[Solved] In a magnifying glass ______ lens is used. - magnifying glass what type of lens

 2024-07-05 04:25:29

Choosing a laser beam shaper can depend on many variants and there is no clear cut answer to which shaper type is the best for what application. The below qualitative table summarizes the differences and advantages of each type and will try to direct you to the correct solution for your needs.

The IC-8 IOL is marketed by AcuFocus to provide 3D of functional range of vision when placed at a target of -0.75D in the non-dominant eye with an accompanying monofocal IOL in the dominant eye, targeted for emmetropia[8].

The IOL is a foldable single piece, hydrophobic, Acrylic lens that has an embedded annular ring composed of polyvinylidene fluoride and carbon nanoparticles. It is 5um thick and the aperture measures 1.36mm, while the outer diameter measures 3.2mm, an overal 15% decrease in size from the Kamra inlay to adjust for a more posterior position.

How to design a Gaussian to top hatbeamshaper

Caption: Xtrafocus IOL with soft angulated haptics allow for ciliary sulcus placement in a piggy-back fashion in pseudophakic eyes Source: https://crstodayeurope.com/articles/2016-feb/development-of-a-pinhole-implant-xtrafocus/

Patients have to be counseled regarding decreased brightness and possible need for glasses during low light conditions[16].

The microlens array (MLA) is possibly the most common and well known beam shaping solution, but perhaps also the most limited one amongst the solutions offered here for beam shaping purposes. As its name implies, it comprises an array of microlenses arranged in a certain specific periodic grid – typically round, square or cylindrical lenses in a square, hexagonal or a linear grid. Used in a defocus regime, or as a part of a fly-eye-diffuser pair, it can produce diffusion and flat-top shaping for less coherent beams.

Currently two types of pinhole IOLs exist, the IC-8 IOL (AcuFocus) and the Xtrafocus IOL (Morcher), both serving two distinct functions.

A laser beam shaper is an optical component used to manipulate the phase of the beam passing through it and modify the beam’s intensity profile to a well defined shape and size, with controlled intensity distribution within the spot.

in the above table you can find a comparison table between the different options, but the best way to know would be to contact us with your input beam specs and your output requirements and we will offer the most suitable solution for you.

Pi shaper

The IC-8 monfocal IOL uses similar principles to the Kamra corneal inlay[5]. The lens has been approved for use outside of the US in 2014 and currently pending completion of an FDA trial[6]. The IOL is intended for monocular placement in the non-dominant eye, in an effort to provide presbyopic correction while maintains good range of distance vision.

A laser beam is characterized by a coherent, monochromatic irradiance with a Gaussian profile, where the beam intensity is strongest at the center of the beam and decays towards the edges of it. If looking at the intensity profile on the working plane, this radiance profile results in a spot that has strong energy at the center and continuously fades outside of the center until the energy level reaches zero.

The pinhole affect is based on the stenopeic principle, which allows small central rays to enter the eye and eliminates diverging rays, thus reducing the circle of blur on the retina[1]. As a result, the depth of focus is increased, providing patients with good distance and near vision. This concept has been routinely used in ophthalmology in the form of pinhole occluders and glasses and even through the surgical constriction of the iris, however this concept has recently been introduced to the IOL plane. Although viewing through a small aperture increases depth of focus, it comes with the disadvantage of decreased brightness, decreased visual field and decreased optimal visual acuity,[2][3] as depicted in the chart below[4] .

Beamexpander

Laguerre Gaussbeam

In many laser applications, where there is an advantage for a clear border between the treated and the untreated area, this energy profile is not optimal.

There are various types of laser beam shapers with different properties to each:Top-hat beam shaperDiffractive diffuserBroadband diffuserMicrolens array

The Xtrafocus IOL is a small-aperture sulcus IOL designed for implantation as a piggy back lens for patients with a lens already implanted in the capsular bag. This lens is designed to reduce irregular astigmatism or light sensitivity in patients who have undergone PKP or who have other corneal irregularities. The IOL was given a CE mark in 2016 and is currently pending an FDA trial by Morcher. Dr. Trindade, who holds a patent for the design, implanted the IOL in a patient with Urrets-Zavala’s syndrome, suffering from intractable light sensitivity with marked improvement[7].

Flat-topbeam

Data from AcuFocus suggests patients achieve a near visual acuity of 20/30 at 40cm and 20/40 at 33cm. Other Studies show that mean visual acuity remains 20/40 (0.3 logMAR) or better over a range of ±2 D of defocus[9][10]. The lens also corrects astigmatism up to 1.5D without needing to be placed on a certain axis.[11][12][13][14].

