Paul prism (also known as laser linear generator lens) is an optical marking prism, which can be optimized for the input of laser beam with the diameter of 0.8mm. Paul optical prism makes the laser beam can be optimized into a straight line with uniform optical density, good stability and good linearity after passing through. Different from the cylindrical lens which produces the characteristics of central hot spot and faded edge gaussian beam, it can eliminate the distribution of central hot spot and faded edge of gaussian beam and form a straight line with uniform energy distribution.