Optics basics

The basic purpose of a lens of any kind is to collect the light scattered by an object and recreate an image of the object on a light-sensitive ‘sensor’ (usually CCD or CMOS based).

A certain number of parameters must be considered when choosing optics, depending on the area that must be imaged (field of view), the thickness of the object or features of interest (depth of field), the lens to object distance (working distance), the intensity of light, the optics type (telecentric/entocentric/pericentric), etc.

The following list includes the fundamental parameters that must be evaluated in optics

  • Field of View (FoV): total area that can be viewed by the lens and imaged onto the camera sensor.
  • Working distance (WD): object to lens distance where the image is at its sharpest focus.
  • Depth of Field (DoF): maximum range where the object appears to be in acceptable focus.
  • Sensor size: size of the camera sensor’s active area. This can be easily calculated by multiplying the pixel size by the sensor resolution (number of active pixels in the x and y direction).
  • Magnification: ratio between sensor size and FoV.
  • Resolution: minimum distance between two points that can still be distinguished as separate points. Resolution is a complex parameter, which depends primarily on the lens and camera resolution.
Next →