<p>The background-oriented Schlieren technique has emerged as a promising method for visualizing density gradients and performing quantitative measurements. However, an inherent constraint of BOS is the compromise between spatial resolution and measurement sensitivity, as the BOS camera typically remains focused on the background pattern. To overcome the resolution-sensitivity constraint, a new BOS variant based on nominally directional rays is proposed in this paper. Instead of using diffuse, reflective background patterns, a spherically concave mirror etched with random dots has been used to create a dotted background that reflects rays in a directional manner. When combined with coaxial LED illumination, we demonstrate that the current setup can improve the spatial resolution of canonical BOS without compromising measurement sensitivity. Moreover, the proposed setup decouples the requirement for a small lens aperture to achieve a large depth of field, thereby significantly reducing the need for strong background illumination in high-speed BOS applications. To demonstrate the effectiveness of the proposed method in improving the BOS spatial resolution, both synthetic BOS image generations and experiments on low- and high-speed jets are conducted. The results show that the proposed BOS variant can be advantageous for measuring density-varying flows with a limited field of view.</p>