什么是物体的一维实空间分布函数?

[TripleY]

看论文遇到了：

Consider the discretized one-dimensional (1-D) real-space distribution function of an object: x(extension of the formulation to higher dimensions is straightforward). In CDI, for example, this corresponds to the transmittance function of the object.The fact that x is generally complex corresponds physically to the fact that the electromagnetic field emanating from different points on the object has not only magnitude but also phase (as is always the case, for example, when 3-D objects are illuminated and light is reflected from points at different planes). 

不明白什么是(1-D) real-space distribution function of an object。