Working principle
An integrating sphere is a hollow cavity whose inner wall is coated with a near-perfect diffuse (Lambertian) reflector. Light entering the sphere undergoes multiple diffuse reflections, so the irradiance on any point of the wall becomes proportional to the total flux entering the sphere — independent of the source's spatial distribution or beam shape. A detector viewing the wall (shielded from direct illumination by a baffle) therefore reads a signal directly proportional to total luminous or radiant flux.
Why the coating matters
PTFE-based coatings offer >97% reflectance from 250 nm to 2500 nm. Higher reflectance increases the sphere multiplier (average number of reflections), improving both throughput and spatial uniformity. Coating choice also sets the usable spectral range — UV-grade, gold and standard PTFE coatings each cover different bands.
Selecting a sphere
- Diameter: as a rule of thumb, total port area should stay below 5% of the sphere's inner surface; larger samples or lamps need larger spheres to keep uniformity.
- Ports: define the measurement geometry (2π/4π flux, reflectance, transmittance). Confirm port sizes and positions before ordering.
- Baffles: prevent first-reflection light from reaching the detector directly. Removable baffles allow reconfiguration.
- Detector: a factory-calibrated photodiode or fiber assembly with a traceable certificate removes one whole layer of uncertainty.
Checklist before ordering
- Source type and maximum dimension (lamp, LED, panel?).
- Quantity to measure — flux, reflectance, transmittance or irradiance.
- Spectral range of interest.
- Required detector and calibration documentation.
Hangxin HX-IS and HX-JFIOS series spheres cover 50–500 mm with configurable ports, baffles and pre-calibrated detectors. Contact our application engineers with your geometry and we will recommend a configuration.