A light flux diameter expanding element (a pupil expanding element) used in a retina scanning display device includes first to fourth diffraction gratings which are provided with grating patterns extending in a first direction, and fifth to eighth diffraction gratings which are provided with grating patterns extending in a second direction, and includes a half-wave plate between the first diffraction grating and the fifth diffraction grating. A first light flux of polarized light in which an electric field vector oscillates in the first direction enters the first diffraction grating. A second light flux of polarized light in which the electric field vector oscillates in the second direction enters the fifth diffraction grating due to the half-wave plate. Therefore, it is possible to expand a diameter of the incident first light flux in the first direction and the second direction and emit the result as the third light flux.

A laser projection device is described for projecting laser beams onto a projection plane, including a controllable multibeam laser diode unit; including a controllable optical deflection unit, which is designed in such a way that laser beams generated by the multibeam laser diode unit are deflected with the aid of the deflection unit; and including a control unit, which is designed in such a way that it controls the deflection unit to move laser beams deflected by the deflection unit onto a projection plane along a scanning line in such a way that different deflected laser beams run in the projection plane on the same scanning line.