KAGRA Logbook

AOS (Cameras)

tomotada.akutsu - 20:27 Friday 11 June 2021 (17092)

Strange GigE behavior at MCE

K. Tanaka, Akutsu

As reported here, we found a strange behavior of the GigE camera for MCE_TRANS.

When we recovered the IMC lock, the MCE_TRANS seemed shifted very much (Fig. 1). We felt this was strange, as I did not feel the Nihon boshin guys shock the MCE optics table to this level… And we found a strange behavior of the relationship between the real-world and the camera image.

We firstly tried to align the beam to the camera with tweaking a steering mirror in front of the camera, and started to find the strange relationship.
When we took Fig. 2, the real-world camera aperture was left-half curtained by me . But as you see, the image started to disappear from the edge, not from the center.

I hope this is just due to our tired… if this is true, how do we trust the GigE views…

Looking at the config file of the cameras, it seems only MCE camera has different numbers for maxX and maxY comparing to the others, but I'm not sure.

Images attached to this report

17092_1623409783_Screenshot from 2021-06-11 18-29-36.png

17092_1623409786_Screenshot from 2021-06-11 18-30-36.png

Comments to this report:

kenta.tanaka - 10:12 Tuesday 15 June 2021 (17115)

[2021.06.14]

Oshino, K.Tanaka

As it turned out, the GigE camera was misaligned. We aligned the camera and then we did not see the strange behavior.

First, we checked for anything strange in the software. We tried rebooting the camera service, but the position of the camera image did not change.
Next, we used the beam spot detection function of the camera to find out where the software recognized the beam spot to be on a light-receiving surface of the camera. According to this function, the software recognized that the beam spot was off the center of the camera surface, just like the camera screen. Therefore, we judged that the software of the camera was working properly.
We tried to move the steering mirror in front of the camera to bring the beam spot to the center of the screen. We found that the shape of the beam clipped before it reached the center of the screen. This led us to believe that either the camera or the beam was misaligned. we thought that the beam does not misalign judging from the IMC oplev before and after the installation of the cover. So we thought that the camera was misaligned. In other words, it is supposed to look like Fig. 1.
Based on the above, we moved the camera to bring the beam spot to the center of the screen.

Images attached to this comment

17115_1623719341_2021-06-15 10 08 22.png

tomotada.akutsu - 16:26 Tuesday 15 June 2021 (17122)

Thank you for isolating the problems each and finding the solution. I see.

The lesson is that the cover installation might slighlt displace the optics table. Particulalry, the MCE trans optics table is not fixed with clamps due to mismatch of the footprint and the screw holes on the floor...