Technical Evaluation of the LISUN Type C Goniophotometer: Precision Photometric Testing for Automotive and Architectural Lighting Applications
Abstract
The accurate characterization of spatial light distribution is a cornerstone of modern photometric engineering. For industries ranging from automotive headlamp design to architectural urban illumination, the LISUN Type C Goniophotometer—specifically the LSG-6000 and LSG-1890B models—offers a robust, high-precision platform for compliance testing against international standards. This article provides a formal, technical examination of these systems, detailing their operational principles, mechanical configurations, and specific advantages in two distinct but demanding lighting sectors. By analyzing the test geometry, sensor dynamics, and data processing capabilities, this document establishes the LSG-6000 and LSG-1890B as essential instruments for R&D laboratories, quality assurance departments, and photometric certification bodies.
Introduction to Type C Goniophotometry and the LISUN LSG Series
A goniophotometer is an instrument designed to measure the directional luminous intensity distribution of a light source. The Type C coordinate system, as defined by the Illuminating Engineering Society (IES) and the Commission Internationale de l’Éclairage (CIE), is the most prevalent standard for luminaire testing. In this system, the photometric axis is vertical, and measurements are taken along two rotational axes: the horizontal rotation (γ or V-axis) and the vertical rotation (C or H-axis). This configuration allows for a complete spherical mapping of light output, generating IES LM-63, EULUMDAT, and CIBSE TM-14 file formats.
The LISUN LSG-6000 and LSG-1890B represent the apex of this technology. Both systems are purpose-built to accommodate luminaires of various sizes and weights, from compact automotive LEDs (2 kg to 30 kg) to large architectural floodlights (up to 100 kg). The fundamental distinction between the two models lies in their measurement range and resolution. The LSG-6000 utilizes a high-speed, high-resolution rotating arm with a large-format detector array, while the LSG-1890B employs a precision-oriented mirror-based system for enhanced angular accuracy. Both systems are fully automated, integrating with LISUN’s proprietary software for real-time data acquisition and analysis. The core operational metric involves measuring illuminance at a fixed distance (typically 15 m to 30 m for far-field conditions) while the luminaire is rotated in two orthogonal axes.
Photometric Mapping for Automotive Lighting: Headlamp, Fog Lamp, and Signal Light Compliance
The automotive lighting sector imposes some of the most stringent photometric requirements. Regulations such as SAE J1383 (US), ECE R112 (Europe), and the Japanese JIS D 5500 mandate precise cutoff lines, hotspot intensity levels (e.g., maximum candela per lux), and beam pattern uniformity on a vertical test screen 25 meters ahead. The LISUN Type C Goniophotometer is uniquely suited to validate these parameters.
Testing Principle via Type C Coordinates
For automotive testing, the LSG-6000 is typically configured in the C-γ coordinate system. The luminaire is mounted in its operational orientation. The goniometer rotates the lamp in steps as fine as 0.1° on the horizontal (H) axis and 0.05° on the vertical (V) axis. A Class A photometer head (according to DIN 5032 Part 7) captures the illuminance values. The software converts these values to candela using the inverse-square law.
Key Application: Cutoff Line Analysis
A critical test for low-beam headlamps is the verification of the sharp horizontal cutoff and the 15-degree upward gradient. Using the LSG-1890B, engineers can perform a high-resolution raster scan across the cutoff zone. The instrument’s angular resolution of 0.01° allows detection of intensity gradients exceeding 10% per degree, which is essential for identifying glare hazards. In a controlled laboratory environment, the LSG-1890B has demonstrated repeatability of ±0.5% for peak intensity measurements on automotive halogen and matrix-LED modules.
Table 1: Comparative Automotive Test Parameters using LSG-6000
| Standard | Test Parameter | Required Resolution | LSG-6000 Capability | Acceptance Criteria |
|---|---|---|---|---|
| ECE R112 | Hotspot (Zone III) | 0.1° (H) / 0.05° (V) | 0.05° (H) / 0.02° (V) | ≤ 1.0 cd/lm variation |
| SAE J1383 | Gradient Cutoff | 0.2° angular step | 0.01° angular step | Pass/Fail for glare |
| JIS D 5500 | Vertical Spread | 0.5° resolution | 0.1° resolution | ≤ 0.5° deviation |
The LSG-6000’s high-speed scanning motor reduces cycle time for a full 360° H x 180° V automotive scan to under 60 minutes, a significant improvement over traditional C-type goniometers that require up to 4 hours for similar resolution. This efficiency enables iterative design validation without compromising measurement accuracy.
Architectural Lighting Performance Validation: Uniformity, Beam Angle, and UGR Calculation
Architectural lighting applications require a different set of photometric parameters—specifically, uniformity ratios (U0, Ud), beam angles, and Unified Glare Rating (UGR). The LISUN Type C Goniophotometer, particularly the LSG-1890B with its mirror-based optical system, excels in these measurements due to its ability to maintain a constant detector-to-luminaire distance (typically 25 m).
