Pentacam . Airborne Multi-Spectral Imager Instruction Manual August 2007 Version 1.0
Pentacam.
Airborne Multi-Spectral Imager
Instruction Manual
August 2007
Version 1.0
Table of Contents
36Specification Sheet13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Installing the Pentacam software to additional computers12 . . . . . . . . . . . . . . . .31Radiometric calibration software11.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Co-registration software11.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29ENVI Software11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Mechanical and Electrical Specifications10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Modulation Transfer Function9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Settings for Airborne Imaging8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Camera gain linearity7.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Radiometric Calibration7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Image files6.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22GPS and AHRS files6.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Files and Headers6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Frame Rate Study5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Alignment / boresight4.6.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Settings menu4.6.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16File menu4.6.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Additional menus4.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Zoom control4.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Live view controls4.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14GPS/AHRS control and display4.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Video controls4.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Image display4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Software4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Driver Installation3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Bandpass Filter Installation2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Optics1.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4External connections1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Camera alignment hardware1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Pentacam sensor mounting1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Sensor Hardware1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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List of Figures
33Gain image file selection pop-up44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32DN pop-up43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32Exposure time and f/# inputs42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31RGB co-registration image41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Reference cube pop-up40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Pentacam on ENVI toolbar39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Pentacam electrical schematic38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Pentacam dimensions - 237 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Pentacam dimensions - 136 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Normalized response vs. camera gain35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Calibration data34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Calibration setup using a calibrated irradiance lamp33 . . . . . . . . . . . . . . . . . . . . . . . . . .23Irradiance calculation with bandpass filter32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Crosshair on alignment target31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21Adjustment tool and hardware30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Alignment pop-up29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Set Directory pop-up28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Gain/Offset pop-up27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Camera Settings pop-up26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Settings menu selection25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16File menu selection24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Live view23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14GPS/AHRS22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Video controls21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Graphical user interface20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Sixth driver installation pop-up19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Fifth driver installation pop-up18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Fourth driver installation pop-up17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Third diver installation pop-up16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Second driver installation pop-up15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Initial driver installation pop-up14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Filter holder removal13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Set screw loosening12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Filter cover removal11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Spring removal10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Pentacam system with cover and fore optics removed9 . . . . . . . . . . . . . . . . . . . . . . . . . .7Filter holder8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Imaging sensor with filter cover7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-style mounting provisions6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5External connections5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Alignment hardware4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Pentacam mounting3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Camera housing2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1System components1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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34Image cube save pop-up46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Dark field file selection pop-up45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Tables
34Contents of radiance cube header file16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Pentacam’s MTF results15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Suggested ‘starting point’ camera settings for airborne imaging14 . . . . . . . . . . . . . . . . .24Calibration camera settings13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Frame rate study12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Alignment controls11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Gain/Offset controls10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Camera Setting controls9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Digital zoom controls8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Live view controls7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14GPS/AHRS controls and display6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Video capture controls5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Dimensions allocated for bandpass filter4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Lens specifications3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Camera housing component description2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1System level component description1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Pentacam Instruction Manual Version 1.0 OKSI
1 SENSOR HARDWARE
While it is not necessary to have a comprehensive understanding of the Pentacam hardware tocollect data, a low-level understanding of the components will help the user better understandhow the system operates.
The items seen in Figure 1 represent the main components of the Pentacam system. A descrip-tion of each of these components is found in Table 1.
1
23
4
5
6
Figure 1. System components.
Table 1. System level component description.
Used to point a sensor housingAlignment screw6Used to fixture the PentacamMounting provision5Contains a CMOS imaging arraySensor housing4Connection allowing USB communication with each image sensorUSB connection3Connection used to provide 5VDC to the image sensorsPower connection2Converts a single USB signal into 5 signals and vice-versaUSB hub1
FunctionComponent#
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Figure 2 shows the features of each camera housing. A description of these features is containedin Table 2.
