US 4,698,816 A · Optical transmission filter

Abstract

The present invention deals with an optical transmission filter for effecting differential phase delay upon light in a beam polarized in a P dimension, as a function of position within the filter aperture. The filter employs two lenses of birefringent material, the crystal optic axes of the respective lens materials being oriented in mutually orthogonal positions and at a 45.degree. angle to the P dimension. The lenses have their adjacent surfaces respectively concave and convex with the same radius of curvature and their non-adjacent surfaces flat. The phase response of the filter is a function of the radial distance of a beam element from the filter axis with spherical lenses and a function of a linear coordinate distance from the filter axis with cylindrical lenses. A two-part construction for one lens, which permits adjustment of the difference in center thicknesses between the two lenses, allows adjustment of the differential phase delay with respect to a spacial reference.

Claims13

Dependent claims

An optical transmission filter for effecting continuous phase compensation of a beam of light polarized in a P dimension, the elements of said beam having a phase which deviates from an ideal reference phase as a continuous function of element position, said filter having an optical axis which is concentric with the beam axis and comprising:

A. a first lens of birefringent material of a first center thickness having a first surface which is flat and a second surface which has a predetermined radius of curvature,
B. a second lens of birefringent material of a second center thickness having a first surface which is flat and a second surface which has a radius of curvature equal to the radius of curvature of said first lens but of opposite sign,
the surfaces said lenses being oriented orthogonal to and concentric with said optical axis, the crystal optical axes of the materials of said lenses being oriented in orthogonal positions along said optical axis and at angle of 45.degree. to said P dimension, with said second surfaces adjacent.

An adjustable optical transmission filter for effecting a differential phase delay upon light in a beam polarized in a P dimension as a continuous function of position, said filter having an optical axis which is concentric with the axis of said beam, and comprising:

A. a first lens of birefringent material of a first center thickness having a first surface which is flat and a second surface which has a predetermined radius of curvature, the surfaces of said lens being oriented orthogonal to and concentric with said optical axis;
B. a second, compound lens of birefringent material of an adjustable center thickness, having a first surface which is flat and a second surface which has a radius of curvature equal to the radius of curvature of said first lens but of opposite sign, said second lens consisting of,
a wedge shaped first lens element with flat surfaces, having a cross-section tapered at a first angle, and
a second lens element having a crosssection tapered at said first angle, assembled in sliding engagement with said wedge shaped lens element, the external surfaces of said compound lens being oriented orthogonal to and centered on said optical axis,
said angle of taper being small enough to permit adjustment of the differential delay accorded to transmitted light to a fraction of a wave length as said lens elements are mutually displaced,
the crystal optical axes of the materials of said lenses being oriented in mutually orthogonal positions along said optical axis and at an angle of 45.degree. to said P dimension with said second surfaces adjacent, the lenses providing compensatory phase shift over the cross-section of said beam.

3 more elements

Dependencies are inferred from the claim text.

Optical transmission filter

Life of this patent

Optical transmission filter

Life of this patent

Abstract

Claims13