Optical Design
ECEn 466 Introduction to Optical Engineering
425 CB
Laboratory objective:
Use OSLO to create a camera lens in which the focal length can be varied and to analyze
lenses using OSLO.
Preliminary
A camera is characterized by the effective focal length of the optical system.
For a given incident angle the camera lens focuses the rays to the position on the focal
plane of h=f. For a typical camera the normal focal length is f=50mm.
1. If the pixel size on the CCD array is 12m, what is the pixel size of the image if the
scene is located 30m away from the camera?
2. If the CCD array is 1024x1024, what is the total size of the picture?
3. What is the total field of view (FOV) of the camera?
Laboratory
Section 1: Analyze an f=50mm camera lens that consists of a double convex lens.
1. Set the basic parameters.
a. Set the lens units to be mm.
b. Set the only wavelength to be =550nm.
c. Set the entrance radius to 4mm.
d. Set the field angle to 7o, which is close to the FOV calculated in the
preliminary.
e. Turn Draw On
2. Insert 2 extra surfaces. You should have 4 surfaces (AST, IMS, and 2 other surface).
3. Set surface 1 (AST) to have a radius of curvature of 40mm, a thickness of 4mm and a
material of BK7.
4. Set surface 2 to have an equal and opposite radius of curvature.
a. We want the curvature to be R2=0-1*R1.
b. Click on the box to the right of the radius value for surface 2.
c. Select curvature pickup.
d. The source surface should be the previous surface (2).
e. The constant should be 0.
f. The multiplier should be -1.0
5. Set the thickness of surface 2 to be 50mm.
6. Use the slider wheel to optimize the radius of curvature down to 1e-5.
a. Click on optimize and then Slider-Wheel Design (at the top).
b. Select Spot Diagram, 1 slider wheel, surf 1, Curvature (CV)
c. Slide the value until the spot diagram is the smallest. Change the step when
you get close to 0.001.
7. Plot the ray trace with 11 rays
8. Plot the spot diagram. Notice that the spot diagrams for the full-field does not stay
circular. This is called astigmatism.
9. Plot the ray-intercept curve and describe what the ray intercept curve is.
10. Adjust the entrance beam radius until the camera is diffraction limited.
a. Plot spot diagram with Airy disk plotted (this is the diffraction limit.), with
object point equal to (0,0,0).
b. Adjust Ent beam radius until Geometrical RMS R size is equal to less than
Diffraction Limit.
c. Readjust the lens curvature using the slider bar with each change in entrance
beam radius.
11. Adjust the entrance beam radius until the camera is diffraction limited.
a. Plot spot diagram with Airy disk plotted (this is the diffraction limit.), with
object point equal to (1,0,0).
b. Adjust Ent beam radius until Geometrical RMS R size is equal to less than
Diffraction Limit.
c. Readjust the lens curvature using the slider bar with each change in entrance
beam radius.
12. Plot the lens ray trace, the ray-intercept, and the spot diagram for the final design.
Section 2: Analyze an f=50mm camera lens that consists of a cemented doublet.
1. Set the basic parameters.
a. Set the only wavelength to be =550nm.
b. Set the entrance radius to 4mm.
c. Set the field angle to 7o, which is close to the FOV calculated in the
preliminary.
d. Turn Draw On
2. Insert an extra surface. You should have 3 surfaces (AST, IMS, and 1 other surface).
3. Add an achromatic doublet.
a. Right click on the 1st surface and click on Insert Catalog Lens.
b. Choose (1) cemented doublet, (2) Edmund, (3) Efl=50, and (4) Central
Diameter = 50
c. Click on the check mark.
4. Ungroup the lens.
a. Click on the 1st surface
b. Right click
c. choose Ungroup
5. Add rays to the lens drawing
a. Click on Lens menu
b. Click on Lens Drawing Conditions
c. Number of ray fans in lens drawings: 2
d. For Frac Y Obj 0.0 choose 11 rays
e. For Frac Y Obj 1.0 choose 11 rays
6. Use the slider to vary the distance from the lens to the surface.
7. Change the aperture stop to the first surface
a. Right click on the box for the 1st surface under the APERTURE RADIUS
column
b. Select Aperture Stop
8. Repeat steps 10-12 from the first section with only varying the distance from the lens
to the image.
Section 2: Analyze an f=50mm camera lens that consists of the separate lenses.
1. Load in the Cooke Triplet from the class web page.
2. Verify that the effective focal length of the lens system is f=50mm.
3. Change the wavelengths to only have =550nm.
4. Change the Field angle to 7o.
5. Add another surface at the end to get OSLO to trace rays to the image plane
6. Look at the effect of moving the aperture stop.
a. Place the aperture stop on surface 1, surface 3, and surface 6.
b. Explain what moving the aperture stop is doing.
c. Put the aperture stop back onto the middle lens
7. There are fewer rays that reach the image plane for the full-field.
a. What does this mean in terms of system performance?
8. Plot the through focus spot diagrams.
a. Notice how the full-field rays are more circular (less astigmatism) than the
doublet lens was.
b. Notice how the best focus for the full-field is close to the same location as that
of the zero-field. (less field curvature).
9. Repeat steps 10-12 from the first section with only varying the distance from the lens
to the image.
Now open the fish eye lens (fish.len).
1. Why is this lens called a fish eye lens?
2. What would be a possible use for this type of lens?
3. What happens if you move the aperture stop of this lens to the first surface?