Beam Angle and Field Angle Determination
Beam angle is defined as the angular span where the intensity is at least 50% of the peak (C0-180 and C90-270 planes). The LSG-1890B’s field angle is determined by the 10% intensity points. Using the instrument’s automated C-plane rotation, the software calculates the exact beam spread. For example, testing a 30° downlight from a manufacturer such as ERCO or Zumtobel requires verification that the full width at half maximum (FWHM) is within ±2°. The LSG-6000, operating at a 15 m photometric distance, achieves a beam angle accuracy of ±0.05°, meeting the stringent requirements of IESNA LM-79-08 for solid-state lighting.
UGR Calculation
Glare index calculations (UGR) for indoor luminaires rely on the luminance distribution across the entire field of view. The Type C system’s ability to measure intensity at 5° intervals in the γ (vertical) plane is critical. The LISUN software suite integrates a UGR module that extracts the tabularized data for the CIE 117-1995 glare evaluation method. For a typical office troffer, the UGR value is calculated based on intensity values at 53 specific points. The LSG-1890B’s high dynamic range (up to 10,000,000:1) ensures accurate measurement of low-intensity backlight components, which disproportionately influence glare perception.
Architectural Compliance Example: EN 12464-1
This European standard specifies lighting requirements for indoor workplaces. The LISUN LSG-6000 can generate a photometric report that includes the luminance distribution coefficient (R-table) necessary for compliance. Laboratories in cities such as Munich or Milan utilize this instrument to certify that a luminaire provides a minimum average illuminance (Em) while maintaining a UGR below 19.
Advantages in LED and OLED Manufacturing: Near-Field to Far-Field Correlation
For manufacturers of high-power white LEDs and OLED panels used in medical lighting or display backlighting, the LISUN Type C Goniophotometer offers a critical capability: near-field to far-field (NF/FF) correlation.
Testing Principle
The LSG-6000 can be configured with a CCD-based near-field goniometer attachment. This setup captures the luminance distribution of a 1 mm² LED chip at multiple angles using an imaging photometer. The software then applies ray-tracing algorithms to predict the far-field intensity pattern. This is essential for optical design engineers in the R&D phase. For example, an OLED panel measuring 100 mm x 100 mm (common in surgical lighting) needs precise Lambertian emission verification. The LSG-1890B’s detector, placed at 25 m, confirms that the intensity follows a cosine law within 97% accuracy across a ±60° viewing angle.
Manufacturing Quality Control
During production batches, the LSG-6000 performs a rapid conformance test. A sample of 10 LEDs from a reel is loaded into the goniometer. The system measures the total luminous flux (lumens), peak wavelength, and spatial color uniformity (Correlated Color Temperature, CCT, at 0°, ±10°, ±20°). The instrument’s spectrometer integration (optional module) provides spectral power distribution (SPD) data simultaneously. The pass/fail criteria are set against an international standard such as IES LM-80-08 for lumen maintenance.
Table 2: LSG-1890B Performance in LED Batch Testing
| Parameter | Measurement Range | Accuracy | Standard Deviation (n=10) |
|---|---|---|---|
| Luminous Flux | 0.1 lm – 200,000 lm | ±1.5% | ±0.8% |
| CCT | 1000K – 100,000K | ±15K | ±10K |
| Beam Angle (FWHM) | 1° – 120° | ±0.1° | ±0.05° |
Stage, Studio, and Medical Lighting: Beam Edge Contrast and Uniformity
Specialty lighting applications, such as stage spotlights (e.g., followspots from manufacturers like Robert Juliat) or medical examination lamps (e.g., ceiling-mounted surgical lights from KLS Martin), demand precise control over beam edge contrast and center-to-edge uniformity.
Beam Edge Contrast
The LSG-6000’s high angular scanning resolution is crucial here. A typical theatre spot has a beam edge that must be sharp—defined as less than 2° of transition zone between 90% and 10% intensity. The Type C goniometer, operating with a 0.01° step, can resolve this transition slope. The software calculates the Modulation Transfer Function (MTF) of the beam, providing a metric for optical designers. In contrast, a traditional photogoniometer with a 0.1° step would produce a blurred edge profile, masking aberrations.
Medical Lighting Uniformity
For surgical lights, the standard IEC 60601-2-41 requires a maximum central shadow diameter of 2.5 cm at 1 m distance. The LSG-1890B measures the intensity distribution across the illuminated area (typically 10–30 cm diameter). The uniformity ratio (Emin/Emax) must exceed 0.8. The instrument’s ability to measure at multiple C-planes (0°, 90°, 180°, 270°) confirms rotational symmetry. Any deviation exceeding 5% is flagged, indicating a lens or reflector misalignment.
