The update to version 15.44 incorporates the following changes:

Features:

1. If you run ELD with a negative surface number, which disables the drawing but fills in the data boxes, the program will also disable listing aspheric coefficients. The latter are shown by default and make sense if the surface is rotationally symmetric -- but only symmetric terms are then shown. Now you can simply copy the terms from the ASY listing and paste them into the ELD drawing, along with PER drawings, as instructed in Section 7.7. Then all terms will appear on the picture, along with the drawings, which you can further annotate as needed. This is useful with free-form decentered elements, which the default ELD drawing does not render properly.

2. BTOL has been much improved. Now, if you declare a surface or collection of surfaces a GROUP, it will defeat the default tilt and decenter tolerance on those surfaces and instead calculate tolerances of all six degrees of freedom (X, Y, X, and alpha, beta, and gamma). This is intended for off-axis and free-form surfaces and mirrors, where one needs all six tolerances. It will also defeat the TH tolerance before the group, since the ZDC tolerance does much the same thing, but not after, since there are two airspaces involved.

3. The file saved by the BTOL SAVE command has been restructured. It now includes the new group tolerances, and it has also been reduced in size. Before, a .BTO file was over 30 MB in size; now for a typical system it is around 500 KB. This means that all previously saved BTOL files are now obsolete, and if you need them, you should run BTOL again and save a fresh copy. The previous file form will no longer open in BTOL.

4. The MOF command (MTF over field) now accepts the color number "S", which causes the MTF to be calculated in each color separately. This is intended for systems using a digital display of some kind, where one can compensate for substantial lateral color with software, thus eliminating the requirement to correct that error in the lens itself. This can sometimes result in a better image in each color, since one can then use the GPR raygrid request in the merit function (correct relative to the principal ray) instead of GNR, which corrects relative to the major-color chief ray.

5. The Worksheet dialog is now somewhat larger, so you don't have to scroll up and down as often as before.

6. The FPU command (PUPIL plot over field) now has a form FFPU, which covers the full field, from -1 to 1, instead of 0 to 1.

7. MC now treats decenters differently: it only perturbs the lens in Y, according to the budget, unless an explicit XDC range has been declared. This makes more sense, since one often only monitors the image in the Y-Z plane, and a decenter in X would appear less sensitive than it really is. If a system is not rotationally symmetric, the new GROUP tolerances, if applicable, get tolerances in X, Y, and Z, and that option is recommended in that case.

Bugs Fixed:

1. The BTOL summary listed the tolerance on XDC the same as on YDC, even though they were actually different in the budget listing.

2. The TFG plot drew the horizontal scale too wide.