The wide acceptance of digital cinema depends on the ability of the projector to at the very least match film in color gamut, contrast, brightness, and resolution consistently. In most cases, digital projection is expected to even outperform film as a requirement for switching from film to digital because of digital projection cost. This paper examines DLP based digital projection and the optics required to produce an acceptable digital image that exceeds theatrical release film. Optical path efficiencies, tolerances, coating properties and the DMD are important parameters for color, brightness, contrast, and uniformity of the image. The efficiency and tolerancing of the optical system are key drivers for obtaining consistent high brightness and uniformity, while coatings and the DMD mainly affect consistency in color and contrast. DLP Cinema projection, based on the optics discussed, is shown to deliver a stable color gamut slightly smaller than film having consistent uniformity <300 K across a native white image with consistent brightness of 12 ft-L on screens up to 15 m. The contrast and resolution are native to the DMD but contrast can be influenced using apertures in the lenses and illumination system. Contrasts up to 3000:1 on/off are possible by the use of asymmetric apertures. These results are compared to the color gamut, contrast, brightness, and resolution of typical theatrical release film.
We outline results obtained from Schlieren and dye laser resonance absorption imaging of the plume ejected from an aluminum target in a nitrogen atmosphere of 1 bar and 100 mbar by a KrF excimer laser (lambda equals 248 nm, FWHM equals 30 ns). The results show that for relatively low and high laser fluences (14 J/cm2 and 36 J/cm2), the plume closely follows the shock wave which is generated by the ablated material pushing against the surrounding gas. Calculations of the evolution of the ambient gas and ablated material show that the temperature and electron density vary greatly depending on the laser fluence and the external gas pressure. We report maximum plasma temperatures of 39888 K and electron densities of 4.2 multiplied by 1026 m-3 for a laser fluence of 36 J/cm2. These results indicate that inverse bremsstrahlung may play a very significant role in how the laser pulse energy is distributed in the plume for high laser fluences.
In this contribution, the condensation theory of I. M. Lifshitz and V. V. Slyozov is used to calculate the formation of metal clusters in the plasma/vapor regime above an aluminum target in a nitrogen atmosphere of 1 bar irradiated with 248 nm, 30 ns FWHM pulses. This theory takes into account formation of clusters by fluctuations in the supersaturated medium (plasma/vapor). It also accounts for both cluster growth due to atom-cluster-collisions (nucleation) and collisions between clusters (coalescence state). This condensation model is integrated in a gasdynamic code which calculates the flow field and the thermodynamic properties of the plasma/vapor. In addition, the density of electrons, clusters, and neutral particles are determined and, finally, with the appropriate polarizability the refraction index can be calculated. The theoretical data are discussed together with the results of interferometric measurements.
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