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OC Library 3D Macro Scanner

Scanner Calibration

Calibration is typically done once every couple of uses. It is only required when the cameras have been moved from their current positions, or if the camera focus/zoom is altered. If you conduct a scan and notice that the cameras are not picking up all of the data, then that is usually a sign the cameras need to be calibrated as well. At least 30 captures are needed to complete calibration. More calibration captures can be done to increase the % coverage. An acceptable coverage range for our purposes is 85 to 90%. 

 If either of the cameras on the tripod are physically moved by unscrewing them from the mount and repositioned, calibration must be done again from scratch. Do not unscrew the cameras from the mount or move them in any way once calibration has been started and completed

*NOTE* The cameras seem to be a little offset and will not perfectly align. You can try placing something in between the base and the camera to offset this balance before starting calibration, but they will not be completely perfect.

Place the Calibration Board on the center of the turntable with the 3mm side facing the camera.

  • The board is typically about 6" to 10" from the camera, but use the camera view image in Flexscan to position the board as centered within the image display as possible
  • Use the 5 black dots in the shape of a diamond that are displayed by the projector to center the calibration board so that the dots are appearing in relatively the same spot on both camera views (because the cameras are slightly off, it will never be absolutely perfect)
  • Move the rotary table with the calibration board so that once the board is perfectly centered, it is also sitting in the middle of the rotary table
  • Move the cameras, rotary table, and tripod as much as you need to to get the calibration board as perfectly centered in both camera views as possible (once you start the calibration process you wont be able to adjust these things as much)
  • The board does not have to be sitting up right at exactly 90 deg.; it can be tilted back slightly so that the board stays in place on the stand

In the "Advance" settings menu on the right side:

  • Set the "Pattern" to "Focus" (note: after a period of inactivity, or if the scanner connection is lost, this will reset to "Black")
  • Exposure should be "16.67ms"
  • "Capture Test" should be set to "Phase"
  • Adjust the brightness so that the Calibration Board is in clear view and there are no red areas (red areas indicate that an area is too bright/overexposed)

In the "Calibration Board" settings menu on the left:

  • "Size" should be "3mm" (this # corresponds with the 3mm side of the calibration board that you set facing the cameras)
  • "Pattern" should be "Chess Board"

Adjust the "Focus" nodule on the projector until the projected pattern is bright and in focus

Capturing the First 10 Images for the Calibration:

  • Start the calibration scans by moving the Calibration Board towards you to where the chess board pattern is lined up with the left side of the image box in Flexscan (keep the board facing perpendicular to the cameras)
  • Note that the Camera 1 relay (top) shows the Calibration Board perfectly aligned, while the Camera 2 relay (bottom) shows that the image is slightly off set; it is easiest to base your alignment off of one of the cameras (usually Camera 1) but make sure both are still completely visible in the camera view and no part of the chess board pattern is cut off
  • Once the board is aligned, click "Capture" to take your first image
  • NOTE - under the "Image" column, you will see your pictures start to show up; a picture labeled "Position" is a good scan; if you get a picture labeled "Camera 1" or "Camera 2" that means that only one camera was able to scan and the scan is no good (usually means part of the Calibration Board pattern was cut off in the image); if you get a picture labeled "failed" then the scan is no good and needs to be repeated
    • If you have to redo a scan, select the bad scan and click "delete" at the bottom of the "Images" column
  • After you have taken the first image and it is labeled "Positon_0", you will take a series of 5 pictures with the calibration board moving from the left edge of the camera view, shifting over to the right. You will do this by moving the board about 1/5 of the total length of the board to the right and clicking "Capture"
    • The calibration board should still be centered along the horizontal line as you move it across the rotary table
    • The entire chess board pattern on the Calibration Board should be in view on the camera view in Flexscan for each image captured
    • You should end up with a total of five pictures labeled "Picture_0" through "Picture_4" under the "Images" column
  • Once you have 5 good images, turn the Calibration Board to either the right or left (does not matter which direction) until it is at about a 45 deg. angle from perpendicular (where it was positioned before)
    • Your camera views will look somewhat like this:
    • Make sure that the entire chess pattern is still visible in the camera views (you may have to move the board back an forth a little to do this but try to keep it in relatively the same spot)
    • Once the Calibration Board is positioned, click "Capture"
    • You will, again, be taking a series of 5 images, moving the board from the right of the camera view to the left (you should be moving the board towards you here)
      • Again, make sure the pattern is completely visible for all images and the board is moving along the same horizontal plane
  • Once you have a total of 10 satisfactory images, move the calibration board so that it is perpendicular to the cameras and centered in the MIDDLE of the camera view
  • The "Calibrate" button will turn red and it will say "This scanner is ready to calibrate" BUT DO NOT CLICK CALIBRATE
  • The scanner only requires 10 images for calibration, but we want to take 30 images to make sure we have a sufficient coverage range (remember we need 85% ,or higher, coverage)

