Laser Cutter vs. Mirrorshades: Rear

Continuing with the same battered sunglass lens:

It’s now oriented with the back side of the lens toward the unfocused beam going into the laser head.

The front surface remains undamaged after two pulses at 500 ms 50% power:

The red disk in the middle of both wounds is new this time.

As seen from the rear, the first pulse shattered the rear glass layer:

The image is about 7 mm from side to side.

A chip of glass popped out of the upper part of the fracture, but the other pieces remained in place.

The distinct blue ring is 3 mm OD and marks the inner boundary of a purple disk surrounding the central burn. The disk appears only in reflected light (which is impossible to photograph with any setup I can manage), suggesting it comes from diffraction in a surprisingly uniform air layer blown between the glass and the plastic polarizing sheet.

Also seen from the rear, the second pulse produced a neater wound:

The blue ring is again 3 mm OD and the image is 7 mm across.

The central red spot probably comes from damage to the polarizing sheet.

The most surprising things, at least to me, didn’t happen:

• the glass lens didn’t disintegrate
• the laser beam didn’t punch completely through

Protip: Don’t depend on ordinary glasses, even fancy sunglasses, to protect your eyes from CO₂ laser beams.