Projection display device for projecting and imaging

A projection display device comprising:

• an imaging element that images received light;
• a light source;
• a light valve that modulates light from the light source and emits modulated light;
• and
• an imaging optical system that projects an optical image of the light modulated by the light valve onto a magnification side imaging surface and forms an image of light incident from a magnification side on the imaging element,
• wherein the imaging optical system comprises a first optical system that comprises at least one lens and is used in common in projection and imaging, a second optical system that comprises at least one lens and is used only in projection, a third optical system that comprises at least one lens and is used only in imaging, and a separation member that separates an optical path from the second optical system toward the first optical system from an optical path from the first optical system toward the third optical system, and
• the third optical system comprises a first light shielding member that is arranged in a vicinity of a stop position of the third optical system and shields a part of a luminous flux,
• wherein, in a case where a distance on an optical axis from a surface of the first optical system on a most magnification side to the separation member is L1, and a distance on the optical axis from the surface of the first optical system on the most magnification side to a surface of the second optical system on a most reduction side is L, a conditional expression (2) is satisfied,
• 0<L1/L<0.7 (2).