Seiko Epson Corporation

Shoichiro Toyoda

Koji Shiokawa

A projection system includes a first lens group that does not move when the projection magnification is changed with the aid of the zoom function, and the first lens group includes a correction lens group that is moved in the direction of the optical axis to correct worsened astigmatism. The projection system satisfies the following conditional expressions (1) and (2):|&#x394;20|&#x3c;&#xd7;&#x221a;2&#x2003;&#x2003;(1)1.5&#x3c;|1/&#x2003;&#x2003;(2)where P represents the pixel pitch in an image displayed by liquid crystal panels, FNO represents the F number of the entire lens system, &#x394;BF represents the amount of movement of the back focus position in a case where the correction lens group is moved by the amount of movement for correction of the aberration that changes when the temperature changes by 20&#xb0; C., f represents the focal length of the entire lens system, and f1 represents the focal length of the correction lens group.

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Shiojiri, Japan

Shoichiro Toyoda