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Figure 4. Section Information window. Change for SHIL Image
B. Camera Setup and and Calibration
The laboratory technician calibrates the system when needed by adjusting camera settings and analyzing an imaged Xrite Color Checker Mini standard (MacBeth card). Be sure to use a 2014 or newer version of the Xrite Color checker because the RGB values used for correction uses the values from the newer standard. The RGB values on the standard are calculated from the L*ab values provided by Xrite. As of we are using RGB values calculated under an illuminant A. The excel spreadsheet of RGB values of the Xrite color checker using varying illuminants and can be found here. The white square has R=240, G=242, B=235 and the black square R=50, G=50, B=50. A 3-D standard that holds the Xrite color checker and a grey silicon mat is in the SHIL calibration drawer, PP-2B (Figure .
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 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 (white, greys and black). 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 Camera Setup Utility, the 4th step is done using Image Correction Utility. Before opening the utility it is best to you must disable Motion Control so that you can move the camera by hand.
Disable Drive:
1. 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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