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36-2: Invited Paper : Lasers, Lamps, or Phosphors - Choices for the Future of Digital Cinema
Abstract
The first generation of digital-cinema projectors has now been deployed into the majority of movie theaters around the world. The illumination technology used for that first generation was xenon lamps. When that choice was made xenon was the only viable technology that could achieve digital cinema’s goals. Today, cinema has a new set of challenges and a new set of technologies to choose from. Now that laser and laser-phosphor are mainstream illumination technologies cinema-projection engineers have an entirely new set of design decisions to make.
... Notably, the advent of the pico-projector has brought display technology into the mobile space with great potential to revolutionize heads-up display (HUD) systems [3]. Large number of projection systems is still relying on lamps [4] and light-emitting diodes (LEDs) [5] as light sources launched into the light engines. The problems that plague these display technologies can be effectively overcome with the use of laser sources, which have increased brightness, wider color gamut, longer lifetime, and increased optical efficiency [6]. ...
A method of speckle reduction suitable for use in a laser projector was proposed in the paper. Speckle contrast ratio (SCR) reduction was achieved by combining wavelength diversity and angular diversity methods. First, wavelength diversity was demonstrated by the use of two green laser sources (a 520 nm laser diode (LD) and a 532 nm diode-pumped solid-state (DPSS) laser) at a power ratio of 4:1. Second, angular diversity was achieved via the vibration of two lenses in two orthogonal directions placed directly after the laser source. The vibrating lenses are small and do not require changes to the beam path of the laser source, allowing for more compact projector designs. The frequency of vibration of these lenses was optimized to minimize the SCR in the output image. A SCR of less than 4% was achieved without the use of optical diffusers, which significantly reduces optical losses. Optical transmission could be further increased with the optimization of optical coatings on the lenses. This result shows great promise for applications such as laser pico-projectors within the realm of heads-up displays (HUDs) and mobile devices.
Laser-driven projection technology urgently requires green emitters with a narrow bandwidth, high quantum efficiency, and long-term stability to compensate for the “green gap”. Herein, a highly stable CsPbBr3–SiO2 glass ceramic film was synthesized by co-sintering high-photostability CsPbBr3–SiO2 powder and low-melting glass frit on sapphire, where the high thermal conductivity of sapphire and the SiO2 barriers could help maintain the stability of CsPbBr3 nanocrystals (NCs), endowing the well-known CsPbBr3 material with the possibility of application in the field of laser-driven projection displays. Furthermore, a “fluorescence wheel” was fabricated by pasting the CsPbBr3–SiO2 glass ceramic film on a micro motor, which could effectively alleviate the thermal quenching and increase the laser saturation threshold. Benefiting from its elaborate design, the operating temperature of the glass ceramic film was reduced from 351 °C to 75 °C and its luminescence intensity was maintained at 86% of its initial brightness at the laser power density of 4.5 W mm−2 for 60 min. As a proof-of-concept experiment, an all-inorganic multi-color fluorescent plate with red and green light emissions was obtained by combining the K2SiF6:Mn4+ phosphor and CsPbBr3–SiO2 powder in a patterned manner on sapphire, which provides an idea for the application of CsPbBr3 NCs and K2SiF6:Mn4+ phosphor in laser projection systems.
In recent years, the laser phosphor technology is becoming a mainstream one in the industry of projection display. In this paper, we first review the development of different light source technologies used in projectors. Thereafter, we review the evolution of our laser phosphor technology and then present its latest progress ‐ RGB laser phosphor.
High dynamic range for digital cinema projectors demands both increased brightness and darker black levels. Projector contrast is commonly described as the ratio of peak white luminance to black state luminance, where these extremes are measured sequentially. However, in a typical movie, bright highlights and deep blacks coexist in the same frame, introducing a number of other factors greatly affecting perceived dynamic range. This paper reports on the relative impact of such factors, including lens veiling glare, port glass, room reflectivity, audience reflectivity, and room ambient lighting. We will report on recent studies that have measured typical auditorium and lens parameters, as well as a representative luminance of recent movies, which greatly impacts the degree to which stray light is reflected back onto the screen. Based on these factors, the resulting “system contrast ratio” of typical cinema screenings is calculated.
This paper analyzes and explains the technical parameters of digital cinema stereoscopic projection (luminance, sequential contrast, intraframe contrast, crosstalk, light efficiency, etc.) based on the newly released GD/J 047-2013, “Technical Requirements and Methods of Measurement for Digital Cinema Stereoscopic Projection.” Methods of inspection and evaluation for stereoscopic projection are discussed, and guidelines for improving stereoscopic projection quality are suggested.
We have developed technologies for a high-output light source consisting of blue laser diodes and a reflective phosphor wheel for next generation 4K Ultra-Short-Throw Projector, and have achieved a fluorescence output of 87 W. As far as we know, it is the highest fluorescence output for projectors. We adopted a newly developed phosphor cooling mechanism and an inorganic binder for high reliability of the phosphor wheel. Therefore, no deterioration in the phosphor wheel could be observed over a time period of 7,500 hours. In this paper, we report on these lightsource technologies for achieving high output and high reliability.
Achieving low cross‐talk in polarization‐based 3D cinema is challenging. Factors include screen characteristics, quality of encoding/decoding hardware (and their relationship), geometry, and the associated angle dependence of all elements of the system. We describe technologies and system level considerations that are essential to achieving high Stereo Contrast Ratio (SCR).
SMPTE Motion Imaging Journal
- B. Gong
SMPTE Motion Imaging Journal
- M. Schuck
- P. Ludé