5
4
3
21
Figure 2. Camera housing.
Table 2. Camera housing component description.
Connection allowing USB communication USB connection5Connection providing power to the imaging arrayPower connection4Provides access to bandpass filterFilter cover3Used to point the sensor housingAlignment screw2Holds the sensor housing during alignmentAlignment spring1
FunctionComponent#
1.1 Pentacam sensor mounting
The Pentacam system has been designed so that it can be mounted on its side or from the bottom.The side and bottom mounting provisions, which are shown in Figure 3, allow data to becollected in either the horizontal (e.g., on a tripod) or vertical (e.g., airborne) directions.
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¼ - 20 holes for tripod mount
¼” through holes breadboard mounting
Figure 3. Pentacam mounting.
As seen in Figure 3, the mounting hardware provides both ¼ - 20 tapped holes and ¼ inchthrough holes. The hole pattern has been machined so the unit can be attached to a standardoptical breadboard (¼ - 20 tap on 1 inch centers) or a heavy tripod.
1.2 Camera alignment hardware
Each of the five CMOS sensors have been equipped with a three degree-of-freedom (DOF)fixture allowing it to be accurately aligned. Specifically, each sensor can be rotated, tipped, andtilted via the special mounting screws shown in Figure 4.
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(b)(a)
Tip - Tilt Screw
Rotation Fixture
Figure 4. Alignment hardware: (a) shown with image sensor, and (b) 2D CAD rendering of atip-tilt screw.
The rotation fixture labeled in Figure 4 allows the imaging sensor to rotate about the center of itsCMOS array (i.e., the optical axis). This rotation gives the user the ability to orient each sensorso the images returned are square with each other.
The tip-tilt screws seen in Figure 4 provide camera pointing. These special screws work byusing a threaded nipple (1) to manipulate the separation between the adjustment and base plates.Using three tip-tilt screws together allows the user to change the azimuth and elevation angles ofeach sensor. After alignment, the position of each sensor is locked in place with a ¼ - 28 capscrew (3). A thorough description of the alignment procedure is found in Section 4.6.3.
1.3 External connections
Only two connections are needed to operate the Pentacam hardware. A single USB connectionis needed for transferring image data, while 5 VDC is needed to power the image sensors andsupporting electronics. The external connections are shown in Figure 5.
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USB
+5VDC
Figure 5. External connections.
1.4 Optics
Each of the five imaging sensors has a provision for C-mount fore optics. The C-style mountingprovisions are shown in Figure 6.
‘C’ mount thread
Figure 6. C-style mounting provisions.
While C-style lens mounts have been chosen for Pentacam’s sensors, adapters can be used forF-mount lenses.
Pentacam’s 1.3 megapixel (1,280×1,024) CMOS arrays require a lens capable of producing a19.67 mm image circle. Therefore, F-mount and large format C-mount lenses are needed toprevent image degradation due to vignetting. Five F-mount Sigma lenses (f = 105 mm) and five
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F-mount Nikkor lens (f = 35 mm) have been shipped with the Pentacam hardware. Themechanical specifications of these lenses are listed in Table 3.
Table 3. Lens specifications.
FFMount53 mm97.5 mmLength (when focused to ∞)
64.5 mm74 mmDiameter205 g457 gMass
f/2 - f/22f/2.8 - f/32Iris RangeNikkor (f = 35 mm)Sigma (f = 105 mm)Feature
2 BANDPASS FILTER INSTALLATION
In each Pentacam sensor, a bandpass filter can be inserted in between the fore optics and theCMOS array. This feature eliminates the need to purchase a custom filter to match the uniquethreads on different lenses. The filter covers, which are labeled in Figure 7, hide the volumeallocated for the filter assembly. The dimensions of the filter volume are listed in Table 4.
Figure 7. Imaging sensor with filter cover.
Table 4. Dimensions allocated for the bandpass filter.
