<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">alethoscopes</topic></authority><related type="broader"><topic>photograph viewing equipment</topic></related><variant type="other"><topic>alethoscope</topic></variant> <note xml:lang="en"><![CDATA[ Optical devices invented by Carlo Ponti in 1860, and patented in 1861. These were used to view photographic transparencies or prints. It was claimed that stereoscopic relief was obtained from a single photograph, though the stereo effect was due to the nature of an illusion caused by the single viewing lens of the alethoscope. ]]></note></mads>