远心镜头在痕迹物证照相中的应用

Applicability of Telecentric Lens in Photographing Evidential Traces

目的通过对比实验探讨远心镜头在痕迹物证照相中的应用效果。方法在相同光环境下,用等倍率常规相机微距镜头和远心镜头拍照相同的痕迹物面,从景深、清晰度、变形、边缘效果等方面进行比较。结果常规微距镜头大光圈景深较差,小光圈(F/16)景深较好,但有变形,清晰度下降,图像亮度不均匀;远心镜头景深和变形兼顾较好,拍摄的图像亮度均匀,锐度较高,便于现场实时观察。结论远心镜头在痕迹物证照相中具有一定的应用价值。

Objective To probe into the applicability of telecentric lens in photographing evidential traces by way of comparative experiments.Methods Under the identical light circumstance,the same surface was respectively photographed with a conventional magnification-constant camera equipped of lens of either macro or telecentric.The comparison was made into the items of field depth,definition,deformation,and edge fidelity of the shot images.Results The conventional macro lens rendered poor field depth when the large aperture as the choice,in contrast to utilization of small aperture(F/16)having achieved the improved field depth yet occurrence of deformation,the decreased clarity and nonuniform brightness.The telecentric lens delivered the shot image of better balancing in both the field depth and deformation together with the even brightness and high sharpness.Conclusion The telecentric lens is of certain applicability in photographing evidential traces.