Coloured filters

The colour filters used with absorptiometers should be examined from time to time by measuring the absorbance in a spectrophotometer if the results depart markedly from those expected for the filter, it should be replaced. Normally a filter as supplied with the instrument will be used, but if necessary, filters from the Wratten range supplied by Kodak Ltd or from the Spectrum Filter or Bright Spectrum Filter series supplied by Ilford Ltd may be used. 

Verheijen, J., Bongaerts, P., and Verspui, G., Low Pressure Chemical Vapour Deposition of Temperature Resistance Colour Filters, Proc. 10th. Int. Conf. on CVD, (G. Cullen, ed.), pp. 977-981, Electrochem. Soc., Pennington, NJ 08534 (1987)... 

Figure 10.4 Organic pigments used in colour filters for flat-screen displays...

Photoelectric or CCD photometry through colour filters is widely used for quantitative classification , i.e. to measure major spectral features with low wavelength resolution but rapidly and precisely to obtain major properties of large numbers of stars, such as... 

C = Filter wheel with a series of colour filters,... 

The simplest types of photometric instrument are designed for measurements in the visible region of the spectrum only and rely on coloured filters and simple photoelectric detectors. The name colorimeter is often used to describe such instruments although this is not necessarily correct and the word should probably be reserved for visual comparators rather than photoelectric instalments. 

They give transmission spectra with considerably reduced bandwidths (10-30 nm) compared with coloured filters (Figure 2.19) and can be used over the spectral range varying from the near ultraviolet (350 nm) to the near infrared (5 gm). 

Non-flammable scenery, coloured filter holders for studio and theatre spotlights. .. 

A colorimeter fitted with coloured filters corresponding to certain wavelengths In the visible region can be used to measure the absorbance of coloured solutions. A filter of the... 

Colorimetry can be used to determine the concentration of coloured substances in solution. A colorimeter essentially consists of a light source, a coloured filter, a light detector and a recorder. The filter chosen is the complementary colour to the solution as this will result in the maximum absorbance. The light passes through the filter and then through the coloured solution. The difference in absorbance between the coloured solution and water is detected and noted as an absorbance value. Colorimetry uses the relationship between the intensity of the colour of the solution and the concentration. 

The colour filter layer consists of the RGB colour elements set inside the so-called black matrix, which prevents leakage of light from the different pixels and also stops any photoelectrical conversion in the TFT. The structure of the colour filter layer, illustrated in Figure 5.7, is constructed on a clear substrate, and consists of the RGB hlter units, the black matrix interlayer, an overcoat layer, and an ITO him. Amongst the preferred methods for constraction of pigment based colour hlter layers are photolithographic printing and electrodeposition processes. ... 

Figure 5.7 Schematic of colour filter for LCD display. % Transmission...

Figure 5.8 Transmission spectral characteristics of a colour filter.

Janus Green B (3-dimethylamino-7-[4-dimethylaminoazo]-5-phenylphenazonium chloride (2869-83] M 511.1. Dissolves in H2O to give a bluish violet soln which becomes colourless when made lOM in. NaOH. Dissolve in EtOH to give a blue-violet colour, filter from insoluble material then add dry Et2O whereby the dye separates out leaving a small amount of blue colour in soln. Filter off the solid and dry in vacuum. Store in a dark bottle. 

Flame photometric analyses are much simpler. For example, when sodium is inserted in a flame at 200CTC, the sodium atoms are the only ones emitting radiation. Light measurement can be conducted using a simple coloured filter that isolates the relatively large spectral band corresponding to the yellow colouration in the flame. 

Figure 7.6 Examples of transmission spectra of colour filters. Horizontal axis, wavelength in nm vertical axis, absorbance...

Unlike colour filters, interference filters and gratings can lead to some optical artefacts of which all workers in this field should be aware. All processes of interference of light waves depend on the difference in optical path between the beams, as illustrated in Figure 7.7. The general law for constructive interference is then... 

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