Effects of mask-alignment error on point spread function for multi-level Fresnel diffractive lenses

The full aperture complex amplitude transmittance function of a multi-level diffraction lens with mask- alignment errors was derived based on scalar diffraction theory. The point spread function （PSF） was calculated by the Kirchhoff diffraction integral. It is found that the radius of the Airy disk increases with the increase of the error in the direction of misalignment, and the image center shifts along the direction of misalignment. A fourlevel diffractive lens with a diameter of 80 mm was fabricated, and its PSF and diffraction efficiency of ＋1st order were calculated and measured. The distribution of PSF is consistent with the calculated results, and the tested diffraction efficiency is slightly smaller than the calculated value; the relative error is 5.71%.

Diffractive multifocal intraocular lens implantation in patients with monofocal intraocular lens in the contralateral eye

AIM:To evaluate clinical outcomes of unilateral implantation of a diffractive multifocal intraocular lens(IOL)in patients with contralateral monofocal IOL.METHODS:Twenty-two patients who already had implantation of a monofocal IOL in unilateral eye underwent implantation of a diffractive multifocal IOL in contralateral eye were enrolled.After 1,6,and 12 mo,uncorrected and distant corrected distant visual acuity(UCDVA and DCDVA),uncorrected and distant corrected intermediate-visual acuity(UCIVA and DCIVA),uncorrected and distant corrected near visual acuity(UCNVA and DCNVA),and contrast sensitivity were obtained.Halo/glare symptoms,spectacle dependence,and patient satisfaction were also evaluated.RESULTS:The mean age was 67.86±7.25 y and the average interval between two IOL implantations was 645.82±878.44 d.At 1 mo,binocular UCDVA was lower than 0.20 logMAR in 76%of patients(mean 0.12±0.13 logMAR),which increased to 90%by 6 and 12 mo.The binocular UCDVA was significantly better than the monocular results(P<0.05)at 1,6,and 12 mo.Additionally,UCNVA was lower than 0.40 logMAR in 82%of patients,increasing to 90%by 6 and 12 mo.Mean UCNVA in the multifocal IOL implanted eye was statistically significantly better than that in the monofocal IOL implanted eye(P<0.05)at 1,6,and 12 mo.About 5%of patients at 1 and 6 mo,reported"severe glare or halo".Patient satisfaction rates were 95%and 91%at 6 and 12 mo,respectively.CONCLUSION:Unilateral implantation of multifocal IOL in patients with a contralateral,monofocal IOL implantation results in high patient satisfaction rate,with low severe glare or halo rate during follow-up.It can represent a good option for patients who have previously had a monofocal IOL implantation regardless of two year interval duration between two IOL implantations.

Compound diffractive telescope system:design,stray light analysis,and optical test

The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view （FOV）, a lower cost as well as looser fabrication tolerance. In this paper, the design of a compound diffractive telescope composed of one primary lens and twenty-one eyepieces is introduced. Then the influence of diffraction orders on the performance of the system is analysed. A modified phase function model of diffractive optics is proposed to analyse the modulation transfer function （MTF） curves for 0° FOV, which provides a more accurate prediction of the performance of the system. In addition, an optimized mechanism is also proposed to suppress stray light. The star image and resolution tests show that the system can achieve diffraction limit imaging within ±2° of FOV and 4-4 mm of eccentricity. Finally, a series of pictures of an object are taken from different channels, and the splicing of pictures from adjacent FOVs is demonstrated. In summary, the designed system has been proved to have great potential applications.

Large aperture phase-coded diffractive lens for achromatic and 16°field-of-view imaging with high efficiency

Diffractive lenses(DLs)can realize high-resolution imaging with light weight and compact size.Conventional DLs suffer large chromatic and off-axis aberrations,which significantly limits their practical applications.Although many achromatic methods have been proposed,most of them are used for designing small aperture DLs,which have low diffraction efficiencies.In the designing of diffractive achromatic lenses,increasing the aperture and improving the diffraction efficiency have become two of the most important design issues.Here,a novel phase-coded diffractive lens(PCDL)for achromatic imaging with a large aperture and high efficiency is proposed and demonstrated experimentally,and it also possesses wide field-of-view(FOV)imaging at the same time.The phase distribution of the conventional phase-type diffractive lens(DL)is coded with a cubic function to expand both the working bandwidth and the FOV of conventional DL.The proposed phase-type DL is fabricated by using the laser direct writing of grey-scale patterns for a PCDL of a diameter of 10 mm,a focal length of 100 mm,and a cubic phase coding parameter of 30π.Experimental results show that the working bandwidth and the FOV of the PCDL respectively reach 50 nm and 16°with over 8%focusing efficiency,which are in significant contrast to the counterparts of conventional DL and in good agreement with the theoretical predictions.This work provides a novel way for implementing the achromatic,wide FOV,and high-efficiency imaging with large aperture DL.

Design of double-zone aspheric diffractive intraocular lens with extended depth of focus

A double-zone aspheric diffractive intraocular lens （IOL） was designed and manufactured aiming to regain a continuous range of clear vision for pseudophakic presbyopia. After obtaining the IOL structure parameters through optimization based on an aphakic model eye, its imaging performances were analyzed in the model eye. The modulation transfer function at 50 cycles/mm remained above 0.29 within ±5° field of view for object distance ranging from 6 to 0.66 m. In addition, the imaging qualities are robust for pupil changes, polychromatic light, and different corneal asphericities. The manufactured IOL exhibits the abilitv to extend depth of focus.