ABSTRACT Colour appearance measurement aims to describe, both qualitatively and quantitatively, what a person experiences as colour. Unfortunately, current measurement techniques are fundamentally limited because they give observers a set of component hues - the hues they must use to describe all the colours they experience. This circular approach is also un• satisfactory based on individual variations in retinal photoreceptors. To circumvent these limitations, the technique of Partial Hue-Matching (PHM) was developed, which provides an unbiased estimation of the minimum set of component hues observers use to decompose their colour experiences. PHM does this by asking observers to match colours for common hues, and from this uncovering chromaticity classes: these common hues form the set of component hues. Crucially, PHM does not define to an observer what hue is, and does not suggest which hues should be considered component hues: rather, comparisons among colours reveal their relationships and lead to the establishment of chromaticity classes.

Striking changes in colour appearance can arise when small areas of colour are seen in juxtaposition against a coloured background. These changes are of great interest as a problem in visual physiology since many factors may contribute to the effect. They are also of practical importance since they may have a major influence on colour design. Different techniques of subjective colour measurement are surveyed. Two methods are used to measure these colour changes as' a basis for the quantitative study of the colour contrast phenomena. In the first method: Standard source SA is used for illumination of the test colour in its surround, and its ap)earance is compared with a red-green,blue mixture from a modified form of Donaldson Colorimeter using monocular vision. In the second method: Natural daylight is used as illuminant and the colour appearance is matched by a number of observers having normal colour vision by comparison with colour samples in the Mansell Book of Color. The effects of different simple and compound, one colour and two colour surrounds, are analised. Also the effects of the following different viewing conditions are studied: (1) The luminance of the surround of the comparison patch. (2) The luminance of the surround of the test colour. (3) The luminance of the whole test patch, (4)Th e angle of subtense of the test patch. (5) The inclination of the test patch. (6)Th e orientation of the coloured stripes of the surround. (7) The movement of the test patch (The dynamic colour contrast) Some possible causes of such colon, contrast phenomena in the field of physics, physiology and psychology are discussed.

The aims of this research are to develop an LED based high quality CIE-illuminant simulator, to investigate different visual methods for evaluating the colour rendering properties of different light sources, to test the current CIE colour rendering index and to propose a new index based on an analysis of the visual results. To achieve these aims, a spectrally tunable LED cluster was constructed and this device proved to be both flexible and accurate for CIE-illuminant simulation. In addition, the colour rendering properties of several different light sources have been investigated from various aspects, i.e. colour appearance, colour fidelity, colour preference and colour harmony.

This research is focused on the development of colorimetric tools to improve the current colour management systems which are based on the specifications defined by the International Color Consortium (ICC) and can be only applied in a set of restricted working conditions.

Spectral reflectance is the 'finger print' of the colour of an object. This study investigated a number of the methods to obtain spectral reflectance functions of colours, and to compare their performance. Spectrophotometers are traditionally colour measurement instruments. However, they can only measure one spot of flat uniform colour patches with direct contact. Using digital cameras as a means of colour measurement device to predict spectral reflectance can overcome this limitation, but system performance in terms of accuracy and precision is expected to be lower than using spectrophotometers. In the present work, the metrology and prediction of measuring colours were studied. The former included the evaluation of spectrophotometer performance. The latter considered characterisation models using digital cameras to predict spectral reflectance from camera responses. Large efforts were spent to develop camera based technology. The characterisation model which was typically applied to transform the camera primary responses to device independent primaries (XYZ or CIELAB) requires a characterisation target. To make a successful model depends upon the selection of effective colours in the characterisation target. In the present research, a method for developing the characterisation target and the importance of colour regions for colour selection were proposed.

Trichromatic images of natural scenes contain information about the reflecting surfaces in those scenes. Colour is a very important source of information for identifying surfaces and making judgements about them. Judgements about surfaces in a scene by the formation provided by their colour can be done only if such colours remain stable under changes in the illumination. This approxmiate constancy of colours is not straightforward, as the spectra of the light reflected towards the eye can change considerably with the spectrum of the illummation. Therefore, the three photoreceptors in the eye respond differently to the different spectra reflected by the same surface under different ihuminants. Nevertheless, for a given scene, patterns of receptor responses under different illuminants are intrinsically mterrelated, and the Strength of these interrelations allow for the generation of approximately illuminantinvariant surface-colour codings. The aim of this thesis was to quantify objectively how much trichromatic information is potentially available to the eye and how much of it is actually retrieved for natural scenes under changes in illumination.

