Patent ID: 8197104

Claim:
A secondary optical lamp guard, being a circular cylinder made of polycarbonate (PC), comprising: an upper half portion, being a first arc length portion of the circular cylinder, and including a plurality of refractive angles formed on an internal side of the upper half portion; two clamp portions, being a second arc length portion formed separately on both sides of the upper half portion, and having a clamp element installed on internal sides of the clamp portions separately; and a lower half portion, being a third arc length portion of the circular cylinder; wherein angles resulted from the first arc length portion, the second arc length portion and the third arc length portion respectively sums up to 360 degrees, and the upper half portion includes a plurality of upper holes, and the lower half portion includes a plurality of lower holes, and a ratio of internal diameter to external diameter of the circular cylinder is equal to 0.807 to 0.929, and a ratio of thickness to external diameter of the optical refractive angle is equal to 0.021 to 0.024.