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Electromagnetic Waves and Lasers
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
Polarized light is also obtained by using polarizers, as the polarizers have the ability to block one of the components of the electric field more effectively and transmits the other components. Such type of ability is known as dichroism. Actually a dichroic polarizer selectively absorbs the electric field oscillations in a specific direction and transmits electric field oscillation in the perpendicular direction, i.e. along the transmission axis. The material of which such polarizers are made up of are known as dichroic materials. Such type of polarization is a result of chemical composition of the material, which consists of long chains of molecules aligned in one particular direction. While manufacturing, these long chains are stretched along the entire length of polarizer to give them a polarization axis. Then the oscillations parallel to this axis are transmitted and the other ones are blocked.
Optical System and Design
Published in Shen-En Qian, Hyperspectral Satellites and System Design, 2020
A beam splitter is an optical device for dividing a beam into two or more separate beams. A simple beam splitter may be a very thin sheet of glass inserted in the beam at an angle to divert a portion of the beam in a different direction. A more sophisticated type consists of two right-angled prisms cemented together at their hypotenuse faces. A dichroic mirror, also referred to as a dichroic filter, is the optical device commonly used as a beam splitter in imaging spectrometers to divert the beam to VNIR and SWIR spectrometers. It spectrally separates light by transmitting and reflecting light as a function of wavelength. A long-pass dichroic mirror is highly reflective below the cutoff wavelength and highly transmissive above it, while a short-pass dichroic mirror is highly transmissive below the cutoff wavelength and highly reflective above it.
Light
Published in J. R. Coaton, A. M. Marsden, Lamps and Lighting, 2012
Interference is exhibited when a screen is illuminated by two separate but mutually coherent sources of light. Mutual coherence means that both sources are radiating light of exactly the same wavelength, and have a constant phase relation (section 5.1.3). The result of combining the light from both sources is that at some places on the screen the light waves are in phase and add together; at other places the waves are out of phase and cancel each other. Interference between the two sets of waves is normally seen as a pattern of light and dark bands on the screen. In practice mutually coherent sources of light are produced by splitting a beam from a single source, and this is usually achieved by using partially reflecting films on glass. One application of interference in present-day lighting technology is in the dichroic filters which are used to reflect or transmit certain selected parts of the spectrum (section 6.9). These also make use of the fact that a beam of light, reflected at normal incidence from the surface of a medium of higher refractive index, suffers a phase change of 180° (Ditchburn 1976).
Seamless holographic image generation for a multi-vision system
Published in Journal of Information Display, 2022
Woonchan Moon, Hosung Jeon, Sungjae Park, Soobin Kim, Hwi Kim, Joonku Hahn
This system employs a 5-inch transmission-type commercial LCD with full color FHD resolution and opaque bezels including the gate driving circuit and metal electrodes (Figure 1[a]). These bezels create rectangular seam lines inside the multi-vision configuration (Figure 1[b]), thus leading to discontinuous images and lower image quality of the resulting multi-vision display. It is difficult to completely remove the seam in the display image of a multi-vision system. The experimental setup is presented in Figure 1(c). We use an RGB light-emitting diode (LED) system to illuminate the multi-vision system. The system parameters are shown in Table 1. The central wavelengths of the RGB LED system are 640, 525, and 450 nm, respectively. The multi-vision system consists of eight SLMs, has a diagonal size of 13.13 in., and has a total of approximately 16M pixels. The size of the viewing window generated by this system is 2828. Figures 1(d), (e), and (f) present the 42 LCD multi-vision section, the RGB LED light sources, and the optical components of the system (i.e. the parabolic mirror and beam splitter). The parabolic mirror used as a field lens has a focal length of 1.8 m, and the viewing distance in the multi-vision system is 3.6 m, which is twice the focal length [13]. A dichroic prism is used to combine the RGB beams.
Optical design of a simultaneous polarization and multispectral imaging system with a common aperture
Published in Journal of Modern Optics, 2020
Xin Liu, Jun Chang, Yue Zhong, Shuai Feng, Dalin Song, Yaoyao Hu
In our work, a simultaneous polarization and multispectral imaging system was proposed. Instead of employing three discrete systems, we utilized two dichroic mirrors to integrate the three systems performing at VIS, MWIR, and LWIR. The first dichroic mirror is used to split the incoming light into visible and infrared light. The reflected visible light is focused by an on-axis optical system onto the polarization detector. The second dichroic mirror is used to split the refracted light into MWIR and LWIR light. The reflected MWIR and refracted LWIR light are focused by two divided aperture systems equipped with a set of polarizers onto an uncooled and cooled detector, respectively. This system has the capability of operating at visible (400–750 nm), mid-wave infrared (3–5 µm), and long-wave infrared (8–12 µm), and it acquires polarization information on four polarization states of 0°, 45°, 90°, and 135°; thus, this system can acquire the spatial, spectral, and polarization information of an object simultaneously. Based on this ability, the system shows outstanding potential for use in the detection and identification of low-contrast targets.
Minreview: Recent advances in the development of gaseous and dissolved oxygen sensors
Published in Instrumentation Science & Technology, 2019
Q. Wang, Jia-Ming Zhang, Shuai Li
In 2015, a luminescence ratiometric oxygen sensor based on gadolinium labeled hematoporphyrin monomethyl ether (Gd-HMME) and filter paper was proposed by Zhao et al.[35] The experimental setup of the sensing system is shown in Figure 5. The light source was reflected by a dichroic mirror and collected by a quartz lens. The light was coupled into an optical fiber and guided into a gas chamber equipped with a quartz window. The luminescence-based oxygen sensor was in the center of the gas chamber. The luminescence of oxygen sensor was coupled into the optical fiber and collected by the quartz lens. The optical parameter (OP) was defined as the ratio of filter paper background fluorescence to oxygen sensitive gadolinium labeled hematoporphyrin monomethyl ether Gd-HMME phosphorescence, as shown in Figure 6. This ratiometric method demonstrated that the OP was independent of the excitation intensity. The results showed that the detection limit of this sensor system was 0.01%, so it could be applied for very low-oxygen concentrations.