Electromagnetic radiation has electric and magnetic wave components, which oscillate at 90° to each other in the direction they are traveling. These two fields are usually in phase with each other. There are four properties due to its wave nature:

• Wavelength: The color of light. While humans can only perceive visible light, machine vision sensors are also sensitive to ultraviolet and infrared light. The most common wavelengths used in machine vision extend from 365 nm in the UV to 940 nm in the IR region.

• Amplitude: The higher the wave amplitude, the higher the light intensity. The right level of intensity produces an image bright enough to see features consistently, even over long periods of operation.

• Direction of propagation: The direction the light moves relative to the workpiece affects how light reflects towards or away from the camera and thus the resulting image (see Section 6).

• Plane of oscillation: Concerns the use of polarization (see Section 6.6).