OSLO FAQS

Why does the public lens database in OSLO LT 6.05 produce errors?

OSLO LT and OSLO Light are the same program, but OSLO LT is restricted to systems having fewer than 10 surfaces. Some of the lenses at the end of the database listing exceed this limit. You can resolve this issue by recompiling the public database as follows:

1. Use Explorer or My Computer to remove the read-only attribute from the lib_public.cdb file in the OSLO public/cdb directory.

2. In OSLO, enter the command "mklib ?" and select the "public" option.

This will create a new database specifically for OSLO LT. Please note that before using the database for the first time, you need to have opened a lens (any lens) to initialize some data structures.

Why don't my lens drawings show the correct ray paths?

There are three principal reasons why you might have such a problem.

You have entered your data incorrectly. This is the "good" reason for a lens drawing problem. The lens drawings prepared by OSLO are primarily intended to give you a visualization of how your system performs, not to produce a pretty picture. Check the magnitudes and signs of all data, including the lens drawing conditions.
OSLO does not have the capability to draw your system, or some element of your system. In this case, it may be that the ray trajectories are actually correct. OSLO is a numerical analysis program, and can correctly analyze lots of systems that it can't draw. If you need to have a drawing than includes a non-standard geometry, you can use bdi data, or the internal 3d drawing commands, to attach a drawing to a surface.
You are not looking at what you think you are looking at. You might be looking at the virtual extension of a ray, rather than the ray itself.

Why don't the image analysis routines work with my system?

By far the biggest problem encountered in this area is the failure to use adequate pupil sampling to characterize the image. To compute a spot diagram, point spread function, or MTF, OSLO traces a grid of rays from the current object point to determine the wavefront in image space. For systems in which diffractive effects are important, there should be several grid cells per wavelength OPD, to prevent inadvertent order skipping. For analyses produced using FFT (e.g. point spread function) the pupil sampling is determined using the number of rays across the pupil, one of the parameters of the analysis command. For analyses produced using general ray tracing (e.g. spot diagrams or interferograms) the pupil sampling is determined using what is called the aperture division factor, also one of the parameters of the analysis command. The aperture division factor is also a spot diagram condition, and can be set independently of a particular analysis command.

Why does my program crash when I use aspheric surfaces (rev. 5.4 only)?

Your program may crash because of an issue in the Microsoft C++ compiler, combined with a defective graphics display driver. If the other software in your computer is bug-free, this won't happen. The origin of the problem is relatively obscure, and comes from drivers that reset the control word in the Intel floating-point coprocessor and then leave it in an altered state. This can happen whenever OSLO produces any output to the display, so it is very diffficult for us to fix. Nevertheless, the problem occurs in so many different computers that we are adding a special workaround to Rev. 6 of OSLO. Until Rev. 6 is generally available, you will need to cure it by using a proper set of display drivers. One of the principal culprits is Hewlett-Packard. If you have a Hewlett-Packard computer or printer, be sure that you have the latest release of the drivers.