The lights used for image sensors can be largely classified by the type and shape of the light source. There are various types of light sources such as fluorescent lamps, LEDs, and halogen units. The following is a classification of lights by shape.
Ring Type
This is the most common shape, allowing uniform intensity of light to be obtained over the entire ring. There are various types of light sources such as fluorescent lamps, LEDs, and halogen (fiber) units, with internal diameters varying from a few dozen to a few hundred mm.
Bar Light (Line)
Uniform light can be obtained in a linear shape. This is suitable for lighting up the front of a sheet widthwise and the size ranges up to 2 m.
Backlight
Uniform light can be obtained over the flat surface. Generally, this is used as a backlight to light up a transparent container or lead frame from the back. The size varies from a few dozen square mm on the side to 500 x 800 mm.
Spot Light
This mostly includes fiber lights using halogen light, allowing high illumination light to be locally obtained. This is also suitable for expanded images, etc. Various branched types, such as single, twin, and triple are available.