50.8 mmLength50.8 mmWidth4 mmThickness
ValueDimension
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Commercial off the shelf (COTS) filters of many different sizes can be inserted into the filterspace by machining custom filter holders. Five filter holders that accommodate 25 mm diameterfilters have been shipped with the Pentacam system. One such filter holder is shown in Figure 8.
Filter
Set Screw
Figure 8. Filter holder.
Removal and installation of the bandpass filters is very straightforward. First, remove the topcover and fore optics as illustrated in Figure 9.
Figure 9. Pentacam system with cover and fore optics removed.
Next, remove the spring in the rotation fixture in order to gain access to the filter cover(Figure 10).
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Figure 10. Spring removal.
Removal of the filter cover comes next. This process is illustrated in Figure 11.
Figure 11. Filter cover removal.
After the filter cover is removed, loosen the two set screws in the C-mount ring. These setscrews are used to secure the filter holder. This step is illustrated in Figure 12.
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Figure 12. Set screw loosening.
The final step, which is illustrated in Figure 13, involves removing the filter holder. It is impor-tant to note the orientation of the filter holder as it is removed from the camera body. Orienta-tion is critical because the holder is not symmetrical about the center hole.
aa
Figure 13. Filter holder removal.
With the filter holder removed, a new filter can be inserted and secured with the holder’s setscrew (see Figure 8). After changing the filter, the filter assembly should be repositioned insidethe camera body and secured. It is important make sure that the set screws used to hold the filterholder in place are securely tightened because these screws also aid in holding the lens in place.
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3 DRIVER INSTALLATION
If it is necessary to install the sensor drivers, a pop-up window will be displayed after the systemis connected via USB. The initial pop-up screen is shown in Figure 14. As seen, the bottomradio button, which is labeled ‘No, not this time,’ should be selected.
Figure 14. Initial driver installation pop-up.
After selecting the ‘Next’ button, the screen shown in Figure 15 appears. Select, ‘Install from aspecific location (Advanced).’
Z
Figure 15. Second driver installation pop-up.
In the next pop-up, which is shown in Figure 16, the second option should be selected. Specifi-cally, choose ‘Include this location in the search’ and ‘Browse’ to C:\Pentacam\.
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A
Figure 16. Third driver installation pop-up.
Figure 17 shows the fourth driver installation pop-up screen. On this screen, select the topoption and hit ‘Next.’
Figure 17. Fourth driver installation pop-up.
Select ‘Continue Anyway’ when the fifth pop-up appears.
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Figure 18. Fifth driver installation pop-up.
The final pop-up is shown in Figure 19. On this screen, select ‘Browse,’ then point to C:\Penta-cam, select ezusb.sys, and press ‘OK.’ This completes the driver installation.
Figure 19. Sixth driver installation pop-up.
4 SOFTWARE
The Graphical User Interface (GUI) used to control the Pentacam system is shown in Figure 20.Notice that the GUI has been divided into seven sections. Each of these sections is describedbelow in detail.
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1
2
3
4
5
6
7
Figure 20. Graphical User Interface.
4.1 Section 1 - Image display
The image window, labeled ‘1’ in Figure 20, is used to display data collected by the imagingsensors. Specifically, one to five images can be displayed depending on the user’s preference.
4.2 Section 2 - Video controls
The video capture controls are shown in Figure 21. A description of each control is found inTable 5.
.
Figure 21. Video controls.
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Table 5. Video capture controls.
Stops live image display and/or data captureButtonStopInitiates the saving of image data to diskButtonCaptureInitiates live image display without saving to diskButtonLive
When checked, the image display is updated during imagecapture. Live image display during image capture willdecrease the rate at which frames are saved to disk.
Check boxLive Capture
DescriptionControl TypeControl Label
4.3 Sections 3 and 5 - GPS/AHRS control and display
Sections 3 and 5 of the GUI contain the controls and display needed for GPS and AHRS datacapture. In order to activate these features, the user must request the system to search for GPSand AHRS devices upon startup. This procedure is described in greater detail in Section 4.6.2.
