All my enclosures are glass tanks and I have 6 Pacman Frogs all healthy and their climates maintained. Always look at the package of the bulbs because they should state their effective distance from the surface of the substrate. Infrared bulbs are not as bad as some basking bulbs so Yours should pose no threat to your frog.
Didn't realize how far you had it from your frog. When offering advice on something like a heat lamp and bulb wattage include the distance so that someone doesn't just place a 100 watt bulb in a lamp and sitting directly on the top of the their lid and cook their frog.