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Unlike a "normal" distal photo sensor with a square sensor array, similar to a postage stamp, a line scan camera's array consists of a single line of pixels. Whereas a normal camera captures frames, the line scan camera sees only a single line at a time and sends this line image to a capture card on a dedicated computer. Line by line, the computer compiles the final image.
In some applications, the photographic subject may move in front of the camera on a conveyor belt at a specific combination of object speed and shutter speed. In the case of the SHIL, the camera moves across the sample via a motorized gantry. The combination of gantry travel speed and camera shutter speed is critical and is explained in the Camera Configuration Advanced User Guide.
The line scan camera images only one line of pixels rather than an area and therefore what happens outside the line of view is of no consequence. The line scan camera effectively masks everything other than the single line of pixels being imaged. This fact is key to the effectiveness of the line lights in providing even illumination at different distances from the lens.
The camera lens on the imaging track, Nikon 60 mm macro, does not have 1/2 or 1/3 stops, only whole F/stops: 5.6, 6.3, 8, 11, 16, 22, and 32. F/16 is the minimum aperture needed to achieve the required depth of field to image the subject at varying heights.
System Operation
SHIL system operation involves a number of processes, some performed only once upon initial installation, some only when lighting or camera equipment is replaced, and some on a routine basis at the beginning of each expedition or at the beginning of each batch of samples. The following procedures are covered in this manual:
- Installing and calibrating light array (see Light Array User Guide).
- Setting black and white saturation gain levels (see Maximum Dynamic Sensor Range).
- Setting color balance Author: Where is this covered?
- Making camera corrections (see Routine Camera Adjustments).
- Setting track velocity (see Track Speed Example).
- Adjusting knee slope, if needed (see Procedure: Iterative Adjustment).
- Performing QA/QC to confirm camera settings (see Quality Assurance/Quality Control).
Apparatus
Hardware
The core imaging track system includes the following hardware components:
Apparatus
Hardware
The core imaging track system includes the following hardware components:
- Camera
- 3CCD (charge-coupled device) line scan camera: JAI model CV107CL
- Macro lens: AF micro Nikkor 60 mm (1:2.8)
- LED Light system
- Linear encoder: Newall 2 µm/72 in. model SHG-TT
- Motor system
- Motors: Galil model BLM-N23-50-100
- PCI controller card: model DMC-1846
- Motor amplifier: model AMP-
- Camera
- 3CCD (charge-coupled device) line scan camera: JAI model CV107CL
- Macro lens: AF micro Nikkor 60 mm (1:2.8)
- Light system
- High-current line lights: Advanced Illumination model LL068
- Power supply: 24 V/6 A
- Current source: model CS420-0103 constant (modified)
- Linear encoder: Newall 2 µm/72 in. model SHG-TT
- Motor system
- Motors: Galil model BLM-N23-50-100
- PCI controller card: model DMC-1846
- Motor amplifier: model AMP-19520
- Breakout board: ICB-90044-M 44-pin
- Power supply: CPS 56V/12A
- Connectors for motor extension cords: AMP 4-pin connectors (172167-1 male, 172159-1 female)
- Robot modules: NSK 2-meter model XY-HRS200-F06246
- PC Workstation
- NI frame grabber card model PCIe-1429
- NI camera link I/O extension board
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Before taking images make sure the lights and camera are set up and calibrated properly. See section Light Array Setup and Camera Calibration for instructions on procedures.
Instrument Settings
- DAQ > Image Capture Motion Setup (Figure 1)
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Sample Preparation and Loading
Sediment
If the The surface of the archive half is rough use a flat spatula to provide a "clean" surface for imaging to generally needs to be scraped after splitting to clean the sections and better reveal layering and structures. Sediment cores should be imaged as soon as possible after splitting and scraping are completed to minimize color change through oxidation and drying.
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- Speed: This is the speed in cm/sec the camera moves while measuring the section. This speed must be set lower than or equal to the speed determined by the Camera Calibration (can it also be equal to the Max Image Scan Speed in the Calibration?).
- Acceleration: The rate in cm/sec the camera ramps up to when not measuring a section.
- Deccelaration: The rate in cm/sec the camera will slow down when not measuring a section.
- Start Position: This is the position the imaging begins. Note it will be a negative number. The top of the core starts at 0 cm in order to image the standard gray-scale card in front of the core, that location will be negative.
Start A Measurement
1.Click Click the green Start button in the IMS Control panel (Figure 9).
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5. The SHIL Section Information window for whole round will open and the rotation angle will default to the next quadrant, in this case 90 Degrees.
