{"id":9306,"date":"2026-07-20T18:02:49","date_gmt":"2026-07-20T10:02:49","guid":{"rendered":"https:\/\/www.ledtestsystem.com\/?p=9306"},"modified":"2026-07-20T18:02:49","modified_gmt":"2026-07-20T10:02:49","slug":"integrating-lisun-integrating-sphere-for-precision-photometric-and-colorimetric-measurement-in-led-testing","status":"publish","type":"post","link":"https:\/\/ledtestsystem.com\/ja\/%e3%83%96%e3%83%ad%e3%82%b0\/integrating-lisun-integrating-sphere-for-precision-photometric-and-colorimetric-measurement-in-led-testing\/","title":{"rendered":"Integrating LISUN Integrating Sphere for Precision Photometric and Colorimetric Measurement in LED Testing"},"content":{"rendered":"

Integrating \u30ea\u30b9\u30f3<\/a> \u7a4d\u5206\u7403<\/a> for Precision Photometric and Colorimetric Measurement in LED Testing<\/strong><\/p>\n

Introduction to High-Accuracy Photometric and Colorimetric Metrology for Solid-State Lighting<\/strong><\/p>\n

The proliferation of solid-state lighting (SSL) technologies, including high-power LEDs, OLEDs, and micro-LEDs, has necessitated a paradigm shift in optical measurement methodologies. Traditional goniophotometric approaches, while accurate for total luminous flux measurement, are time-intensive and ill-suited for rapid production-line testing or chromaticity characterization. The \u7a4d\u5206\u7403<\/a>, combined with a high-resolution spectroradiometer, has become the de facto standard for simultaneous photometric and colorimetric evaluation. This article examines the metrological principles underpinning integrating sphere\u2013based systems, with specific emphasis on the LISUN LPCE-2 (LISUN High Precision Spectroradiometer and Integrating Sphere System) as a reference instrument for laboratory-grade and industrial-scale LED testing. The discussion encompasses spectral flux determination, correlated color temperature (CCT) accuracy, color rendering index (CRI) computation, and compliance with international standards including CIE 127, IES LM-79, and JIS C 8152.<\/p>\n

1. Architectural Principles of the LISUN LPCE-2 Integrating Sphere System<\/strong><\/p>\n

The core measurement apparatus consists of a barium sulfate (BaSO\u2084) or polytetrafluoroethylene (PTFE) coated integrating sphere, coupled with a high-speed, array-based spectroradiometer. The LPCE-2 system employs a 0.3m, 0.5m, or 1.0m sphere diameter, selected based on the physical dimensions and total luminous flux of the device under test (DUT). The sphere internal coating achieves a diffuse reflectance of approximately 94\u201397% across the visible spectrum (380\u2013780 nm), ensuring Lambertian scattering and spatial integration of the emitted flux. A baffle system prevents direct illumination of the detector port, thereby minimizing measurement errors arising from non-uniform radiance distribution. The spectroradiometer utilizes a back-thinned CCD array (2048 pixels) with a stray light correction algorithm, enabling a wavelength resolution of 0.2 nm and a photometric linearity of \u00b10.3%. The system is calibrated against a NIST-traceable standard lamp for absolute spectral irradiance, enabling direct computation of luminous flux (in lumens), radiant flux (in watts), and chromaticity coordinates (u\u2019, v\u2019, CIE 1931 x,y).<\/p>\n

2. Optical Configuration and Spectral Flux Measurement Protocol<\/strong><\/p>\n

Auxiliary lamp compensation is a critical feature in the LPCE-2, particularly for self-absorbed flux correction when testing low-power LEDs or devices with significant heat sink absorption. The measurement sequence proceeds as follows: (a) background dark current subtraction; (b) measurement of the reference auxiliary lamp with the DUT powered off; (c) DUT activation and full spectrum acquisition; (d) post-measurement auxiliary lamp re-measurement to quantify absorption changes. The system firmware applies a correction coefficient (k_abs) derived from the ratio of auxiliary lamp irradiance before and after DUT installation. The corrected spectral power distribution (SPD) is then integrated across wavelength intervals of 1 nm using a trapezoidal summation method. This protocol ensures that the photometric uncertainty remains below \u00b11.5% for total luminous flux and \u00b10.002 for chromaticity coordinates (\u0394u\u2019v\u2019). For high-power LED modules exceeding 10,000 lumens, the 1.0m sphere with forced-air cooling is recommended to mitigate thermal drift in the photodetector.<\/p>\n

3. Colorimetric Parameter Extraction and CRI Calculation<\/strong><\/p>\n

The LPCE-2 spectroradiometer computes colorimetric parameters according to CIE 13.3 and CIE 224:2017 specifications. The spectral data are weighted using the CIE 1931 2\u00b0 standard observer color-matching functions (x\u0304(\u03bb), \u0233(\u03bb), z\u0304(\u03bb)) at 1 nm intervals. The system calculates CCT using the McCamy approximation algorithm for CCT below 50,000 K, with an accuracy of \u00b15 K for standard fluorescent and LED sources. For CRI evaluation, the eight standard test color samples (TCS01\u2013TCS08) are employed to compute the general color rendering index (Ra), while the extended set (R9\u2013R15) is reported for saturation and skin-tone rendering. The spectroradiometer\u2019s high dynamic range (>10^6) allows simultaneous measurement of low-level blue-pump emissions and high-intensity phosphor conversion bands, a critical capability for evaluating dual-band or tunable-white LED systems. The system outputs include the full R-series values, the CIE 1976 u\u2019v\u2019 uniformity metrics, and the TM-30 color fidelity index (Rf) and gamut index (Rg) when operating in expanded mode.<\/p>\n

