Stray light, reduction

Various methods to achieve stray light reduction include spectrometer interior redesign improved optical surfaces (e.g. gratings) and modifications of the dispersion... 

Experience at Barringer Research Laboratory demonstrated that the most effective method to reduce stray light is to combine several reduction procedures. The lead/calcium selectivity of the instrumentation as received was 160, but this has been increased to greater than 1,000,000 with the manufacturer s modifications. The actual steps included replacement of the calcium 393.3 nm line with the 315.9 nm line, replacement of the lead 405.8 nm line with the 220.3 nm line, installation of an interference filter mask over the lead photomultiplier, and computer correction of the residual calcium interference. The stray light reduction obtained by installation of interference filters is presented for three common concomitants in Table II. In many cases the stray light levels were less than or equivalent to the detection limit. The interference filters and the photomultiplier masks (which reduce the entrance angle to the photomultiplier to include only the receiver mirror) improved the detection limits for many elements in the array by decreasing the system band pass. 

Interference Filter Stray Light Reduction Factors Obtained on the Barringer Research ICP. 

Baffling, reduction of stray light implied by the availability of intermediate foci and pupil images ... 

The introduction of a pinhole into an image plane of the light path to the detector of a wide-field microscope also leads to a reduction in stray light (Fig. 1, pinhole detector). This occurs because light rays arising in regions outside of that defined by the pinhole are unlikely to strike the detector. Recommended practice in microscope photometry (2) is a combination of a narrowly delineated area of illumination, defined by a pinhole or a sharply restricted field... 

As early as 1940, Reitz used a double spectrograph with combined positive and negative dispersion for the reduction of stray light as he recorded Raman spectra of crystal powders on photographic plates. 

The goal for this analysis was to measure the prompt fluorescence decay time for each polycrystalline YSZ thickness. Results from this analysis are shown in Table 2. Visible fluorescence was observed through all three YSZ thicknesses at each of the tested laser wavelengths. It was not possible to measure the prompt fluorescence decay time for YAG Eu because the reduction of light intensity did not follow a simple exponential curve. This phenomenon is most likely caused by electrical noise, stray light, or the absorption and re-emission of fluorescence from the YSZ. 

Emissivity and Reflectivity in the Infrared Design Decisions for Background Level Effect of Ambient Temperature on Background Reduction of Stray Light... 

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