The radiometric data shown at the end of this section was measured in our Standards Laboratory. The wavelength calibrations are based on our spectral calibration lamps. Irradiance data from 250 to 2500 nm is based on an NIST traceable calibrated quartz tungsten halogen lamp. We validated the measurements using calibrated detectors. We used a calibrated deuterium lamp for wavelengths below ~300 nm. In both cases, we use interpolation to infer the irradiance of the calibrated lamp at other than the discrete NIST calibration wavelengths. We measured each of the lamps to be calibrated, in the most favorable orientation.Fig. 1 QTH lamps with dense flat filaments have highest irradiance along the axis normal to the filament plane through the filament center. We orient the arc lamp so the seal-off tip and, in some cases, the starter wire does not interfere with the measurement.
The lamps are operated vertically and the measurement is made in the horizontal plane through the center of the radiating filament or arc. The lamps are rotated for maximum flux at the measurement site. This is particularly important for our planar filament quartz tungsten halogen lamps. At 0.5 m the flux density of all our lamps is uniform over at least a 25 x 25 mm2 area. As you move out of the plane but still maintain the same 0.5 m distance and face the source, the recorded power should in principle fall according to Lamberts Law for a planar source and remain constant for a point source. Measurements show something in between, with the arc lamps resembling point sources up to the electrode shadowing limit.Fig. 2 Set-up for a radiometric measurement.Fig. 3 Example of the spectral irradiance curves we show for our arc, quartz tungsten halogen, and deuterium lamps.
As you change the measuring distance from 0.5 m, the irradiance follows the inverse square law providing the distance, d, is larger than 20 to 30 times the radiating element size. The shortest distance we use in our measurements is 300 mm.
Working with Semi-Log Displays
The advantage of the semi-log display is the range our graphs cover, from very low levels to large peaks. Fig. 4 shows the linear display of the graph in Fig. 3. You get a much better sense of the height of the peaks, but the values at lower levels are lost.Fig. 4 Linear display of the graph shown in Fig. 3.Fig. 5 Calculating the FWHM from a log graph.
The logarithmic compression can be deceptive when it comes to estimating the area under a portion of the curve, to determine the total irradiance from λ1 to λ2, for example. You cannot rely on a rapid visual comparison unless you remember that the area at the bottom must be discounted appropriately. The peaks are much more important than they seem! So, you should calculate the area using the data values you read from the curve.
The logarithmic scale complicates estimation of the amount of irradiance in any peak. The half maximum is no longer halfway between the peak top and the bottom of the graph. You can easily find the half maximum by measuring the distance from 1 to 2, or 10 to 20, etc., on the logarithmic axis scale. Moving down this distance from the peak locates the half maximum (Fig. 5). We discuss the spectral peaks in the discussion on see Calculating Output Power.
How Good is the Data?
We measured the irradiance data on all our lamps using both multichannel detectors with our MS257 Spectrograph, and scanning monochromators. We used integrating spheres for most of the measurements. This effectively averages the polarization of the incoming radiation. Stress birefringence in the arc lamps and the filament structure of the lower power QTH lamps cause noticeable polarization of the output that may enhance or detract from your application.
We have a high degree of confidence in our data and cross check them with full radiant power meters and calibrated filters. The measurements are of lamps early in their life, operated in open air. Thermal conditions are different for lamps operated in lamp housings, and the spectral distribution changes slightly as the lamps age. Mercury lamps are particularly sensitive to thermal changes.
We see ±15% variation in output from lamp to lamp even within the same batch of lamps. We see substantially more variation in the UV output (<ca. 280 nm). Envelope materials, both for standard and ozone free versions, are continuously changing, and envelope thicknesses are not subject to tight tolerance.
In short, we believe that this set of data is the most comprehensive and reliable you will find for lamps of this type and are an excellent resource for first estimates. But don't base a tightly toleranced system design on the data without additional characterization of the lamp in its intended operating environment.
Finding the Right Spectral Irradiance Curve
Refer to Table 1 to find the model of a lamp you are interested in. You can then click on the model for the spectral irradiance graph and additional information and specifications.
Table 1 UV-IR Radiation Sources
|70620 and 63131
||~160 to 400 nm
||High Uniformity, Ozone Free, 30 W
|70623 and 63131
||High Uniformity, Full Spectrum, 30 W
|70621 and 63131
||High Irradiance, Ozone Free, 30 W
|70624 and 63131
||High Irradiance, Full Spectrum, 30 W
|70622 and 63131
||High Irradiance/ Stability, Ozone Free, 30 W
||200 to 2500 nm
||75 Watt Xenon Arc lamp
||75 Watt Xenon, High StabilityArc Lamp
||75 Watt Xenon, Ozone Free Arc Lamp
||100 Watt Xenon, Ozone Free Arc Lamp
||150 Watt Xenon UV Enhanced Arc Lamp (Ozone Producing)
||150 Watt Xenon Arc lamp (Ozone Free)
||150 Watt Xenon, UV Enhanced Arc lamp
||Xenon Arc Lamp, 150 W
||300 Watt Xenon Arc lamp (Ozone Free)
|| 450 Watt Xenon Lamp
||Replacement Lamp, 450 Watt Xenon Short Arc, Ozone Free
||450 Watt Xenon Lamp, UV Enhanced
||500 Watt Xenon Short Arc Lamp, Ozone Free
||1000 Watt Xenon, UV Enhanced Arc Lamp (Ozone Producing)
||1000 Watt Xenon Arc lamp (Ozone Free)
||1600 Watt Xenon, Ozone Free Arc Lamp
||200 to 2500 nm
||50 Watt Mercury Lamp
||100 Watt Mercury Arc Lamp
|| 200 Watt Mercury Lamp
||350 Watt Mercury Lamp
||500 Watt Mercury Lamp
||1000 Watt Mercury Lamp
||200 to 2500 nm
||Hg(Xe) Arc Lamp, 200 W
|| 200 Watt Hg(Xe) Lamp, Ozone Free
||500 Watt Hg(Xe) Lamp
||1000 Watt Hg(Xe) Lamp
||1000 Watt Hg(Xe) Lamp, Ozone Free
||1600 Watt Hg(Xe), Ozone Free Arc Lamp
||EmArcTM Enhanced Metal Arc
||200 to 2500 nm
|| 200 Watt EmArcTM Enhanced Metal Arc
||200 to 2500 nm
||Xenon Flash Lamp, 3 x 2.5mm Guided Arc, 0.32J, 16W, 1.6µs Pulse Width, 100 Hz
||Xenon Flash Lamp, 3 x 2.5mm Large Bulb, 5J, 60W, 9µs Pulse Width, 60 Hz
||Quartz Tungsten Halogen
||240 to 2700 nm
|| 10 Watt Quartz Tungsten Halogen
|| 20 Watt Quartz Tungsten Halogen
|| 50 Watt Quartz Tungsten Halogen, Short Filament
||50 W, Quartz Tungsten Halogen, Long Filament,
|| 100 Watt Quartz Tungsten Halogen
||250 Watt Quartz Tungsten Halogen
||600 Watt Quartz Tungsten Halogen Lamp
||1000 W Quartz Tungsten Halogen
||1000 W QTH
||1 to 25 µm
||IR Emitter, 140 W Element
||Infrared Ceramic Element, 22 Watt
||Low Cost Infrared Element, 9 Watt
||Miniature Infrared Element, 0.8 Watt, Miniature
||24 W SiC Source Element
Spectral Irradiance Data
Spectral irradiance curves for our lamps and solar simulators can be found below. Please review Using the Spectral Irradiance Curves for more information on how to use the curves.