40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Message ID: 521     Entry time: Thu Jun 5 13:35:23 2008
Author: josephb 
Type: Configuration 
Category: Cameras 
Subject: GC750 looking at 1064nm scattered light 
I've taken 200 images of the GC750 (CMOS) camera while holding it by hand up to a beam card (also held by hand) in the path of ~5mW of beam power. I then averaged the images to produce the fourth attached plot.

Rob has pointed out the image looks a lot like PCB traces. So perhaps we're seeing the electronics behind the CMOS sensor?

I repeated the same experiment with HeNe laser light (again scattered off a card). These show none of the detailed structure (just what looks to be a large reflection from the card moving around depending on how steady my hand was). These are the first 3 attached plots. So only 1064nm light so far sees these features.

As a possible solution, I did a quick and dirty calibration by dividing a previous PSL output beam by the 1064 average scatter light values. These produce the last attached pdf (with multiple images). The original uncalibrated image is on top, while the very simply calibrated image is on the bottom of each plot.

It seems as the effect may be power dependent (which could still be calibrated properly, but would take a bit more effort than simply dividing), as determined by looking at the edges of the calibrated plot.
Attachment 1: GC750_HeNe_scatter_avg.pdf  40 kB  Uploaded Thu Jun 5 14:59:25 2008  | Hide | Hide all | Show all
Attachment 2: GC750_HeNe_scatter_avg2.pdf  43 kB  Uploaded Thu Jun 5 14:59:32 2008  | Hide | Hide all | Show all
Attachment 3: GC750_HeNe_scatter_avg3.pdf  46 kB  Uploaded Thu Jun 5 14:59:39 2008  | Hide | Hide all | Show all
Attachment 4: GC750_scatter_avg.pdf  32 kB  Uploaded Thu Jun 5 15:23:06 2008  | Hide | Hide all | Show all
Attachment 5: GC750_nitrogen_white.pdf  428 kB  Uploaded Thu Jun 5 15:52:30 2008  | Show | Hide all | Show all
ELOG V3.1.3-