MEASUREMENT OF RAY DATA OF AN LED USING THE GONIOPHOTOMETER RIGO801-LED

Measurement Principle

Mounting the LED on the Test Fixture

The LED is mounted on the goniophotometer's test fixture. The fixture includes a heat sink (75 mm x 75 mm) with a threaded grid plate, a fan, and a leveling unit. The heat sink ensures stable thermal conditions, with the fan activated as needed.

Aligning the LED in the Goniometer Coordinate System

The Theta and Phi axes of the goniophotometer define a spherical coordinate system linked to a Cartesian coordinate system. Ray data are output within this system, making it essential to document and precisely align the LED. Using the Measurement - Align Measuring Object function, the LED can be accurately positioned. A dialog displays the camera image with the coordinate system and provides controls for the goniometer axes. The camera is aligned along the Cartesian axes to capture images for positioning and leveling.

Camera Images with Coordinate System for Alignment

The horizontal alignment is performed using the X/Y adjustment unit of the telescopic axis. Height and rotation are adjusted by moving the telescopic tube, while leveling is done with the integrated leveling unit of the test fixture.

Key Positioning Guidelines:

• The center of the light-emitting area or volume should be positioned as centrally as possible due to the lens's limited depth of field.
• Rotation and leveling of the LED should be based on clearly identifiable edges or contours.
• Alignment features should match datasheet drawings or CAD data to precisely determine the position of the coordinate center.

Setting Up the Measurement

The measurement program then guides the user step by step through various dialogs to configure the settings and input details for the measurement.

Angular Range and Resolutions

The angular range should cover the relevant emission area. Typically, this includes ±90°, but many LEDs, like in this case, emit over a larger range. Beyond 90°, higher luminance levels occur, which, although secondary emissions, are crucial for realistic emission characterization. Here, ±100° was chosen, as shading from the circuit board or fixture occurs beyond this point. An elevated mounting position would have been beneficial but was not applied in this test measurement.

The angular resolutions of the goniometer axes are typically 0.5° or 0.75°, enabling precise sampling. Thanks to on-the-fly measurement, the duration remains relatively short at about 1.5 to 2 hours.

Camera settings

The camera settings include integration (exposure) time, ND filter, and, for filter wheel cameras, the filter position (here, the V(λ) filter). The integration time is set at the position of maximum luminance using a maximum scan. To achieve an optimal dynamic range, the utilization should be around 90%, which was achieved here with 10 ms.

Monitoring of Stabilization Phase

Setting the Start Procedure

The light source must be stable before starting the measurement. Two start options are available:

• Delay Time: A fixed interval before the measurement starts..
• Automatic Stability Monitoring: Following CIE S 025 [8] or IES LM-79-19 [9], the illuminance is monitored, and the measurement starts automatically once the stability threshold (recommended: 0.2% for LEDs) is reached.

LID 3D View

Measurement Results

The measurement results are provided in two files:

• TTL File: ASCII INI format containing the luminous intensity distribution, measurement details, and parameters. Export formats include IES LM-63 [10], EULUMDAT, and ASCII. Further information can be found in the measurement and software manuals.
• TTR File: Contains ray data, additional data, and TTL content. Post-processing is supported by the free TechnoTeam Converter801 software, which exports ray data into formats such as IES TM-25 [11], ASAP, Speos, LightTools, LucidShape, Zemax, and TracePro.

Für die Strahlengenerierung sind spezifische Einstellungen erforderlich, die in der TTR-Datei gespeichert werden können, um externe Nutzung ohne Zusatzkenntnisse zu ermöglichen. Details dazu werden in einer separaten Application Note erläutert.

Download

References