Imaging Fundamentals

Authors: Gregory Hollows, Nicholas James

This is Section 1.2 of the Imaging Resource Guide.

Figure 1: Illustration of the fundamental parameters of an imaging system.

The following terms explain the most basic concepts of imaging and will be referenced throughout the remainder of this guide.

Field of View $ \small{ \left( \text{FOV} \right)} $: The viewable area of the object under inspection. This is the portion of the object that fills the camera’s sensor. This area is commonly reduced to the horizontal $ \small{ \left( \text{HFOV} \right)} $ or vertical $ \small{ \left( \text{VFOV} \right)} $ dimension for ease of calculation.
Working Distance $ \small{ \left( \text{WD} \right)} $: The distance from the front or first surface of the lens to the object under inspection.
Resolution $ \bf{ \small{ \left( \xi_{\small{\text{Object Space}}} \right) }} $: The minimum feature size of the object that can be distinguished by the imaging system typically specified as a spatial frequency in units of line pairs per millimeter $ \left[ \tfrac{\text{lp}}{\text{mm}} \right] $. Learn more in Resolution.
Depth of Field $ \small{ \left( \text{DOF} \right) } $: The maximum object depth that can be maintained entirely in acceptable focus. DOF is also the amount of object movement (in and out of best focus) allowable while maintaining focus. This is not to be confused with depth of focus, which refers to the location at which an image can be in focus on a sensor. Learn more in Depth of Field and Depth of Focus.
Sensor Size $ \small{ \left( H \right) } $: The size of a camera sensor’s active area, typically specified in the horizontal or vertical dimension. This parameter is important in determining the proper lens magnification required to obtain the desired FOV.
Pixel Size $ \small{ \left( s \right) } $: Typically square in shape, pixels make up the sensor grid and have a dimension in the order of micrometers or microns [μm].
Magnification $ \small{ \left( m \right) } $: The magnification of a lens sometimes referred to as PMAG (Primary Magnification) is defined as the ratio between the sensor size and the FOV, see Equation 1.