An optical device is provided. The optical device includes an excitation light source that emits excitation light. A first optical fiber guides the excitation light emitted from the excitation light source. A fluorescent plate includes a fluorescent light emitter that receives the excitation light guided by the first optical fiber and emits fluorescent light. The fluorescent plate further includes a dichroic mirror on a side of the fluorescent light emitter that receives the excitation light. The dichroic mirror transmits the excitation light and reflects the fluorescent light.