Capturing the Next Set of 10 Images

  • For these images, the pattern on the Calibration Board is going to be at the very TOP of the camera view
  • First, make sure that the Calibration Board is positioned perpendicular to the cameras and is centered in the camera view
  • To move the Calibration Board to the top of the camera view, you will have to adjust the back leg on the tripod
    • Do this VERY carefully! The tripod legs are very sensitive and will move a LOT
    • Keep the front two legs in the same position and only move the back leg forward and back to adjust the height of the Calibration Board in the camera view
    • Once positioned properly, the camera views should look somewhat like this:
    • NOTE - if you move the tripod legs too much, you will have to reposition and restart the calibration! If you need help or if you don't feel comfortable calibrating the scanner, just ask a Librarian or Library Assistant for help!
  • Once the Calibration Board is positioned properly, you will repeat the same process you did before
    • Take 5 images with the board sitting perpendicular to the cameras, starting with the pattern lined up all the way to the left and moving by 1/5th to the right until the pattern is in line with the right side of the camera view
    • Without re-centering the board, move the board to the same 45 deg. angle you had it at before and take 5 pictures while moving the board from the right of the camera view to the left
    • Make sure all your pictures are of good quality (aka labeled "Picture_X")
  • After you have taken 10 satisfactory pictures (should be labeled "Picture_10" through "Picture_19"), readjust the Calibration Board and position it so that it is in the UPPER MIDDLE of the camera view

Capturing the Last Set of 10 Images

  • For these last 10 images, you will adjust the back leg of the tripod so that the Calibration Board pattern is sitting in line with the bottom of the camera view
  • Again, repeat the same 5 images with the board perpendicular to the cameras, and the same 5 images with the board at that same 45 deg. angle
  • Make sure you have 10 satisfactory pictures (they should be labeled "Picture_20" through "Picture_29")

Officially Calibrating!

  • Once you have 30 images that are labeled "Picture_0" through "Picture_29" and all pictures are satisfactory, you can finally click "Calibrate"!
  • Check to make sure the coverage range is 85% or higher
  • If the coverage range is satisfactory, then the scanner is calibrated successfully, and you can click "OK" to accept the calibration!
  • When you hit ok, this same calibration will pop up the next time you reopen Flexscan and will continue to do so until it is calibrated again.
  • You can also save this calibration on the computer by clicking "Export" in the top menu tab and saving it to the computer; be sure to name the saved calibration "FlexScan_Calibration_XX-XX-XXXX" and include the date (XX-XX-XXXX)
  • Once the calibration is complete, DO NOT MOVE THE CAMERAS OR TOUCH THE FOCUS ON THE PROJECTOR! You can adjust the tripod as much as you need but if either of these things are moved, then the calibration is off and will need to be re-done.
  • Any time the scanner is moved to a different location or after the scanner has been used for a couple days and you start to notice the scan data fall off a little bit, the scanner will need to be re-calibrated.
  • Once you hit "OK", you can navigate to the "Project" tab at the top left corner