Hi Julian,

When things like this happen, I tend to check if I can reproduce the problem with the user interface only. If you create a Merit Function like so:

Then, you can’t set the Data column of the second NSDD operand to 4 (OpticStudio puts it back to zero automatically). Therefore, I’m not expecting this to work in your ZPL macro either. If you specify a valid pixel number (say 1 for example), then you can have Data = 4 for this particular pixel.

However, you want to know the total abosrption of your object and not for a single pixel.

I’m not sure how you should cannonically go about this problem, but here’s what I’ve done. First, I created a 1 x 1 x 1 mm^3 STEP file and uploaded it to OpticStudio as a Detector. I’ve assigned all its faces to Face 0 and used a coating like so:

IDEAL REFLABSORB 0.00 0.80

Meaning, 0% transmission, 80% reflection, and, thus, 20% absorption.

Then, I’ve made a 1W Source Ray go through the cube and saved the raytrace (sanity check):

Ray 1, Wavelength 1 (0.5500 µm), 2 segments, 1 branches:
Seg#      Prnt      Levl      In      Hit      Face      XRTS     DGEF      BZ              Intensity      Comment
   0        0        0        0        0        0      ----     ----     --       1.000000000E+00      Source 1: 
   1        0        1        0        2        0      -*--     ----     --       1.000000000E+00      111_Cube.STEP
   2        1        2        0        0        0      *---     -*--     --       8.000000119E-01      Missed

After that, I’ve opened a Detector Viewer and in the Text Tab, I found the total number of pixels on my cube was:

CAD Part: STEP/IGES/SAT 2, NSCG Surface 1: 111_Cube.STEP
Number of pixels: 172, Total Hits = 1

In the pixel list, I searched for the pixel where my Source Ray hit:

Pixel             Flux       Irradiance             X             Y             Z             R    Angle (deg)
    1   0.00000000E+00   0.00000000E+00  -3.05556E-01  -4.16667E-01   0.00000E+00   5.16697E-01    -126.25384
    2   0.00000000E+00   0.00000000E+00  -1.38889E-01  -5.00000E-01   1.66667E-01   5.45039E-01    -105.52411
    3   0.00000000E+00   0.00000000E+00  -3.05556E-01  -5.00000E-01   8.33333E-02   5.91869E-01    -121.42957
    4   0.00000000E+00   0.00000000E+00  -1.38889E-01  -3.33333E-01   0.00000E+00   3.61111E-01    -112.61987
    5   0.00000000E+00   0.00000000E+00  -5.00000E-01  -3.05556E-01   8.33333E-02   5.91869E-01    -148.57043
    6   0.00000000E+00   0.00000000E+00  -4.16667E-01  -3.05556E-01   0.00000E+00   5.16697E-01    -143.74616
    7   0.00000000E+00   0.00000000E+00  -3.33333E-01  -1.38889E-01   0.00000E+00   3.61111E-01    -157.38013
    8   0.00000000E+00   0.00000000E+00  -5.00000E-01  -1.38889E-01   1.66667E-01   5.45039E-01    -164.47589
    9   1.00000000E+00   3.20000000E+03  -1.66667E-01  -8.33333E-02   0.00000E+00   1.86339E-01    -153.43495

Fortunately, it was early on in the list. I went back to my Merit Function and tried the absorption at pixel 9, and this is the result:

As expected, since I have only one ray of 1 W hitting a single pixel, then 20% or 0.2 W is absorbed.

Finally, I’ve made a macro to go through all the pixel and sum the absorbtion:

pixel_number = 172

total_absorbed = 0

clear_detectors = NSDD(1, 0, 0, 0)
NSTR 1, 0, 1, 1, 1, 1, 0

FOR pixel_id, 1, pixel_number, 1
    total_absorbed = total_absorbed + NSDD(1, 2, pixel_id, 4)
NEXT

PRINT "Total flux absorbed = ", total_absorbed

As a last sanity check, I changed the Source Ray to a Source Ellipse (1E5 rays) with a 0.2 by 0.2 size and checked that I would still get the 0.2 W absorption. I’ve uploaded my file for you to check:

Executing C:\Users\David Nguyen\Documents\Zemax\MACROS\Total_absorbance.ZPL.
Total flux absorbed = 0.2000

The draw back is that you need to figure out the total pixel number (by going to the Detector text tab) by hand (I couldn’t find an automatic way to get this number, perhaps @Csilla Timar-Fulep, @Berta.Bernad, or @Sandrine Auriol can further comment on this last issue). EDIT: I guess you could also parse the text file of the detector created by GETTEXTFILE for example.

Let me know if this helps.

Take care,

David