and Fox Talbot in 1830 were almost certainly made using a single double convex lens which were in common use at that time in Camera obscuras.
As photography developed the simple lens was replaced by achromatic couplets taken from telescope objectives.
By 1840 Chevalier, a Parisian optician, and Wollaston in Britain had developed meniscus achromats.
However in 1841 Voigtlander and Professor Pet
유아는 놀이를 통해 즐거움을 얻을 뿐만 아니라 신체적인 발달 면에서 좀더 진보되고 운동기술을 습득하게 된다(Christie, 1987). 유아는 자신을 둘러싼 외부와의 상호작용을 통해 성장하는데, 어른처럼 일과 휴식이 구분되어 있는 것이 아니라 놀면서 배우고, 놀면서 탐색한다. 즉, 유아에게 있어서 놀이란