Screen Photometry – Indirect Luminous Intensity Distribution Measurement
In numerous lighting applications, luminous intensity (I in cd), illuminance (E in lx), and color coordinates in various color spaces (xy, u′v′, WST, and others) are critical parameters. These quantities define the optical performance of luminaires, and headlamps, and are key metrics in photometric and colorimetric evaluation.
Measure 100× faster than Sequential Goniophotometry
Compared to sequential scanning goniophotometry, complete luminous intensity distributions or derived quantities such as illuminance or luminous flux can be measured within just a few seconds using an LMK Imaging Luminance Measuring Device (ILMD).
This method is more than 100 times faster than traditional mechanical goniophotometric systems.
The enormous speed advantage enables high-precision light distribution measurements not only in research and development laboratories but also directly in production environments and even for end-of-line (EOL) testing.
How Screen Photometry works
The measurement technique is based on screen photometry. In this setup, a geometrically and photometrically calibrated reflective screen is illuminated by the light source under test. The LMK imaging photometer then captures the reflected luminance distribution from this screen.
Flexible Measurement Geometry and Resolution
The image size and field of view are configured according to customer requirements, depending on both the desired resolution and the available measurement space.
With the LMK system, geometric resolutions down to 0.005°—as required for modern automotive headlamp development—can be achieved.
For general lighting applications, aperture angles up to ±85° are possible, making this method ideal for evaluating luminaires, LED modules, and other light sources across a wide range of applications.
Typical Applications
- Automotive lighting systems – headlamps, rear lamps, daytime running lights, signal lamps
- General lighting products – indoor and outdoor luminaires
- LED modules and arrays – production line quality control
- Research and development – fast evaluation of prototypes and optical designs
Find the Right Screen Photometry System for Your Needs
Several system configurations are available depending on measurement task and installation environment. Each configuration employs LMK imaging photometry and is adapted to specific spatial, spectral, and throughput requirements. The KMP is best suited when only a very small installation space is available, offering a compact setup for efficient screen photometry.
For applications involving large headlights or oversized luminaires, the BV system provides the necessary measurement volume and flexibility.
When measurements must conform to regulatory standards, the screen goniophotometry systems developed in cooperation with LMT offer the required precision and compliance.
For tasks focused specifically on license plate illumination, the LPL Checker is the optimal choice, providing automated and reproducible measurement routines.
