The typical behavior of brightness and contrast ratio as a function of the f-number for a lamp projector. By increasing the f-number of the projector, less of the the light of the lamp is used, but the contrast ratio increases.

The typical behavior of brightness and contrast ratio as a function of the f-number for a lamp projector. By increasing the f-number of the projector, less of the the light of the lamp is used, but the contrast ratio increases.

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During the last years, a trend to replace commonly used short arc lamps in projection systems with alternative light sources is seen. Next to LEDs for low light output products, lasers try to enter the projection area and have the ambition to infiltrate from low (picoprojection) towards high light output systems (digital cinema). One of the benefit...

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... a projector using a lamp one always has a trade-off between brightness versus contrast ratio, efficiency and depth of focus. Figure 3 shows the typical behavior of brightness and contrast as a function of the f-number for a projector with a lamp. There is not such a trade-off for projectors based on lasers, or it comes only into play for very high brightness levels. ...

Citations

... Diode lasers have obtained excellent reliability and power and cost efficiency. They are increasingly used in applications that require high-power laser light, such as solid-state laser pumping [15], industrial processing, and laser projection systems [16]. Often, it is desired to couple the laser light of all diodes into an optical fiber. ...
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We demonstrate a laser beam combiner based on four photo-patterned Pancharatnam–Berry (PB) phase gratings, which is compact and has high diffraction efficiency for incident circularly polarized light. The nematic liquid crystal mixture E7 is used as anisotropic material, and the thickness of the layer is controlled by spacers. The beam combiner can bring two parallel laser beams closer to each other while remaining parallel. This work shows the potential to realize components based on flat optical LC devices.
... So far, various speckle reduction methods have been investigated, such as wavelength diversity, angular diversity and polarization diversity [1,7,8]. Speckle reduction by wavelength diversity can be achieved by broadening spectral bandwidth of a light source [9,10] or using multiple wavelength lasers [11][12][13]. ...
... But this is not a simple replacement; the laser light is bringing here unbeatable colors and excellent energetic economy. However, as these video and movie projectors requires very high optical power, from 20 up to 200 W, the laser source of the light must meet strong requirements concerning the optical power, beam quality, light polarization and economy of production and use 1 . For optical projectors, which make use of Digital Light Processing (DLP) technology the ideal sources of light, characterized by a very high optical power, are laser diode arrays, which combine compact construction, strong, linearly polarized light, and economy. ...
Article
We demonstrated the fabrication of 10 emitters InGaN laser diode array of the maximum output power of 9 W at 420 nm. The device as a whole has the differential efficiency of above 1 W/A. The maximum output power is limited to 9 W (pulse operation) by catastrophic mirror damage or to around 5 W in CW operation by thermal roll-over. Larger arrays with stripes width of around 15 µm and numbers of emitters up to 20 should enable reaching 20 W, which is suitable for light engine of desktop projectors and a building block of cinema theater projectors.
... DCI X'Y'Z' color space (1.1) compared to DCI reference projector gamut "P3ref" (1.2) and the gamut of a prototype laser projector "P3laser" (1.3) from the OSIRIS project3 . The lower axes x and y are the CIE 1931 chromaticity diagram x-and y-axes, the vertical axis is the Y-component of the CIE 1931 2° standard observer. ...
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To ensure consistent presentation of wide gamut Digital Cinema Packages (DCPs) on standard gamut screens, a mandatory gamut mapping strategy has to be chosen. In this paper, current gamut mapping algorithms are evaluated with respect to their application in digital cinema. These algorithms include: "Simple Clip", "Cusp Clip", "Minimum delta E" (MindE), "Hue preserving MindE", "Weighted MindE" and the mapping strategy which is used in current projectors. The investigated gamut mapping algorithms will be provided as 3D lookup tables for comparison. These can also be used to retrofit a more advanced gamut mapping strategy to standard gamut projectors. Therefore, the paper closes with an analysis of the losses introduced by using 3D lookup tables for gamut mapping. The intent of this paper is to initiate a discussion about gamut mapping strategies for digital cinema, which may ultimately lead to an addendum to the SMPTE standards for digital cinema.
... Speckles occur in laser projection display systems and can be uncomfortable to the viewer's eye [5,7,8]. The speckles appearing in displayed images are the result of interference between random phases associated with distinct differences in the optical paths of coherent light rays through the projection system. ...
... Speckles always appear in images of laser imaging systems and degrade image quality [5,7,19]. This study avoided traditional approaches to the suppression of speckles by temporally integrating multiple speckled images, thereby taking advantage of the SLM for beam shaping [20]. ...
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This paper presents a full-frame laser projection display system in which a spatial light modulator (SLM) is used for beam shaping and speckle suppression. Phase-only computer-generated holograms (CGHs) are used to transform a cross section of the incident laser beam into a square nearly the same size as that of the display device. Under different initial conditions, the diffraction patterns generated by the CGHs possess identical intensity distributions but differ with regard to random phase distribution. Image speckles can be suppressed via the temporal addition of diffraction patterns from the CGHs when displayed by the SLM. The addition of 16 speckled images resulted in speckle suppression ratios of 0.290 in simulations and 0.345 under experimental conditions. Not only were the speckles suppressed, but the quality of the overall image was also improved considerably. The proposed approach presents a simple design with low power consumption and stable display architecture for application in pico-projectors.
