Measuring Light in Colors Other Than White|
Article - March 14, 2016 By LarsonElectronics.com
Measuring Light in Colors Other Than White
Lighting manufacturers have several tools at their disposal for measuring light in colored fixtures. Such devices capture specific wavelengths or bands within the visible electromagnetic spectrum that colored lights emit during output. For example, when viewed using a spectrometer, an LED light with a high color temperature rating appears to generate generous amounts of blue and yellow wavelengths.
This article provides information on three light measuring tools that are widely used on professional and industrial levels. The devices are ranked according to accuracy and technical features.
Spectroscopes or spectrometers measure a light source’s spectrum via diffraction grating. Such devices are used in the field of spectroscopy, or the study of light dispersion, interaction and energy. On the most basic level, it is possible to build a DIY spectroscope using a tube, mirrors and a compact disc panel. But for professional and accurate measurements, one would need to use a manufactured, high-quality spectroscope with digital measuring features.
During operation, one initiates a reading by pointing the unit at a light source. The beam of light enters the device and is “dissected” as it goes through diffraction grating, which acts like a prism by breaking down the beam into different bands. The end result is an array of colored wavelengths that make up the source’s illuminative characteristics. It is important to consider that a spectroscope can handle colored light sources. For instance, when viewing a yellowish candle flame through a spectroscope, one will be able to see dominant red and orange bands, with weak green wavelengths and almost no blue. Applying salt on the wick of the candle will allow one to see a clear, thick orange emission line. In another example, shining a red discharge tube on a spectrometer will generate distinct red bands and hazy or faded orange wavelengths.
A chromameter is a portable, handheld device that is capable of measuring standard light sources, including LEDs, halogens and incandescent fixtures. Furthermore, it can also handle colored light sources, such as a yellow CFLs and red bulbs. Using a sensor, the unit acts like a spectroradiometer, but it is important to consider that it does not provide spectral data. An advantage to using a chromameter for light measurements is its ability to be utilized remotely, outside of a testing lab or facility. This tool is ideal for measuring light in the visible spectrum, between 390 nm and 700 nm.
From a distance, the small machine looks like a small digital camera. Operators may point and shoot at various light sources (such as colored automotive luminaries, colored LED billboards and outdoor light panels) to capture data in real-time. It may also be plugged into a laptop or computer, for further data processing using analysis software. The type of light measurements one can view using a chromameter includes the following: illuminance levels, chromaticity, color temperature and dominant wavelengths.
A spectroradiometer is a superior light measuring device that is used to analyze a light source’s spectral characteristics. Compared to the other two options above, this is the most accurate tool for colored and white lights. In most cases, a spectroradiometer is incorporated with other powerful measuring machines, like an integrating sphere or a near-field goniophotometer (the spectroradiometer processes signals between the main measuring machine and the analysis software). It is possible to use the instrument without other supporting devices, and portable variants allow operators to take accurate measurements on the field in real-time.
There are some drawbacks with relying on a spectroradiometer for colored light measurements. By comparison (with the other two tools above), this one is the most expensive. However, it does come with very accurate data gathering features; and when paired with a robust analysis software, one could display almost all types of light measurement information for research and testing, such as CCT, dominant wavelengths, absorption, reflectance, illuminance and spectral characteristics. Next, a spectroradiometer can lose its portable features when it is attached to large, bulky components, like an integrating sphere. When catering to complex configurations, one is forced to use the device in a lab or small room.