|
A projection clock (also called ceiling clock) is an analog or digital clock equipped with a projector that creates an enlarged image of the clock face on any suitable projection screen, most often the ceiling. The advantage of a projection clock is that the "clock" can be placed almost anywhere. Depending on the projector used, the image can be in monochrome or color. The image generated by most projection clocks is large enough that a nearsighted person can see it from distance without glasses or contact lenses. Projection clocks are also used in advertising and merchandising. High-brightness analog projection clocks can superimpose a business' logo on top of the clock face, while there are low-brightness projection clocks designed for home use that project for example a logo in addition to the time. Projection clocks may be connected to and synchronize with an Atomic clock to self adjust their time accurately. ==History== Projection clocks were patented at least twice: once in 1909, and another time in 1940.〔()〕 Both patents have expired. Early projection clocks were universally analog but with the widespread adoption of digital clocks, digital projection clocks became the standard. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Projection clock」の詳細全文を読む スポンサード リンク
|