Optical Glass Filter

Light filters. Optical filters are used in colorimeters (absorptiometers) for isolating any desired spectral region. They consist of either thin films of gelatin containing different dyes or of coloured glass. 

Measures in UV reflectivity mode are thus possible, using a 400 nm peaked narrowband filter. However, because of the glass optics absorption below 400 nm and the low sensor sensitivity in the UV, the quality of the images in UV reflection mode is not particularly good, because of the long exposure time need for compensating the low illumination on the sensor. 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Resin solutions were prepared by mixing selected components illustrated in Table 1 with 1.5 wt% Darocur 1173 and then drawing down onto a glass plate using a doctor s blade. The films were then cured using a 70 W ultraviolet (UV) light mercury lamp with an optical filter at 350 nm for approximately 16 seconds. 

When using optical filters for photometric accuracy measurements, make sure that the filter is placed properly in the sample holder so that the filter is perpendicular to the incident light beam. Problems of reflection from the highly polished surface of the glass filter and interreflection between optical surfaces for metal on quartz filters may occur that affect the readings. 

Figure 15.25 shows the transmission spectra of the optical filters on a glass substrate and on a fluorinated polyimide film. The two spectra are very similar, but an optical filter on a fluorinated polyimide is cheaper and easier to handle than one on a glass substrate. 

Figure 15.25. Transmission spectra of the optical filters on a fluorinated polyimide film and on a glass...

Figure 9 shows the result of testing a Pourable Dressing for the presence of xanthan. The sample was infiltrated into a glass fiber filter and the filter probed sequentially with LBG solution and BS1-FTTC. White areas on the micrograph are sites of xanthan localization. Epiflurescence optics, (x 300). 

Sherwood Stevens (1965) examined glass-fibre filters from personal air samplers worn by workers in the Radiochemical Laboratories at Harwell. The filters were mounted in an Araldite mixture which rendered them transparent and were covered by autoradiographic stripping film. After exposure and development, the samples were viewed with a high-power optical microscope. Particles were sized, and their activity determined from the number of alpha tracks coming from them. An extremely wide range of particle sizes, 0.2 to 90 m, was found. The smaller particles were plutonium compounds or alloys, and the larger were inert particles with one or more small Pu particles attached to them. An example of the latter is shown in Fig. 5.3. 

These data were obtained by die National Institute of Standards and Technology (USA) while developing a transfer standard for verification and calibration of die v-axis of NIR speedometers. Optical filters were prepared from two separate melts, 2035 and 2035a, of a rare eardi glass. Filters from both melts provide seven well-suited adsorption bands of very similar but not exactly identical location. One filter, Y, from one of die two melts was discovered to be unlabelled. Four 2035 filters and one 2035a filter were available at die time of diis discovery. Six replicate speeda were taken from each filter. Band location data from these spectra are provided below, in cm-1. The expected location uncertainties range from 0.03 to 0.3 cm-1. 

Risen and Wang developed a method and compositions for producing microlenses and optical filters. According to their method, carboxylated silicone or polysilicone precursor composition is applied to the surface of a substrate to form a precursor droplet, which is thermally oxidized to form a microlens. The substrates utilized were silica, silicates, borosilicate glasses, and silicones. The precursors, which are present in concentrated solutions, are viscous fluids which are used to form microdroplet precursors. A solvent such as ethanol or acetone is added to the precursors to modify and control their flow and surface tension properties, to facihtate the formation of spherical shape of the precursor on substrates. The precursor droplet volume is 4-600 picoliters and forms a droplet of 20 to 1000 micrometers in diameter. 

For systems that generate a nerve agent aerosol, there are several ways to characterize the chamber atmosphere. Real-time optical aerosol monitors can be used to monitor the concentration and stability of the chamber atmosphere. Alternatively, glass fiber filters can be used to collect aerosol from the chamber. However, this method only provides information about the average concentration of the chamber atmosphere during the period when the sample was collected and does... 

Optical filters can modify the spectral output from spectrally broad light sources and essentially monochromatic light can be obtained from light sources with several sharp but widely separated emission lines, such as the low-pressure mercury arcs. Commercially available glass Liters and readily prepared filter solutions are inexpensive alternatives to... 

An optical filter is essentially a piece of coloured glass. An extensive range of optical filters are readily available as off-the-shelf components. Alternatively, custom filters can be made at a higher cost. Four basic types of filter are used for optical sorting applications ... 

Optical Filters. Various types of optical filters may be used to isolate certain wavelengths of light. There are narrow-bandpass filters, sharp-cut filters, and interference filters. The first two are usually made of glass and contain chemicals (dyes) that absorb all radiation except that desired to be passed. The sharp-cut filters absorb all radiation up to a specified wavelength, and pass radiation at longer wavelengths. 

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