Virtual environmen(VE) is always involved in some visual deficit. In order to avoid causing visual problem by VE

two approaches for design of display system are presented

which are based separately on the inner mechanism of vision and on new technique of system hardware. In the first approach

for further study on VE

a new term named“the depth of field in vision”

which is the max scenes depth imaging clearly on retina when the eye status mainly for vergence and accommodation is fixed

is presented for the first time and is illustrated detailedly with its concept

principle and measurement method. This offers a new theory infrastructure for display system design to make immersion more comfortable against dizziness

eyestrain etc. In the second approach

the principle

application as well as their advantage or disadvantage of some new techniques in VE such as eye tracking system

liquid crystal glasses with microcomputer are analyzed. The adaptive capability of human vision is also concerned at the end of the paper.