The back surface of progressive addition lens (PAL) is a non-rotationally symmetric freeform surface. The local radius varies progressively from the far zone to the near zone along the intermediate zone to give the addition power. Numerical simulation method is performed to calculate the discrete points on the freeform surface in polar coordinate and generate the data files containing the trajectory of diamond tool tip for surface machining. The fabrication of PAL is accomplished by using self-developed single-point diamond turning machine with voice coil fast tool servo. The polished freeform surface profile measured by a 3-axes coordinate measuring machine shows little deviation to the simulation result. Surface power and cylinder of the fabricated PAL is also measured for comparison with theoretical design.
Diffraction efficiency of the structured thin-films phase grating (STFPG) at the visible wavelength is analyzed by the rigorous coupled wave analysis (RCWA) method demonstrating that the TM polarization can be separated from the 0th transmitted order of the TE polarization by ±1st order diffraction. The far field diffraction pattern is simulated by the finite-difference time-domain (FDTD) method to show the polarization beam splitting effect of the STFPG at wavelength of 633nm. In the near field, polarization dependent Talbot effect of the STFPG is also elaborated. FDTD simulations reveal that the spatial distribution of the interference fringes forming the self-image can be shifted by a half of grating period by changing the incident wave polarization within a particular wavelength range.
In this paper, the application background of anti-IR thin films for resin lens is outlined. SiO2 and Si3N4 are chosen as
coating materials. Mid-frequency pulse magnetron sputtering is adopted to prepare the thin films. Deposition rate is
calibrated by fitting the measured transmission spectrum of high-reflective thin films, which can improve the precision of
film thickness monitoring. Anti-IR thin films and visible range anti-reflective thin films are successfully deposited on the
convex and concave surface of CR39 resin lens, respectively. The spectral properties, surface morphology and microstructure
of the deposited thin films are characterized by ultraviolet-visible spectrophotometer, scanning electron
microscopy (SEM) and atomic force microscope (AFM), respectively. The results show that the averaged transmittivity
of the resin lens after coating exceeds 97% in 420~680 nm, and is below 55% in 800~1350 nm at normal incidenct angle.
Anti-IR thin films have a uniform distribution and compact microstructures on the lens.
Video magnifiers as a low-vision devices require special zoom lens which has finite conjugate distance for shooting
close object. Unlike the zoom lens using zoom cam developed previously, here the optical and mechanical design of
zoom lens which is driven by stepping motor and has the potential to realize auto-focus and manual-focus is introduced.
This mechanical compensated zoom lens which has a tube length of 81.8 mm and a front intercept distance of 310 mm comprises four groups which are objective, variator, relay and compensator. The optical system can realize continuous zoom from 9.6~186 mm and 10X zoom ratio with stable image quality. System performance is evaluated by using modulation transfer function (MTF), diffuse spot in diameter and tolerance sensitivity analysis. The mechanical structure designed to realize auto-focus and manual-focus function of the zoom lens is depicted in detail.