Few questions about ScanCenter

Write here about construction, ideas, equipment, tips n tricks etc. related to structured light scanning
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Few questions about ScanCenter

Post by mdesign »

When I`ve tried to configure my DIY scanner for ScanCenter based on Daheng cameras and Acer K132 I`ve met a few problems:

1) When I`ve tried to configure my custom build I`ve noticed that my crosses are dis rotated (not perfectly aligned with the vertical axis). It`s quite strange because the cameras lay flat on my ruler board. Do you fix that kind of small disrotation in some way or should I just leave it like that?
error_scan_center_.jpg
2) I have two 12mm lenses ZLKC for my DAHENG MER2 cameras. At the beginning of the configuration process software tells me that I should have 12.5mm lenses on my cameras. Is that mean I should add 0.5cm macro rings between lenses and cameras to have a 12.5mm focal lens?

3) What type of blue filter should I add to my cameras to handle the blue light feature in this software? Could anybody share link to optical filter like that to have the full support of the blue light feature?

Thanks in advance.

Cheers!!!
User avatar
OBNRacerMan
Posts: 347
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Re: Few questions about ScanCenter

Post by OBNRacerMan »

Hello.
1. A slight deviation of the "crosses" during calibration does not play a role.
2. The dimension of the focal length of 12mm or 12.5mm lenses also does not matter.
3. To realize full-fledged blue-light processing, BP470 type band-pass filters with a bandwidth of 470nm are required.
Soft: RangeVision DIY, Calibration panel/Rotary tables - RangeVision, Prj: LG PF1500G, Cam: Daheng Mercury MER-630-60U3M-L (USB3.0, monochrome) x2, Obj: ZLKC HM1628MP10 (F2.8, 10Mp, 16mm) x2 & ZLKC FM12036MP5 (F2.8, 5Mp, 12-36mm).
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Re: Few questions about ScanCenter

Post by mdesign »

Thanks for your response. I was afraid that I should rotate the camera also in the lens axis to correct that misalignment problem.
User avatar
OBNRacerMan
Posts: 347
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Re: Few questions about ScanCenter

Post by OBNRacerMan »

You also need to understand that working with blue backlight severely limits both the power of the projector (since only one (blue) LED works in this case) and the band-pass filter itself limits the sensitivity of the camera.
P.S. And this mode (as far as I know) is required only if it is not possible to create sufficient darkening at the scanned area.
Soft: RangeVision DIY, Calibration panel/Rotary tables - RangeVision, Prj: LG PF1500G, Cam: Daheng Mercury MER-630-60U3M-L (USB3.0, monochrome) x2, Obj: ZLKC HM1628MP10 (F2.8, 10Mp, 16mm) x2 & ZLKC FM12036MP5 (F2.8, 5Mp, 12-36mm).
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Re: Few questions about ScanCenter

Post by mdesign »

Thanks for that last info. I`ve thought that a blue light filter is more important to the whole process. I will omit it.
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Re: Few questions about ScanCenter

Post by mdesign »

Could you tell me what camera angles should be performed?

10 degrees from the top view is ok? I`ve heard also about the range from 10-11 degrees but 10 should be better as far as I know.
User avatar
OBNRacerMan
Posts: 347
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Re: Few questions about ScanCenter

Post by OBNRacerMan »

Convergence angle between cameras - 20-22°. I have an angle of 20 ° fixed in the mounts. The vertical angles are also fixed by the scanner frame design. When working, I only set the distance between the cameras according to the calibration tables used.
My setup - 01
My setup - 01
My setup - 02
My setup - 02
Soft: RangeVision DIY, Calibration panel/Rotary tables - RangeVision, Prj: LG PF1500G, Cam: Daheng Mercury MER-630-60U3M-L (USB3.0, monochrome) x2, Obj: ZLKC HM1628MP10 (F2.8, 10Mp, 16mm) x2 & ZLKC FM12036MP5 (F2.8, 5Mp, 12-36mm).
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Re: Few questions about ScanCenter

Post by mdesign »

I`m not sure If I understood you well.

The convergence angle between both cameras equals 20degrees means that every camera has a rotation of 10 degrees (alpha angle from the picture below). Am I right?
angle_alpha.jpg
I`ve built my own frame based on not fixed elements (photographic dual rod rig). I`ve thought that the Beta angle (from the picture below) is also known.
angle_beta.jpg
So beta angle may be set based on the preview without knowing the exact angle. Am I right?
User avatar
OBNRacerMan
Posts: 347
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Re: Few questions about ScanCenter

Post by OBNRacerMan »

According to the horizontal position of the cameras, everything is correct, the angle between the centers of their directions is 20° (in fact, there are disputes about this value here ... someone likes 22° or even 25° more :D )

The vertical angle of deviation of the optical projection from the lens axis can be calculated experimentally - by placing the projector on a flat surface / table at a distance, for example, 1 meter, from the wall. Then measure the height from the table to the center of the lens and from the level of the table to the center of the projection - then calculate the value of the angle. For LG PF1500/HF60 projectors this angle is 10.65° - this is exactly the angle I set when designing the "paws" on which a linear rail with carriages for cameras is installed.
scheme
scheme
photo_2021-02-18_15-27-42.jpg (9.76 KiB) Viewed 1087 times
But in any case, a test assembly is desirable in order to accurately calculate the height of the stands under the cameras so that they not only shine parallel to the projector beam, but also coincide with its center - if this can be done, but on any standard calibration table, the center of projection must coincide with the center of the axis cameras.

P.S. In the first photo, you can see the washers laid under the top of the camera mount - this was the first option when I missed the height a little. I printed the final version with a slightly higher spacer.
Soft: RangeVision DIY, Calibration panel/Rotary tables - RangeVision, Prj: LG PF1500G, Cam: Daheng Mercury MER-630-60U3M-L (USB3.0, monochrome) x2, Obj: ZLKC HM1628MP10 (F2.8, 10Mp, 16mm) x2 & ZLKC FM12036MP5 (F2.8, 5Mp, 12-36mm).
mdesign
Posts: 37
Joined: 03 Jan 2022, 14:51

Re: Few questions about ScanCenter

Post by mdesign »

Thanks a lot for your answer. I need to check it in my case. I still wait for the LG projector (same as yours- newer type). I`ve tested it with old K132 (ex David SLS2) and after the first test, it was promising. I`ve set vertical angles only by targeting crosses in the middle (only on preview without calculating exact data).
Post Reply