Figure 22 displays the GPS/AHRS controls and display. Table 6 describes the contents ofFigure 22 in detail.
(b)(a)
..
Figure 22. GPS/AHRS: (a) controls, and (b) display.
Table 6. GPS/AHRS controls and display.
Displays altitude data during GPS data captureNumeric DisplayAltDisplays latitude data during GPS data captureNumeric DisplayLatDisplays longitude data during GPS data captureNumeric DisplayLonDisplays yaw data during AHRS data captureNumeric DisplayYawDisplays pitch data during AHRS data captureNumeric DisplayPitchDisplays roll data during AHRS data captureNumeric DisplayRollStops GPS and/or AHRS data capture Button controlStopInitiates GPS and/or AHRS data capture Button controlCapture
When checked, a data file containing GPS data will becreated in the root directory Check box GPS Log
When checked, a data file containing AHRS data will becreated in the root directory Check box AHRS Log
DescriptionTypeLabel
The Pentacam software is configured to work with the AHRS400 made by Crossbow(www.xbow.com). Because different inertial systems have different packet protocols and serialcommands, the Pentacam software does not support other INS devices.
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The GPS system used during software testing was the GARMIN GPSMAP76. However, theGPSMAP76 produces standard NMEA packets via RS-232 (4800 baud). Therefore, other GPSsystems that comply to this protocol should work with the Pentacam software.
4.4 Section 4 - Live view controls
Section 4 contains controls used to select which cameras will be displayed when the ‘Live’button (see Figure 21) is pressed. In addition, Section 4 contains a Pentacam schematic to helpthe user determine the physical position of each sensor and a ‘Sync Time’ button used tosynchronize the Windows clock with the incoming GPS signal (when GPS is active).
Figure 23 shows the controls and the Pentacam schematic. Table 7 describes each in moredetail.
(c)(b)(a)
...
Figure 23. Live view: (a) controls, (b) Pentacam schematic, and (c) ‘Sync Time’ button.
Table 7. Live view controls.
Used to synchronize the Windows clock with GPS time. Note that theWindows clock is automatically synchronized at software start up whena GPS signal is present
ButtonSyncTime
Used to provide the user with a reference location for each of thecameras. The numbers shown indicate the position of each sensorrelative to the USB and power inputs
ImageCameraView
When checked, data captured by Cam5 is displayed during live previewCheck box Cam5When checked, data captured by Cam4 is displayed during live previewCheck box Cam4When checked, data captured by Cam3 is displayed during live previewCheck box Cam3When checked, data captured by Cam2 is displayed during live previewCheck box Cam2When checked, data captured by Cam1 is displayed during live previewCheck box Cam1
DescriptionType Label
4.5 Section 6 - Zoom control
Section 6 contains the controls used to manipulate the display’s digital zoom. It should be noted,however, that the digital zoom buttons are only active when a single camera is selected for liveviewing or alignment.
The digital zoom controls are shown and described in Table 8.
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Table 8. Digital zoom controls.
When pressed, a control box appears in the upper right-hand corner ofthe display window. This control box can be dragged with the mouseto change the region of the image displayed in the preview window.
Button
Eliminates all digital zoom and decimationButton
Decreases the display’s digital zoomButton
Increases the display’s digital zoomButton DescriptionControl TypeImage
4.6 Section 7 - Additional menus
Section 7 contains menu controls used to set the root directory, change camera settings, andperform camera alignment. The contents of each menu is described below.
4.6.1 File menu
When the ‘File’ menu is selected, as shown in Figure 24, the user is given the option to exit theprogram.
Figure 24. File menu selection.
4.6.2 Settings menu
Several options are available when the ‘Settings’ menu is selected. These options are shown inFigure 25.
Figure 25. Settings menu selection.
