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% Document Info
\author{sannyyy}
\pdfinfo{
  /Title (optical-aberrations-and-best-form-lenses.pdf)
  /Creator (Cheatography)
  /Author (sannyyy)
  /Subject (Optical Aberrations and Best Form Lenses Cheat Sheet)
}

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\noindent
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    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Optical Aberrations and Best Form Lenses Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{sannyyy} via \textcolor{DarkBackground}{\uline{cheatography.com/188301/cs/39266/}}}
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\noindent
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  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}sannyyy \\
  \uline{cheatography.com/sannyyy} \\
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 19th June, 2023.\\
   Page {\thepage} of \pageref{LastPage}.
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  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
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\begin{document}
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\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Optical Aberrations and Best Form Lenses}}  \tn
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{\bf{Lens Form - Types}} & {\bf{Curved Lenses}} \tn 
% Row Count 2 (+ 2)
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Curved surface determines whether plus or minus & Meniscus lenses are convex-concave lenses they have one outward faced curved and one inward \tn 
% Row Count 7 (+ 5)
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Flat surfaces are plano and have 0 power & Outward curve shaper than inward curve? Lens has a positive focal length and acts as a magnifier. Forms either real or virtual image. \tn 
% Row Count 14 (+ 7)
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\SetRowColor{white}
Lenses are determined by their surface curvatures, can be flat or curved & Toric lenses are curved surfaces. One surface spherical, the other toroidal. Used when cylinder in prescription. \tn 
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\mymulticolumn{2}{x{5.377cm}}{Curved surfaces are either meniscus or toric lenses} \tn 
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\mymulticolumn{2}{x{5.377cm}}{} \tn 
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\mymulticolumn{2}{x{5.377cm}}{F1 + F2 = F Total is the nominal power of a lens} \tn 
% Row Count 23 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Aberrations}}  \tn
% Row 0
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\mymulticolumn{1}{x{5.377cm}}{Lens aberrations can reduce image quality as the wearer gazes away or looks obliquely from the optical axis.} \tn 
% Row Count 3 (+ 3)
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\mymulticolumn{1}{x{5.377cm}}{There are 6 different lens aberrations that impact quality of peripheral vision through a lens:} \tn 
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% Row 2
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\mymulticolumn{1}{x{5.377cm}}{Oblique Astigmatism, Power Error, Spherical Aberrations, Coma, Distortion. These are monochromatic and occur independently of colour.} \tn 
% Row Count 8 (+ 3)
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\mymulticolumn{1}{x{5.377cm}}{Chromatic Aberrations are the consequence of the dispersive properties of the actual lens material.} \tn 
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\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{As the eye rotates behind the lens, the far point moves with the eye at a fixed distance from the Centre of rotation. This movement is known as the far point sphere. \newline The far point sphere is a spherical surface that represents the ideal focal points for a lens as the eye rotates to look through it. \newline Lens aberrations arise when light refracted by a lens fail to focus on the far point sphere.}  \tn 
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\end{tabularx}
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\begin{tabularx}{5.377cm}{X}
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\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Distortion}}  \tn
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\mymulticolumn{1}{x{5.377cm}}{Distortion is an optical aberration that deforms and bends straight lines and makes them appear curvy in images.} \tn 
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\mymulticolumn{1}{x{5.377cm}}{There are 3 types of optical distortion:} \tn 
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\end{tabularx}
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Oblique Astigmatism}}  \tn
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\SetRowColor{LightBackground}
An abberation that occurs when lightrays from an object in the periphery strike the lens obliquely and are then refracted by the tangential and sagittal meridians differently. & Oblique astigmatism can also be induced by tilting the lens, as this places the line of sight at a significant angle to the optical axis. \tn 
% Row Count 9 (+ 9)
% Row 1
\SetRowColor{white}
The Tangential meridian (T) refracts more incident lightrays than the Sagittal meridian (S). Consequently, incident light from an off-axis object are brought to a focus at 2 different points. & OA due to lens tilt can be minimised by ensuring that the optical axis of the lens passes through the centre of rotation in the eye. \tn 
% Row Count 19 (+ 10)
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The image of the object point is no longer focused at a single point, but is separated at 2 different foci, the Tangential Focus and the Sagittal Focus. & This can be achieved by manipulating the relationship between the pantoscopic tilt. \tn 
% Row Count 27 (+ 8)
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Oblique astigmatism occurs when the wearer looks at an angle (obliquely) through the lens or through the lens periphery. & The pantoscopic tilt is the lens tilt towards the cheeks and the height (H) of the wearer's pupil centre above the optical centre (OC) \tn 
% Row Count 34 (+ 7)
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\vfill
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Oblique Astigmatism (cont)}}  \tn
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 & {\bf{1mm of Optical Centre Drop (H) for Every 2 Degrees of Pantoscopic Tilt}} \tn 
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\mymulticolumn{2}{x{5.377cm}}{Oblique astigmatism is an astigmatic focusing error, and has a similar effect to unwanted cyl power in a prescription.}  \tn 
