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INTEGRATING SPHERE

Lighting Sciences Inc. one of the world's leading suppliers of test equipment for lighting manufacturers and laboratories, offers integrating sphere assemblies used for the measurement of the total luminous output of lamps.  With the optional spectrophotometer attachment, high speed measurement of spectral power distribution also can be made.

The integrating spheres are constructed in accordance with technical specifications, which provide compliance with the requirements of the IES of North America, SAE, and CIE.  spheres are available in a variety of sizes to accommodate lamps up to 1.5 meters maximum dimension.

The integrating sphere uses the principle of multiple internal reflections, and it is possible to show mathematically that the intensity of reflected light incident at any point on sphere surface is directly proportional to the total lumen output of the test lamp.

Features

• A precision photo-detector is embedded in the sphere surface, and a small screen is placed between the photo-detector and the light source to block direct light.  Thus, the photo-detector signal is proportional to the lumen output of the lamp.  The inside of the sphere is painted diffuse white with barium sulfate paint or equivalent, which is spectrally neutral (i.e. causes no color shift which would introduce inaccuracies).  The front of the photo-detector consists of a white diffuser which is flush with the sphere wall.

• The photo-detector signal is processed using a linear operational amplifier and is transmitted to an IBM-compatible computer.

• Calibration of the integrating sphere requires the use of standard lamps calibrated in terms of luminous flux, which are provided as accessories.  The standard lamps and test lamps are substituted in the sphere, and the test lamp output is calculated from the ratio of photo-detector readings applied to the known luminous output of hr standard lamps.  Calculations are performed automatically by the  system computer and lamp lumens are displayed.  Thus the operator does not need to be familiar with techniques for calibration, measurement and calculation of luminous flux; the computer software provides all the prompts and routines necessary.

• A source of inaccuracy in integrating sphere measurements is the absorption of light by objects such as lamp bases and even the lamps themselves, which may not be highly reflective.  To compensate for this, Lighting Sciences' spheres are equipped with an auxiliary lamp and screen which allows measurement of absorption losses, which are then applied to the readings by the computer, for highest accuracy.

Quality Control Capability

The computer software supplied with the Integrating Sphere is capable of savings readings to disk to provide for quality control monitoring.  Measured values are automatically saved to a file to perform data logging for each lamp type.  The data file is compatible with standard computer spreadsheet software to allow for further analysis.

Spectral Measurements

As an optional extra to the sphere, the high speed spectrophotometer system manufactured by Lighting Sciences Canada Ltd. can be added. The spectrophotometer is a CCD (Charge Coupled Device) measurement system which obtains near-instantaneous spectral data for the test lamp.  data is provided from 400 to 780 nm.

The spectrophotometer software is integrated with that of the sphere, allowing collection of spectral data simultaneously with lumen output.  Data provided includes CIE XY Chromatically Coordinates, Correlated Color Temperature (CCT).  Color Rendering Index (CRI) as well as Spectral Power Distribution.

Software

The sphere system and optional spectrophotometer operates in a windows '95 environment.  The  operator is guided through the test procedure and all computations are automatically provided.

Detailed Specifications could be obtained upon request.