6. Replace the aluminum strip and rotate the tray to the next position, remove the aluminum strip facing up. Ensure that the rotation angle setting in the window is that same as on the tray. Click TAKE A PICTURE.
7. Continue the cropping, rotating and scanning process until all quadrants are complete. Once the images are uploaded to the database, the Imaging Specialist will create the 360 composite image and upload it to the database. If an image needs to be discarded, the software returns to the main screen and the user will need to start over, however, the user can select which quadrant to start on.
Maintenance
Instrument Preparation
Preparing the SHIL for imaging cores requires adjusting the light system height and calibrating the camera (applying corrections). The position of the lights once set should be stable through out the expedition unless changes are needed for variations in core height (hard rock versus sediment versus 360 imaging). The technical staff will calibrate the camera settings when ever the light source is moved or unwanted artifacts are present in the images.
Setting up the Lights (Section for old lighting system, delete when new lighting system is approved)
Initial light installation and fine adjustment procedures are described in the SHIL: Light Array AUG. For routine operation, follow these steps:
- Rotate the lights to the desired rough angle to the camera (usually ~30° to the camera axis for sediment cores). Fine-tune the light position by observing the camera output using MAX.
- Manually turn on one line light at a time to full power by pressing the "+" button on the light controller until you reach 100%.
- Loosen the brackets on both sides of the light mounts and make small position adjustments until the brightest image is achieved.
- Turn off the light by pressing the "–" button and press Select to enable the other light.
- Repeat Steps 2–4 for the second light.
6. Replace the aluminum strip and rotate the tray to the next position, remove the aluminum strip facing up. Ensure that the rotation angle setting in the window is that same as on the tray. Click TAKE A PICTURE.
7. Continue the cropping, rotating and scanning process until all quadrants are complete. Once the images are uploaded to the database, the Imaging Specialist will create the 360 composite image and upload it to the database. If an image needs to be discarded, the software returns to the main screen and the user will need to start over, however, the user can select which quadrant to start on.
Calibration
The laboratory technician calibrates the system when needed by adjusting camera settings and analyzing an imaged QP 101 V4 Color Standard. 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. For uneven hard rock cores the height can be set higher but illumination intensity will drop, exposure times lengthen, f-stop opened and scanning speed reduced. 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. While these to 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 Advanced SHIL Calibration (in development) for further reading.
Note: the following instructions are divided into 2 sections. Calibration Check and Calibration.*Method based on Instructions sent by Bill Mills. BILL and SARAH please review, correct, and update. Any questions are highlighted with an inline comment or marked in red. Calibration Check and Calibration.
Safety Concerns
- These lights get hot and can damage or burn surfaces if left stationary and on for over 20secs20 secs. This is not an issue during normal imaging operations and will not heat the core surface at all. Bus during Caution is needed when technicians perform the calibration process when . Here, the lights are stationary and you must be aware conscious of the length of time the lights are on. You can use the manual power switch to turn the lights on and off or the buttons in the software. Use the heat resistant grey silicone mat for the shading and pixel corrections. Do not use the plastic Gray card. (testing needs to be completed on which color silicone mat is best to use, or if color difference matters)
- Never look at the LEDs directly. Even the reflected light can be painful. When working under the track make sure that the power is off.
- NOTE: if you are concerned with the heat dissipation, you can use our FLIR cameras to confirm that the temperature is ok.
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Gamma: a digital camera setting that controls the grayscale reproduced on the image. An image gamma of unity (Figure. 19 missing) indicates that the camera sensor is precisely reproducing the object gray scale (linear response). A gamma setting much greater than unity results in a silhouetted image in black and white.
White Balance: a camera setting that adjusts the color balance of light the you’re shooting in so that it appears a neutral white, and it’s used to counteract the orange/yellow color of artificial light.
Before Starting:
neutral white, and it’s used to counteract the orange/yellow color of artificial light.
Before Starting:
- Note which version of standard you are using. Each color standard values vary based on the version and the manufacturer of the standard. Color Standard values vary based on the standard and the manufacturer of the standard. Verify the values of the MacBeth Color Standard (multi color squares on the 3D standard, Figure 20) before starting (How do we do this?). Check the grayscale card to determine what the percentage of gray. The target calibration values will vary based on the percentage of gray because the target values depend on the percent grayscale card. Max RGB value is 255. If using a 50% grayscale card, target red and green value is 127, a 25% grayscale card target value is 64, etc. For our QP 101 v4 card, the RGB values are 235, 111, and 80 (Figure 21). All SHIL calibration standards are found in drawer PP-2B.
- Obtain the 3D standard (Figure 20), the heat resistant gray silicone gray mat and standardand the lens cap from PP-2B.
