Has anyone ever played around with bar code scanning wands?

I'm trying to build a device to measure the infrared reflectance of
something (to measure the heart rate of snails, incidentally).  I found in
the scrap-box a bar-code scanning pen that looks to have all the parts I
need, but can't find any information on what the inputs and outputs might be.

The pen is labeled IBM FRU p/n 33F9703

The board seems to have a photodiode, some misc. components and a chip
labeled HP1987 5021-6284 a 8938 3547-02

Does anyone have any information about what this chip might be doing and
what its output might be?  I'd just like to get a voltage proportional to
the intensity of the reflected IR... I'm suspecting that this chip may be
converting bar codes into ASCII or some such.

Thanks for any suggestions.

mike

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