22.3 LIGHTING AND SCENE

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There are certain features that are considered important in images,

- boundary edges

- surface texture/pattern

- colors

- etc

Boundary edges are used when trying to determine object identity/location/orientation. This requires a high contrast between object and background so that the edges are obvious.

Surface texture/pattern can be used to verify various features, for example - are numbered buttons in a telephone keypad in the correct positions? Some visually significant features must be present.

Lighting,

- multiple light sources can reduce shadows (structured lighting).

- back lighting with luminescent screens can provide good contrast.

- lighting positions can reduce specular reflections (light diffusers help).

- artificial light sources provide repeatability required by vision systems that is not possible without natural light sources.