Optical system

An optical system comprising:

• an image display device that emits an image;
• a linear polarizer through which light associated with the image passes;
• a first quarter wavelength plate which receives the light from the linear polarizer;
• a half mirror;
• and
• a reflective polarizer which selectively reflects circularly polarized light,
• wherein the reflective polarizer has one or more cholesteric liquid crystal layers, and at least one of the cholesteric liquid crystal layers has a pitch gradient structure in which a spiral pitch changes in a film thickness direction.

An optical system comprising:

• an image display device that emits an image;
• a linear polarizer through which light associated with the image passes;
• a first quarter wavelength plate which receives the light from the linear polarizer;
• a half mirror;
• and
• a reflective polarizer which selectively reflects circularly polarized light,
• wherein the reflective polarizer has one or more cholesteric liquid crystal layers,
• the image display device is an image display device using a light source in which a spectrum during white display has two or more maximal values in a visible range, and a full width at half maximum of a peak corresponding to each maximal value is 60 nm or less, or a self-luminous image display device, and
• a reflection wavelength range of at least one of the cholesteric liquid crystal layers, which corresponds to any one maximal value of the spectrum during white display of the image display device, is equal to or wider than a wavelength range of the full width at half maximum of the peak of the corresponding maximal value and is equal to or narrower than a wavelength range at 5% of the corresponding maximal value.