Laser Flare Measurements and Kinoform Applications

Doctoral thesis, 1997

This thesis has two main parts. The first part treats the construction and use of a laser flare meter (Papers A and B). The second part deals with applications of kinoforms and consists of the sections "Kinoforms in laser machining" (Papers C and D) and "Diffractive retroreflectors" (Paper E). Visible light scattering (flare) from a light beam passing through the anterior chamber of the eye has long been used as a sign - and sometimes the only sign - of an intraocular inflammation. The amount of light scattering is subjectively assessed through a slit-lamp microscope and used as a qualitative measure of the degree of inflammation. To achieve accurate quantitative in vivo measurements of the light scattering, a laser flare meter was constructed, the design, calibration and testing of which are described in the first part of this thesis. Measurements were performed in normal human eyes as well as in eyes with uveitis. Flare measurements and subjective assessments were compared. How different parameters affect the measurements were studied. In particular, we studied the flare in the eyes of patients suffering from Fuchs heterochromic uveitis. Experiments incorporating phase only diffractive optical elements (kinoforms) were carried out with the aim to make laser machining more efficien: in excimer laser machining by steering the laser power to the pattern of the mask and thus avoid to waste power on the blocking parts of the mask; in Nd:YAG laser machining by splitting up the laser beam into several equal beams that are used for simultaneous machining of patterns. Diffractive optical elements can be mass produced at a low cost by hot embossing replication. A suggested application for such elements is thin diffractive retroreflecting sheets for traffic signs. Computor simulations of the optical performance of diffractive retroreflector designs was carried out, with particular emphasis on dispersion and angular dependence. Some manufacturing considerations are also discussed. Both ray tracing and wave optics analysis were performed.