The effects of the two physical parameters, background and gap, on the perception of small colour differences (AE* < 5) were investigated by use of 248 colour-difference pairs around 21 colour centres made from painted samples. Each pair was assessed by an average of 30 times under each viewing condition using a grey-scale method and/or a paired-comparison method. From the visual data, colour-difference ellipsoids (ellipses) or tolerances were determined by use of a logistic or a probit maximum-likelihood analysis model, or by a least-square method. The perceived tolerance sizes along the three colour-difference directions AL*, OC1 and AH` in the CIELAB space were found to be little influenced by a change of lightness of the grey background but significantly influenced (i. e., decrease in tolerance size) by a 0.51'g ap between a pair of samples. The gap factor for the lightness component was greater than that for chroma or hue components, both the latter having similar magnitudes. This could be an explanation for the increase of the lightness relative tolerance I (or parametric factor KL) by a factor of 2 in the three modified CIELAB formulae (CMC, BFD and CIE94) for acceptability judgements, in which textile samples, having an unclear dividing line between them, are mainly used. In addition, the value of the relative tolerance Q used is thought to be practically the ratio between the lightness and chroma tolerances. The experimental uncertainties from non-physical parameters were also quantified. The degrees of precision (i. e., standard error) of colour measurements and observer judgements were found to be good (±4% and ±7%, respectively). The different methods of scaling and data analysis were found to have little impact on the results. The lightness, chroma and hue tolerances with respect to the standard colour position in the CIELAB space were studied in detail using the various existing datasets and the set from this study. The lightness tolerance showed a clear dependency upon the metric lightness for medium to light colours, but in the case of dark colours there was a discrepancy between the datasets. Both the chroma and hue tolerances showed dependency upon both the chroma and hue-angle and not the single dependency upon the metric chroma, as assumed in the CIE94 formula. New weighting functions were derived from the above experimental evidence, and finally a new formula, LCD (Leeds Colour Difference) was proposed. The LCD formula is nearly as simple and flexible as CIE94 but smoothes the individual weighting functions compared to CMC and BFD, especially for lightness tolerances for light colours and chromaticity discrimination near the blue region. It was also found that the reliability of the BFD formula is improved when the size of the chroma weighting function is increased by 1.5 times and the form of lightness weighting function is made parallel to those of the other modified CIELAB formulae.

An electrochromic (EC) material is able to change colour under the influence of an electric potential. The development of energy efficient smart windows for architectural applications is at present the subject of intense research for both economic and environmental reasons. Thus there is now a considerable research effort to develop smart windows with natural colour switching properties, i.e. shades of grey. In this regard, a promising metal oxide with a brown-black anodic colouring state is NiO or hydrated nickel oxide (also called nickel hydroxide , Ni(OH)2). The present work outlines the preparation and optimisation of EC nickel oxide-based ceramic precursor films onto various conducting substrates towards smart window applications. The literature review chapter outlines the different methods used for generating ceramic materials, a review of electrochromism and history of nickel oxide-based EC materials are also provided. Thins films have been deposited by an electrochemical cathodic deposition and by aerosol assisted chemical vapour deposition (AACVD) technique. For hydrated NiO films prepared by electrochemical cathodic deposition, various deposition factors at small-scale area (30 x 7 mm) have been investigated in order to optimise the films properties towards EC applications. With deposition on fluorine-doped tin oxide (SnO2:F, FTO) on glass, use of nickel nitrate (0.01 mol dm-3) solution at an applied current of -0.2 mA (-0.1 mA cm-2) for 800 s was optimal for preparing uniform deposits with a porous interconnecting flake-like structure, which is generally regarded as favourable for the intercalation/deintercalation of hydroxide ions during redox cycling. The as-deposited hydrated NiO films showed excellent transmittance modulation (Δ%T = 83.2 at 432 nm), with average colouration efficiency (CE) of 29.6 cm2 C-1 and low response times. However, after 50 voltammetric cycles, the cycle life was found to fade by 17.2% from charge measurements, and 28.8 % from in-situ transmittance spectra measurements. In an attempt to prepare films with improved durability, AACVD has been used for the first time in the preparation of thin-film EC nickel(II) oxide (NiO). The as-deposited films were confirmed to be cubic NiO from analysis of powder X-ray diffraction data, with an optical band gap that decreased from 3.61 to 3.48 eV with an increase in film thickness (in the range 330 820 nm). The EC properties of the films were investigated as a function of film thickness, following 50, 100 and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm-3). Light modulation of the films increased with the number of conditioning cycles. EC response times were < 10 s and generally longer for the colouration than the bleaching process. The films showed excellent stability when tested for up to 10000 colour/bleach cycles. Using a calculation method based on the integration of experimental spectral power distributions derived from in-situ visible region spectra over the CIE 1931 colour-matching functions, the colour stimuli of the NiO-based films, and the changes that take place on reversibly switching between the bleached and coloured forms have been calculated. Films prepared by both deposition techniques gave positive a* and b* values to produce orange. However, in combination with low L* values, the films were perceived as brown-grey. Hydrated NiO prepared via electrochemical cathodic deposition suffers from two well-known limitations; firstly, it shows catalytic properties towards the oxygen evolution reaction (OER), which is a process very close to the Ni(II)/Ni(III) redox process. Secondly, hydrated NiO shows poor cycling durability in alkaline solution. The co-deposition of single or bimetallic additives is an effective way to overcome these problems. Electrochemical studies revealed that the combination of cobalt (10%) with lanthanum (5%) was found to be the optimal composition for preparing hydrated NiO films with improved film durability. Finally, the emphasis of this work was on scale-up of deposition. Therefore, optimised deposition conditions from small scale (3.0 x 0.7 cm) have been used to successfully deposit films on two different sized large-area (10 x 7.5 and 30 x 30 cm) conducting substrates.