Contrast properties of reflective liquid crystal light valves in projection displays

Rosenbluth, Alan E.; Dove, D. B.; Doany, F. E.; Singh, Rama N.; Yang, K. H.; Lu, Minhua

doi:10.1147/rd.423.0359

Cited by 24 publications

(24 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If the necessary price points can be achieved and reliability sufficiently demonstrated, laser projectors may in fact prove to be the preferred technology path for electronic cinema. 6. ACKNOWLEDGMENTS…”

Section: Resultsmentioning

confidence: 99%

<title>Laser-based SXGA reflective light valve projector with E-cinema quality contrast and color space</title>

et al. 2000

View full text Add to dashboard Cite

Laser light sources present many advantages for projection displays over the currently employed incoherent light sources. Perhaps the most significant attribute is the laser's high degree of polarization, which greatly improves the efficiency of liquid crystal light valve (LCLV) projectors. The maximum achievable efficiency of an LCLV projector is severely limited with the use of an unpolarized light source such as an arc lamp. The polarized emission from a laser can be coupled to the screen much more efficiently, offering the possibility of smaller projectors with higher luminous efficacies. Additionally, the RGB primaries of laser light fall along the spectrum locus of the chromaticity diagram allowing for a much expanded color gamut over dichroically-separated lamp spectra. This provides the possibility of offering unprecedented color reproduction for the emerging digital cinema industry. The combined properties of polarization, monochromaticity, and low divergence result in a significant increase in image contrast when coupled to LCLV image engines. Substituting lasers for lamp light sources have shown to increase sequential contrast by as much as five-fold. This simple substitution has also resulted in broad improvements to the projector's entire MTF, thereby increasing the apparent resolution of the image. These are all striking arguments as to the potential of lasers in the emerging e-cinema market and the impetuous behind our current development effort presented here.

show abstract

Section: Resultsmentioning

confidence: 99%

<title>Laser-based SXGA reflective light valve projector with E-cinema quality contrast and color space</title>

et al. 2000

View full text Add to dashboard Cite

show abstract

“…Skew-ray depolarization is due to the rotation of the s-and p-polarization axes in projection systems with a MacNeille PBS. This effect is described in detail in other publications [11]. Correction for skew-ray depolarization is crucial to obtain a sufficiently high contrast ratio.…”

Section: A Color Management System With Two Lcos Light Valvesmentioning

confidence: 93%

LED projector with two liquid crystal on silicon light valves and a fly’s eye integrator

et al. 2008

View full text Add to dashboard Cite

“…[2] for an alternate approach.) It is important that no mixing of bright and dark states take place in double-pass traversal of the beamsplitter, and this task becomes more difficult when NA is increased for better flux collection [7,8]. In multi-LV projectors the optics must also contain tilted dichroic coatings that divide the beam on the basis of color.…”

Section: Introductionmentioning

confidence: 99%

“…A portion of the light leakage that arises from thermally induced stress cannot be relieved even by free expansion; according to a simple model this leakage decreases at least quadratically as prism size is reduced, and decreases even faster as the time constant of thermal excursions approaches or exceeds the thermal equilibration time of the substrates ('C c width2) [4]. The general theory of compound angle depolarization has been published elsewhere [8]. If the beam that is input to the PBS and prisms is pre-polarized with a sheet polarizer, the electric field vectors along different rays will be parallel to each other to within terms of order NA2 (assuming that the vectors are viewed in projection onto a plane that is perpendicular to the central [principal] ray of the beam).…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we will show how the ref. [8] theory can be used to design coatings for the Figure 1 system that nearly eliminate compound angle depolarization. To our knowledge, the only previously published prism set designed with this intention is that of Baumeister[1 1], though the general issue of polarization control in multi-element systems has a long history, e.g.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

<title>Correction of contrast in projection systems by means of phase-controlled prism coatings and band-shifted twist compensators</title>

Rosenbluth

Yang

et al. 2000

SPIE Proceedings

View full text Add to dashboard Cite

Projectors that use LCOS lightvalves face special contrast requirements. Most configurations for reflective light valves employ tilted beam-dividing coatings that see both bright and dark polarization states. The optics must then be designed to eliminate polarization mixing at these coatings, which ordinarily arises when the S and P planes for different rays are non-parallel. We show how phase-controlled coatings can exploit the double-pass symmetry of the Plumbicon tn-prism geometry to correct this effect, reducing cross-polarized reflectivity to ---1E-3 when the light valve is mirror-like in black-state. Though contrast in different rays varies as a function of both ray skew component and coating angle of incidence, we show that for NA0.2 the computation involved in calculating beam contrast is essentially equivalent to tracing a single ray. Light valves that use a normally-black TN mode exhibit a non-mirror-like phase dispersion in their black-state, complicating contrast control in the optics. Scatter depolarization at the edges of pixel electrodes is enhanced in these light valves, because the inherent twist causes the backplane polarization to be rotated out of alignment with pixel edges. We show that all of these contrast degradation mechanisms can be addressed by incorporating into the light valve a compensating layer having opposite birefringence to the black-state TN active layer. Moreover, when the compensating layer and driven layer are blue-shifted to a shorter LC thickness than would ordinarily be appropriate for the wavelength band of interest, a highly achromatic response is obtained at all gray levels.

show abstract

Contrast properties of reflective liquid crystal light valves in projection displays

Cited by 24 publications

References 18 publications

<title>Laser-based SXGA reflective light valve projector with E-cinema quality contrast and color space</title>

<title>Laser-based SXGA reflective light valve projector with E-cinema quality contrast and color space</title>

LED projector with two liquid crystal on silicon light valves and a fly’s eye integrator

<title>Correction of contrast in projection systems by means of phase-controlled prism coatings and band-shifted twist compensators</title>

Contact Info

Product

Resources

About