Light source unit including a laser as a light source and a light emitting wheel with a diffusion layer opposite to the laser

A light source unit comprising:

• a blue laser light source for emitting laser light in the wavelength band of blue;
• a circular-shaped substrate as a light emitting wheel which is configured so as to be rotatably driven, in which fluorescent material layers for emitting light by using the laser light emitted from the blue laser light source as excitation light are disposed in a circumferential direction of the circular-shaped substrate in an annular shining area so as to be positioned on an optical axis of the blue laser light source;
• wherein the circular-shaped substrate is formed by a material having heat conducting properties and has a reflecting layer as a diffusion layer which is formed all over a surface at a side of the circular-shaped substrate opposite the blue laser light source and which is made up of minute irregularities at intervals ranging from 10 μm to 100 μm;
• wherein the fluorescent material layers are disposed on the reflecting layer and are constituted by a red area and a green area each of which respectively emits light in the wavelength band of red and light in the wavelength band of green by using the laser light emitted from the blue laser light source as excitation light;
• wherein an opening is formed in a part of the circular-shaped substrate, a light transmissive plate having a function as a diffusion layer made up of minute irregularities on the light transmissive plate is disposed so as to seal the opening, and the opening diffuses and transmits the blue laser light emitted from the blue laser light source;
• wherein when the blue laser light emitted from the blue laser light source is incident on the fluorescent material layers as excitation light, the reflecting layer reflects toward the blue laser light source both the lights which are respectively emitted by the fluorescent material layers, and the laser light from the blue laser light source that is transmitted through the fluorescent material layers so that the laser light from the blue light source that is transmitted through the fluorescent material layers is reflected to be incident again on the fluorescent material layers as excitation light;
• and
• wherein a dichroic mirror is disposed between the blue laser light source and the circular-shaped substrate so as to transmit the laser light emitted from the blue laser light source and reflect the lights emitted from the fluorescent material layers.