When ‘Camera Settings’ is selected, a pop-up screen appears. This pop-up screen, which isshown in Figure 26, allows the user to control various aspects of image capture and display.Details associated with these controls are listed in Table 9.
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blue green red IR1 IR2
Figure 26. Camera Settings pop-up.
Table 9. Camera Setting controls.
Changes the current camera settings to the default camerasettingsButtonGo to Default
Saves the current camera settings as defaultButtonSet As Default
Removes the ‘Camera Settings’ pop-up from the screen withoutimplementing the current settingsButtonCancel
Implements the current settings ButtonOKUsed to select the baud rate of an incoming GPS signalList BoxGPS Baud Rate
When checked, the Pentacam software will look for a GPSdevice during startupCheck box Use GPS
When checked, the Pentacam software will look for a AHRSdevice during startupCheck box Use AHRS
Determines the number of frames saved to disk after the‘Capture’ button (Figure 21) is pressedNumeric Capture Frames
Allows the user to enter a name for each camera (this nameappears in Section 4 of the GUI)String Cam Name
When checked, image data is saved after the ‘Capture’ button(Figure 21) is pressedCheck box Cam Capture
Time, from 1 to 321 ms, that each sensor integrates Numeric Exposure Time
DescriptionControlType Label
The second option located on the ‘Settings’ menu brings up the gain and offset controls. Thesecontrols are shown in Figure 27 and described in Table 10.
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.
Figure 27. Gain/Offset pop-up.
Table 10. Gain/Offset controls.
Changes the current settings to the default settingsButtonGo To DefaultSaves the current settings as defaultButtonSet As Default
Removes the ‘Gain/Offset’ pop-up from the screen withoutimplementing the current settingsButtonCancel
Implements the current settings ButtonOK
Number, between -3300 and 3300, used to set the sensoroffset Slider/Txt BoxOffset
Number, between 0 and 3300, used to set the sensor gain(Note: high number is actually lower gain.)Slider/Txt BoxGain
DescriptionControl Type Label
The final option on the ‘Settings’ menu is ‘Set Directory.’ When this option is selected thepop-up in Figure 28 appears.
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Figure 28. Set Directory pop-up.
The ‘Set Directory’ pop-up allows the user to select the folder in which captured data files (GPS,AHRS, image) are saved.
4.6.3 Alignment / boresighting
As discussed in Section 1.2, the Pentacam system has special alignment screws that allow theazimuth and elevation angles of each sensor to be manipulated. Alignment is achieved wheneach lens is oriented so that it is parallel with the other lenses. When the lenses are parallel toeach other, the difference between each sensor’s field of view is minimized (when the lenses arefocused to near infinity).
There is no immediate need to modify the alignment when the system is received (the system isaligned before shipment). However, all of the hardware and software tools needed for alignmentare available if alignment becomes necessary.
Camera alignment begins by removing the cover of the Pentacam system (see Figure 9).
Next, use the ‘Alignment’ menu to open up the pop-up seen in Figure 29. The contents of theAlignment pop-up are described in Table 10.
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.
Figure 29. Alignment pop-up.
Table 11. Alignment / boresighting controls.
Stops live image displayButtonStopApplies the current settingsButtonApply
Overlays a crosshair on the center pixels of the displayedimageCheck boxCenter Cross
Displays the Align Camera imageRadio buttonAlign CamDisplays the Ref Camera imageRadio buttonRef Cam
Initiates a routine where the Align Camera image is added tothe Ref Camera image Radio buttonSummation
Initiates a routine where the Align Camera image is subtractedfrom the Ref Camera imageRadio buttonSubtraction
Controls which sensor is the align sensorRadio buttonAlign CameraControls which sensor is the reference sensorRadio buttonRef Camera
DescriptionControl Type Label
Adjustment of the alignment screws is done with a special tool. This tool is used to manipulatethe hardware described in Figure 4. The tool, along with the alignment hardware, is shown isFigure 30.