... Secondly, combining a large number of LEDs can provide huge amounts of light at the light source level, however, the additional light does not lead to increased screen brightness in projection systems due to the increased etendue of the combined LEDs degrading the coupling efficiency at the system level [7,8]. On the other hand, high power red, green and blue (RGB) lasers that can generate enough light at suitable etendue for cinema applications are under development [7,[10][11][12][13]. However, they suffer from a relatively moderate efficacy and a serious high cost problem that has stifled their commercialization. ...
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We present experimental results on a low-cost light source that utilizes commercially available 405-nm/445-nm lasers to drive phosphor-based optical cavities generating speckle-free red, green, and blue (RGB) light at selected etendue and power values. By combining more 405/445-nm laser beams to drive the optical cavities, enough RGB light can be generated for the most demanding etendue-limited applications such as automotive headlights, biomedical devices and projection systems. We report efficacies of 17, 18, and 14 lm/W for the red (610 nm), green (530 nm), and white light, respectively, at an etendue of 27 mm $^{2}$ .sr.
... In other applications, statistical data of speckles within images can be analyzed to ascertain the tissue structure [6,7], surface roughness [8], and vibration of an object [9]. Optical imaging systems that employ a laser light source always produce speckles in the display images, which degrade image quality [10][11][12][13]. As a result, developing the means to reduce the appearance of speckles is a key issue in laser projection displays [14][15][16][17][18][19] and digital holography [20][21][22]. ...
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Evaluating the contrast in speckle patterns produced by laser projection displays can facilitate the development of methods to suppress such imperfection. Computer simulations were first conducted to characterize the contrast (Cgs) of fully developed speckle patterns with spatial factor k and power factor r. Results showed that 0.1≤r≤2.0 and k≥4.0 were required to obtain a Cgs with less than 5% error. Experimental results, however, revealed that a power factor within the range 0.5≤r≤2.0 was needed, meaning that the speckle dimension was at least four times the pixel pitch and the largest speckle intensity was of the order of magnitude of the saturation level of the camera. The method proposed here is that the spatial factor be determined by adjusting the distance between the object and the camera, and the power factor be determined by monitoring the real-time histogram representing the speckle pattern.
... One of the most effective methods of speckle suppression is the speckle averaging mechanism that is based on a vibrating random diffuser or a regular diffractive optical element (DOE) [9][10][11][12][13][14][15][16]. In our previous publication, we proposed a method of a speckle suppression based on Barker code and M-sequence DOEs and worked out its mathematical model [17][18][19][20]. ...
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This paper reports the findings from an experimental evaluation of speckle suppression efficiency using a method based on a moving 2D Barker code diffractive optical element (DOE). The optical setup and the optical scheme parameters of the method are presented. A speckle contrast of ∼4.4-5.3% and speckle suppression coefficient (coefficient of speckle contrast reduction) of k>8 was obtained in experiments. However, the experimentally obtained speckle suppression coefficient was approximately 1.5 times smaller than the theoretical prediction. It is speculated that the discrepancy between the theoretical and the experimental data is due to an inexact match between the optical setup and the optimal optical parameters of the method. Analysis of the experimental data revealed that once the optical scheme is optimized, it will be possible to obtain a speckle suppression that is closer to the theoretical prediction.
... The engineering advantages and peculiarities of laser projectors are summarized in [1]. However, speckle phenomena arising from the coherence of laser light [2,3] severely degrades the image quality and has inhibited the widespread application of lasers in image systems [1,4]. The subjective speckle (the speckle created in image systems) is granular light-intensity modulation in the image due to the interference effect when coherent light is used for illumination [2,3]. ...
Article
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The mathematical model of a speckle-suppression method based on two Barker code-type diffractive optical elements (DOEs) moving in orthogonal directions is developed. The analytic formulae for speckle suppression efficiency are obtained. The model indicates that the one pair of DOEs can be used for laser beams of different colors. The speckle contrast is not dependent on the distance from the viewer to the screen until the distance decreases below the distance where the spatial resolution of the eye on the screen is less than the length of the image of the DOE structure period on the screen. The analysis of the simulated results demonstrates that the method can decrease the speckle contrast to less than 5%, which is below human eye sensitivity, with an optical efficiency greater than 90%.
... Besides, owing to the fact that the LCOS's primary-driver and active-pixel matrix can be fabricated on silicon chip by using the complementary metal oxide 2 semiconductor craftworks, it is indicated that this progress actually serves as a substrate for the liquid-crystal-gap. As a consequence, the liquid-crystal gap occupies not only the small sizes in the spatial volume but also the high resolution which can be measured from received images[1,2]. The working principle of the LCOS panels can be decomposed into the following procedures: first, the LCOS panels provide a laser light (source beam). ...
... These applications often require band-stop filters with high in-band rejection and low out-of-band insertion loss. Conventional E-plane and H-plane waveguide filters involve physical alterations of the waveguide[1][2][3][4][5]and result in complex and costly structures that are several wavelengths long. It has recently been suggested that metamaterials with negative permeability could be used as an alternative means for creating compact waveguide filters[6]. ...
Article
Based on the theoretical analysis of the generation of laser speckles, a specific scheme is proposed to reduce composite speckles in the tricolor liquid‐crystal‐on‐silicon laser projector.The rotated diffuser is relatively simple in its optical structure which can be easily implemented. Furthermore, the experiment with regard to the detected images at the receiver is also performed to verify the feasibility of our method. It is shown by simulated results that the rotated diffuser plate can effectively suppress the contrast ratio of laser speckles. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:138–141, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27221