- Set camera f/stop to 22 (Figure 22). F/22 is preferred for standard scanning with the current light set up; F/16 is also acceptable. For hard rock cruises, where 360° whole round scanning is required, a larger ? F/stop number is required.
- If you haven’t set the camera’s height, now is the time to do so! See the section Camera Height Adjustment at the end of the calibration section.
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7. Select Open Test Image and select the image you just took (Figure 28-1), located in C:/DATA/IN/IMAGE. It does not matter if the JPEG or TIFF file is loaded. The image loads into both the Original and Corrected windows. - at this point not tested to confirm it doesn't matter if a jpeg is loaded and used to perform the tiff correction. loads into both the Original and Corrected windows.
8. Draw a ROI box loosely around the color checker in the Original box (Figure 28-2)
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4. In the Tiff Correction tab adjust the LUT polynomial order values for the Red, Green, and Blue channels (Figure 29-5). Adjust these values to create the lowest residual error with the smoothest curve in the Uncorrected Image tab. Poly values should be around 4. Make sure that the curve does not wave about. If it does the order values need to be lowered. Also check that the corrected ROI and MacBeth values should be very close. Make sure that the white does not exceed the MacBeth value. If you are unable to produce a reasonable correction curve, it is necessary to redo your white balance correction in the Calibration section below. (see TIFF corrections cheat sheet in SHIL lab notebook, to be added).
Figure 29: Steps for Tiff Correction illustrated on image. 1. Redraw box on color squares. 2. Select Tiff Correction Mode. 3. Put graph on Uncorrected Image. 4. Select Tiff Correction to view polynomial order. 5. Adjust polynomial order. 6. Check graph for linear relationship.
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1. Confirm the camera F-stop is set to 22 (Figure 31). F/22 is preferred for standard scanning with the current light set up; F/16 is also acceptable. For hard rock cruises, where 360° whole round scanning is required, a larger F-stop number is required. See the Advanced SHIL Calibration (in development) for further information on F-stop.
Figure 31: Setting the F Stop on the Camera.
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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. If color streaking is evident in the image, this correction is needed to remove the unwanted streaking.After discussion with JAI we learned the order of corrections should be Pixel Black, Shading, and Pixel Gain. Previously our order was Shading, Pixel Gain, and Pixel Black. The order has been updated here. We were also to told to do all exposure and gain adjustments before doing these three camera corrections. This manual has been updated to reflect those changesCorrection also corrects for some shading effects and should be done after the shading correction. If color streaking is evident in the image, this correction is needed to remove the unwanted streaking.
Pixel Black Auto Correction
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7. Select Open Test Image and select the image you just took (Figure 52-1), located in C:/DATA/IN/IMAGE. It does not matter if the JPEG or TIFF file is loaded. The image loads into both the Original and Corrected windows. - at this point not tested to confirm it doesn't matter if a jpeg is loaded and used to perform the tiff correction.
8. Draw a ROI box loosely around the color checker in the Original box (Figure 52-2)
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4. In the Tiff Correction tab adjust the LUT polynomial order values for the Red, Green, and Blue channels (Figure 53-5). Adjust these values to create the lowest residual error with the smoothest curve in the Uncorrected Image tab. Values should be around 4. Make sure that the curve does not wave about. If it does the order values need to be lowered. Also check that the corrected ROI and MacBeth values should be very close. Make sure that the white does not exceed the MacBeth value. If you are unable to produce a reasonable correction curve, it is necessary to redo your White Balance by Shutter Correction in the Calibration section above. (see TIFF corrections cheat sheet in SHIL lab notebook, to be added).
Figure 53: Steps for Tiff Correction illustrated on image. 1. Redraw box on color squares. 2. Select Tiff Correction Mode. 3. Put graph on Uncorrected Image. 4. Select Tiff Correction to view polynomial order. 5. Adjust polynomial order. 6. Check graph for linear relationship.
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3. Click JPEG Corrections tab (Figure 54-3). Adjust the Brightness, Contrast, and Gamma levels (Figure 54-4) to achieve a straight line in the Applied Corrections tab and the ROI Corrected box should have values near 250 243 for the white square (is this correct or should they be 243). We want a linear relationship between the measured and given values. Each BCG setting adjusts the line in different ways and there are many different ways to adjust the values to achieve a linear relationship. You want to achieve a good image with good brightness, where the image has good saturation and not too washed out. (see JPEG corrections cheat sheet in SHIL lab notebook, to be added). The Applied Corrections Graph should be a straight line and the ROI Corrected Box should have values near 250. These may change depending on the instance of extreme colors, extremely white or extremely dark cores, in which the settings may have be tweaked more to get a user friendly consumer image.
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