# Y-NU Ray Trace Worksheet

## Worksheet Info

This worksheet strictly adheres to the sign, notation, and variable convention found in the Field Guide to Geometrical Optics by John E. Greivenkamp, and is the notation used in the University of Arizona "Introduction to Geometrical Optics" (OPTI 202 and OPTI 502) courses.

This worksheet only displays properly on desktop and laptop monitors with a horizontal window width of at least 1170 pixels; no tablets or phones (sorry).

Forward Ray Reverse Ray
Refraction/Reflection $n'u' = nu-y\phi$ $nu = n'u' + y\phi$
Transfer $y'=y+u't'$ $y=y'-u't'$

## Instructions

#### Specifying Trace Type

Step 1 Using the Trace type drop down menu, select whether you want to perform a standard ray trace, where surfaces are specified by their curvatures and indicies, or a thin lens ray trace, where surfaces are specified by their focal length and all indicies are assumed to be 1.0

Step 2 Using the Number of Surfaces drop down menu, select the number of surfaces in the system. Number of surfaces include any physical surfaces, pupils, and stops. Objects and images do not count toward the number of surfaces. You can specify up to 8 surfaces with this worksheet.

Step 3 Using the Ray Type drop down menu, select which type of ray you want to trace:

Ray Type Description Initial $y$ Initial $nu$
Forward parallel ray Traces a ray parallel to the optical axis from object to image space 1 0
Backward parallel ray Traces a ray parallel to the optical axis from image to object space 1 0
Object ray Traces a ray starting at the axial object point and terminates at the axial image point 0 0.1
Image ray Traces a ray starting at the axial image point and terminates at the axial object point 0 0.1
Stop test ray Traces an object ray for the purpose of finding which surfaces acts as the aperture atop 0 0.1
Chief ray Traces a chief ray for the purpose of determining entrace and exit pupil location 0 0.1
Arbitrary forward ray You pick the initial conditions You pick You pick
Arbitrary backward ray You pick the initial conditions You pick You pick

#### Filling Out Ray Trace Worksheet

Step 4 Enter the curvature C of each physical surface if doing a standard ray trace, or the focal length f of each thin lens if doing a thin lens trace. When entering for a surface with no power (e.g. a stop or pupil), enter 0 for that surface. Surfaces are entered in optical order as opposed to physical order, which means surfaces are entered in the order in which a paraxial ray parallel to the optical axis strikes each surface.

Step 5 Enter the separation t of each physical surface. Note you generally do not enter a separation t value for the object-to-first-surface distance or the last-surface-to-image distance, because these are typically the values you are solving for. If you know the object distance and want to solve for the image distance, e.g., there is a separate box to enter that information that appears after you select "Object ray" from the ray type drop down menu.

Step 6 Enter the index n for each optical region. Every time the ray encounters a mirror, the sign of the index flips. If performing a thin lens ray trace, all indicies are specified as 1.0 and any value entered into the worksheet will be ignored.

Step 7 Depending on the ray type, you may have to enter additional initial condition information as prompted.

Step 8 Click Calculate.

## Worksheet

0                         1                         2                         3                         4                         5                         6                         7                         8                         9

C

t

n

-phi

t/n

y

nu

u