Abstract: In the double prism interference experiment in measuring laser wavelength,the major factors which result in measuring error are the measuring value of the distance between interference fringes using the second focus method,narrow distance between double slit,and the distance between two virtual light sources.An improvement of measuring method is introduced in our experiment:The distance between two virtual light sources is measured by the first focus method,and the distance between the slit lamp and the double-prism and the distance between the slit lamp and the viewing screen are greatly increased in our experiment.Our experimental results are proved to be in agreement with the theoretical results well.

Key words: double-prism, secondary imaging, first imaging