Definition:
The CMS luminance and contrast reproduction test simulates the lighting challenges of real-world driving environments to verify the CMS's ability to maintain contrast under various lighting scenarios, including direct sunlight, diffuse ambient daylight, dusk, and night. It evaluates whether the system can maintain stable visual clarity of the image, avoiding the loss of critical information due to abnormal brightness or darkness and glare, thereby ensuring driving safety and meeting mandatory regulatory requirements.
Contrast is defined as the ratio of high luminance $L_{High}$ to low luminance $L_{Low}$.

Metric Requirements:
(Based on standards ISO 16505 and GB 15084)
Luminance and contrast reproduction shall meet the following requirements:
a) When reproducing a high-contrast pattern, the minimum luminance contrast of the monitor (including any screen saver) shall meet:
— For direct sunlight conditions: 2:1;
— For diffuse ambient daylight conditions: 3:1;
— For sunset conditions: 2:1;
— For night conditions: 10:1, and 5:1 for Class I mirrors and CMS dual-function systems.
b) Night scenes for the camera shall be simulated in a dark environment, and the maximum illuminance on the surface of the test object shall not exceed 2.0 lx;
c) Under night conditions, the background luminance of the monitor shall be limited, and the maximum background luminance shall be less than 2.0 cd/m²;
d) Sunlight or other strong light sources shining on the monitor will reduce the luminance contrast, which may require the driver to be particularly vigilant and attentive.

Environment Setup:
The required setups for different conditions are as follows:
Direct Sunlight: Test chart (1), chart illumination light source (2), camera under test (5), monitor illumination light source (6), monitor (7), and imaging luminance meter (8).
Diffuse Ambient Daylight Conditions: Test chart (1), chart illumination light source (2), camera under test (5), monitor illumination light source (6), monitor (7), imaging luminance meter (8), and diffuse illumination light source (9).
Night Conditions: Test chart (1), chart illumination light source (2), camera under test (5), monitor (7), and imaging luminance meter (8).
Dusk Conditions: Test chart (1), mirror (3), chart illumination light source (2), high-intensity point light source (4), camera under test (5), monitor (7), and imaging luminance meter (8).

Test Method:
Direct Sunlight
By simulating the scenario where sunlight shines directly onto the display through the vehicle's front windshield, the luminance contrast (CR) at the center of the monitor is measured.
Measure the luminance of the black and white patches assigned to the measurement positions, and calculate it using the formula $CR = \frac{L_{monitor/chart/white/ambient}}{L_{monitor/chart/black/ambient}}$.

Main equipment used:
Contrast chart (Reflective checkerboard chart), chart illumination light source (Vertical fill light source), camera under test, monitor under test illumination light source (Solar point light source), test monitor, and reference camera (imaging luminance meter).
The illumination light source for the monitor under test must be a point light source, producing parallel and uniform incident light at the measurement point.

Test conditions:

Result analysis:
Use the luminance contrast item in the RIQA Image Quality Software CMS Module to analyze the test samples. The RIQA luminance contrast module supports selecting 2*2, 3*3, and 4*4 ROIs. After selecting the center area with the ROI box, click analyze to directly obtain the result data.
The regulatory standard requires a minimum contrast of 2:1 for direct sunlight conditions; therefore, the test result for this sample meets the requirements.

Diffuse Ambient Daylight Conditions
By simulating the scenario where diffuse light from the external environment reflects onto the monitor surface, the luminance contrast (CR) at the center of the monitor is measured.

Main equipment used:
Contrast chart (Reflective checkerboard chart), chart illumination light source (Vertical fill light source), camera under test, monitor under test illumination light source (Diffuse light source), test monitor, and reference camera (imaging luminance meter).
The illumination light source for the monitor under test must be an extended light source to ensure uniform reflected light within the measurement field of view on the monitor surface.

Test conditions:

Result analysis:
Use the luminance contrast item in the RIQA Image Quality Software CMS Module to analyze the test samples. The regulatory standard requires a contrast of 3:1 for diffuse ambient daylight conditions; therefore, the test result for this sample does not meet the requirements.

Dusk Conditions
By simulating the scenario of strong glare produced by the low-angle sun near the horizon, the luminance contrast (CR) of the monitor is measured.

Main equipment used:
Contrast chart (Reflective checkerboard chart), chart illumination light source (Vertical fill light source), high-intensity glare light source (Fiber optic point light source), camera under test, test monitor, and reference camera (imaging luminance meter).

Test conditions:

The camera under test and the point light source must meet the following conditions:
a. Adjust the distance between the point light source and the camera so that the field of view angle formed by the camera and the emitting surface of the incident light source is 30-34 arcmin;
b. Adjust the light source so that the angle between the normal to the camera sensor plane, the center point of the sensor, and the light source is 10°.

Result analysis:
Use the luminance contrast item in the RIQA Image Quality Software CMS Module to analyze the test samples. The ROI analysis area is the region close to the light source but unaffected by the halo. The regulatory standard requires a minimum contrast of 2:1 for sunset conditions; therefore, the test result for this sample meets the requirements.

Night Conditions
By simulating the camera scene in a night environment, the luminance contrast (CR) at the center of the monitor is measured.

Test equipment:
Contrast chart (Reflective checkerboard chart), chart illumination light source (Vertical fill light source), camera under test, test monitor, and reference camera (imaging luminance meter).

Test Conditions
At this time, the ambient illuminance on the camera side is 2 lux (lx), corresponding to a typical luminance value of 0.5 cd/m² to 0.7 cd/m². On the monitor side, the automatic brightness adjustment function of the monitor should be enabled; if automatic adjustment is unavailable, the manual brightness adjustment of the monitor must be set to the standard mode for low-light environments.

Result Analysis:
Use the luminance contrast item in the RIQA Image Quality Software CMS Module to select the corresponding test conditions and analyze the test samples. The regulatory standard requires a minimum contrast of 10:1 for night conditions; therefore, the test result for this sample meets the requirements.