Direct-view oblique plane microscopy

The ability to rapidly image mesoscopic samples is critically important for many areas of biological research. Owing to its high through-put and gentle, volumetric imaging nature, light-sheet fluorescence microscopy (LSFM) is an attractive modality to image such samples. However, the orthogonal dual-objective geometry of LSFM makes sample mounting challenging. Oblique plane microscopy (OPM) circumvents these issues by achieving light-sheet imaging through a single objective near the sample, with a further two objectives acting to image a tilted, oblique plane in the specimen. However, at low magnification, as required for mesoscopic imaging, conventional OPM systems suffer from a complicated and inefficient light path and/or a limited numerical aperture. Here we present a simple method for mesoscopic OPM that enables efficient light collection at any numerical aperture. By placing the camera directly in the remote space, the oblique plane can be imaged without the need for a third microscope system. Using a commercially available camera with 1.4 {micro}m pixels, we demonstrate imaging over a 5.3 x 3 x 2.6 mm3 field of view with a lateral resolution of [~]2 {micro}m and axial resolution of [~]22 {micro}m. Our technique is then used to image a 4x-expanded brain organoid.