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Figure 30. Adjustment tool and hardware.
In order to achieve parallel lens orientation, an alignment target is placed at a distance and thetip-tilt screws are adjusted until the center crosshair is on top of its target. This process is shownin Figure 31.
A
Figure 31. Crosshair on alignment target.
The alignment target shown in Figure 31 is simply a true-scale print out of Pentacam’s base. Acopy of the alignment target has been shipped with the system. Alignment is achieved when
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each sensor’s center crosshair is overlayed on its target. The software’s digital zoom capabilitiesshould be used increase the ability to achieve true alignment.
5 FRAME RATE STUDY
The maximum frame rate of the Pentacam system, shown in Table 12, was determined by reduc-ing the exposure time to 1ms and collecting 10 images. Therefore, the frame rate reported is theaverage frame rate during the capture of 10 images. Note that the ‘Live Capture’ check box(Figure 21) was disabled during this study.
Table 12. Frame rate study.
7.1507.078156.9405.781146.6304.563136.1203.281125.2101.90611
Frames/secImagesCaptured
Total CaptureDuration (s)
IntegrationTime (ms)
# ofCameras
6 FILES AND HEADERS
When image, GPS, and AHRS data is captured, Pentacam’s software creates data files and savesthem in the folder selected from the Settings menu (Figure 28). Sections 6.1 and 6.2 describe thesaved files.
6.1 GPS and AHRS files
GPS and AHRS data files are saved in the root directory as a text file. The files are named usingthe start time, date, and file type. For example, a GPS file captured on December 1, 2006 at 1:00PM is given the following name:
13.00.00 12 01 2006 gps.txt
GPS and AHRS files are space delimited. Therefore, they are best viewed using a spreadsheetprogram.
6.2 Image files
When image data are captured, a header and an image file are created. The header is a text filethat contains information about camera settings and capture time. Header files are named usingthe capture time, date, and camera number. For example, a header captured on December 1,2006 at 1:00 PM with camera 4 is given the following name:
13.00.00 12 01 2006 Camera4.hdr
The second file created during image capture is the image data file. This file has a .fla extensionand is saved in binary format. The image file, combined with its header, is formatted to openusing ENVI (http://www.ittvis.com/envi/index.asp).
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7 RADIOMETRIC CALIBRATION
Before shipment, each of the five image sensors was radiometrically calibrated using a lamp ofknown irradiance. Specifically, Equation 1 was used to calculate the gain needed to convertdigital numbers (DNs) into radiometric units. The calibration is valid for specific gain/offsetsettings of the camera.
[1]DN = DF + G $ L $ ETf/#2
Where DN is digital number, DF is dark field (in DN units), G is gain, ET is exposure time, f/#is the f-number of the fore optics, and L is irradiance at the entrance to the fore optics. Units forL do not matter as long as they are consistent when performing the calibration and subsequentlyconverting image data to radiance.
In general, the terms in the equation, DN, DF, G, and L are matrices represented as a 2D image.The L matrix has the same value at all elements. ET and f/# are scalars. All these analyses canbe performed as “image” analysis within ENVI.
In order to calculate the incident irradiance on the fore optics, the area under the lamp’s irradi-ance curve is determined in the region bounded by a bandpass filter. A graphical representationof the area calculation is shown in Figure 32, while the mathematical representation is seen inEquation 2.
Irradiance Calculation
0
10
20
30
40
50
60
70
80
90
400 420 440 460 480 500 520 540
wavelength (nm)
tran
smis
sion
(%)
0
5
10
15
20
25
30
35
40
45
irrad
ianc
e (m
W/m
^2/n
m)
Bandpass filterCalibration lamp
Irradiance Area
Figure 32. Irradiance calculation with bandpass filter.
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[2]L ==0
∞FT $ LL $ ¿
In Equation 2, FT is the filter transmission, LL is the irradiance of the calibration lamp, and is the wavelength step size used for numerical integration.
