, the locked state is released, and the light cut-off plate moves to cover an area corresponding to the area on the diffusion plate where the light is shone from the light source before the diffusion plate comes off.