noun
magnifying glass; magnifier; loupe
General term for a handheld magnifying lens, including jeweler's loupes and reading magnifiers.
See also: 虫眼鏡
細かい文字を読むために拡大鏡を使った。
I used a magnifying glass to read the small print.
虫眼鏡 is a more common, everyday word for a magnifying glass, while 拡大鏡 is slightly more formal or technical.
Compound of 拡大 (かくだい, 'magnification') and 鏡 (きょう, 'mirror' or 'lens').