Patent ID: 7315381
Filing Date: 2008-01-01
Classification: G01B

Abstract:
1. A monolithic quadrature detector for providing variable signals indicative of a variable phase difference between orthogonally polarized components of an input beam, comprising: a first non-polarizing beamsplitting element including a first pair of prisms that share a first beamsplitting interface that receives the input beam and divides the input beam into a first transmitted beam having orthogonally polarized components and a first reflected beam having orthogonally polarized components; a second non-polarizing beam splitting element that includes at least one beamsplitting interface, the at least one beamsplitting interface of the second non-polarizing beam splitting element receiving the first transmitted beam and the first reflected beam and dividing the first transmitted beam into a second transmitted beam and a second reflected beam that each have orthogonally polarized components and dividing the first reflected beam into a third transmitted beam and a third reflected beam that each have orthogonally polarized components; a first polarizer that receives the second transmitted beam and outputs interfering components to a first detector that outputs a first signal responsive to the variable phase difference; a second polarizer that receives the second reflected beam and outputs interfering components to a second detector that outputs a second signal responsive of the variable phase difference; a third polarizer that receives the third transmitted beam and outputs interfering components to a third detector that outputs a third signal responsive of the variable phase difference; a fourth polarizer that receives the third reflected beam and outputs interfering components to a fourth detector that outputs a fourth signal responsive of the variable phase difference, wherein the first, second, third and fourth signals can be analyzed to determine the variable phase difference between the orthogonally polarized components of the input beam, wherein the first transmitted beam and the first reflected beam each undergo reflection at respective surfaces of the first non-polarizing beamsplitting element that are symmetrically located relative to the first beam splitter interface, before entering the second non-polarizing beam splitting element; a first phase shifting coating is provided at the first beamsplitting interface, wherein the first phase shifting coating imparts a first relative phase shift (Δ a second phase shifting coating is provided at the at least one beamsplitting interface of the second non-polarizing beam splitting element, wherein the second phase shifting coating imparts a third relative phase shift (Δ