Calculate detector element size, camera focal length, or IFOV from any two inputs, with results in mm, radians, degrees, arcminutes, or arcseconds.
IFOV Formula
The IFOV calculator uses the small-angle relationship between detector element size and camera focal length. Length values are converted to the same unit before the formula is applied. IFOV is calculated in radians first, then converted to the angle unit you select.
IFOV = D / F
D = IFOV * F
F = D / IFOV
- IFOV = instantaneous field of view, in radians unless converted to degrees, arcminutes, or arcseconds
- D = detector element size
- F = camera focal length
The calculator can solve for any one missing value when you enter the other two values.
- Calculate IFOV: enter detector element size and focal length. The calculator divides detector size by focal length.
- Calculate detector element size: enter IFOV and focal length. The calculator multiplies IFOV by focal length.
- Calculate focal length: enter detector element size and IFOV. The calculator divides detector size by IFOV.
IFOV Angle Unit Conversions
These conversions are useful when comparing IFOV values in different angle units.
| Angle unit | Radians | Common use |
|---|---|---|
| 1 degree | 0.0174533 rad | Larger optical field angles |
| 1 arcminute | 0.000290888 rad | Fine angular resolution |
| 1 arcsecond | 0.00000484814 rad | Very small angular measurements |
Example IFOV Calculations
Example 1: Calculate IFOV
You have a detector element size of 0.025 mm and a camera focal length of 50 mm.
IFOV = D / F
IFOV = 0.025 / 50 = 0.0005 rad
The IFOV is 0.0005 radians. This is about 0.028648 degrees or 103.132 arcseconds.
Example 2: Calculate detector element size
You have an IFOV of 0.001 rad and a focal length of 75 mm.
D = IFOV * F
D = 0.001 * 75 = 0.075 mm
The detector element size is 0.075 mm.
FAQ
What does IFOV mean?
IFOV means instantaneous field of view. It is the angular field covered by one detector element or one pixel. A smaller IFOV means each detector element sees a smaller angle, which usually gives finer angular detail.
Why does the calculator use radians for the main formula?
The formula IFOV = detector size divided by focal length gives the angle in radians. Radians are the natural unit for this ratio because both length values cancel out. The calculator can then convert the radian result to degrees, arcminutes, or arcseconds.
Do detector size and focal length need to use the same length unit?
They need to be in the same unit before the formula is applied. The calculator handles this conversion automatically. For example, if detector size is entered in micrometer-scale millimeters and focal length is entered in centimeters, both are converted to a common length unit before calculating IFOV.
