how to remove the parallax error of convex lens by u-v method using an optical bench??

In the event that the estimation is made wrong by survey from a wrong position rather than the right position prompts a mistake in the estimation, this blunder is called parallax blunder. 

Or, on the other hand 

The evident move between the two items when the eye is moved sideways is called parallax. 

Redress of parallax mistake: 

On the off chance that two articles are set at a similar separation from the eye, there will be no relative move between them. On the off chance that they are at various separations, the closer question moves toward a path inverse to that of the eye and more distant one in a similar bearing.