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the Philips Infraphil KL7500 heat lamp was equipped with a segmented spherical lens, a so-called Fresnel lens
Philips Infraphil KL7500
heat lamp
Fresnel lens
Fresnel lens
FRESNEL-LENS
A Fresnel lens was a segmented spherical lens
which bundled the light like a convex lens while its
segmented structure limited the weight of the lens.
Made from impact-proof pressed glass, lamps with
such a Fresnel lens were very suitable for heat lamp
appliances like the Philips Infraphil KL7500 heat
lamp on display here.
building