Optical design of mesoscope objective with high resolution and large field of view

Abstract

The demand for high-resolution imaging of large-sized samples is increasing in current biomedicine and life sciences. Nevertheless, traditional microscope objectives encounter a compromise between resolution and field of view. This paper introduces a mesoscope objective that has a high space-bandwidth product, allowing it to attain high resolution and large field of view (FOV) at the same time. Based on aberration correction principles, a mesoscope objective is designed with focal length of 60 mm and numerical aperture of 0.47. This design allows a maximum FOV of 6 mm by optimizing materials and structure. This objective contains 14 spherical lenses made of common optical glass materials, achieving flat-field apochromatism over the wavelength range of 400-700 nm. Consequently, the modulation transfer function (MTF) curve of the mesoscope objective is close to the diffraction limit, and the RMS wavefront error throughout the whole field of view is below 0.08λ. The distortion is intended to be less than 0.5% at the periphery of the field. The lateral resolution of the objective is 0.68μm, and the field curvature is less than 5 μm. Based on the tolerance analysis results, MTF at the Nyquist frequency exceeds 0.2 when using a suitable compensator. This meets the necessary criteria for processing and practical applications. The mesoscope objective proposed in this paper exhibits considerable promise in the realm of tumour cell imaging, cranial nerve imaging, and embryonic tissue visualization.