There are two main methods for measuring projection system contrast: Full On / Full Off (FOFO) and checkerboard patterns, such as the IEC 61947 contrast standard (ANSI contrast). FOFO contrast is more commonly used by optical module manufacturers.

FOFO contrast measures the ratio of brightness between a fully white versus black projected image. The checkerboard pattern method measures contrast using a 4 × 4 array of black and white rectangles. Both methods normalize the measurement to a x to 1 ratio.

When measuring contrast, FOFO is impacted by the inherent contrast ratio of the DMD as a function of the illumination and projection optic characteristics and design (for example, wavelength, F/#'s, illumination angle, and so forth). Checkerboard patterns are influenced by both the inherent contrast of the DMD and the contrast performance of the projection optics. FOFO has higher contrast ratios than checkerboard patterns. Additionally, checkerboard contrast serves as a more accurate indicator of the true contrast performance of an optical module when displaying video content.

One effective method to improve contrast ratios in an optical module is through Stray Light Mitigation. While off-state light is typically redirected away from the projection lens, managing this light effectively is crucial to prevent the light from re-entering the system. Contrast degradation and image artifacts can result from stray light entering the projection lens pupil within the field of view of the DMD active array, particularly when mirrors are in the off-state. The primary causes of stray light in DLP projectors include: light scattering from optical components and mechanical structures, mismatched illumination or projection lens pupil configurations, and light scattering from the DMD mirror structure.

Higher contrast optical modules create a more vibrant, colorful projected image, while lower contrast optical modules appear washed out (see Figure 2-5). For more detailed information regarding contrast and methods on stray light mitigation in an optical system, see slides 24 - 27 (contrast) and 84 - 98 (stray light mitigation) of the DLP Optical Design Guidelines presentation.