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This work is to investigate the instrumentation implementing issues of back focal plane (BFP)-typed apertometer. Firstly, we introduce a general instrument architecture of the BFP-typed apertometer, including the hardware (optics and mechanics) of the system, operation procedures of control and measurement system, and also the digital image processing algorithm/software. Secondly, we are the first to discuss the gradual rising effect of total-internal-reflection (TIR) phenomenon, the criteria on how to “exactly” locate the reference ring on BFP images, and the corresponding accuracies. As a significantly important complement, we further discuss three important issues: 1) the influence of Goos–Hänchen shift on numerical aperture (NA) measurement; 2) comparison of one-dimension and two-dimension identification algorithms; and 3) comparison of center locating using Fourier correlation analysis (FCA) and Hough transformation (HT) algorithms. [ABSTRACT FROM AUTHOR]

A solid immersion objective is generally composed of a truncated solid ball and a commercial objective lens. It features higher numerical aperture (NA) than oil-immersion objectives and thus shows capabilities in some applications requiring higher NA or spatial resolutions. Different from commercial products of oil-immersion objectives and their pre labeled NA values, solid immersion objective is generally home-designed/developed, and the theoretical NA is taken as its practical value, which is not suggested. So far, there has been no proper and commercial apparatus to measure this NA value especially for bare solid immersion objectives. In this work, we propose an extremely simple but very practical approach for the measurement, which inherits the concept of Fourier optics but offers some specific features. Furthermore, we specifically propose an algorithm of multipoint reference to achieve high accuracy of NA value. Detailed comparisons between the proposed algorithm and the previous algorithm of single-point reference are elaborated. An experimental prototype of apertometer for solid immersion objective is built up to verify the proposed approach and algorithm. To the best of the authors’ knowledge, this is the simplest, cheapest, and most practical approach and apparatus for the NA measurement of bare solid immersion objective. [ABSTRACT FROM AUTHOR]