Object masks

It should be noted that the MTF expresses the modulation in the image plane of a sinusoidal object and is useful only for incoherent illumination. Under practical conditions for large features (> 3.0 m), the sinusoidal object (mask) is not a good choice when what is really relevant is a binary object. However, as the mask features approach 1.0 pm, the light intensity through the mask becomes sinusoidal and the mathematical formulation for MTF becomes relevant. 

Next, fluorescence intensity statistics from these pools can be used to distinguish the remaining puncta (i.e., object masks in different channels that partially overlap Fig. 5). 

Object masks that partially overlap are also useful for identifying apposed presynaptic (e.g., the vesicular GABA transporter— vGAT) and post synaptic (e.g., the subunit of the GABAa receptor) structures. Specifically, after deconvolution the x-y resolution of LSCMs and SDCMs is -100 nm, whereas the average width of a synaptic cleft is 20-30 nm. Thus, the fluorescence of many labeled presynaptic and postsynaptic proteins partially overlaps (e.g., see Fig. 6). 

The schlieren microscope is able to detect refractive index variations to six decimal places. Any small difference in optical path (index difference, film thickness, etc) is very precisely detected by the schlieren microscope, especially in the Dodd modification. It is, in effect, a darkfield method. The specimen is illuminated with light in a portion of the illuminating cone and that direct light is masked in the conjugate back focal plane of the objective (Fig. 3). The only light to pass through this plane is refracted, reflected, or diffracted by the specimen. 

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. 

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