Zemax for Beginners: Spherical Aberration Basics

Discover why no lens is ideal and how spherical aberration limits focusing light to a point. Embrace real aberrations rather than myths of perfect lenses.

Demonstrate a perfect lens by showing how a function theta(y) bends parallel rays to a single point, using tangent theta = y/f and small-angle theta ≈ y/f.

Explore how a real, spherical lens causes spherical aberrations and deviates from the ideal focus, using the paraxial approximation, ray angles, and focal length concepts.

Explore aspheric surfaces, defined as not spherical, and learn how the coning constant k appears in aspheric equations to describe deviation from a perfect sphere.

Explore how aspheric lenses correct aberrations by shaping surfaces beyond a sphere, compare with spherical lenses, and learn to optimize focus and trade‑offs in fabrication while minimizing aberrations.

Examine conic constant k and sag height as a function of radius, showing how k shapes sphere, paraboloid, hyperboloid, and ellipsoid forms with radius of curvature at the vertex.

Explore how the conic constant turns a spherical lens into a plano convex aspheric lens, reducing spherical aberration and focusing rays to almost a single point in Zemax for beginners.

Explore parabolic mirrors and how conic constants affect spherical aberration, showing that a conic constant of -1 yields a single focus with no spherical aberration.

Aberration is the deviation from an ideal image caused by non-ideal lenses, such as spherical aberration, reducing sharpness, contrast, and resolution; it splits into monochromatic (geometry-related) and chromatic (dispersion-related) types.

Explore monochromatic aberrations, focusing on spherical aberration, coma, astigmatism, field curvature, and image distortion, with defocus excluded as a corrective focus issue.

Explore marginal rays, starting at the optical axis and passing through the edge of the stop to define the system’s maximum angle and its numerical aperture.

Show how the stop and CCD size define the field of view, with chief rays from the field edge governing visibility and the exit pupil forming across the optical axis.

Explore how the aperture stop restricts light in an optical system, changing the light bundle while keeping the field of view constant, with physical and animated examples.

Understand the entrance pupil as the image of the aperture stop seen from object space, whose location can be real or virtual and changes when the stop moves.

The exit pupil is the image of the aperture stop seen from image space, and moving the stop changes the exit pupil, which can lie inside or outside the lens.

Explore the transfer ray fan plot, a graph of ray aberration versus pupil coordinates, showing how a real lens diverges from an ideal focus across the y and x directions.

Explore how aberrated rays differ from ideal rays, and how tangential (y) and sagittal (x) errors influence the image plane, entrance and exit pupil, and four lens surfaces.

Explore Cartesian and polar coordinate systems, defining points as x0, y0 or (r, theta); learn how x = r cos theta, y = r sin theta, and theta = arctan(y/x).

Explore the ray coordinate system in zemax for beginners, using polar coordinates where x and y relate to rho and theta by y = rho cos theta and sine theta.

Explore ray coordinates using object plane, entrance pupil, and image plane; apply -1 to 1 scaling and determine h x h y and p x p y with sample cases.

Explore third-order aberrations through Seidel expansion, using two paraxial rays, marginal and chief, to estimate surface contributions and understand spherical aberration, coma, astigmatism, curvature, and distortion.

Explain how wavefronts relate to rays, and how aberrations distort a spherical wavefront, comparing wavefront error and ray plots to show ideal versus aberrated optics.

Explore on-axis ray errors and the optical axis in rotationally symmetric lenses, emphasizing spherical aberration as the sole third-order on-axis aberration in such systems.

Explore a singlet lens example with Zemax, detailing a Thorlabs LA 1251's focal length, diameter, radii of curvature, thickness, and wavelength, then import and verify in Zemax.

Model a singlet lens in Zemax for beginners, setting aperture 25 mm and wavelength 550 nm, two surfaces; use marginal ray height to focus infinity rays into a single point.

Explore the distinction between minimum focus and paraxial (practical) focus in Zemax. Learn to identify paraxial focus, evaluate RMSE spot sizes, and compare geometrical versus RMSE beam diameters.

Learn to set marginal ray height to zero, compare paraxial and minimum focus, and use Zemax's quick focus to place the image surface at optimum focus based on spot size.

Explore how the focal point of a pair of rays depends on entrance pupil position, revealing spherical aberration and paraxial focus, using ray tracing and a pupil coordinate graph.

Explore longitudinal spherical aberration in Zemax by analyzing paraxial and marginal focus, adjusting radius of curvature, and using quick focus to optimize focus points.

