A single LED (point light source) will cast an image through the holes that expands the farther you go from the tape. Just move the photodiodes back an inch or so from the tape, to where the projected dot spacing matches the photodiode spacing.
@Chester: For what it's worth, here is what the paper tape looks like:
Hi David -- I think you were trying to include a link to the image of your short paper tape program on Flickr, but for some reason it's not appearing -- if you email me the image I will make it available to folks.
Thanks for posting the request, Max. The paper tape in question is about 56 cm long, and it seems to be 4 bytes per cm, so 224 characters.
Of course I could simply re-write it, and I don't know where I'd get a BASIC interpreter, but if there is too much human in the loop I'm not sure if it's "authentic". (Ideally I want my printout written with a type ball using a well-used ribbon. :-) ) OCR might feel authentic enough; I suppose I could type in each byte if the tedium doesn't induce errors, and write a quick translator. (Graphics is not my strength, so I can't write the program to read the image.)
IIRC, the ASR-33 paper tape reader and keyboard are independent from the printer and punch, unless you switch to off-line mode and turn on echo. So just reading the paper tape over the serial line (probably current loop rather than RS-232) should work fine, as long as you can set your serial input to 110 Baud.
Back when I was in high school and undergrad, like proper computer nerds I could read ASCII paper tape pretty well by eye. But that was a long time ago :-) But yes, it's pretty easy, especially with BASIC where each line starts with a line number and you know where the spaces are and you keep seeing the same keywords like GOTO over and over. ASM is even easier, where half the instructions are MOV. The hard part of doing it manually is that it's easy to screw up your program by mistranslating variable I for J and things like that.
[Pedantic note: Max has an ASR-33 (Automatic Send/Receive), which means it has paper tape reader and punch. The KSR-33 (Keyboard Send/Receive) does not have paper tape.]
Just as an aside, Air Zimbabwe in the old days used to have some paper tape punches connected to their reservation system. Most of the outstations were served by Telex (remember that) and messages were output to these punches by the Res system and the tapes were then sent to the relevant station on Telex using a machine like your KSR (in Zimbabwe we used to use Siemens machines. We only used to use 5-hole tape though - Baudot code, not Ascii.