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Thanks for all your helpful suggestions. I thought the following might be
interesting:

I used my laser power meter to check the power density for different lenses
and light sources that we have. 

At 740 nm (Chroma SP-106 excitation filter is 740±35) 

No lens - 43 mW with Hg and 58 mW with Halogen (3200K)
20x/0.45 Achroplan Ph2  - 79%T
40x/1.2 W C Apochromat - 81%T
63x/1.4 oil PlanApo - 67%T

At 774 nm (peak absorption for IRDye 800)

No lens - 40 mW with Hg and 50 mW with Halogen (3200K)
20x/0.45 Achroplan Ph2  - 50%T
40x/1.2 W C Apochromat - 60%T
63x/1.4 oil PlanApo - 42%T

There is a lot more light out there with the Hg than you might think even
though the Halogen is better. The %Ts at 740 nm are pretty similar to the
"typical" curves for these lenses found on the Zeiss website. The drop off
when going up to 774 nm was quite a bit more than expected. 

Licor tech support does not have information on the power density of the
laser in the Odyssey but they thought it was pretty low. We put the power
meter in the Odyssey and never recorded more than 3 mW during the scan.

So compared to the Odyssey we have plenty of light.

Kate