In short
- One closed-cover station checks every unit before shipment: about twenty multi-wavelength LEDs and a seven-digit display per unit under test (UUT).
- Radiometry decides pass or fail. Each LED is measured for the expected wavelength (colour) and intensity; OCR reads the display text.
- Results are live and logged: real-time monitoring, a minimal API for the production line and a report per test with LED ID, LED colour and recognised text.
- Why it pays: fewer field failures and recalls, consistent quality and test data that drives process improvement.
In LED-based products, quality assurance (QA) decides whether a product performs reliably and meets the specification. IZAK Scientific developed an LED and screen inspection system for a leading manufacturer of precision instruments, to verify that every product meets its quality standards before shipment. The system uses radiometry to measure LED performance, and its software adds real-time monitoring and QA reporting. This article covers why QA matters, the role of radiometry, and what the system can do.
Overview of the LED and screen inspection system
IZAK Scientific designed the system to check products before they are shipped. A closed-cover design gives a controlled test environment. Each unit under test (UUT) carries about twenty LEDs, each able to operate at a different wavelength, and a seven-digit display. Optical character recognition (OCR) verifies the text on the display, and every LED is checked for the expected wavelength and intensity. The results are compiled into a detailed QA report.
Key features of the system
The system brings together several features that make the inspection fast and complete:
The UUT is isolated during the test, so ambient light does not affect the optical measurement.
Each LED is tested individually for colour and intensity, against the values expected for that LED.
The seven-digit display is read and compared with the expected text. Any discrepancy is flagged.
Live display of LED colour status and OCR results while the test runs.
A minimal API enables or disables detection and runs tests, for easy integration into the production line.
A detailed file after each test, with the LED colour, LED ID and recognised text.
Real-time monitoring and software interface
The software shows live data on LED status, OCR results and test progress. This real-time view helps operators find and fix issues quickly, so defective products do not move further down the production line.
The interface is easy to use and lets operators focus on quality assurance. The software compiles detailed reports automatically, and the data can be analysed for trends and recurring issues.
Case study: pre-shipment QA at a precision-instrument manufacturer
The system was recently implemented at a manufacturer that puts rigorous pre-shipment QA at the centre of its process. It was integrated into the customer’s quality control procedure and helps make sure that every LED module and screen display meets the required performance and reliability standards. Its monitoring and reporting tools are now a central part of the customer’s QA workflow.
Watch: the LED and screen tester in action
Scientific background: radiometry in LED measurement
Accurate LED measurement rests on radiometry, the science of measuring electromagnetic radiation, including visible light. Radiometric quantities such as radiant flux (W), radiant intensity (W/sr), irradiance (W/m²) and radiance (W/(m²·sr)) characterise the optical performance of an LED. Applying these principles makes sure the light output of every LED is measured correctly.
When the question is how bright an LED looks to a person, the radiometric values are weighted by the eye’s photopic sensitivity curve V(λ), which peaks at 555 nm. That gives the photometric quantities: luminous flux in lumens (lm) and luminous intensity in candela (cd). At 555 nm, 1 W of optical power equals 683 lm; at other wavelengths the same watt gives fewer lumens. For a deeper introduction, read The Basics of Light Measurement: Radiometry and Photometry, and for the detectors behind these measurements see Optical Sensors in Radiometry.
LED radiant-to-luminous flux converter
Enter the LED’s peak wavelength, spectral width (FWHM) and radiant flux. The tool weights a Gaussian LED spectrum with the CIE photopic curve V(λ) and returns the luminous flux, the luminous efficacy of the radiation, the photon rate and the luminous intensity. Set the width to 0 for a laser or other monochromatic source.
Model: Φv = 683 lm/W · ∫ Φe(λ) V(λ) dλ with CIE photopic V(λ). Lambertian on-axis intensity I = Φv/π; average intensity in a uniform cone I = Φv / (2π(1 − cos θ)). Real LED spectra are not exactly Gaussian, so use a spectro-radiometer for acceptance values.
The importance of quality assurance in LED inspection
Quality assurance makes sure that LED systems perform reliably in real-world conditions and meet the required standards before they reach customers. It matters for four reasons:
Product reliabilityfewer failures in the field
QA finds malfunctioning LEDs, wrong wavelengths and incorrect display text before shipment, which reduces failures in the field.
Preventing costly recallsstop defects before the market
Defective products are stopped before they reach the market. That saves time and money and protects customer trust.
Consistent qualityuniform performance, protected brand
Every unit performs the same way, which avoids variations that could harm the brand.
Data-driven improvementtest data finds recurring issues
The test data reveals recurring issues, so the production process can be improved and made more efficient.
The LED market is highly competitive, so quality and reliability matter more than ever. This inspection system is a significant step forward in QA technology: it combines radiometric principles with real-time monitoring and reporting, prevents defects and improves consistency and customer satisfaction. For high-volume lines, see how the same approach scales to batch testing in LED Inspection Part 2, and how an integrating sphere measures total flux in LED Inspection Part 1.
Whether you are a physicist, an engineer or a QA manager, this system offers the precision and reliability you need. IZAK Scientific’s LED tester checks colour, intensity and position on the production line, and the multi-channel spectro-radiometer measures full spectra for lab and acceptance testing.
Frequently asked questions
QHow do you convert LED radiant flux in watts to lumens?
QWhat does an LED inspection system check?
QWhat is the difference between radiometry and photometry?
Tzachi Sabati
CEO, IZAK Scientific
Physicist specializing in photonics and quantum technologies, with deep expertise in quantum sensors and advanced optical systems. Leads the Advanced Quantum Lab course at the Technion, bridging academic excellence with industry innovation. At IZAK Scientific, provides cutting-edge photonics-based solutions, developing customized inspection and sensing systems for R&D and production. Passionate about advancing quantum sensing applications and integrating novel technologies to meet industry needs.
