As a kind of excellent photoluminescent material, carbon quantum dots have been extensively studied in many fields, including biomedical applications and optoelectronic devices. They have been dispersed in polymer matrices to form luminescent films which can be used in LEDs, displays, sensors, etc. Owing to the total internal reflection at the flat polymer/air interfaces, a significant portion of the emitted light are trapped and dissipated. In this paper, we fabricate free standing flexible PVA films with photoluminescent carbon quantum dots embedded in them. We disperse silica microspheres at the film surfaces to couple out the total internal reflection. The effects of sphere densities and diameters on the enhancement of photoluminescence are experimentally investigated with a homemade microscope. The enhancement of fluorescence intensity is as high as 1.83 when the film is fully covered by spheres of 0.86 $${\boldsymbol{\mu }}$$µm diameter. It is worth noting that the light extraction originates from rather the scattering of individual spheres than the diffraction of ordered arrays. The mechanism of scattering is confirmed by numerical simulations. The simulated results show that the evanescent wave at the flat PVA/air interface can be effectively scattered out of the film.

A multi-aperture compound eye infrared optical system is designed for the imaging of cooled medium wave infrared detector. The optical system includes an infrared lenslet array arranged on the front spherical surface, and a relay infrared optical system matched with a cooled infrared detector. The problem of matching and connection between the infrared lenslet array arranged on a spherical surface and the relay infrared optical system matching with a cooled infrared detector is solved, and a set of multi aperture infrared bionic compound eye optical system that can match the cooled infrared detector is designed. Through the relay optical system, the focal surface imaged by the curved infrared lenslet array of compound eye is re-imaged on the focal plane of the cooled infrared detector. The waveband of the designed compound eye infrared optical system is 3.7-4.8μm. The total focal length is 3.5mm, the total field of view of the multi aperture compound eye optical system is 108°, the distortion of the full field of view is less than 6%. The design result shows that the image quality of the system with different aperture approaches the diffraction limit, and has the advantages of multi-aperture, large field-of-view, low distortion and ideal image quality.

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