Optical system for use in an image projector

A projector optical system comprising:

• a reflection-type display panel;
• an illumination optical system for illuminating the reflection-type display panel;
• a projection optical system for protecting images displayed on the reflection-type display panel onto a screen, the projection optical system including, from a screen side,
• a front lens unit;
• a rear lens unit;
• and
• a light-deriving means for directing illumination light toward the reflection-type display panel, the light-deriving means being disposed between the front and rear lens units, wherein the following condition is fulfilled,
• 0.2<φF/φ<0.9
• where
• φF represents an optical power of the front lens unit of the projection optical system;
• and
• φ represents an optical power of the entire projection optical system, and
• wherein the projection optical system is built as a zoom lens system, and zooming is performed by moving only the front lens unit.

A projector optical system comprising:

• a reflection-type display panel;
• an illumination optical system for illuminating the reflection-type display panel;
• a projection optical system for projecting images displayed on the reflection-type display panel onto a screen, the projection optical system including, from a screen side:
• a front lens unit;
• a rear lens unit;
• and
• a light-deriving means for directing illumination light toward the reflection-type display panel, the light-deriving means being disposed between the front and rear lens units, wherein the following condition is fulfilled:
• 0.2<φF/φ<0.9
• where
• φF represents an optical power of the front lens unit of the protection optical system;
• and
• φ represents an optical power of the entire projection optical system, and
• wherein focusing is performed by moving a portion of the front lens unit.

A projection optical system for projecting images displayed on a reflection-type display panel onto a screen, comprising, from the screen side:

• a front lens unit;
• a rear lens unit;
• and
• a light-deriving means for directing illumination light toward the reflection-type display, the light-deriving means being disposed between the front and rear lens units,
• wherein the following conditions are fulfilled:
• 0.2 < ϕ ⁢ ⁢ F / ϕ < 0.9 ⁢ ⁢ and 0.2 < FL / ( FNO × D ) < 0.8
• where
• φF represents an optical power of the front lens unit of the projection optical system;
• φ represents an optical power of the entire projection optical system;
• FL represents a shortest focal length of the entire projection optical system;
• FNO represents an F number;
• and
• D represents an aperture diameter.