Marek Zajac

Placement of a crystalline lens and intraocular lens: retinal image quality

The influence of changes of both crystalline lens and intraocular lens (IOL) misalignment on the retinal image quality was investigated. The optical model of the eye used in investigations was the Liou-Brennan model, which is commonly considered as one of the most anatomically accurate. The original crystalline lens from this model was replaced with an IOL, made of rigid polymethylmethacrylate, in a way that recommend obligatory procedures. The modifications that were made both for crystalline lens and IOL were the longitudinal, the transversal, and the angular displacement.

Aberrations of holographic lenses in image quality evaluation

The imaging quality of holographic lenses depends on parameters that include the shape of a holographic lens surface or an input pupil position. Based on the formulas for third-order aberration coefficients derived for such cases, conditions that ensure the correction of aperture and field aberrations are given. The possibility of joint correction of spherical aberration, coma, and astigmatism is discussed. The formulas presented are illustrated with a number of examples; two types of holo-lenses are taken into account: imaging and focusing. For imaging quality assessment an aberration spot calculation method based on numerical evaluation of an appropriate diffraction integral is used. The results of this method are compared with the results of imaging quality estimation using the geometrical ray tracing method.

Holographic optical elements used in spectroscopy: some remarks on image quality.

Because of their significant chromatic aberration, holographic optical elements (HOEs) can be used as narrowband optical filters or scanning spectroscopes. Although it is impossible to obtain aberration free imaging over the whole spectrum of light wavelength, by an appropriate choice of HOE recording and imaging geometries, the aberrations can be seriously minimized. As an example, the imaging quality of several different HOEs used in multichannel spectroscopy is analyzed with the aid of numerical evaluation of the respective diffraction integrals. Such computer modeling of imaging gives more adequate results than the geometric ray tracing method.

Simple achromatic hybrid lens

The simplest achromatic hybrid lens consists of a refractive (glass) lens with a diffractive microstructure deposited on one of its surfaces. In such lens the reasonable aberration correction is possible only for very limited aperture and field angles. Better possibilities of aberration correction appear if we split the refractive lens onto two identical parts separated by certain distance and locate the diffractive element between the glass lenses. We show that in such way it is possible to obtain hybrid lens of the same or even smaller aberrations for substantially greater aperture and field angles.

Direct interferometric measurement of the holographic lens wave aberration

Classical interferometric methods for measurement of wave aberrations of holographic lenses have certain drawbacks. The limited diffraction efficiency of such lenses is the reason. To overcome this problem a new type of interferometer is suggested. The holographic lens under test is a basic element of the interferometer itself. The interference pattern is formed by adding the undiffracted and the diffracted waves.

Measurement of contrast sensitivity function in laser light

Visual quality depends on many factors of different nature and therefore it is not easy to define. Different measures are used to describe vision quality, such as: two point resolution, visual acuity, contrast sensitivity function (CSF) etc. We concentrate especially on CSF. There are two important factors affecting character of CSF. One of them is connected with the Optical Transfer Function (OTF) of the eye and the second one with the retinal response. Typically CSF is measured in incoherent light. Due to it is dependence on both mentioned above factors simultaneously it is impossible to extract the information on the eye optical system only. We hope that additional information offered by CSF measured in coherent light can help to solve this problem.

Measurement of wavefront aberrations of diffractive imaging elements

Diffractive optics is more and more widely used nowadays. One of its most important applications is diffractive imaging element (DIE). The DIE can be a lens (Holo-lens, diffractive lens, hybrid lens) or a part of complex imaging system (e.g. an aberration corrector). Apart of such problems occurring when dealing with DIE as its design, manufacture or copying the problem of its control is important. By this we mean the measurement of wavefront generated by DIE, i.e. the evaluation of wavefront aberrations. To this aim we propose two different experimental methods: one of them employs diffraction interferometer, the other one holographic shearing interferometer.

Hybrid imaging element: possibilites of aberration correction

In the case of a single-element imaging system, aplanatic correction is of major importance. It can be achieved for single holographic lens, if recorded on a spherical surface. For this reason, however, a diffractive microstructure of high spatial frequency has to be recorded. From technological point of view, a combination of classic, glass lens giving most part of overall refractive power with a diffractive structure of relatively low spatial frequency acting as an aberration corrector seems to be more advantageous. In this paper the possibility of aplanatic correction if assuming that the object point is located in infinity and both refractive surfaces are spherical is analyzed.

The third-order aplanatic correction of a hybrid lens

The third-order of a hybrid lens (composed of a diffractive structure deposited on a surface of a classical lens) is derived to obtain the construction parameters of an aplanatic lens. As an example an infinitely thin piano-convex lens is considered.

Hybrid achromatic spectacle lens

Spectacle lens is a very particular optical imaging element of great practical importance. Although its construction is very simple some demands are specific (in particular remarkable shift of output pupil). A number of classic spectacle lens designs is known for long time, however some new possibilities of aberration correction appear if we use a hybrid (diffractive refractive). Hybrid lens is an optical system composed of a classic refractive (glass) lens and a diffractive microstructure deposited on one of its surfaces. Imaging properties of such lens can be expressed in terms of dimensionless parameters(formula available in paper)(describing the distribution of focusing power between diffractive and refractive part). By proper choice of parameter η we can compensate chromatic aberration. Thanks to other free parameters spherical aberration and astigmatism can be corrected also what is reasonable choice for spectacle lens. In this contribution the possibilities of particular Seidel aberration correction of hybrid lens will be presented. As an illustration some examples of spectacle hybrid lenses will be shown and its imaging characteristics compared with imaging characteristics of commercially available refractive lenses.