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3. In Master Black field, enter 40.
Apply Corrections
We apply three corrections. Find information regarding each correction below:
- Shading Correction - Flat Method -: Shading effects can come from an uneven distribution of light and along the outer edge of the camera lens. Shading is corrected for by averaging the signal across a group of eight pixels to represent the line.
- Pixel Gain Correction - Flat Method -: Each pixel has a different response to a fixed light source. To correct for this non-uniformity a couple lines of data are calculated (with the lights at no more than 80% of max) and the average response of the pixels are calculated. Then each pixel has a correction factor applied to bring all pixels to the average level. The Pixel Gain Correction also corrects for some shading effects and should be done after the shading correction.
- Pixel Black Auto Correction: The pixel black level represents extra energy in the camera independent of a light source and is a consistent pattern in the sensor. To correct for this the light source must be turned off, the lens cap put on, and the camera internal correction circuit collects a few lines of data. An average is taken across the line, and pixels are either added to or subtracted from in order for each pixel to have the average value. (Vendor Manual Reference)
Shading Correction
- Place the gray card on the tray make sure that it is level and perpendicular to the camera’s axis. The card should be positioned at the height of the core surface. This is an important step. If the card is placed closer to the camera your calibration will be off.
- Turn on the lights, with the same method used to turn off the lights, and move the camera over the gray card.
- Unfocus the lens on the camera (Figure 25). Look at the Profile graph and rotate the lens’ focus until the RGB lines are smooth , then rotate the lens’ focus until the RGB lines are noisy showing the maximum difference between the low and high values. The camera is now focus.
Figure 25: The lens being unfocused.
If you haven’t set the camera’s height now the times to so! See the section Camera Height Adjustment at the end.
4. Now move the camera over the gray card and make sure to de-focus the lens until the RGB line on the Profile graph just become smooth and no more (but still variable) (Figure 26). The RGB lines should appear “bowed” evenly across profile and centered in the image. If not check the orientation of the grayscale card. This very important!
Figure 26: Grayscale card are corresponding RGB Profile visible.
5. Click the Shading Correction - Flat Method button. This can take a few seconds, don’t click anything else until it is done. The RGB lines should now be flat (Figure 27).
Figure 27: Grab and profile after the Shading Correction has been applied.
Pixel Gain Correction
1.The camera’s lens should still be de-focused and grayscale card flat and illuminated.
2. Click the Pixel Gain Correction - Flat Method button. This will take several seconds, don’t click anything else until it is done. The RGB lines should still be flat and the individual RGB are the same (may not be equal to each other) (Figure 28).
Figure 28: Grab and Profile after the Pixel Gain Correction has been applied.
Black Gain Correction
1.Turn off the lights. Lens can be focused or unfocused (doesn’t matter).
2. Take the lens cap (Figure 29) and place on lens (Figure 30). The lens cap is located in drawer PP-2B.
Figure 29: Lens cap for the camera
Figure 30: Lens Cap being put on camera
3. Click the Pixel Black Auto Correction. The RGB lines in the Profile graph should be uniform (Figure 31). (Note: half the time a separate window window pops up to confirm lens cap is on, then user clicks 'Proceed' to apply correction. Inconsistency reported in Confluence)
Figure 31: Grab and Profile after the Pixel Black Correction applied.
Color Balancing the Camera
1.Make sure the lens is focused. To focus the camera the lights need to be on and the camera over the section grayscale card or calibration card.
2. Grab the calibration standard and remove from liner (Figure 32). Calibration Standard is located in drawer PP-2B.
Figure 32: The calibration standard in its cover.
3. Put the Calibration Standard in the track (Figure 33). The color square must be oriented as pictured below.
Figure 33: Color standard in track in correct orientation.
4. Select the tab RATES and EXPOSURE (Figure 34).
Figure 34: Rates and Exposure window, the tab is highlighted in red.
5. On the Green Lock control select OFF (Figure 35). The other exposures are now adjustable.
Figure 35: Green Lock control highlighted in red and set to off.
6. Set the Line Trigger Interval until the Max Image Scan Speed is 8 for now. Adjust values by clicking in the field and typing values. We’ll come back to this value later.
7. Turn on lights.
8. Click the Start Grab (Figure 36).
Figure 36: Start Grab button highlighted in red.
9. Move the camera over the Macbeth color standard until you see the white, dark blue, orange and brown color bars in the image. Place the cursor in the white square, right-click and draw a rectangle by dragging diagonally. Release the mouse when you have select most of the white bar. The rectangle (marked in green) should only have the white color and nothing else inside (Figure 37).
Figure 37: The grab window is highlighted in red. A green square is drawn in the white color square of the appropriate row.