4. Application in Automotive Lighting Testing<\/strong><\/p>\n

The automotive lighting sector demands stringent compliance with SAE J578, ECE R112, and FMVSS 108 standards for headlamp, tail-lamp, and signal light chromaticity. The LPCE-2\u2019s 0.5m sphere configuration is particularly suited for testing LED-based automotive light sources, where the DUT may generate asymmetric flux distributions. The system\u2019s fast acquisition time (typically <100 ms) enables the capture of transient luminance behavior during pulse-width modulation (PWM) dimming cycles, a common feature in adaptive driving beam (ADB) systems. Furthermore, the spectroradiometer\u2019s extended measurement range up to 1100 nm allows for accurate determination of near-infrared (NIR) emissions from automotive LiDAR flood illumination sources. A key competitive advantage is the inclusion of a dedicated automotive lighting test suite within the LISUN software, which automates the computation of CIE-recommended chromaticity boundaries for white, amber, red, and blue signal lights. For instance, the system can flag deviations from the ECE-regulated \u201cblue\u201d wedge region (x=0.310, y=0.348 to x=0.453, y=0.410) with 0.001 tolerance.<\/p>\n

5. Deployment in Aerospace, Aviation, and Marine Lighting<\/strong><\/p>\n

Aerospace and aviation lighting applications\u2014including cockpit backlighting, runway edge lights, and emergency exit illumination\u2014require photometric stability under temperature extremes and compliance with RTCA DO-160 and MIL-STD-810 environmental protocols. The LPCE-2 system supports temperature-controlled measurement chambers (ranging from -40\u00b0C to +85\u00b0C) integrated directly into the sphere enclosure. Marine and navigation lighting, governed by IALA recommendations, demands precise photometric measurements at specific observation angles. The integrating sphere geometry inherently provides angle-averaged flux data, which can be correlated with goniometric data for luminous intensity distribution. The LPCE-2\u2019s spectroradiometer employs a thermoelectric cooler (TEC) stabilized at -10\u00b0C, reducing dark current noise to <0.1 counts\/second and enabling reliable low-flux measurements (down to 0.01 lumens) typical of OLED-based marine panel indicators. Additionally, the system\u2019s ability to measure spectral radiance (in cd\/m\u00b2) via a calibrated cosine-corrected input optic allows for direct evaluation of avionic display luminance and uniformity.<\/p>\n

6. Utility in Display Equipment, Photovoltaic, and Scientific Research<\/strong><\/p>\n

For display equipment testing\u2014including LCD backlights, OLED panels, and micro-LED arrays\u2014the LPCE-2 provides simultaneous measurement of white-point chromaticity, color gamut coverage (DCI-P3, sRGB, BT.2020), and gamma curve verification. The system supports pulsed-mode measurement synchronization with external trigger signals, essential for characterizing OLED burn-in effects and PWM-driven brightness modulation. In the photovoltaic (PV) industry, the integrating sphere is adapted for spectral mismatch correction of solar simulators. The LPCE-2\u2019s spectroradiometer measures the relative spectral response of reference cells, enabling calculation of the spectral mismatch factor (MM) as per IEC 60904-9. Scientific research laboratories leverage the system\u2019s <0.5% repeatability for fundamental studies of quantum dot photoluminescence, phosphor efficiency, and degradation kinetics. The device\u2019s USB 3.0 and Ethernet connectivity allow for remote monitoring and data logging over extended aging tests (up to 10,000 hours), a requirement for long-term reliability investigations in both academic and industrial R&D settings.<\/p>\n

7. Urban, Stage, and Medical Lighting Measurement Considerations<\/strong><\/p>\n

Urban lighting design relies on accurate mesopic photometry, which requires spectral measurements under low-adaptation luminance conditions. The LPCE-2\u2019s spectroradiometer can operate in high-gain mode, achieving a signal-to-noise ratio (SNR) > 1000:1 at 10 lux, facilitating the measurement of streetlamp SPDs at operational distances. Stage and studio lighting, particularly moving-head LED fixtures, demand consistent CCT and CRI across variable dimming levels. The system\u2019s real-time chromaticity tracking (update rate of 5 Hz) allows engineers to tune output via DMX control parameters while observing instantaneous CCT drift. Medical lighting equipment, such as surgical headlamps and phototherapy devices, must adhere to IEC 60601-2-41 and ISO 15004-2 for photobiological safety. The LPCE-2 computes weighted irradiance values for actinic UV (400\u2013315 nm), blue-light hazard (300\u2013700 nm), and thermal retinal hazard, using CIE S009\/E:2002 weighting functions. The system\u2019s ability to output both photopic and scotopic flux (in lumens) further supports circadian lighting research.<\/p>\n

8. Competitive Advantages Over Conventional Spectroradiometric Systems<\/strong><\/p>\n

The LPCE-2 differentiates itself from competing solutions (e.g., single-detector scanning monochromators or low-resolution handheld spectrometers) through several critical attributes:<\/p>\n