Flat-field stereograms

Flat-field stereograms are visual images designed to create a sense of three-dimensional depth when viewed with proper focusing. They consist of two nearly identical patterns, slightly offset from each other, which correspond to the images seen by your left and right eyes. When viewed correctly—often by diverging your eyes or using specific viewing techniques—the brain merges these two images, perceiving a coherent 3D scene without the need for glasses. The term "flat-field" refers to the pattern's even, uniform background, which ensures consistent depth cues across the entire image, enhancing the stereoscopic effect.