Filters optical transmittance

Transmittance > 6 mm Higher than Other Material Microwave Windows, Optical Filters, Optical Waveguides... 

This diagram shows the energy spectrum of a given source, coupled with a filter of defined transmittance, which is established by a detector of known spectral response, as modified by a standard source and modified to that of a Standard Observer. Once an instrument has been set up properly with the proper optical... 

The Figure 5 shows the case of absorption of light through an optical filter and includes other processes that decrease the transmittance such as surface reflectance and scattering. 

An optical filter has optical density of 4.0 at a wavelength of 633 nm. (a) Determine the transmittance and the absorbance of the filter at this wavelength, (b) If a laser beam of 1 mW power at 633 nm passes through such a filter, determine the laser power beyond the filter. 

The fundamental elements of an ultraviolet-absorption analyzer include (a) a radiation source (b) suitable optical filters (c) a sample cell and (d) an output meter. A transmittance measurement is made by calculating the ratio of the reading of the output with die sample in the cell to die reading widi the cell empty (of ultraviolet-absorbing materials). The concentration can be calculated from the known absorptivity of the substances as previously demonstrated by the equations or it may be determined by comparison with known samples. 

Figure 1.2 Spectral transmittances of the filters. The filters were placed in front of the projectors which were used to illuminate the Mondrian image. (Reproduced from Land EH and McCann JJ 1971 Lightness and retinex theory. Journal of the Optical Society of America 61(1), 1-11, by permission from The Optical Society of America.)...

Optical filters have, in the past, been widely used in the sugar industry to isolate desired spectral regions, and three essential points must be considered in evaluating transmittancy data so obtained. It is necessary to... 

Fig. 1. Complete experimental setup for monitoring and control system for fermentor. T, feed tank V, control valve v, valves F, fermentor t, thermocouple c, coils A, dilutions tanks Bm, multichannel pump C, controller Tt, temperature transmitter Tb, biomass transmitter Sb, biomass optical sensor D, equipment to remove air bubbles R, rotammeter Ft, tangential filter Co, computer So, ethanol colorimetric sensor Vi, injection valve d, waste E+R, reagents-enzymes tanks B, pumps.

Figure 8.9 The combination of the visual acuity of the human eye and the transmittance of a red glass filter acts to restrict the detected wavelength to a narrow band [7], The effective wavelength for optical pyrometers of this form is 0.653 /jm [8].

The total transmittance of the filter to the incident solar radiation changes according to the amount of ozone and the optical depth of the air mass. The instrumental calibration for determining the total amount of ozone was made through simultaneous observations with Dobson s spectrophotometer. The results of these calibrations are shown in Figure 2, in which the amount of ozone is expressed in 10 cm. 

Solution filters are readily prepared in any photochemical laboratory. Their compositions and optical properties are available throughout the literature.137,157 158 Figure 3.3 shows, for example, the transmission curve of a band-pass solution filter made of Cr(SC>4)2 dissolved in dilute aqueous H2SO4, which transmits radiation at 325 20 nm. As a result, the 313.9 nm band, available in the emission spectrum of medium-pressure mercury lamps, can be isolated. However, some of the reported solutions have limited photochemical stability and should be regularly checked for transmittance. 

Figure 10.11 Non-dispersive analyser for measuring CO2 in gaseous media. This assembly is representative of many portable detectors. The selectivity is assured by an adapted optical illter (F2) and by a membrane at the entrance to the cell which only permits gas to pass through to the detector. The assembly contains a second filter (FI) chosen in a non-absorption zone which authorizes to a computation of the transmittance. On the diagram are shown the bandwidths of the two filters and the spectrum as function of transmittance of a gas, here COj. The detectors are thermistors. Left, a chart which presents a choice of wavelengths in the mid-IR and the near IR for several gases (reproduced courtesy of Edinburgh Sensors, GB).

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