If you are going to use a line generator you have to be very careful it can be done a number of ways.
The way you need it to be done is optically on the lens
http://www.edmundoptics.com/optics/optical-lenses/cylinder-lenses/laser-line-generator-lenses/1910
That lens is worth $180 USD
http://www.edmundoptics.com/optics/optical-lenses/cylinder-lenses/laser-line-generator-lenses/1910That is why most cheap laser systems don't do it like that and the technique is patented
http://www.faqs.org/patents/app/20100309565What you appear to be dealing with is this type of laser line generator
http://www.bosontech.com.cn/catalog/laser_lg_e.pdfThey discuss your problem you think is cool and even give it a name "laser speckle" look at page 3 on the PDF.
They tell you how to avoid laser speckle
As a diffuse reflective and thus an optically rough-textured surface is essential for the utilization of the laser light section method, laser speckling is not to be avoided in principle.
A mirror is the exact opposite of what you need to avoid laser speckle from these generators and that is why you have such bad speckling.
