How to evaluate luminance uniformity on Barco Diagnostic Displays

Article number: [2849] - Legacy code: [7540]

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Introduction

With this procedure, Barco provides information to QA managers on how to evaluate luminance uniformity on their Barco diagnostic display systems. These recommendations are based on existing guidelines from global working groups such as AAPM TG18 and IEC 62563-1.

Preparation

Before starting the evaluation:

Allow the display to warm up (typically at least 30 minutes)
Ensure ambient lighting conditions match the calibrated environment (avoid reflections and stray light)
Verify that the diagnostic imaging monitor is operating in its clinical (calibrated) configuration

How to display test patterns using QAWeb Enterprise

QAWeb test patterns are generated pixel-by-pixel at native resolution, ensuring accurate evaluation without scaling artifacts.

https://www.barco.com/en/support/knowledge-base/2167-how-to-launch-test-patterns-in-qaweb-enterprise

Qualitative assessment of display uniformity (visual test)

Test pattern	Method	Evaluation
TG18-UNL80	Verify the TG18-UN80 TEST PATTERN and look for gross non-uniformities from the center to the edges.	No disturbing non-uniformities shall be seen on the screen³

Test pattern

TG18‑UNL80 (80% luminance level)

Procedure

Display the test pattern in full screen
Observe the image from a typical viewing position
Check for:
- Brightness differences between center and edges
- Visible gradients or patchiness
- Any disturbing luminance variations

Evaluation criteria

No disturbing non-uniformities should be visible across the display

Note: If non-uniformities are detected visually, IEC 62563-1 (edition 1, 2009, §7.3.5) recommends visually evaluating the luminance uniformity on 80% video³ In case the visual test result is not OK, Barco recommends assessment of the display uniformity using the quantitative (measurement) method (see below).

Quantitative assessment of display uniformity (measurements)

Test pattern	Measurement points^1,2	Formula	Evaluation
TG18-UNL80^3,4	Measure luminance at five locations:		Max allowed lum deviation ≤15%

Measurement conditions:

Hold the external photometer sensor perpendicular to the display surface
Please make sure to follow the external photometer sensor vendor recommendations concerning calibration and maintenance

Evaluation

Calculate the luminance deviation between measured points

Acceptance criterion

Maximum luminance deviation should be:
- ≤ 15%

Note: IEC 62563-1 (edition 1, 2009, §7.4.7) recommends evaluating the luminance uniformity only on 80% video.

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Best practices and recommendations

Always use QAWeb Enterprise test patterns instead of third-party tools to avoid image processing artifacts.
Ensure stable ambient lighting conditions during testing
Repeat evaluation:
- After installation
- After environmental or configuration changes
- During periodic QA checks