Appendix C: Approximate Calculation Formulas for Lenses

When WD is longer than approx. 200 mm:
Distance to the object: L [mm]
Focal distance: f [mm]

Field of View (Height) Approximate Calculation Formula
H = L × CCD vertical dimension / (f+l)

• CCD vertical dimension = Pixel size × number of pixels
• For the pixel size, refer to the specification of each camera.

When WD is roughly shorter than approx. 200 mm:

Distance to the object: L
Focal distance: f
Distance from the focal point to the imaging element: l
Distance from the virtual lens to the imaging element (CCD/CMOS): (f+l)

Tip:
“Distance to the object: L” in the above figure differs from the work distance.
“Distance to the object: L” is a distance from the “position of the virtual lens”, while a work distance is a distance from the “lens end”.
Therefore, a relationship of L, (f+l) and WD in the above figure is as follows:
L + (f+l) = WD + Lens length + 17.526mm

Distance from the virtual lens to the imaging element (CCD/CMOS) (f+l)
(f+l) = (L × f) / (L - f)

L including the extension tube (t)
L = f × ((f+l) + t) / (((f+l) + t) - f)

Field of View (Height) Approximate Calculation Formula
H = L × CCD vertical dimension / (f+l)

• CCD vertical dimension = Pixel size × number of pixels
• For the pixel size, refer to the specification of each camera.