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Recording and reproduction
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2012
The beam enters a half mirror prism which is a non-polarizing prism that reflects half of the incident light and lets pass the other half. The light beam, still divergent at this stage, is converged into a parallel beam by the collimation lens. The laser beam is then focused by a simple lens onto the pit surface of the disc. The simple lens is part of a servo-controlled mechanism known as a `two-axis device'. The beam is reflected by the mirrored surface of the disc and converged by the two-axis device lens into a parallel beam. After passing through the collimation lens the laser beam is converged onto the half mirror prism where half of the light is reflected towards the detector part of the pick-up device. The resulting light beam intensity at the detector part is 1 ð 1 D 1 2 2 4 of the original beam. In the detector part the cylindrical lens focuses the laser beam in only one place. As a result, the cross-section of the beam after passing through the lens is elliptical with the degree of ellipticity varying according to the distance from the lens. By detecting the degree of ellipticity an indication of whether or not the beam is focused on the disc surface can be obtained. Six photodetectors enable the read-out of the pit information from the disc. Figure 3.67 shows the arrangement of the four main spot detectors (A, B, C and D) and two side spot detectors (E and F). Optical pick-ups contain an actuator for objective lens position control. The CD player, due to
Recording and reproduction
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2013
Andy Wilson, Kenneth Gundry, Jan Arts, Jan Maes, Douglas Ford, Peter Skirrow
The beam enters a half mirror prism which is a non-polarizing prism that reflects half of the incident light and lets pass the other half. The light beam, still divergent at this stage, is converged into a parallel beam by the collimation lens. The laser beam is then focused by a simple lens onto the pit surface of the disc. The simple lens is part of a servo-controlled mechanism known as a �two-axis device�. The beam is reflected by the mirrored surface of the disc and converged by the two-axis device lens into a parallel beam. After passing through the collimation lens the laser beam is converged onto the half mirror prism where half of the light is reflected towards the detector part of the pick-up device. The resulting light beam intensity at the detector part is i x | |
Detectors
Published in C. R. Kitchin, Astrophysical Techniques, 2020
where R2 is the radius of the surface of the crown glass lens that is in contact with the flint lens (NB: the radius of the flint lens surface is almost invariably R2 as well, to facilitate alignment and cementing) and R1 is the radius of the other surface of the crown glass lens. By a careful selection of λ1and λ2 an achromatic doublet can be constructed to give tolerable images. For example, by achromatising at 486 and 656 nm, the longitudinal chromatic aberration is reduced when compared with a simple lens of the same focal length by a factor of about 30.
Performance evaluation of a box-type solar cooker integrated with Fresnel lenses
Published in International Journal of Ambient Energy, 2022
Gulsavin Guruprasad Engoor, S. Shanmugam, AR. Veerappan
The focal length (f) of the Fresnel lens was calculated by using the simple lens equation where i and o are the image and object distances, respectively. The distance of the object (sun) is taken as infinity; hence, the focal length (f) will the distance of the suns image from the lens. In the present study, the focal length was found to be 358 mm.
Two-dimensional multiplexing scheme both with ring radius and topological charge of perfect optical vortex beam
Published in Journal of Modern Optics, 2019
Le Wang, Xincheng Jiang, Li Zou, Shengmei Zhao
Figure 2 illustrates the proposed multiplexing scheme for both with the ring radius and topological charge. Gaussian beams are generated at the transmitter. They are illuminated onto a series of vortex axicons with different axicon parameters and topological charges to produce different BG beams. Each of them has the axicon parameter and the topological charge . Then, they are transformed into POV beam at the Fourier plane through a Fourier lens. Obviously, beams with the same axicon parameters have the same size rings, and beam rings with large axicon parameters have a bigger size. Due to the POV beams are generated at the Fourier plane, the beam will be changed to a BG beam before and after the Fourier plane (25). We use a method proposed by Zhu et al. (28) to maintain the transmission of the POV beam by placing a microscope objective (MO) at the Fourier plane and followed by a simple lens to collimate the POV beam. The ring radius of the POV beam will remain constant for any topological charge after a certain distance. The information is modulated on the beam by on–off keying (OOK) modulation. All beams are superposed to a coaxial beam through a set of beam splitters. The light field of the superposition beam in the cylindrical coordinate is where is the ring radius of the POV beam with axicon parameter is the modulated signal corresponding to the axicon parameter and the topological charge . The results in Equation (7) clearly show that the intensity distribution of the superposition beam is concentrated in m parts. They are distributed in the vicinity of the radial . This well characteristic can be utilized in the following radius detection.