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Spectrums

Spectrum Description​

Spectrums is the fourth child-element of GeneralDefinitions - the part in the XML where global and reusable elements are defined (imagine them as the building blocks of each luminaire). The definition of spectrums is optional.

A spectrum in the GLDF can be defined in two ways

  1. Through a table with an assignment of intensities to wavelengths, inside the GLDF XML iteself
  2. Through a File reference containing a well-formed spectrum definition, outside the GLDF XML

Location in XSD​

Spectrum location in XSD

XSD description​

Spectrums in XSD

1. Spectrum within GLDF XML​

The first option to define a spectrum is within the GLDF XML as follows

Spectrum inside XSD XML

Simply add a collection of Intensity elements, in which the wavelenth attribute determines the wavelength in nanometer. And the content of the element the intensity of the wavelength.

<?xml version="1.0" encoding="UTF-8"?>
<Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="https://gldf.io/xsd/gldf/1.0.0-rc.3/gldf.xsd">
  <Header/>
  <GeneralDefinitions>
    <Spectrums>
      <Spectrum id="spectrum1">
        <Intensity wavelength="380">0.03</Intensity>
        <Intensity wavelength="385">0.08</Intensity>
        <Intensity wavelength="390">0.12</Intensity>
        <!-- snip wavelength 395-775 -->
        <Intensity wavelength="780">0.02</Intensity>
      </Spectrum>
    </Spectrums>
  </GeneralDefinitions>
  <ProductDefinitions/>
</Root>

2. Spectrum through File reference​

A Spectrum can also reference a File element which describes the location of the spectrum content file.

<?xml version="1.0" encoding="UTF-8"?>
<Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="https://gldf.io/xsd/gldf/1.0.0-rc.3/gldf.xsd">
  <Header/>
  <GeneralDefinitions>
    <Files>
      <File id="spectrumFile" contentType="spectrum/text" 
            type="url">https://example.org/spectrum.txt</File>
    </Files>
    <Spectrums>
      <Spectrum id="spectrum1">
        <SpectrumFileReference fileId="spectrumFile" />
      </Spectrum>
    </Spectrums>
  </GeneralDefinitions>
  <ProductDefinitions/>
</Root>

The Spectrum Element above references a spectrum File stored online, in this fictitious example at example.org/spectrum.txt. Spectrum files must conform to a specific formatting in order to be processed.

The spectrum file...

  • must be a text file
  • contain the assignment of wavelengths to intensities
  • each assignment must be written in a new line
  • wavelengths and intensities must be separated by a specific character
caution

The character between wavelength and intensity must be a single whitespace or a single tabulator!

  • is usually within the range of 380-780(nm), which corresponds to a textfile with 81 lines

An abbreviated example:

380  0.003720622
385  0.003494165
390  0.002572627
780  0.0001542017
tip

A complete spectrum example file can be downloaded here: Mercury-Vapor-Lamp.txt

Referencing a spectrum​

Once declared, all spectrums can be referenced in subsequent XML elements via their id attribute one or several times.

<?xml version="1.0" encoding="UTF-8"?>
<Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="https://gldf.io/xsd/gldf/1.0.0-rc.3/gldf.xsd">
  <Header/>
  <GeneralDefinitions>
    <Files>
      <File id="spectrumFile" contentType="spectrum/text" type="url">https://example.org/spectrum.txt</File>
    </Files>
    <Spectrums>
      <Spectrum id="spectrum1">
        <SpectrumFileReference fileId="spectrumFile" />
      </Spectrum>
    </Spectrums>
    <LightSources>
      <ChangeableLightSource id="lightSource1">
        <Name>
          <Locale language="en">Light source with spectrum</Locale>
        </Name>
        <RatedInputPower>10</RatedInputPower>
        <SpectrumReference spectrumId="spectrum1" />
        <RatedLuminousFlux>80</RatedLuminousFlux>
      </ChangeableLightSource>
    </LightSources>
  </GeneralDefinitions>
  <ProductDefinitions/>
</Root>

The Spectrum with id spectrum1 (line 9) is referenced once inside the subsequent element ChangeableLightSource through the element SpectrumReference. And defines the light source's spectrum in this way (line 19)