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
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\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Curvature of Field - Aspherical Lens}}  \tn
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Any surface that isn't spherical is aspheric & Conic sections are the sections when a plane intersects a cone \tn 
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Toroidal surfaces are aspheric & If a plane intersects a cone at right angles exactly to a vertical line passing through the apex the cut face would be a circle \tn 
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Aspheric surfaces are from concoids: a family of curves & Various curves that represent a section of the cone for aspheric lenses are: Cone, Ellipse, Parabola, Hyperbola \tn 
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% Row 3
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\mymulticolumn{2}{x{5.377cm}}{Eccentricity is the slight variation of angle that the plane has from the circular section, moving into the Ellipse section} \tn 
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% Row 4
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\mymulticolumn{2}{x{5.377cm}}{If the plane of intersection is exactly parallel to one side of the cone, it is the parabola section} \tn 
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The eccentricity for the conic sections are: & e = 0 for Circle, 0 \textless{}e \textless{} 1 for Ellipse, e = 1 for Parabola, e \textgreater{} 1 for Hyperbola \tn 
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\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Aspherical lenses are astigmatic.  \newline As you move away from the central vertex to the periphery of the lens, it results in negative surface astigmatism. \newline The negative surface astigmatism is used to neutralise the positive oblique astigmatism. \newline Positive oblique astigmatism arises off the axis gaze.}  \tn 
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Power Error}}  \tn
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When no OA is present, a lens brings light to a focus on the Petzval Surface - a curved image plane. & Power error is a result of the fact that the focal plane of the lens for off-axis object points departs from the FPS of the eye. \tn 
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Curvature of Field is an aberration that arises from the difference in focus between a flat focal plane and the Petzval surface & PE occurs even when there is no OA \tn 
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Curvature of Field is a concern for flat image planes, such as a camera. However the FPS (ideal plane of the eye) is also curved. & In PE, the Tangential and Sagittal meridians may refract incident light to a single point focus, however this is not on the FPS \tn 
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The Petzval surface is flatter than the FPS. & The FPS is the desired point of focus \tn 
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Power Error arises as the difference in focus between the Petzval surface and the FPS. & The dioptric difference between the actual focus and the desired focus results in a PE \tn 
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\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Unlike oblique astigmatism, power error is a spherical-like focusing error and is similar to unwanted spherical power in a prescription}  \tn 
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\end{tabularx}
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\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Coma}}  \tn
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\mymulticolumn{1}{x{5.377cm}}{Off-axis points of light appear comet shaped} \tn 
% Row Count 1 (+ 1)
% Row 1
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\mymulticolumn{1}{x{5.377cm}}{As lightrays from the edges pass through a lens they vary in magnification and create a series of asymmetrical circular shapes} \tn 
% Row Count 4 (+ 3)
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\mymulticolumn{1}{x{5.377cm}}{Reducing the lens down to a smaller aperture can reduce coma} \tn 
% Row Count 6 (+ 2)
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\mymulticolumn{1}{x{5.377cm}}{Corneal conditions like Keracotonus, corneal injuries or abrasians can result in coma} \tn 
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\hhline{>{\arrayrulecolor{DarkBackground}}-}
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\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Transverse Chromatic Aberrations}}  \tn
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\mymulticolumn{1}{x{5.377cm}}{Off axis blur occurs under low contrast conditions. Wearer may notice colour fringes. Transverse Chromatic Aberrations reduce visual acuity.} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Transverse Chromatism can be eliminated by an Achromatic Lens (a pair of lenses bonded together). Chromatism of one component neutralises the chromatism of the second.} \tn 
% Row Count 7 (+ 4)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Power is given by selecting a material with the highest V-value.} \tn 
% Row Count 9 (+ 2)
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\mymulticolumn{1}{x{5.377cm}}{Wollaston Lens reduce chromatism. The lens is bent into a steep curve. However Woollaston lenses are expensive and very bulbous} \tn 
% Row Count 12 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
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\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Ideal Best Form Lens}}  \tn
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\mymulticolumn{1}{x{5.377cm}}{Significant aberrations are: Transverse Chromatic Aberration, Distortion, Oblique Astigmatism, Curvature of Field} \tn 
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\mymulticolumn{1}{x{5.377cm}}{In practice, best form lenses usually eliminate: Oblique Astigmatism, Distortion, Curvature of Field} \tn 
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\mymulticolumn{1}{x{5.377cm}}{Spherical Aberration and Coma are both aberrations of wide aperture systems such as photography. A spectacle lens may be quite large but it is not a common issue.} \tn 
% Row Count 9 (+ 4)
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\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Aspheric Lens are the most common Best Form Lens} \tn 
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\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
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% That's all folks
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