Learn how spot diagrams visualize ray paths through lenses, interpret focusing behavior, and compare lens performance with practical, location-based visuals in Zemax.

Learn to analyze spherical aberration in Zemax using standard spot diagrams, examining RMS spot size and how radii of curvature affect diffraction-limited performance.

Learn how defocusing in Zemax moves the image surface and affects paraxial focus, using marginal focus and a defocus surface, and optimize spot size with the slider and spot diagram.

Define meridional rays and meridional (tangential) planes in a rotationally symmetric optical system, where any plane through the optical axis and an object point hosts these rays.

Explain sagittal rays and meridional rays, define sagittal plane as perpendicular to incoming rays, compare sagittal and meridional focuses, and note astigmatism in optical systems.

Explore tangential ray error in Zemax for beginners, identifying meridional vs tangential planes, tracing rays from -1 to 1, and plotting y tangential error e_y across z max.

Learn to analyze sagittal ray error in Zemax, quantify each ray's aberration from negative to positive x, plot sagittal ray error in z max, and extract representative data.

Learn to generate and interpret the transverse ray plot in Zemax, analyzing tangential and sagittal fans, field effects, and aberrations to optimize lens performance.

Explore wavefronts and wavefront error, including reference sphere, to understand optical aberrations, compare wavefront analysis with ray fan plots, and learn how to extract optical path difference data in Zemax.

Explain the transverse spherical aberration coefficient (TSP) as the main measure of spherical aberration, showing its dependence on rho and h and its relation to the total error e.

Demonstrate building a singlet lens in Zemax to keep a constant effective focal length while adjusting first-surface curvature and the second surface to compensate spherical aberration.

Explore Seidel aberration coefficients by examining transverse spherical aberration, transfer coefficients, and surface contributions, and see how radii of curvature and thickness influence the total aberration and focal length.

Analyze saddle coefficients and raven plot to examine transverse spherical aberration, linking rho cubed to the graph while adjusting scale on the first surface reveals the lens’s spherical aberration behavior.

Learn to analyze spherical aberration using the OPD optical path difference method, compare plots at different wave scales, and manually choose the optimum value to minimize wavefront error.

Learn how to minimize spherical aberration by stopping down the lens, adjusting the entrance pupil diameter, and analyzing the impact in Zemax.

Use stop down in Zemax to reduce spherical aberration while keeping the effective focal length fixed, and show how reducing entrance pupil diameter from 20 to 12 lowers aberration.

Learn how reversing a lens in Zemax alters spherical aberration. Flip a plano-convex lens to reduce the transverse aberration coefficient and shift the raven plot.

Explore lens bending to minimize spherical aberration by adjusting front and back curvature while keeping focal length constant, showing how shapes affect spot diagrams and reveal an optimum lens shape.

Explore lens shape factor and how varying radii R1 and R2 yield the same focal length, illustrating the x factor and its role in shaping spherical aberration.

Set a lens with constant focal length in Zemax by configuring aperture 20, field 10, and wavelength 550, with object at infinity and the stop on the first surface. Adjust the second surface radii of curvature and the marginal angle to achieve an effective focal length of 50, then set thickness and marginal ray height.

Explore spherical aberration in on-axis lenses by iteratively adjusting radii of curvature to minimize wavefront errors while keeping the effective focal length fixed.

Explore the slider method in Zemax to adjust radii of curvature and observe real-time effects on spherical aberration, enabling quicker lens optimization.

Learn to use a merit-function optimization in Zemax to minimize spherical aberration by adjusting the first surface radius with weights and a single wavelength.

Show how lens orientation affects spherical aberration and coupling efficiency into a fiber. Facing the curved surface toward the laser light minimizes spot size, from about 1300 to 300 microns.

Adjust radii to form a bi-convex lens with a 50 mm effective focal length and determine the transverse spherical aberration in Zemax for beginners: spherical aberration basics, example 2.

Optimize the radius of curvature to minimize spherical aberration for a lens with an effective focal length of 50, using the merit function sbh and BK7 at 588 nm.

Explore fiber-to-fiber coupling with Zemax to minimize spherical aberration and spot size at 1030 nm using NBK7 glass, finding that identical lenses facing the same direction work best.

In Zemax, optimize the optimal radii of curvature of two lenses to minimize on-axis spherical aberration, achieving a good spot size for multimode fiber with an airy disk.

Shows step-by-step optimization of three variables in Zemax to minimize spherical aberration, adjusting the radii of curvature and using surface pickup with small, convergent changes.