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Message ID: 13868     Entry time: Fri May 18 20:03:14 2018
Author: Pooja 
Type: Update 
Category: Cameras 
Subject: Telescopic lens solution for GigE 

Aim: To find telescopic lens solution to image test mass onto the sensor of GigE camera.

I wrote a python code to find an appropriate combination of lenses to focus the optic onto the camera keeping in mind practical constraints like distance of GigE camera from the optic ~ 1m and distance between the lenses need to be in accordance with the Thorlab lens tubes available. We have to image both the enire optic of size 3" and beam spot of 1" using this combination of lens. The image size that efficiently utilizes the entire sensor array is 1/4". Therefore the magnification required for imaging the entire optic is 1/12 and that for the beam spot is 1/4.

I checked the website of Thorlabs to get the available focal lengths of 2" lenses (instead of 1" lenses to collect sufficient power). I have tried several combination of lenses and the ones I found close enough to what is required have been listed below along with thier colorbar plots.

a) 150mm-150mm (Attachment 2 & 3)

With this combination, object distance varies like 50cm for 1" beam spot to 105cm for 3" spot. Therefore, it posses a difficulty that there is a difference of ~48cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

b) 125mm-150mm (Attachment 4 & 5)

With this combination, object distance varies like 45cm for 1" beam spot to 95cm for 3" spot. There is a difference of ~43cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

c) 125mm-125mm (Attachment 6 & 7)

The object distance varies like 45cm for 1" beam spot to 90cm for 3" spot. There is a difference of ~39cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

Sensitivity check was also done for these combination of lenses. An error of 1cm in object distance and 5mm in the distance between the lenses gives an error in magnification <2%.

The schematic of the telescopic lens system has been given in Attachment 8.

 

Attachment 2: plot_2018-05-18_tel-lens_150_150_1.pdf  24 kB  Uploaded Sun May 20 23:56:15 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_150_150_1.pdf
Attachment 3: plot_2018-05-18_tel-lens_150_150_3.pdf  26 kB  Uploaded Sun May 20 23:56:42 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_150_150_3.pdf
Attachment 4: plot_2018-05-18_tel-lens_125_150_1.pdf  24 kB  Uploaded Sun May 20 23:57:04 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_125_150_1.pdf
Attachment 5: plot_2018-05-18_tel-lens_125_150_3.pdf  26 kB  Uploaded Sun May 20 23:57:21 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_125_150_3.pdf
Attachment 6: plot_2018-05-18_tel-lens_125_125_1.pdf  24 kB  Uploaded Sun May 20 23:57:52 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_125_125_1.pdf
Attachment 7: plot_2018-05-18_tel-lens_125_125_3.pdf  26 kB  Uploaded Sun May 20 23:58:06 2018  | Hide | Hide all
plot_2018-05-18_tel-lens_125_125_3.pdf
Attachment 8: tel_design.pdf  45 kB  Uploaded Tue May 22 16:21:47 2018  | Hide | Hide all
tel_design.pdf
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