Object slit

Measuring surface crack depth is performed by calibration samples made of the same material like the object being tested. Calibration samples are the plates having narrow grooves like slits of various depth 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm and made by electric erosion method. The samples have dimensions 50 mm X 150 mm x 6 mm and 25 mmx 150 mm x 6 mm and are made of magnetic... 

In the design of MOEMS components, various parameters have to be tuned. These parameters differ according to the functionality of the component. We will consider two different family of devices, programmable slits for Multi-Object Spectroscopy, including Micro-Mirror Arrays (MMA) and Micro-Shutters Arrays (MSA), and Micro-Deformable Mirrors (MDM) for Adaptive Optics systems. 

Programmable multi-slit mask for Multi-Object Spectroscopy... 

Micro-Opto-Electro-Mechanical Systems (MOEMS) will be widely integrated in new astronomical instruments for future Extremely Large Telescopes, as well as for existing lOm-class telescopes. The two major applications are programmable slit masks for Multi-Object Spectroscopy (see Ch. 12) and deformable mirrors for Adaptive Optics systems. Eirst prototypes have shown their capabilities. However, big efforts have stiU to be done in order to reach the requirements and to realize reliable devices. 

Multi-slit systems in which the field is mapped onto the detector via a mask. This admits only the light of pre-selected objects so that a spectrum is produced at the location of each slitlet. The slit mask is custom-made for each observation. Recent examples include CMOS (Hook et al. 2003 Table 2), VIMOS (Le Fgvre et al. 2003) and DEIMOS (Faber et al. 2003). 

Before the slit. Motion of the image delivered by the telescope with respect to the slit causes both a loss of throughput and an error in the barycentre of the spectral lines recorded on the detector, unless the object uniformly fills the slit (which implies low throughput). This can cause errors in measurement of radial velocities. For MOS, there is the particular problem of variations in the image scale or rotations of the mask. These can cause errors which depend on position in the field resulting in spurious radial trends in the data. Fibre systems are almost immune to this problem because the fibres scramble posifional information. 

Target acquisition is easy there is no need to position the object carefully on the slit. 

The position of the object in the field can be unambiguously determined post facto by summing the datacube in wavelength to produce a white-light image. In contrast, the position of the target with respect to the slit is difficult to determine in slit spectroscopy. 

By making use of the spatial information, the velocity field of an extended, structured object can be obtained unambiguously without errors caused by uncertainty in the position of a feature within the slit. 

Fig. 2.14 The scheme of the cylindrical lens method for diffusion coefficient measurement (1) the source with the horizontal slit (2) the condenser supplying a handle of parallel beams (3) the cuvette with a refraction index gradient where the beams are deflected (4) the objective lens focusing the parallel beams to a single point (5) the optical member with an oblique slit and a cylindrical lens (6) the photosensitive material...

Most of the stars of our sample have been selected from the H K BPS survey ( Beers, Preston Shectman [1], First, stars were selected from the weakness of their H H lines for the Balmer lines intensity on prism-objective Schmidt telescope plates. Then, the candidate stars were observed with a slit spectrograph in order to have a quantitative estimate of their metallicity. The survey has operated on about 7000 square degrees of the sky, mostly on the polar caps. It has supply a vast amount of metal-poor stars, with hundreds of them more metal-poor than the most metal-poor globular clusters. We selected from this sample stars with metallicities estimated to have [Fe/H] < -2.7. The actual metallicity histogram is given for the sample on fig. 1. 

Object to be tested 2, helium leak detector L, slit with a fixed conductivity (Fig. 10 from [2.27]). 

Dark-field illumination is classified into three types. The first one is for a microscope equipped with low numerical aperture (NA) objective lenses (see Fig. 1). To cast a shadow at the objective lens, a ring-slit as shown in Fig. IB is inserted into the light path. The second is for highNA (>0.5) objective lenses. Special, ready-made dark-field condensers or lenses are used for dark-field illumination. The third is independent... 

As described before, special built-in equipment is not always necessary for dark-field microscopy, and one can readily convert bright-field illumination to dark-field illumination. An inverted microscope equipped with long-distance (low NA) lenses is suitable for setup of a dark-fieldmicroscope. A handmade ring-slit is available when objective lenses such as x4 lens withNA 0.13, xlO lens withNA 0.30, and x20 lens... 

In order to adjust the dark-field illumination, project the illumination light onto a piece of paper placed on the microscopic stage or on the obj ective lens. Adjust the position of the slit and the height of condenser so that the transmission light illuminates the sample uniformly and brightly, and that the diameter of the shaded area produced on the surface of the objective lens is larger than that of the objective lens (see Fig 1C). 

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