10. Above the image you will see controls for the average RED, GREEN and BLUE values for all of the pixels within the rectangle. You will also see the ratio values for RED/GREEN and GREEN/BLUE.
11. Adjust the Red Exposure value until the RED value is 245.
12. Adjust the Green Exposure value until the RED/GREEN value is 1.
13. Adjust the Blue Exposure value until the GREEN/BLUE value is 1. Congratulations you just White Balance the upper limit of the camera, but you are not done.
14. Select the tab GAINS-BLACK-SHADE-FLAT and do the following:
15. Move the camera over the Macbeth color standard until you see the black, blue, gold and cyan color bars in the image. Place the cursor in the black square, right-click and draw a rectangle by dragging diagonally. Release the mouse when you have select most of the black bar.
16. Adjust the Master Black gain until the GREEN value is around 15.
17. Adjust the Red Black gain until the RED/GREEN value is 1.
18. Adjust the Blue Black gain until the GREEN/BLUE value is 1.
Setting the Line Rate
The rules:
- Exposure intervals for the Red, Green and Blue channels is a function of the light intensity of the LEDs.
- Led intensity for the three channels is a function of the LED spectrum. Cold lights 65K are very blue while warm lights 55k are reddish. Neutral light is preferred where RGB are nearly equal but all leds are variable. Generally red is the lowest intensity and will require the longest exposure time. That is why in the above procedure we start with red, but you should always start with lowest intensity channel.
- Intensity is also a function of the F-stop. The smallest F-Top is preferred because it gives the greatest depth of focus but also lowers the intensity.
- Intensity is also a function of how closely coupled the lights are to the core surface but for practical reasons we need to keep a minimum clearance for safe operations.
- Don’t forget to check that all of the lights are evenly illuminated or even on. One led can fail without affecting these other. Don’t ever look at the leds directly!
- Line rate must be greater (20us) than the red, green and blue exposure rates set in the above procedure.
- The shorter the line rates the faster the image can be scanned.
- If you move the track faster than the scan rate you will see dropped lies in your image.
So you must balance all of these setting to obtain the best scanning rate. That means the above White balance procedure described above may have to be repeated as you adjust light position, f-stop etcetera.
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Color Balancing the Camera
1.Make sure the lens is focused. To focus the camera the lights need to be on and the camera over the section grayscale card or calibration card.
2. Grab the calibration standard and remove from liner (Figure 32). Calibration Standard is located in drawer PP-2B.
Figure 32: The calibration standard in its cover.
3. Put the Calibration Standard in the track (Figure 33). The color square must be oriented as pictured below.
Figure 33: Color standard in track in correct orientation.
4. Select the tab RATES and EXPOSURE (Figure 34).
Figure 34: Rates and Exposure window, the tab is highlighted in red.
5. On the Green Lock control select OFF (Figure 35). The other exposures are now adjustable.
Figure 35: Green Lock control highlighted in red and set to off.
6. Set the Line Trigger Interval until the Max Image Scan Speed is 8 for now. Adjust values by clicking in the field and typing values. We’ll come back to this value later.
7. Turn on lights.
8. Click the Start Grab (Figure 36).
Figure 36: Start Grab button highlighted in red.
9. Move the camera over the Macbeth color standard until you see the white, dark blue, orange and brown color bars in the image. Place the cursor in the white square, right-click and draw a rectangle by dragging diagonally. Release the mouse when you have select most of the white bar. The rectangle (marked in green) should only have the white color and nothing else inside (Figure 37).
Figure 37: The grab window is highlighted in red. A green square is drawn in the white color square of the appropriate row.
10. Above the image you will see controls for the average RED, GREEN and BLUE values for all of the pixels within the rectangle. You will also see the ratio values for RED/GREEN and GREEN/BLUE.
11. Adjust the Red Exposure value until the RED value is 245.
12. Adjust the Green Exposure value until the RED/GREEN value is 1.
13. Adjust the Blue Exposure value until the GREEN/BLUE value is 1. Congratulations you just White Balance the upper limit of the camera, but you are not done.
14. Select the tab GAINS-BLACK-SHADE-FLAT and do the following:
15. Move the camera over the Macbeth color standard until you see the black, blue, gold and cyan color bars in the image. Place the cursor in the black square, right-click and draw a rectangle by dragging diagonally. Release the mouse when you have select most of the black bar.
16. Adjust the Master Black gain until the GREEN value is around 15.
17. Adjust the Red Black gain until the RED/GREEN value is 1.
18. Adjust the Blue Black gain until the GREEN/BLUE value is 1.
Setting the Line Rate
The rules:
- Exposure intervals for the Red, Green and Blue channels is a function of the light intensity of the LEDs.
