Diffractive optical element and method for producing the same

A diffractive optical element comprising:

• a first optical member comprising:
• a first substrate;
• and
• a first resin layer formed on the first substrate, the first resin layer comprising a first blazed diffraction grating on its surface, the first blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence;
• and
• a second optical member comprising:
• a second substrate;
• and
• a second resin layer formed on the second substrate, the second resin layer comprising a second blazed diffraction grating on its surface, the second blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence,
• wherein the first and second optical members are bonded to each other so that the first and second resin layers face each other, and
• wherein only the vertical facets of the first and second blazed diffraction gratings are frosted by ashing.

A method for producing a diffractive optical element comprising the steps of:

• forming a resin layer on a substrate, the resin layer comprising a blazed diffraction grating on its surface, the blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence;
• forming an antireflection coating only on the inclined facets;
• and
• ashing the blazed diffraction grating to thereby frost only the vertical facets of the blazed diffraction grating.

A diffractive optical element comprising:

• a first optical member comprising:
• a first substrate;
• and
• a first resin layer formed on the first substrate, the first resin layer comprising a first blazed diffraction grating on its surface, the first blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence;
• and
• a second optical member comprising:
• a second substrate;
• and
• a second resin layer formed on the second substrate, the second resin layer comprising a second blazed diffraction grating on its surface, the second blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence,
• wherein the first and second optical members are bonded to each other so that the first and second resin layers face each other;
• and
• wherein only the vertical facets of the first and second blazed diffraction gratings have an opaque film formed thereon.

A method for producing a diffractive optical element, comprising the steps of:

• forming a resin layer on a substrate, the resin layer comprising a blazed diffraction grating on its surface, the blazed diffraction grating having inclined facets and vertical facets arrayed in an alternating sequence;
• applying an opaque film to the inclined facets and the vertical facets of the blazed diffraction grating by dipping;
• and
• removing only the opaque film on the inclined facets by anisotropic etching of the blazed diffraction grating.