Adaptive HELIOS® Uniform Source with Filter Wheels

September 13, 2022

The Technical 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.

The Challenges, and Labsphere’s Solution

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

The Results

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