| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffraction element which corrects light intensity distribution of light emitted from a semiconductor laser without disturbing wavefront while being one element, and can enhance a rim strength, and to provide an optical head device mounting the diffraction element.SOLUTION: A diffraction element is a diffraction element which corrects intensity distribution of semiconductor laser light. A phase type of a diffraction grating is formed on one surface of a transparent substrate. The diffraction grating includes at least one projecting portion with a height having a change of two stages. When a width in a portion having the highest surface in the projecting portion is represented by W, in the diffraction grating, a duty ratio which is a ratio of the width W in one cycle of the lattice continuously or intermittently changes in a predetermined region. |
