Fundamental Principles of Goniophotometric Measurement

A goniophotometer is a precision optical instrument designed to measure the spatial distribution of light emitted from a source. The device operates by rotating a photodetector or the light source along one or more axes to capture luminous intensity at varying angles. This enables the generation of a three-dimensional radiation pattern, critical for evaluating parameters such as luminous flux, beam angle, and candela distribution.

The core measurement principle relies on the inverse-square law, where the detector records luminous intensity at fixed distances while maintaining angular precision. The system integrates a spectroradiometer or photopic-filtered photodetector to ensure spectral accuracy, complying with international standards such as CIE 70, IES LM-79, and IEC 61341.

Mechanical and Optical Architecture of a Goniophotometer

Modern goniophotometers, such as the LISUN LSG-6000, employ a dual-axis rotational mechanism to facilitate full spherical photometry. The instrument consists of:

• Rotating Arm Mechanism: A motorized goniometer arm that positions the detector at precise azimuthal (horizontal) and elevation (vertical) angles.
• Fixed or Movable Light Source Mount: Depending on configuration, the luminaire under test (LUT) may remain stationary while the detector moves, or vice versa.
• High-Sensitivity Photodetector: A CCD array or silicon photodiode calibrated to CIE photopic response (V(λ) curve) for accurate luminous intensity measurement.
• Environmental Control: Darkroom or baffle systems to minimize stray light interference.

The LSG-6000 features a Type C goniophotometer design (moving detector, fixed light source), optimized for high-accuracy testing of LED modules, automotive lighting, and street luminaires.

Compliance with International Photometric Standards

Goniophotometric testing adheres to stringent regulatory frameworks, ensuring consistency across industries. Key standards include:

• IEC 61341: Specifies center-beam intensity and beam angle measurements for reflector lamps.
• IES LM-79: Governs electrical and photometric testing of solid-state lighting products.
• CIE 70: Defines goniophotometry of luminaires for intensity distribution and glare evaluation.
• ANSI C78.377: Standardizes chromaticity and color consistency in LED lighting.

The LSG-6000 complies with these standards, making it suitable for global certification processes, including ENEC (Europe), UL (North America), and JIS (Japan).

Applications in LED and OLED Manufacturing

In LED production, goniophotometry ensures uniformity in beam spread and color consistency. Manufacturers utilize the LSG-6000 to:

• Verify far-field intensity distribution for automotive headlamps (SAE J575).
• Characterize OLED panel angular emission profiles for display uniformity.
• Optimize secondary optics in horticultural LED grow lights (DLC QPL requirements).

Advanced Use Cases in Display and Photovoltaic Testing

For display manufacturers, goniophotometers assess viewing-angle performance of LCDs and microLEDs. The LSG-6000 measures:

• Luminance fall-off at oblique angles (ISO 13406-2 for display defects).
• Angular color shift in medical-grade monitors (IEC 60601-1-8).

In photovoltaics, the instrument evaluates anti-glare coatings and light-trapping structures in solar panels (IEC 60904-9).

Competitive Advantages of the LSG-6000 Goniophotometer

The LSG-6000 distinguishes itself through:

• High Angular Resolution (0.1° step precision): Critical for narrow-beam optics testing.
• Automated Multi-Axis Control: Reduces operator error in large-scale testing.
• Modular Spectroradiometer Integration: Supports spectral power distribution (SPD) analysis per CIE 015:2018.
• Wide Dynamic Range (0.001 cd to 2,000,000 cd): Accommodates low-luminance medical devices and high-intensity stadium lights.

FAQ Section

Q1: What is the maximum sample size supported by the LSG-6000?
The LSG-6000 accommodates luminaires up to 2 meters in length and 300 kg in weight, with customizable fixtures for irregular shapes.

Q2: How does the LSG-6000 ensure compliance with LM-79’s total flux requirements?
It employs an absolute calibration method using an integrating sphere reference, traceable to NIST or PTB standards.

Q3: Can the LSG-6000 measure flicker in LED lighting?
Yes, when paired with a high-speed photodetector, it assesses temporal light modulation per IEEE 1789-2015.

Q4: What industries benefit most from Type C goniophotometers?
Automotive, aerospace, and architectural lighting, where directional intensity profiling is critical.

Q5: Does the LSG-6000 support near-field goniophotometry?
No, it is optimized for far-field measurements (>5x the largest dimension of the LUT). For near-field analysis, a specialized scanner is required.