Once a gain image, G, has been calculated using Equations 1 and 2 for some f/# and ET, thecalibration equation can be generalized to account of any f/# and ET. The general calibrationequation is shown in Equation 3 (DF image should be captured under field conditions, since theDF depends on temperature).
[3]DN = DF + (G $ f/#R2 $ETR $ L)
Where :
[5]ETR =ETnET0
[4]f/#R =f/#0f/#n
The subscript values in Equations 4 and 5 distinguish between the reference f/# and ET (given avalue of 0) and the f/# and ET for measurement n.
Gain images, calculated using Equation 1, for each Pentacam camera (with its specific bandpassfilter in place) have been shipped with the system (on the CD). The calibration f/# and exposuretime (f/#0 and ET0) have already been accounted for in the gain images, and therefore, irradianceat the entrance to the fore optics can be determined by plugging in the values for DN, DF, f/#n,and ETn into Equation 6.
[6]L =(DN −DF) $ f/#n
2
G $ ETn
Section 11.2 describes an ENVI routine shipped with the Pentacam system that can be used toconvert raw images (DN units) to radiometric images (radiometric units). However, all of thecalculations can be done in ENVI once the DN, DF, and G images are saved.
The gain, offset, and exposure settings used during calibration are listed in Table 13. An imageof the setup used to collect the calibration data is shown in Figure 33. As seen, the illuminationproduced by the calibration lamp is reflected off spectralon before being collected by the foreoptics.
Table 13. Calibration camera settings.
2.81000800IR252.810003,200IR142.810001,000Red32.810001,650Green22.810001,200Blue1f/#Exposure Time (ms)Camera OffsetCamera GainFilter Camera#
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Calibration Lamp
Spectralon
Stray Light Shield
Pentacam
Figure 33. Calibration setup using a calibrated irradiance lamp.
Resampled Data
0
10
20
30
40
50
60
70
80
90
100
350 450 550 650 750 850 950 1050 1150
Wavelength (nm)
Perc
ent (
%)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Rad
ianc
e (µ
w/c
m^2
/sr/n
m)
Cam 5
Cam 3
Cam 2
Cam 1
MV13 QE
Sigma Lens
Cam 4
Cal Lamp
Figure 34. Calibration data.
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The transmission of each bandpass filter, detector QE, lens transmission, and lamp radiance isshown in Figure 34. Note that the lens transmission has been normalized to a maximum trans-mission of 90%.
7.1 Camera gain linearity
In order to know if it is appropriate to apply (use in calibration) the gain images generated by thecalibration at a single camera gain to other gain settings , it is import to understand how changesin camera gain affect the response (DNs) of the detector. Figure 35 is a plot of relative responsevs. camera gain setting. Notice that the response is not linear.
Figure 35. Normalized response vs. camera gain.
Because the camera’s response to gain changes is not linear, a full characterization of eachsensor should be completed in order to generalize the calibration equations for all camera gainsettings. Alternatively, a calibration could be completed for all camera settings used during datacollection.
8 CAMERA SETTINGS FOR AIRBORNE IMAGING
A study was conducted in order to determine a reasonable set of camera parameters for airborneimaging. These settings are not absolute but can be used as a starting point during aerial datacapture. Data were collected with each image sensor while looking at plant life illuminated bythe sun. The data were captured at f/2.8 in order to minimize the integration time needed toachieve adequate signal while using narrow bandpass filters. Table 14 shows the camera
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parameters chosen. Notice that the airborne image settings are identical to the settings usedduring calibration.
Table 14. Suggested ‘starting point’ camera settings for airborne imaging.
