POSM Advanced Laser Measurement Calibration

The advanced laser measurement calibration in POSM allows for an increased accuracy of crack, joint and observation measurement with dual lasers on inspection cameras. Calibrating the camera also allows POSM to auto find the lasers and before a basic pipe size estimation. To allow for more accurate pipe size measurement the lasers should be in a slight v formation.

In the POSM folder is a file called PipeMeasureCalibrate.ini.

To begin calibration open this file and place the serial number of the camera into the Serial field, type the current date into the CalibrationDate field.
There are two measurements taken for each pipe size. The calibration is the length of the red lasers at each pipe size level. This measurement is taken with the blue lasers zoomed in as close as possible to keep the camera in focus. The second measurement is pixel width. This is pixel length of the red lasers when the camera is zoomed all the way out. To begin the camera should be placed into the calibration rig.

The next generation rig will lock the camera head and body into the unit and the target will move automatically to each position and take the proper measurements turning the lasers on as needed. This model is moved manually to each position of pipe. Note that radius values are measured as the camera should always be centered into the pipe and looking 90 degrees to the pipe wall for an accurate measurement.
Cover the unit up to provide darkness to the camera as we will only be focusing on the blue and red lasers for calibration. The lights for the camera should be turned off for all calibration as well. It may also help to lower the iris on the camera which will show only the blue (on the rig) and red (from the camera). POSM looks for the blue and red colors and the white burn in area in the middle. The intensity of these colors may be modified if POSM has trouble locating the lasers. On the calibrate tab you can adjust the Blue, Red and Hot Spot (white) color intensity. By default start with blue 100, red 100, and
hot spot 150. The larger the number the more vivid the color is (aka pure red, blue and white). The
exact distance between the centers of the blue lasers should be placed into the blue distance value. This value should be measured with calipers.

Step one is to set the laser calibration search area. This is done on the measure tab.

Set Laser Bounds

Press the Set Laser Bounds button to set the left and right (or top and bottom in some cameras) search area.

Press ok to set the upper left corner area. Select the leftmost upper corner of where the red and blue lasers will go. Then press ok to set the lower right corner of laser 1. Drag the red box to the lower red corner of where the red laser may show up.

Once the red box covers the entire area of where the first laser will go click the screen to continue.

Press OK to select the upper left corner of laser 2. Click the screen where the 2nd laser may move to the maximum upper and left (usually middle of screen).

Draw a blue box to set the area in which POSM will search for the 2nd laser.

It’s important to make this area large enough to cover full zoom in and out areas of the red and blue lasers. If this is too big it slows POSM down searching as each pixel in this boxed area is searched for the lasers. If it’s too small it may miss the lasers.

Calibrating Each Pipe Size

Move the camera to the 3 inch mark to calibrate for 6 inch pipe. Zoom the camera so the blue lasers are as far as part as possible but still on screen and in the search area.

Press the find blue lasers button to have POSM find the blue lasers. Press the Find Red Lasers button to have POSM find the red lasers. Then press Calculate Value to have POSM calculate the calibration value. Enter this value into the PipeMeasureCalibrate.ini value under [Calibration] 6= value.
Zoom the camera fully out then click on the measure tab.

Press the Find Lasers button to have POSM find the red lasers. Enter the value under Calibrate Value into the PipeMeasureCalibrate.ini file [PixelWidth] 6= section.
Move the camera to the 4 inch (8 inch pipe) and repeat. When all pipe sizes have been calibrated the system can be tested.

Measuring with a Calibrated Camera

With the lights still off, zoom in allowing the red lasers to be as far out as possible and still in focus. Click the Find Lasers button to have POSM find the centers of the red lasers.

Turn the lights back on. Then left click and drag a line on the test lines (or a crack in this case), to more accurately measure the line magnify may be used. To turn on the magnify click the magnify button.

The magnify window will magnify the screen anywhere the cursor is placed. Zoom in increases magnification. Zoom out decreases magnification. Close will close the window. Start and End will move the red measurement line one pixel at a time. This can be done with the blue arrows in the screen or by pressing the W key for up, S key for down, A key for left and D key for right.

The measurement value will be placed into the Remarks field. The measurement value may be set in the preferences to be placed into any of the POSM observation fields Value 1-9 or Remarks.

The default value for the camera calibration may also be set in the Setup RS232 / Devices preference page. This is the value measured of the lasers with a caliper from 12 inches. The decimal precision of measurement may also be adjusted for 1,2 or 3 decimals.