科技文献资料中,电子显微镜图片绝大部分都是黑白片。为了教学和交流,传统方法需通过先翻拍成负片,再拷贝出正片即黑白幻灯片放映用。这种方法,对每种图片不需大量拷贝但紧急使用或图片翻拍量多的情况,势必难以迅速制成或造成拷贝后大量负片积压或废弃,费时耗料,极不经济。相反,在每种图片只需一、二张幻灯片时,不论翻拍数量多少, Science and technology literature, the vast majority of electron microscopy images are black and white film. In order to teach and exchange, the traditional method needs to be turned into a negative film first, and then the positive black-and-white slide show is copied. This method does not require a large number of copies of each picture but emergency use or picture remake of the situation is bound to be difficult to quickly make or copy a large number of negative copies or discarded, time-consuming materials, very uneconomical. On the contrary, in each picture only one or two slides, no matter how much the number of remakes,