Patent ID: 8857779

Claim:
An adjustable holder ( 1 ) for a concave holographic grating ( 2 ) providing the correct positioning of the grating vis-à-vis a light entrance port ( 15 ) and a light exit port ( 20 ), the holder comprising a grating hinge ( 10 ); and a holographic grating ( 2 ); the hinge being fixed to said grating ( 2 ), wherein said grating hinge ( 10 ) provides rotational adjustment of the grating position with respect to said holder ( 1 ) about a first adjustment axis and a second different adjustment axis, said rotational adjustment axes extending through the vertex (P) of said grating ( 2 ); wherein said grating hinge ( 10 ) has a spherical surface moveable in a hinge seat of said holder ( 1 ), the center point of the spherical surface being located at the vertex of said grating ( 2 ); and wherein the spherical surface is kept in contact with the hinge seat be means of a spring, which acts on a cylindrical surface having its center axis running through the vertex of the holographic grating.