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Using grating shearing interferometry, a new and simple technique to measure the effective focal length of optical systems is described. The diffraction pattern of a phase grating positioned at the focal point of the lens under test is evaluated for this purpose. The relative lateral shift between the undiffracted zero order and the diffracted first orders caused by the grating is measured. By utilizing knowledge of the wavelength of light, the grating period, and the diameter of an aperture stop placed in front of the test lens, we can determine the effective focal length of the test lens. Results of measurements are presented and compared with calculated values. The dependence of the focal length on the wavelength of the light is shown by using two laser sources of different wavelengths. An analysis of the measurement accuracy is given. Key words: Optical testing, grating shearing interferometry, focal length measurement, phase grating.

A simple method for measuring both the numerical aperture and the f number of a lens system by means of a phase grating is described.

Materials engineering is generally regarded as one of the most effective methods in the construction of photocatalysts, but it still faces many challenges. In this context, we designed and prepared a three-dimensional (3D) heterostructure of nanowires (NWs) formed by C u 2 O core and an Au shell. The C u 2 O - A u NWs not only show fine photocatalytic ability but also proved to have Fenton-like chemical properties and can be used as a hydrogen peroxide sensor. Moreover, this heterostructure realizes an integration of catalytic efficiency, retrievability, and versatility. In further consideration of the facile preparation process and low-cost material source of the structure, the C u 2 O - A u NWs show a promising application prospect in the field of multifunctional photocatalysts.

Our research has shown that the autocorrelation peaks of a binary joint transform correlator are affected by input scenes' backgrounds. An adaptive method is proposed to overcome this problem. The image of interest is first extracted from the background based on the position of the highest correlation peak of the input and reference images. The extracted image is then correlated with the reference to obtain the final correlation peak. Numerical simulations showed that the final autocorrelation peak is the maximum constant for a specified reference image.