The broadband diffuser (BD), also known as engineered diffuser, is a special flat-top beam shaping micro-refractive diffuser much similar to MLA, however with pseudo-random arrangement of the lenslets which results in far better homogenization quality compared to a simple MLA. By modifying the sub-aperture optical functions beyond the profile of a simple lens one can achieve versatile control of the shape, including M Shapes (Bat Wing) or even flat profile rings.

The diffractive diffuser is best used in laser systems with low coherence laser beams. It diffracts the beam and then scrambles it onto itself to achieve a highly homogenous, speckle free beam. The diffractive diffuser can be designed to any desired spot shape and size including free-form spot shapes, with controlled energy distribution within the spot (for example a bat-wing distribution, a non-symmetric tail and many more).

Unlike the diffractive optics beam shaping solutions stated above, a MLA is a refractive beam shaping option making it applicable for use in polychromatic systems where more than a single wavelength requires the same shaping in the same optical path, or where white light or highly divergent sources such as light emitting diodes (LEDs) are in use.

Gaussianbeam

BD are specially designed laser beam shaping solutions for applications where multiple lasers are used in the same optical path for example: RGB module, tunable lasers and frequency doubled lasers operating over a broad spectral range.

A laser beam shaper is an optical component that modifies the intensity profile of the incident beam to create a well distinguished spot shape with sharp edges, so that the ratio between energy level inside the spot and out of it is as close to 100% as possible.

Given the IOL is placed closer to the eye’s nodal point, there are less problems noted with slight decentration from the visual axis as compared to the corneal inlays. The small aperture helps to reduce coma as peripheral light rays are blocked.

Much like the top hat beam shaper, the diffractive diffuser is a DOE and thus it provides the same benefits of sharp transfer region, perfect angular accuracy, very low production tolerances and compactness. Unlike the flat top laser beam shaper, the diffractive diffuser is not sensitive to centration or beam size, making it very easy to integrate into existing systems.

BD elements offer high homogeneity with the same performance over a wide wavelength spectrum from IR to UV, high efficiency and no zero order.

Beamshaper

There are various applications that utilize laser beam shaping and reap the benefits. Some of the more common ones include:

Another characteristic of the laser beam shaper is the energy distribution inside the spot that can be controlled, thus enabling a more accurate, homogeneous and controlled process with minimal energy waste.

Although only anecdotal reports are available, retinal surgery following implantation of an intraocular lens with a pinhole optic seems to be possible without significant obstacle[17].

Laser beamhomogenizer

The Xtrafocus IOL is currently intended for patients with moderate-severe astigmatism resulting from KCN, trauma, PKP or post-RK. Due to its small aperture and opaque nature, peripheral vision may be significantly limited.

The IOL is composed of a foldable acrylic infra-red transparent material but otherwise appears black, opaque. The IOL measures 14mm in diameter with a 6mm optic and a 1.3mm central aperture. The lens has a concave-convex design to prevent contact with the lens already implanted in the capsular bag. It has soft, thin (250um) angulated haptics at 14 degrees that help to prevent uveitis-glaucoma-hyphema syndrome. It is placed in the ciliary sulcus in a piggy-back fashion in pseudophakic eyes. Funduscopic imaging can be obtained with an infra-red OCT imaging system.

The microlens array generates a fairly homogenic beam with high efficiency, and can be designed to produce geometric spot shapes (round, square, line etc.), however due to it’s refractive sub-aperture nature, it has an angular tolerance and fuzzier, softer edge compared to a diffractive diffuser, and is thus less recommended for systems requiring high precision.

DOEs are designed to work with a specific wavelength in which they enjoy a perfect angular accuracy and very low production tolerances thanks to their manufacturing process, making them the best solution for laser applications requiring high accuracy. They are fabricated onto optical windows making them flat, thin and lightweight, properties that bring added value to many customers requiring a compact solution.

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A study comprised of 21 patients with high irregular astigmatism from RK, KCN and PKP showed the median CDVA improved from 20/200 to 20/50 following IOL implantation[15].

A top hat beam shaper, also known as flat top beam shaper, is the high-end option applicable for laser systems that use single mode low M^2 laser beams (typically M^2 < 1.5). A flat top laser beam shaper is a diffractive optical element (DOE) that transforms the Gaussian beam into a flat-top beam with uniform intensity inside a well-defined shape with pre-designed angular dimensions, and a very sharp energy drop at the shape edges (the “transfer region”).