Floating display apparatus and multi-layer display device comprising same

A floating display apparatus comprising:

• an image display unit to have a display plane of an image and to emit display light constituting an initial image from the display plane;
• and
• an optical system to define an object plane and an image plane, the optical system being arranged to receive the display light emitted from the display plane at the object plane, wherein the optical system includes a plurality of optical components that are configured to have different abilities to converge light rays in a first direction and a second direction, the first direction and the second direction are orthogonal to an optical axis of the floating display apparatus respectively, wherein the optical system has an aperture stop for confining light rays from the object plane in the second direction,
• wherein the display light, after propagating through the optical system, forms a floating image at the image plane in the air, an image-side aperture angle in the first direction is larger than an image-side aperture angle in the second direction, and
• wherein the plurality of optical components include:
• a first optical component including a one-dimensional optical element for modulating light rays in the second direction;
• and/or
• a second optical component including a conjugate imaging element having a one-dimensional grating structure for converging light rays in the first direction.