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The laboratory technician calibrates the system when needed by adjusting camera settings and analyzing an imaged XRite Color Checker Standard (MacBeth card). The current light system obtains nearly uniform illumination intensity from the core’s surface (half or whole round) to the bottom of the liner by a combination of high intensity, overlapping large diameter light source, close coupling to the imaged surface and the “line” image plane. The bottom edge of the brass led mount should be set between 2 and 4cm from the image surface. Note, any height change to the lights requires re-calibration. Heat is removed from the LEDs and transferred to the surrounding air via the copper heat pipes and is cooled with mini fans. While the copper rods can get hot they are not a burn hazard. However they are very delicate and bend at the slightest touch, so use care when working with the camera lens. For more detailed information on the theory behind the calibration please refer to the Understanding the SHIL Calibration for further reading. Maintain temperature of the lights at 30-40 °C during calibration. LED's of temperature is located above the camera. During a section scan the temperature ranges between 30-36 °C.
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- Physically set the camera at the correct height and focus . See Camera Height and Focusing.
- Set the saturation range for each channel of the CCD while maintaining the white balance between these channels for neutral colors. See Setting Exposures and Setting Gains.
- Correct for uneven lighting, dark noise and pixel flatness. See Pixel Black, Shading and Flat Corrections.
- Calibrate and create a correction LUT for each RGB channel. See Image Calibration.
The first three steps are done using the JAI JAI Camera Setup Utility. Before opening the utility it is best to disable Motion Control so that you can move the camera by hand.
Disable Drive:
- In the IMS control panel select Motion and then Drive Disable from the dropdown menu (Figure 19). You will have to move the camera by hand for the calibration, disabling the motor allows manual movement of the camera on the track.
2. Open JAI Camera Setup utility:
In the IMS control panel click Instruments > JAI Camera Settings (Figure 20). The lights turn on automatically when the JAI Camera Setup window opens.
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The goal is to set the across image pixel pitch with a focused camera. Warning this can be very tedious and requires two people.
1) . Move the camera so that it is scanning just the centimeter marks on the QP 101 card (Figure 22). Also, it is important that the QP 101 card is mounted straight so that the scale lines are parallel to the direction of motion.
Figure 22. QP 101 card showing centimeter marks for pixel pitch calibration.
2. On the screen you will see this..the cm lines and vertical peaks on the Profile graph (Figure 23).
Figure 23. Example of the QP-101 marks and the profile graph.
2) 3. On the Profile graph, drag the purple and yellow cursors to the center of two adjacent peaks near the center of the image. These peaks are the centimeter lines in the QP card.
3) 4. Use the graph controls and expand (zoom) the graph horizontally and you should see this…(Figure 24).
Figure 24. Cursor placement on the QP 101's centimeter marks in Profile graph.
5) . In the expanded view, adjust the cursors so that the are centered in the peak's width (not necessarily the max value).
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You want to achieve a Pixel Delta of 200 pixels/cm (+/-1px) (Figure 25).
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25. Cursor pixel values and span.
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6) Change camera height
7) Focus
8) Adjust cursors
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10) Repeat steps 6 through 9 as necessary.
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Be careful how you tighten the clamps holding the camera to the T- Slot. Make sure to tighten with even pressure on both sides, if you don't the camera can be offset and you will see the image in the Grab window shift. The camera attachment method is not ideal and should be replace. After performing this process you need to check the home position. When at the home position, the camera should be scanning the edge of the tray where the section is placed against (red strip). If not, you will need to adjust the home switch on the track until it does. An improperly set home switch will affect the placement of the crop window and potentially the offsets assigned to the RGB values! |
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1. Click the Gains-Black-Shade-Flat tab (Figure 2526).
Figure 2526. JAI Camera Setup Window showing the Gains-Black-Shade-Flat tab. The Gains-Black-Shade-Flat tab is outlined in red.
2) . Click the Clear All Gains, Clear Black Gains, Remove Pixel Black Correction, Remove Shading Correction, and Remove Pixel Gain Correction (Figure 26). You will notice all values in the Master and Black gains go to zero.
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