Surface Light Source Device with Light Flux Control

The patent introduces a vertical dimension constraint by designing the light flux controlling member with a specific height that prevents light from reaching adjacent light emitting elements. This dimensional parameter (height) controls the light path to ensure light travels primarily in the intended direction without passing through multiple lenses, thereby maintaining luminance uniformity while still achieving broad light distribution through the diffusion plate.

The patent optimizes the height parameter of the light flux controlling member to achieve the desired effect. By carefully selecting this dimensional parameter, the design ensures that light emitted at angles of 80° or less from the optical axis reaches the diffusion plate without passing through adjacent light emitting elements, thus preventing luminance unevenness while maintaining effective light distribution.

The patent uses the vertical dimension (height of light flux controlling member) to control light paths in a multi-element array. This dimensional parameter ensures that light from each element remains confined to its intended propagation direction, preventing cross-contamination between adjacent elements while maintaining wide coverage through the diffusion plate.

The light flux controlling member acts as a segmentation barrier that divides the optical space into distinct regions for each light emitting element. By physically separating the light paths through the height constraint, each element's light contributes uniformly to the overall illumination without interference from neighboring elements, enabling wide coverage with uniform luminance.