- Led intensity for the three channels is a function of the LED spectrum. Cold lights 65K are very blue while warm lights 55k are reddish. Neutral light is preferred where RGB are nearly equal but all leds are variable. Generally red is the lowest intensity and will require the longest exposure time. That is why in the above procedure we start with red, but you should always start with lowest intensity channel.
- Intensity is also a function of the F-stop. The smallest F-Top is preferred because it gives the greatest depth of focus but also lowers the intensity.
- Intensity is also a function of how closely coupled the lights are to the core surface but for practical reasons we need to keep a minimum clearance for safe operations.
- Don’t forget to check that all of the lights are evenly illuminated or even on. One led can fail without affecting these other. Don’t ever look at the leds directly!
- Line rate must be greater (20us) than the red, green and blue exposure rates set in the above procedure.
- The shorter the line rates the faster the image can be scanned.
- If you move the track faster than the scan rate you will see dropped lies in your image.
So you must balance all of these setting to obtain the best scanning rate. That means the above White balance procedure described above may have to be repeated as you adjust light position, f-stop etcetera.
Note: when you adjust the Line Rate interval it will automatically adjust the speed of the track to a scan speed that will not cause dropped lines. You can override this value in the Motion Control Setup …be careful.
Apply Corrections
We apply three corrections. Find information regarding each correction below:
- Pixel Black Auto Correction: The pixel black level represents extra energy in the camera independent of a light source and is a consistent pattern in the sensor. To correct for this the light source must be turned off, the lens cap put on, and the camera internal correction circuit collects a few lines of data. An average is taken across the line, and pixels are either added to or subtracted from in order for each pixel to have the average value. (Vendor Manual Reference)
- Shading Correction - Flat Method -: Shading effects can come from an uneven distribution of light and along the outer edge of the camera lens. Shading is corrected for by averaging the signal across a group of eight pixels to represent the line.
- Pixel Gain Correction - Flat Method -: Each pixel has a different response to a fixed light source. To correct for this non-uniformity a couple lines of data are calculated (with the lights at no more than 80% of max) and the average response of the pixels are calculated. Then each pixel has a correction factor applied to bring all pixels to the average level. The Pixel Gain Correction also corrects for some shading effects and should be done after the shading correction.
Black Gain Correction
1.Turn off the lights. Lens can be focused or unfocused (doesn’t matter).
2. Take the lens cap (Figure 29) and place on lens (Figure 30). The lens cap is located in drawer PP-2B.
Figure 29: Lens cap for the camera
Figure 30: Lens Cap being put on camera
3. Click the Pixel Black Auto Correction. The RGB lines in the Profile graph should be uniform (Figure 31). (Note: half the time a separate window window pops up to confirm lens cap is on, then user clicks 'Proceed' to apply correction. Inconsistency reported in Confluence)
Figure 31: Grab and Profile after the Pixel Black Correction applied.
Shading Correction
- Place the gray card on the tray make sure that it is level and perpendicular to the camera’s axis. The card should be positioned at the height of the core surface. This is an important step. If the card is placed closer to the camera your calibration will be off.
- Turn on the lights, with the same method used to turn off the lights, and move the camera over the gray card.
- Unfocus the lens on the camera (Figure 25). Look at the Profile graph and rotate the lens’ focus until the RGB lines are smooth , then rotate the lens’ focus until the RGB lines are noisy showing the maximum difference between the low and high values. The camera is now focus.
Figure 25: The lens being unfocused.
If you haven’t set the camera’s height now the times to so! See the section Camera Height Adjustment at the end.
4. Now move the camera over the gray card and make sure to de-focus the lens until the RGB line on the Profile graph just become smooth and no more (but still variable) (Figure 26). The RGB lines should appear “bowed” evenly across profile and centered in the image. If not check the orientation of the grayscale card. This very important!
Figure 26: Grayscale card are corresponding RGB Profile visible.
5. Click the Shading Correction - Flat Method button. This can take a few seconds, don’t click anything else until it is done. The RGB lines should now be flat (Figure 27).
Figure 27: Grab and profile after the Shading Correction has been applied.
Pixel Gain Correction
1.The camera’s lens should still be de-focused and grayscale card flat and illuminated.
2. Click the Pixel Gain Correction - Flat Method button. This will take several seconds, don’t click anything else until it is done. The RGB lines should still be flat and the individual RGB are the same (may not be equal to each other) (Figure 28).
Figure 28: Grab and Profile after the Pixel Gain Correction has been applied.
Create Correction Curve
1.Click the Save button and leave the JAI Camera Utility.
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