DAVID 4 Scanner missing parts in scan

Write here about construction, ideas, equipment, tips n tricks etc. related to structured light scanning
Post Reply
Bubble-Flow
Posts: 2
Joined: 17 May 2018, 16:38

DAVID 4 Scanner missing parts in scan

Post by Bubble-Flow »

Hello everyone.

I am trying to scan the surface of a plate with corrugations on it for a university project. I'm using a high speed camera that does not allow live viewing on windows so I am limited to the image grabber function of david 4.
I have managed to get it to work by projecting the images through a BenQ projector using VLC and recording the sequence with my camera in a dark room. The calibration is successful, however if I try to view the calibration panels, my images are noisy and have missing parts and holes on them. I have tried anything from changing the brightness and contrast of my projector to changing the camera exposure time from 41000 to 1000 μs as well as the exposure index. I get some minor improvement but my images are still low quality and essentially useless for my project.
The sin waves on the panels are also very jittery and uneven and nothing seems to change them.
Can anyone give me any tips what I could be doing wrong or what camera/beamer properties I should be using? What could be causing the missing parts?
I have included a picture of one of my many useless results.
https://imgur.com/a/nS43UX3

Thanks
User avatar
Micr0
Posts: 585
Joined: 15 Nov 2016, 15:20
Location: New York City

Re: DAVID 4 Scanner missing parts in scan

Post by Micr0 »

First off, the frame rate of the camera should be 1/60th sec. You will then need to better sync the projector and camera. Try adjusting the frame rate of the projector in the monitor setting till you get less jitter. nVidia and AMD both offer control panels that offer fairly precise control over this (whether they work with your specific card remains to be seen). I found that on my system an projector frame rate ~64hz worked well.
µ
bigbomber
Posts: 114
Joined: 14 Dec 2017, 18:08

Re: DAVID 4 Scanner missing parts in scan

Post by bigbomber »

Hi friend. Actually I didn't understand the problem well. But how much is the frame rate of camera? 1/60 is exposure time or shutter speed.
Why ussing high speed cam? My cam is 30 fps but when I calculate the rate on scanning it never go uppr than 23. Because my camputer hardware (cpu,Ram, GPU, ...) do not let for it. Actually david will fo a image preprocessing exactly after each frame grabbing.
As i know in omage grabber you must project the pattern one by one manually and take photos; so high speed function is unusable.
bigbomber
Posts: 114
Joined: 14 Dec 2017, 18:08

Re: DAVID 4 Scanner missing parts in scan

Post by bigbomber »

Also if u have very strange problem pn image grabber, I have good experiencesfor it. I mean fully distorted photo or rotated photos.
Bubble-Flow
Posts: 2
Joined: 17 May 2018, 16:38

Re: DAVID 4 Scanner missing parts in scan

Post by Bubble-Flow »

Micr0 wrote: 17 May 2018, 18:48 First off, the frame rate of the camera should be 1/60th sec. You will then need to better sync the projector and camera. Try adjusting the frame rate of the projector in the monitor setting till you get less jitter. nVidia and AMD both offer control panels that offer fairly precise control over this (whether they work with your specific card remains to be seen). I found that on my system an projector frame rate ~64hz worked well.
Just an update, this had nothing to do with the frame rate. My camera was taking exactly one picture of each projected image. I found out that the quality of the scanned calibration panels wasn't important. My scans of the corrugated sheet turned out okay. The missing parts are due to reflection on the surface of the panel and since this is not a fusion of different scans with different light intensities the missing parts will almost always be present on the scanned calibration panels. However this doesn't change the outcome of subsequent scans using the calibration.
User avatar
Micr0
Posts: 585
Joined: 15 Nov 2016, 15:20
Location: New York City

Re: DAVID 4 Scanner missing parts in scan

Post by Micr0 »

Bubble-Flow wrote: 13 Oct 2019, 01:28
Micr0 wrote: 17 May 2018, 18:48 First off, the frame rate of the camera should be 1/60th sec. You will then need to better sync the projector and camera. Try adjusting the frame rate of the projector in the monitor setting till you get less jitter. nVidia and AMD both offer control panels that offer fairly precise control over this (whether they work with your specific card remains to be seen). I found that on my system an projector frame rate ~64hz worked well.
Just an update, this had nothing to do with the frame rate. My camera was taking exactly one picture of each projected image. I found out that the quality of the scanned calibration panels wasn't important. My scans of the corrugated sheet turned out okay. The missing parts are due to reflection on the surface of the panel and since this is not a fusion of different scans with different light intensities the missing parts will almost always be present on the scanned calibration panels. However this doesn't change the outcome of subsequent scans using the calibration.
Thanks for the update.

This is one of the reasons to use an inverted calibration panel set up. Especially with smaller panels, the light intensity due to reflection in the corners can be a problem.
µ
Post Reply