mark
---------- Forwarded message ----------
From: Mike Kehoe <kehoe@resonon.com>
Date: Wed, May 6, 2015 at 5:26 AM
Subject: Re: infrared artifact
To: feinholz@mlml.calstate.edu
Cc: Mark Yarbrough <yarbrough@mlml.calstate.edu>
Hi Michael,
Sorry for my confusing emails. Sometimes things that seem obviously when you are looking at them are far from obvious when you are distant from it.
I was referring to BS1 in the preceding email. To my knowledge, it had three optical problems:
1) Fiber bundle focus: the spacing between the fiber bundle end face and the slit was too great, resulting in defocus of the fibers on the image plane. This in turn caused cross talk between fibers. This problem was resolved by reducing the space between slit and fibers.
2) 350 nm 2nd order effects: This effect is known and can/will be addressed with an order blocking filter.
3) Infrared artifact: I should have described this phenomenon differently. When Casey placed an Edmund 730 nm low pass filter in front of the halogen light source, the phenomenon went away. The artifact can be seen in isolation by placing a piece of RG850 filter glass in front of the halogen source. Please see the attached image illustrating the artifact in isolation. My struggles this week have centered on finding the cause of that line/arc in the image. In the future, this problem will be resolved by specifying a filter on the prism that blocks radiation out to 1100 nm rather than 900 nm, as is the case for the current prism filter. The filter is an integral part of the prism-grating-prism unit, however, so it would be nice to find the cause of the problem and to correct it directly.
-Mike
From: Mike Kehoe <kehoe@resonon.com>
Date: Wed, May 6, 2015 at 5:26 AM
Subject: Re: infrared artifact
To: feinholz@mlml.calstate.edu
Cc: Mark Yarbrough <yarbrough@mlml.calstate.edu>
Hi Michael,
Sorry for my confusing emails. Sometimes things that seem obviously when you are looking at them are far from obvious when you are distant from it.
I was referring to BS1 in the preceding email. To my knowledge, it had three optical problems:
1) Fiber bundle focus: the spacing between the fiber bundle end face and the slit was too great, resulting in defocus of the fibers on the image plane. This in turn caused cross talk between fibers. This problem was resolved by reducing the space between slit and fibers.
2) 350 nm 2nd order effects: This effect is known and can/will be addressed with an order blocking filter.
3) Infrared artifact: I should have described this phenomenon differently. When Casey placed an Edmund 730 nm low pass filter in front of the halogen light source, the phenomenon went away. The artifact can be seen in isolation by placing a piece of RG850 filter glass in front of the halogen source. Please see the attached image illustrating the artifact in isolation. My struggles this week have centered on finding the cause of that line/arc in the image. In the future, this problem will be resolved by specifying a filter on the prism that blocks radiation out to 1100 nm rather than 900 nm, as is the case for the current prism filter. The filter is an integral part of the prism-grating-prism unit, however, so it would be nice to find the cause of the problem and to correct it directly.
-Mike
