Optimal visibility is critical for road safety. In Camera Monitor Systems (CMS), high-resolution monitors serve as the digital replacement for traditional mirrors.

How can driver visibility be ensured if a monitor exhibits dimmer corners than the center, or varying luminance from one direction to another?

In this post, we break down the core performance metric of CMS: Monitor Isotropy, and reveal its standardized testing methods.

What is CMS Monitor Isotropy?

It defines two critical dimensions of display consistency:

● Lateral uniformity: Measures the luminance consistency across different areas of the monitor.

● Directional uniformity: Measures the luminance consistency of the same area on the CMS monitor across different viewing angles, compared to the designed viewing angle.

These two indicators determine the CMS monitor’s spatial and angular display consistency—critical for clear driver observation and accurate judgment. Therefore, we need standardized, unified, and repeatable testing to evaluate CMS monitor isotropy and keep driving safe.

Yanding CMS Automated Test System

Accurate and stable test results rely on a standardized test system.Yanding’s CMS Automated Test System strictly complies with international and domestic regulations such as ISO 16505 and GB 15084. High-precision, high-efficiency hardware and our in-house developed RIQA image quality analysis software enable standardized quantitative evaluation of CMS Monitor Isotropy.

(RDBUY)

How We Test CMS Monitor Isotropy?

Next, we will introduce the complete test flow in three sections: Test KPIs, test steps and result analysis.

Lateral Uniformity(RDBUY)

● Test KPIs (ISO 16505)：The maximum luminance difference among the 9 measurement points for CMS lateral uniformity shall be less than 35%.These measurement points are positioned at different percentages based on the monitor’s defined horizontal and vertical dimensions, covering the screen center, four corners, and midpoints of the edges.

● Test Steps: Start by displaying a 70% grayscale image on the monitor. Align the luminance meter’s optical axis with the surface normal of the monitor, capture the screen once measurements stabilize, then use RIQA software to analyze the 9-point luminance distribution and calculate the luminance deviation ratio.

Directional Uniformity(RDBUY)

● Test KPIs (ISO 16505)：

Standard Isotropy Range (±6° vertical, ±7° horizontal from the designed viewing angle):The luminance deviation between any measurement direction and the design viewing angle shall be less than 35%.

Extended Isotropy Range (an additional ±5° in both vertical and horizontal directions beyond the standard range, i.e., ±11° vertical, ±12° horizontal):The luminance deviation between any measurement direction and the design viewing angle shall be less than 50%.

● Test Steps: Display a 70% grayscale image on the monitor. Measure the luminance at the center of the screen with a goniometer or a conoscopic measurement system or equivalent, then import the data into RIQA software to calculate the uniformity.

What challenges have you faced in testing CMS monitor isotropy? Tell us in the comments!

For further information, please feel free to contact us at sales@yanding.com.

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