**2.2 Camera image**

132 Advanced Topics in Measurements

can be processed by a computer. Generally the goal is to attain a signal from an object in such a form that we know where it is (geometry) and what it is or what properties it has

The human visual system is limited to a very narrow portion of the spectrum of electromagnetic radiation, called visible light. Image processes are sensitive to wavelengths and additional information might be hidden in the spectral distribution of radiation. Using different types of radiation allows taking images from different depths or different object

The measurement of images is often a principal method for acquiring scientific data and generally requires that features or structure be well defined, either by edges or unique colour, texture, or some combination of these factors. The types of measurements that can be performed on entire scenes or on individual features are important in determining the

Colourimetry is the measurement of the wavelength and the intensity of electromagnetic radiation in the visible region of the spectrum. Colourimetry can help find the concentration of substances, since the amount and colour of the light that is absorbed or transmitted depends on properties of the solution, including the concentration of particles in it. A colourimeter is an instrument that compares the amount of light getting through a solution with the amount that can get through a sample of pure solvent (Fig. 1.). A colourimeter contains a photocell is able to detect the amount of light which passes through the solution under investigation. The more light that hits the photocell, the higher the current it produces, hence showing the absorbance of light. A colourimeter takes 3 wideband (RGB) readings along the visible spectrum to obtain a rough estimate of a colour sample. Pigments

The use of imaging photometers and colourimeters for fast capture of photometric and colourimetric quantities with spatial resolution has attracted increasing interest. Compared with measuring instruments without spatial resolutions, such as spectrometers, this

Substantial time-savings with simultaneous capture of a large number of measurements

Image-processing functions integrated in the software permit automated methods of

However, the absolute measuring precision of imaging photometers and colourimeters is not as high as spectroradiometers. This is because of the operational principle using a CCD Sensor in combination with optical filters, which can only be adapted to the sensitivity of the

(Jähne & Haußecker, 2000).

**2. Acquiring images** 

properties (Nixon & Aguado, 2002 ).

appropriate processing steps (Russ, 2006).

absorb light at different wavelengths.

in a single image,

human eye with limited precision.

Analysis of luminous intensity.

technology offers the following advantages:

analysis, e.g. calculation of homogeneity or contrast.

Measurement of homogeneity, contrast of products,

Imaging photometers and colourimeters are the instruments of choice for:

Measurement of luminance and colour distribution of industrial products,

**2.1 Imaging photometers and colourimeters** 

In recent years, a massive research and development effort has been witnessed in colour imaging technologies in both industry and ordinary life. Colour is commonly used in television, computer displays, cinema motion pictures, print and photographs. In all these application areas, the perception of colour is paramount for the correct understanding and dissemination of the visual information. Recent technological advances have reduced the complexity and the cost of colour devices, such as monitors, printers, scanners and copiers, thus allowing their use in the office and home environment. However, it is the extreme and still increasing popularity of the consumer, single-sensor digital cameras that today boosts the research activities in the field of digital colour image acquisition, processing and storage. Single-sensor camera image processing methods are becoming more important due to the development and proliferation of emerging digital camerabased applications and commercial devices, such as imaging enabled mobile phones and personal digital assistants, sensor networks, surveillance and automotive apparatus (Lukac & Plataniotis, 2007).
