Abstract: A display apparatus (500) for displaying a virtual image (VIMG1) comprises: an optical engine (ENG1) to form input light (IN1), which represents an input image (IMG0), an expander device (EPE1) to form light beams (B3P0,R,B3P1,R) of output light (OUT1) by expanding light beams (B0P0,R,B0P1,R) of the input light (IN1), the expander device (EPE1) comprising: a waveguide plate (SUB1), a diffractive in-coupling element (DOE1) to form first guided light (B1a) and second guided light (B1b) by coupling input light (IN1) into the waveguide plate (SUB1), wherein the display apparatus (500) comprises a base (BASE1) and an actuating mechanism (MOTOR1) to cause rotary motion of the expander device (500) with respect to the base (BASE1), wherein an angle (?1) between an optical axis (AX0) of the optical engine (ENG1) and the axis (AX1) of rotation of the expander device (500) is in the range of 10° to 45°.

Abstract: A display device (500) includes an expander device (EPE1) to form output light (OUT1) by diffractively expanding input light (IN1) that includes input light beams (B0P1, B0P2) representing an input image (IMG0). The output light (OUT1) includes output light beams (B3P1, B3P2) representing the input image (IMG0). The expander device (EPE1) includes: a waveguide plate (SUB1), a diffractive in-coupling element (DOE1) to couple the input light (IN1) into the waveguide plate (SUB1), a diffractive out-coupling element (DOE3) to form the output light (OUT1) by diffracting guided light (B1, B2) out of the waveguide plate (SUB1). The out-coupling element (DOE3) includes buried diffractive ridges (PR1) and complementing regions (FIL2) between the ridges (PR1), the buried diffractive ridges (PR1) have a first refractive index (n1), the complementing regions (FIL2) have a second different refractive index (n2). A slant angle (?S) of the ridges (PR1) is in a range of 20° to 70°.

Abstract: A display apparatus (500) for displaying a virtual image (VIMG1) comprises: an optical engine (ENG1) to form input light (IN1), which represents an input image (IMG0), an expander device (EPE1) to form light beams (B3P0,R,B3P1,R) of output light (OUT1) by expanding light beams (B0P0,R,B0P1,R) of the input light (IN1), the expander device (EPE1) comprising: a waveguide plate (SUB1), a diffractive in-coupling element (DOE1) to form first guided light (B1a) and second guided light (B1b) by coupling input light (IN1) into the waveguide plate (SUB1), wherein the display apparatus (500) comprises a base (BASE1) and an actuating mechanism (MOTOR1) to cause rotary motion of the expander device (500) with respect to the base (BASE1), wherein an angle (?1) between an optical axis (AX0) of the optical engine (ENG1) and the axis (AX1) of rotation of the expander device (500) is in the range of 10° to 45°.