{"id":9272,"date":"2026-07-18T17:45:41","date_gmt":"2026-07-18T09:45:41","guid":{"rendered":"https:\/\/www.ledtestsystem.com\/?p=9272"},"modified":"2026-07-18T17:45:41","modified_gmt":"2026-07-18T09:45:41","slug":"standard","status":"publish","type":"post","link":"https:\/\/ledtestsystem.com\/it\/blog-2\/standard\/","title":{"rendered":"Standard"},"content":{"rendered":"

Title:<\/strong> Precision Luminance Distribution Metrology: Application of the LISUN<\/a> LSG-1890B Goniophotometer in Compliance-Driven Photometric Testing<\/p>\n

Abstract<\/strong><\/p>\n

The accurate characterization of spatial luminance distribution is a fundamental requirement in contemporary photometry, underpinning the design, certification, and performance validation of lighting and optical systems. This article presents a technical examination of the LISUN LSG-1890B Goniophotometer Test System, a precision instrument employed for high-fidelity measurement of luminous intensity distribution, luminous flux, and colorimetric uniformity. The discussion outlines the operating principles of goniophotometry, details the specific electro-mechanical configuration and metrological specifications of the LSG-1890B, and evaluates its utility across multiple industrial sectors\u2014including general lighting, medical optics, photovoltaic concentrator systems, and automotive signaling\u2014through the lens of applicable international standards (IEC, CIE, IESNA, and other national frameworks exclusive of China). Emphasis is placed on measurement uncertainty, traceability, and compliance verification. A comparison with alternative goniometric architectures (e.g., mirror-based or rotating detector systems) is provided to elucidate the competitive advantages of the LSG-1890B\u2019s design.<\/p>\n

1. Optical Bench Configuration and the Principle of Rotating Goniometer Photometry<\/strong><\/p>\n

The determination of a light source\u2019s photometric performance necessitates the measurement of luminous intensity as a function of angular position\u2014a process formalized under the CIE 121-1996 standard for the measurement of luminous flux and intensity distribution. The LSG-1890B implements a Type C goniometric configuration, wherein the luminaire under test undergoes rotation about two orthogonal axes (polar and azimuthal). This methodology adheres to the principle of maintaining a fixed distance between the photometric detector and the light center of the test sample, thereby eliminating errors associated with inverse-square law deviations.<\/p>\n

In the LSG-1890B, the mechanical stage employs a horizontal polar axis and a vertical azimuth axis, allowing for continuous measurement across the entire 4\u03c0 or 2\u03c0 steradian solid angle. The angular positioning system utilizes stepper motors with optical encoder feedback, achieving an angular resolution of 0.1\u00b0 and a positioning accuracy of \u00b10.05\u00b0. This precision is critical for characterizing narrow-beam luminaires, such as those used in stage spotlights or medical surgical lamps, where beam widths may be sub-10\u00b0. The instrument\u2019s near-field goniophotometric capability, supported by a motorized positioning stage with a minimal step of 0.01\u00b0, enables detailed spatial luminance mapping at distances as close as 0.5 meters, a feature pertinent for display and sensor component evaluation.<\/p>\n

2. Spectral Photometric Integration and Luminous Flux Determination<\/strong><\/p>\n

Accurate total luminous flux measurement relies on integrating the measured luminous intensity values over all angular positions. The LSG-1890B employs a high-speed, charge-coupled device (CCD)-based spectroradiometer as its primary detector, calibrated against a NIST-traceable standard lamp. The spectroradiometer operates over a spectral range of 380 nm to 780 nm, with a bandwidth of 2 nm. This configuration permits simultaneous determination of photometric parameters (illuminance, luminous intensity, chromaticity coordinates) for each measurement angle.<\/p>\n

The system calculates luminous flux (\u03a6v) using equation (1):
\n[
\nPhiv = sum<\/em>{i=1}^{n} I_i cdot Omega_i
\n]
\nwhere ( I_i ) is the luminous intensity measured at incremental solid angle ( Omega_i ). For full 4\u03c0 scanning, the LSG-1890B typically completes a measurement cycle in 10 to 30 minutes, depending on angular step size and spectral integration time. The total luminous flux measurement uncertainty for a standard 3600 lm reference source is \u00b11.2% (k=2). This uncertainty budget includes contributions from distance measurement (\u00b10.2%), angular positioning (\u00b10.1%), and spectroradiometric calibration stability (\u00b10.5%).<\/p>\n

3. Compliance Verification for General Illumination Equipment (IEC\/CIE Standards)<\/strong><\/p>\n

The LSG-1890B is routinely deployed for compliance testing against IEC 62612 (self-ballasted LED lamps), IEC 62717 (LED modules for general lighting), and IEC 60598-1 (luminaire safety and photometric performance). The system fulfills the requirements of CIE 121-1996, CIE 13.3 (color rendering index), and IES LM-79-08 (electrical and photometric measurements of solid-state lighting products).<\/p>\n

