Optical system and display apparatus

An optical system configured to guide a light beam from an image display element to an exit pupil, the optical system comprising, in order from an exit pupil side to an image display element side:

• a first transmissive reflective surface;
• a second transmissive reflective surface;
• and
• an optical element disposed closer to the exit pupil than the first transmissive reflective surface,
• wherein the optical element includes, in order from the exit pupil side to the image display element side, a first optical element made of a first optical material and a second optical element made of a second optical material different from the first optical material,
• wherein the first optical element and the second optical element are cemented together, and a diffraction grating is formed on a cemented surface of the first optical element and the second optical element,
• wherein the diffraction grating includes a grating surface contributing to diffraction and a grating wall surface adjacent to the grating surface in a radial direction, the grating surface having a convex shape facing the image display element side, and
• wherein the following inequalities are satisfied:
• 0.5
• ≤
• d
• ⁢
• 1
• ≤
• 2
• ⁢
• 0
• .
• 0
• 0.02
• ≤
• d
• ⁢
• 2
• ≤
• 0
• .
• 4
• ⁢
• 0
• where d1 [mm] is a thickness of the first optical material in an optical axis direction,
• and d2 [mm] is a thickness of the second optical material in the optical axis direction.