China
Africa
Explore chapters and articles related to this topic
Deposition Methods
Published in Andrew Sarangan, Optical Thin Film Design, 2020
Many variations of this concept are used in the field, and one such example is shown in Figure 14.12. This setup utilizes a fiber optic spectrometer and a broadband light source such as a tungsten–halogen lamp. The light is delivered to the sample through a fiber bundle. A collimator is useful for reducing the losses due to beam divergence. Light is incident on the backside of the substrate through a suitable view port, and the reflected signal is collected by the same collimator and sent through one of the fibers in the bundle to the spectrometer. With fast CCD-based spectrometers, it is possible to monitor the reflectivity in-situ without retrieving the sample from the vacuum chamber.
Evolution of Radiation Protection Guidance in the United States
Published in Shaheen A. Dewji, Nolan E. Hertel, Advanced Radiation Protection Dosimetry, 2019
Among his numerous contributions to radiation safety, the following items are particularly noteworthy. Concluding that scattered radiation was of no value for radiography and actually increased the dose to the patient without concomitant benefit, he proposed the use of collimation to restrict beam size and reduce scatter, which also had the benefit of improving radiographic quality (Rollins 1898,1899). He created the non-radiable tube housings and promoted their use in conjunction with beam collimation (Rollins 1900, 1902a,b).
Alignment and Angle Measurement Techniques
Published in Rajpal S. Sirohi, Mahendra P. Kothiyal, Optical Components, Systems, and Measurement Techniques, 2017
Rajpal S. Sirohi, Mahendra P. Kothiyal
A collimator is a device for projecting parallel rays. It consists of an objective lens, a cross-hair graticule placed at the focal plane, and a low-power light source that illuminates the cross-hair. The light rays from the cross-hair will be parallel as they leave the collimator, effectively projecting them at infinity.
A Comprehensive Survey on the Detection of Diabetic Retinopathy
Published in IETE Journal of Research, 2022
Spectral-domain OCT (SDOCT) consists of a super-luminescent diode that generates light of 840 nm wavelength and a 150 nm bandwidth. A spectrometer is fixed to compute the interference spectra of reflected light from the tissue and light from a stationary reference arm [20]. The imaging speed of SD-OCT is 50 times greater than that of TD-OCT providing more excellent images per unit area. The source of low coherence light of SD-OCT is identical to that of TD OCT. However, the stationary mirror is used rather than using moving reference mirror for the signal acquisition. The diffraction grating separates the interference pattern into frequency components. A charge-coupled device detects the separated frequency components, shown in Figure 3 [17]. The function of a collimator is to align the beam of light in a different direction, making it parallel or collimated.