Adaptive HELIOS Uniform Source with Filter Wheels

September 25, 2021

Situation

A client needed to perform important calibrations on a hyperspectral sensor they were developing to be used in satellites and drones to detect anomalies a standard camera couldn’t. In addition to standard white-light testing, they intended to perform other specific tests using NIST-calibrated absorption filters over the light sources. This client had used a similar uniform source system in the past, however; new developments required a wider aperture and subsequently, a larger sphere.

Challenges and Action

A standard Labsphere HELIOS system is capable of achieving the desired radiance using a selection of lamps and detectors. However, with the inclusion of NIST’s filters, some unique features needed to be incorporated to keep the system reliable and easy to use.

  • Four halogen lamps positioned symmetrically around the exit port
  • Filter wheels with six slots to fit an open aperture and up to five NIST filters – operated with simple button controls
  • Air cooling system to control the heat generated by the lamps
  • Air intake is filtered and blown directly to the filter wheel through flexible duct tubes
  • Three additional lamps to achieve the requested spectral radiance
  • Variable attenuator for continuous adjustability
  • Adapter for client’s spectrometer
  • Silicon and InGaAs detectors for readings across the full active spectrum
  • Both equipped with light-tight filter and aperture sliders featuring pin-hole and dark shutter, as well as a photopic filter and slot for an additional filter

Results

Benefits

  1. With the application-specific mounts built for the filter wheels, the client is able to apply and use their filters easily
  2. The cooling system prevents any heat damage from occurring to the filters
  3. Labsphere exceeded the client’s spectral requirements, ensuring that they can perform any test they need
  4. With 98.1% spatial and 96.2% angular uniformity, the system ensures accurate results on every test
  5. Broad spectral control and availability, allowing easy adjustment of spectral radiance, color temperature, and wavelength distribution with Labsphere’s HELIOSense software
  6. Labsphere was able to design, build, test, and ship the system within a tight deadline of just over two months