城建系统的档案是多种多样的。有些建设项目的峻工图装订成册,一般厚40～50毫米左右,最厚达到56毫米,又不能拆开,无法确定能否在景深范围内清晰拍摄,这直接影响缩微的质量。 面对问题我们进行了多方面的研究,采用了计算景深值方法。我们知道,拍摄机的平台即是摄影系统的对焦面,为此,利用前景深公式:△=Pε/（2a+Pε）。 式中:P 平台至物镜距离 Urban construction system files are varied. In some construction projects, the finished maps are bound in volumes of 40 to 50 millimeters in thickness and 56 millimeters in the thickest and can not be disassembled. Therefore, it is impossible to determine whether they can be clearly taken within the depth of field, which has a direct impact on the quality of microfilming. Faced with the problem we conducted a multi-faceted study, using the method of calculating depth of field value. We know that the camera’s platform is the focal plane of the camera system. To do this, use the foreground depth formula: Δ = Pε / (2a + Pε). Where: P platform to the objective distance