Uniformity, Pixel Defects and Replacement Matching

Measure the image under a defined condition

Uniformity describes variation across a display under a specified pattern and observation geometry. Set the working luminance, source format, calibration state and warm-up condition before comparing areas. A full white field is useful, but dark gray, mid-gray and primary-colour fields can reveal different behaviour.

Choose a measurement grid appropriate to the display and record its coordinates. A centre-and-corners sample does not characterize every module boundary on a large wall. Add points around seams, replacements and areas important to the content, while keeping the main grid consistent between tests.

Name the metric

One simple project metric is U = Lmin/Lmax × 100%, computed from the specified measurement set. Another metric may reference the mean or measure maximum deviation; results from different definitions cannot be compared directly. State the formula, point count and pattern beside the result. This simple ratio is a project calculation and is not presented as a complete IDMS uniformity procedure.

Measure colour variation separately from luminance. Two regions can have similar luminance and different tint. Record the chromaticity coordinates or selected colour-difference metric, reference condition and instrument configuration.

Classify defects by behaviour and location

Separate persistently bright, persistently dark, intermittently failing and colour-channel defects. Record the test pattern and the physical and pixel coordinates. State whether a count is per subpixel, pixel, module or entire screen. Treat clusters and defects in critical information areas explicitly in the agreed acceptance criteria.

Visual inspection requires a specified viewing distance, direction, ambient light and observation time. Close-up photographs are useful records but can exaggerate or conceal patterns through exposure, focus and resampling. Preserve original images with the setup details and use the agreed inspection conditions for the decision.

Check replacement matching

1. Confirm the replacement part, revision, receiving hardware and configuration compatibility.
2. Save the existing calibration and identify the replaced position.
3. Apply the documented configuration and correction workflow.
4. Inspect white, dark/mid-gray, primary colours and representative content across the boundary.
5. Repeat measurements at the working preset and archive the before/after results.

Agree tolerances and the repair/retest procedure before shipment. IDMS chapters 4, 7 and 8 provide a map to defect and uniformity measurement topics; formal test specifications should reference the exact complete method. The companion service guide addresses spare-part compatibility and recovery planning.