High-order achromatic quarterwave combination plates and tuners.
Achromatic quarterwave combination plates are formed from two high-order birefringent plates having even and odd multiples of quarterwave retardation at some nominal wavelength. Eleventh- and twelfth-order plates at 1315 nm combined with their axes 77 degrees apart are shown to have 90 +/- 0.25 degrees of retardation between 1275 and 1355 nm. They can be used to construct two- and four-waveplate tuners for birefringent filters.
Improvement of birefringent filters. 3: effect of errors on wide field elements.
The properties of nontunable and tunable Lyot wide field elements are examined when the components of the elements deviate from their proper values. Special emphasis is put on determining what variations cause light to be transmitted at the transmission minima. The analysis shows that the nine- and ten-element plastic waveplates described in Paper 2 of this series can be used to make a Lyot filter that is tunable from 3500 A to 10,000 A.
Optical rotatory dispersion and absolute configuration—III
Abstract Optical rotatory dispersion measurements on pyrrolidine, piperidine, and tetrahydro-isoquinoline alkaloids indicate that the absolute configuration of the α-asymmetric center may be assigned directly from the dispersion curve, provided either that the nitrogen atom is not protonated, or that the compound contains a chromophore absorbing above 200 mμ.