In one general LDV class , the two beams are made to intersect at their focal points where they interfere and generate a set of straight fringes .
In most devices , the original laser light is divided into two beams .
In one general LDV class , the two beams are made to intersect at beams ' focal points where they interfere and generate a set of straight fringes .
In most devices , the original laser light is divided into two beams .