Optical computing devices are disclosed. One optical computing device includes an electromagnetic radiation source that emits electromagnetic radiation into an optical train to optically interact with a sample and at least one integrated computational element, the sample being configured to generate optically interacted radiation. A sampling window is arranged adjacent the sample and configured to allow transmission of the electromagnetic radiation therethrough and has one or more surfaces that generate one or more stray signals. A first focal lens is arranged to receive the optically interacted radiation and the one or more stray signals and generate a primary focal point from the optically interacted radiation. A structural element defines a spatial aperture aligned with the primary focal point such that the optically interacted radiation is able to pass therethrough while transmission of the one or more stray signals is substantially blocked by the structural element.