Optical system, display apparatus having the same, and control apparatus

A display apparatus comprising:

• a display element;
• and
• an optical system that includes, in order from a side of an exit pupil to a side of the display element, a polarization selective half-transmissive reflective element, a first quarter waveplate, an optical member including a half-transmissive reflective surface, a second quarter waveplate, and a polarizer, and is configured to guide light from the display element to the exit pupil,
• wherein the optical system is changeable between a first state in which polarization directions of the polarization selective half-transmissive reflective element and the polarizer are orthogonal to each other, and a second state in which the polarization directions of the polarization selective half-transmissive reflective element and the polarizer coincide with each other.

A control apparatus for a display apparatus that includes a display element and an optical system that includes, in order from a side of an exit pupil to a side of the display element, a polarization selective half-transmissive reflective element, a first quarter waveplate, an optical member including a half-transmissive reflective surface, a second quarter waveplate, and a polarizer, and is configured to guide light from the display element to the exit pupil, the control apparatus comprising:

• a memory storing instructions;
• and
• a processor configured to execute the instructions to:
• control a polarization direction the polarizer so as to set a first state in which a polarization direction of the polarization selective half-transmissive reflective element and the polarization direction of the polarizer are orthogonal to each other in a case where the display apparatus is not in a predetermined state, and
• control the polarization direction the polarizer so as to set a second state in which the polarization directions of the polarization selective half-transmissive reflective element and the polarizer coincide with each other in a case where the display apparatus is in the predetermined state.