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Other Techniques
Published in C. R. Kitchin, Astrophysical Techniques, 2020
The Herschel wedge or solar diagonal (Figure 5.20) was, in the past, a common telescope accessory, but its use is now strongly to be discouraged. When the typically available commercial telescopes had apertures of only 25–50 mm, then the Herschel wedge did reduce the solar brightness to not-very-dangerous levels provided that high (> × 300 or so) magnifications were also used. But with many amateur astronomers now using 200- to 300-mm aperture telescopes, the Herschel wedge’s effective optical density of about 1.3 (transmission ~5%) is quite inadequate and observers still using them are at serious risk of incurring significant eye damage. The device is a thin prism with unsilvered faces. The first face is inclined at 45° to the optical axis and, thus, reflects about 5% of the solar radiation into an eyepiece in the normal star diagonal position. The second face also reflects about 5% of the radiation, but its inclination to the optical axis is not 45° and so it is easy to arrange for this radiation to be intercepted by a baffle before it reaches the eyepiece. The remaining radiation passes through the prism and can be absorbed in a heat trap, or more commonly (and dangerously) just allowed to emerge as an intense beam of radiation at the rear end of the telescope. The device should also incorporate a separate infrared filter (but often does not).
Use of a Robotized Laser Powder-Feed Metal Additive Manufacturing System for Fabricating Metallic Metamaterials
Published in T. S. Srivatsan, T. S. Sudarshan, K. Manigandan, Manufacturing Techniques for Materials, 2018
Yaoyu Ding, Meysam Akbari, Xin-Lin Gao, Li Ai, Radovan Kovacevic
The schematic and photo of the robotized laser powder-feed metal additive manufacturing system are shown in Figure 3.1. It mainly includes (a) a 4-kW fiber laser with a wavelength of 1070 nm, (b) a six-axis robot arm coupled with an additional two-axis tilt and rotatory positioning system, (c) a powder delivery module, and (d) a laser head equipped to the end of the robot arm. During the addition process, two powder feeders developed by RCAM [61,62] feed two different powders independently, as needed. The opto-electronic sensor monitors the powder flow rate at the outlet of the powder feeder. The design of the powder feeder and the opto-electronic sensor are detailed in Section 3.2.3.1. The carrier gas (argon) feeds the powder particles into an annular cone nozzle and injects them into the molten pool formed by the laser beam. The shielding gas (argon) is directed through the nozzle toward the molten pool in order to protect the molten material from contact with the atmosphere. A charge-coupled camera equipped with an infrared filter is installed on the laser head to monitor the molten pool. A firewire 1394 adapter is used to capture the infrared images. The National Instruments (PCI-6221) data control board was used to control the laser powder and powder flow rate by sending analog signals to the laser control box and servomotor of the powder feeder. LabVIEW was used to implement image processing [63,64], control tasks, and end user interface design.
Thermal Issues
Published in Mark Steven Csele, Laser Modeling, 2017
A laser of this type is pictured in Figure 5.22, which shows the components of such a laser in the foreground and a complete system in the background in which all components are mounted in a brass tube. The components, from left to right, are the pump laser diode, a lens to focus the pump radiation mounted inside a metal disc, hybrid vanadate/harmonic generator crystal complete with integral cavity mirrors (of the same type as employed in the previous laser), infrared filter on the same mount as the hybrid crystal (the square glass affixed to the front of that element), and focusing lens for the 532nm output beam. While a lens is included in this design to focus pump radiation from the laser diode onto the crystal, some very compact and inexpensive designs (e.g. green laser pointers) omit even this element, in which case the amplifier is situated extremely close to the pump diode since the beam emerging from the diode is highly divergent. Another feature of this design is the IR filter, which removes both residual 808nm pump radiation and residual 1064nm vanadate radiation from the output since some IR will often pass through the OC. It has been found that many inexpensive green laser pointers omit this infrared filter, resulting in a safety hazard. While the green output may be well under 5mW (and hence the laser pointer falls into a class-IIIa laser product category), the residual infrared output can exceed 30mW on such a laser, which represents a significant danger!
Effects of Illumination on Paper and Silk Substrates of Traditional Chinese Painting and Calligraphy Measured with Raman Spectroscopy
Published in LEUKOS, 2020
Rui Dang, Huijiao Tan, Gang Liu, Nan Wang
The four narrow-emitting light sources with different peak wavelengths in the red (650 nm), amber (583 nm), green (510 nm), and blue (450 nm) regions of the visible spectrum were prepared using a museum-specific tungsten halogen lamp (PHILIPS 6423FO) combined with an infrared filter and a 20-nm-wide narrowband filter, which was custom-made by the Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences. The SPDs of the four light sources were tested (Fig. 2) using a spectrophotometer (Photo Research PR 670). Due to the long duration of the illumination experiment, in order to avoid effects of light source decay on the experiment results, we periodically tested the illuminance on the surface of the specimens, as well as the SPDs of the four light sources. When we detected attenuation of an existing light source or a change in SPD, the aging light source was replaced by a new one.
A new approach to controlling metal transfer by dynamic modification in gas composition of arc atmosphere: studies on pulsed gas MAG welding*
Published in Welding International, 2020
Masahiro Ohara, Takashi Mizuguchi, Kanto Miyata, Tadahisa Tsuyama, Kohei Fujiwara
The welding current and voltage were recorded at 0.1 ms intervals using a data logger. A high-speed video was also taken from the side of the welding direction at 2500 frame/s or 2000 frame/s of the arc generation site. An infrared filter with a transmitting area of 950 nm or more was used to reduce the arc light and photograph the metal transfer in greater detail.
Exploring Intuitive Visuo-Tactile Interaction Design for Culture Education: A Chinese-Chess-Based Case Study
Published in International Journal of Human–Computer Interaction, 2023
Qingshu Yuan, Keming Chen, Qihao Yang, Zhigeng Pan, Jin Xu, Zhengwei Yao
SARChess’s hardware consists of a projector, a camera with an infrared filter, a computer, an infrared lamp, and a projection tabletop. Figure 2 describes the schematic diagram of the hardware setup and the physical setup.