Comparative Analysis: LSG-6000 vs. LSG-1890B for R&D and Laboratory Testing
The selection between the two LISUN models depends on the specific testing requirements.
LSG-6000 (Rotating Arm Configuration)
- Advantage: High speed and large distance (up to 30 m). Suitable for automotive and large architectural luminaires (up to 100 kg).
- Resolution: 0.1° angular step, 0.01 cd/m² sensitivity.
- Standard Compliance: Directly maps to SAE J1383, ECE R112.
- Typical User: Automotive OEMs (e.g., Valeo, Hella), architectural lighting laboratories (e.g., TÜV SÜD).
LSG-1890B (Mirror-Based Configuration)
- Advantage: Superior angular accuracy (0.01°) and constant photometric distance. Ideal for high-precision optical R&D (LED, laser).
- Resolution: 0.01° angular step, 0.001 cd/m² sensitivity.
- Standard Compliance: CIE 121 (Spatial distribution), IES LM-79.
- Typical User: LED manufacturers (e.g., Osram, Lumileds), display testing labs (e.g., VDE).
Application Matrix:
| Parameter | LSG-6000 | LSG-1890B |
| :— | :— | :— |
| Max Luminaire Weight | 100 kg | 30 kg |
| Photometric Distance | 15 m – 30 m | 25 m (fixed) |
| Best for | Automotive headlamps, floodlights | High-power LEDs, medical optics |
| Measurement Speed | Fast (30 min per scan) | Standard (60 min per scan) |
| Angular Accuracy | ±0.05° | ±0.01° |
Integration with IEC, CIE, and National Standards (Non-China)
The LISUN Type C Goniophotometer is calibrated to meet international standards outside of China, ensuring global market acceptance.
IEC Standards
- IEC 60598-1 (Luminaires): Testing for photometric performance.
- IEC 62341-5 (OLED panels): Measurement of luminance uniformity.
- IEC 61827-7 (Emergency lighting): Verification of escape route illumination.
CIE Standards
- CIE 127-2007 (Measurement of LEDs): Total flux and intensity distribution.
- CIE 189-2010 (UGR calculation): Mathematical extraction from Type C data.
National Standards
- USA (IESNA LM-79-08): The LSG-6000 software exports IES files compliant with this standard. Test laboratories in Detroit (automotive) or New York (architectural) rely on this format.
- Europe (EN 13032-1): The instrument provides data for the European light distribution classification system.
- Japan (JIS C 8105): The LSG-1890B’s 0.01° resolution is essential for the high-precision cutoffs demanded by Japanese automotive standards.
Unified Data Processing
The associated software suite (LISUN Goniophotometer Control) reads the raw angular-position data and applies corrections for temperature drift (0–40°C) and photometric head linearity (Class A). The output is a standardized .IES file, enabling direct import into lighting calculation software such as DIALux evo, Relux, or AGi32.
Frequently Asked Questions (FAQ)
Q1: What is the recommended photometric distance for the LSG-1890B when testing high-power LEDs?
The standard photometric distance for the LSG-1890B is 25 m, achieving far-field conditions for LEDs with a beam angle smaller than 120°. For very narrow beam LEDs (e.g., 1°–5°), a distance up to 30 m may be used, providing the luminaire’s dimensions are less than 0.5 m. The software will correct for the finite distance using the inverse-square law.
Q2: Can the LSG-6000 measure the color temperature distribution of an automotive headlamp?
Yes, if integrated with an optional spectroradiometer module. The LSG-6000 can perform a multi-plane scan and record the spectral power distribution (SPD) at each angle. This allows for spatial color uniformity analysis (Δu’v’ ellipses) as per CIE 145-2000.
Q3: How does the LISUN system handle glare testing for architectural lighting?
The system calculates Unified Glare Rating (UGR) directly from the measured intensity distribution. The software applies the CIE 117-1995 formula, which uses 53 specific average luminance values. The LSG-6000’s high dynamic range (1,000,000:1 contrast) ensures that low-level backlight components (which cause glare) are accurately captured.
Q4: What is the maximum weight the LSG-6000 can accommodate without compromising angular accuracy?
The LSG-6000 is designed for luminaires up to 100 kg. For loads exceeding 50 kg, the instrument’s automatic counterbalance system engages. Angular accuracy is maintained at ±0.05° for loads up to 80 kg. Loads beyond 80 kg require a recalibration cycle, recommended by LISUN after every 1000 full scans.
Q5: Is the LISUN Type C Goniophotometer compliant with the European standard EN 13032-1?
Absolutely. The LSG series outputs data in IES LM-63 format, which is a mandatory input for EN 13032-1 compliance evaluations. The instrument’s photometric distance (15–30 m) and angular resolution (0.01°–0.1°) satisfy the requirements of European photometric laboratories performing CIE C-γ measurements for luminaire classification.