1. A lined trifocal design with three areas of focus: Distance (carrier), Intermediate and Near (reading addition).

2. Methods The internal trifocal distractor was used to reconstruct the mandibular segmental defects of 4 canine model.

3. The trifocal tensor is the mathematical expression of trifocal geometry, it has strict constraints to correspondence points and lines in three images.

4. The trifocal tensor can eliminate the wrong matches while the epipolar geometry algorithms of feature point and line match can not find them.

5. It doesn't take a genius to know that wooing a woman requires a trifocal effort of body, soul and spending power.

6. It consist of computation of fundamental matrix in two views and of trifocal tensor in three views .

7. Thereinto, the problem of matching feature points and feature lines introduce the trifocal tensor as the constraint condition.

8. Then in vivo animal experiments were performed. Radiographics of the mandible showed that two transport plates reached the designed location in the trifocal distraction osteogenesis.

9. This paper mainly researches the application that one uses the trifocal tensor to get feature points and feature lines.