Table 1: Critical Photometric Parameters Measured by the LSG-1890B per IEC 62612<\/em><\/p>\n\n\n\n\n\n\n\n\n
Parameter<\/th>\nStandard Requirement<\/th>\nLSG-1890B Capability<\/th>\nMeasurement Uncertainty<\/th>\n<\/tr>\n<\/thead>\n
Luminous Flux (lm)<\/td>\n\u00b110% tolerance<\/td>\n0.1 \u2013 200,000 lm<\/td>\n\u00b11.2% (k=2)<\/td>\n<\/tr>\n
Correlated Color Temperature (CCT)<\/td>\n\u00b1100 K<\/td>\n1,500 \u2013 25,000 K<\/td>\n\u00b130 K<\/td>\n<\/tr>\n
Color Rendering Index (Ra)<\/td>\nminimum 80 or 90<\/td>\n0 \u2013 100<\/td>\n\u00b11.5<\/td>\n<\/tr>\n
Beam Angle (degrees)<\/td>\n\u00b110% nominal<\/td>\n0.1\u00b0 resolution<\/td>\n\u00b10.3\u00b0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

In a practical example, an outdoor LED luminaire intended for urban lighting design\u2014with a nominal luminous flux of 12,000 lm\u2014was evaluated for compliance with IEC 62717. The LSG-1890B recorded a measured flux of 11,813 lm, a CCT of 4,052 K (target 4,000 K), and an Ra of 84.6. The resultant spatial intensity distribution data were used to generate an IES LM-63 standard photometric file, enabling direct import into lighting simulation software for urban planning optimization. Such data fidelity is crucial for municipal street lighting revamp projects that must adhere to EN 13201-2 (road lighting classes) or the British Standard BS 5489-1.<\/p>\n

4. Photometric Characterization of Medical Lighting Equipment (IEC 60601-2-41)<\/strong><\/p>\n

Medical lighting, including surgical luminaires and examination lamps, requires precise control of illuminance uniformity, color temperature stability, and shadow formation parameters. The IEC 60601-2-41 standard specifies maximum permitted deviations in illuminance (\u226540,000 lx at 1 m) and a CRI of \u226590 for general surgery. The LSG-1890B\u2019s capability to measure at fixed working distances through the motorized height adjustment system (travel range: 0.5 m to 4 m) allows direct compliance testing with this medical standard.<\/p>\n

For instance, a prototype LED surgical light was evaluated using the LSG-1890B with a detector positioned at 1.0 m. The system successfully mapped a central illuminance of 48,200 lx, a light field diameter of 22.4 cm (within the 15\u201330 cm requirement), and a color temperature homogeneity of \u00b1150 K across the illumination field. The angular intensity distribution data also illuminated the device\u2019s \u201cshadow dilution\u201d effect\u2014a measure critical for cavity illumination\u2014by quantifying intensity loss at 45\u00b0 off-axis. This testing methodology is routinely adapted for certification bodies in Germany (DIN 5035) and the United Kingdom (HTM 06-01).<\/p>\n

5. Application in Photovoltaic Concentrator Testing (IEC 62108, IEC 62670-1)<\/strong><\/p>\n

Beyond conventional lighting, the LSG-1890B finds utility in the characterization of concentrated photovoltaic (CPV) modules and solar concentrator optics. CPV systems utilize Fresnel lenses or reflective optics to concentrate sunlight onto multi-junction cells, requiring precise measurement of the angular acceptance function. The standard IEC 62108 mandates quantification of the off-axis rejection characteristics, often termed the \u201cacceptance angle\u201d at 90% of peak short-circuit current.<\/p>\n

Using a high-power collimated light source attachment (often a xenon arc or tunable laser), the LSG-1890B can replicate the angular sweep necessary to generate the normalized current versus angle profile. The system\u2019s angular accuracy (better than 0.1\u00b0) is sufficient to discriminate between loss mechanisms such as chromatic aberration, manufacturing misalignment, and thermal deformation. In one qualification test for a German CPV module manufacturer, the LSG-1890B measured an acceptance half-angle of \u00b11.6\u00b0, in contrast to the design value of \u00b12.0\u00b0, leading to redesign of the secondary optical element. Such sensitivity is essential for maximizing the performance ratio required by IEC 62670-1 in outdoor power rating tests.<\/p>\n

6. Display and Backlight Uniformity Metrology (TCO\/VESA Standards)<\/strong><\/p>\n

Display equipment testing, including LCD panels, OLED monitors, and direct-view LED screens, demands uniformity measurement of luminance and chromaticity across the full viewing cone. The Video Electronics Standards Association (VESA) Flat Panel Display Measurements Standard (FPDM) 2.0 outlines angular luminance uniformity criteria (e.g., \u0394Lv \u2264 10% at \u00b160\u00b0). The LSG-1890B\u2019s rotating arm can support displays weighing up to 50 kg, with a maximum measurement area of 2.0 m diagonal.<\/p>\n

A typical characterization for an OLED television panel (55-inch, 4K) involved measuring white field luminance at 50\u00b0 increments from 0\u00b0 to 80\u00b0 in the horizontal and vertical axes. The LSG-1890B registered a luminance drop of 62% at 80\u00b0, consistent with emissive OLED angular roll-off, and a chromaticity variation \u0394u\u2019v\u2019 of 0.012. These values were applied for compliance with the TCO Certified Displays 9.0 requirement (\u0394u\u2019v\u2019 \u2264 0.015 at 40\u00b0). The instrument\u2019s low stray light acquisition (better than 0.01% of full scale) allows accurate measurement even for the deep blacks of high-dynamic-range displays.<\/p>\n

7. Competitive Electro-Mechanical Architecture Versus Alternative Goniometric Systems<\/strong><\/p>\n

The LSG-1890B\u2019s architecture distinguishes itself from three prevalent goniophotometer<\/a><\/a> designs: the rotating mirror system (Type A), the rotating detector system (Type B), and the fixed-source rotating chamber system. Each introduces specific systematic errors.<\/p>\n