2.81000800IR252.810003,200IR142.810001,000Red32.810001,650Green22.810001,200Blue1f/#Exposure Time (ms)Camera OffsetCamera GainFilter Camera#
9 MODULATION TRANSFER FUNCTION (MTF)The MTF for each sensor/filter/lens combination was calculated using Imatest software. Imatestsoftware is a commercially available package available at www.imatest.com. The Imatestsoftware outputs MTF50, which is a numeric representation of perceived image sharpness. Details regarding the setup used to collect the MTF, as well as, the mathematics behind thecalculation are discussed in detail at:
http://www.imatest.com/docs/sharpness.html#interpretation
Table 15 summarizes the results of the MTF study carried out using the Pentacam system.
Table 15. Pentacam’s MTF results.
16.5OS02219IR2529.1OS02090IR1429.8OS02749Red331.0OS02329Green227.8
Sigma105 mm
OS02792Blue1
MTF 50(cycles/mm)LensFilter
Model #Filter Camera#
Notice that the MTF50 is relatively constant when the blue, green, red, and IR1 filters are used.However, there is a steep drop-off in the MTF50 for the IR2 filter. This drop-off is most likelydue to the poor lens performance in the IR region.
10 MECHANICAL AND ELECTRICAL SPECIFICATIONS
A mechanical schematic (with dimensions) of the Pentacam system is shown in Figures 36 and37. An electrical schematic of the system is shown in Figure 38. The mass of the system isapproximately 24 pounds with five 105 mm Sigma lenses attached.
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12.0”
12.9”
13.1”
2.0”
4.0”
2.5” 4.5”
1.8”
Figure 36. Pentacam dimensions - 1.
10.1”
Figure 37. Pentacam dimensions - 2.
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Cam1
Cam2
Cam3
Cam4
Cam5
USB
+5VDC
GND
TRIGGER
USB Hub
Fan
Figure 38. Pentacam electrical schematic.
11 ENVI SOFTWARE
Two analysis software programs have been shipped with the Pentacam system. The firstprogram is used for image co-registration and the second program is used to apply gain imagesto convert raw images (DN units) to radiometric images (radiometric units).
Before using the ENVI software, the folder named, ‘PentaCam_sav’ must be put in the correctEnvi directory.
C:\RSI\IDLXX\products\enviXX\save_add
Note that ‘XX’ in the above address refers to a specific version number. Once the folder isplaced into the directory, a ‘Pentacam’ option will appear on the main Envi toolbar. The updatedPentacam toolbar is shown in Figure 39.
Figure 39. Pentacam on ENVI toolbar.
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11.1 Co-registration software
The objective of the co-registration software is to spatially warp one or more images to match areference image. Warping reduces the spatial differences between images that have not beenremoved by hardware alignment, and correct for paraxial shift due to the displacement of thelenses. However, parallax correction is best applied at infinity, and can not be applied to imagewith objects at different depth of field.
After ‘Co-registration’ has been selected on the Envi toolbar (Figure 39), the pop-up screenshown in Figure 40 appears.
.
Figure 40. Reference cube pop-up.
The pop-up shown in Figure 40 asks the user to select a reference file. The reference file is atime series of images, i.e., an image cube (.fla extension) produced by a single Pentacam sensor.The images in the reference cube are not warped by the co-registration software. Instead, it isused as the ‘master’ image to which all other images are matched. Typically, the center sensor(Cam5) is used as the reference sensor due to its physical location. After the reference cube hasbeen selected, the software prompts the user to select up to four additional time-series forco-registration. If less than four are desired the user can stop the analysis by selecting ‘Cancel.’
The co-registration, not only co-registers the time sequence of images, but also parses the time-sequence and creates multispectral image cubes (of time-synchronized images). Therefore the
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output of the co-registration analysis is a series of image cubes (file extension ‘cub’) saved in thesame directory as the reference data file. The total number of cubes is equal to the number ofimages in each input data file. Each cube contains five (if all cameras are used) images whichcan be selected to form a RGB color image. This process is further illustrated in Figure 41.
.
Available Bands
Output RGB Image
Figure 41. RGB co-registration image.
Note that the co-registration procedure produces the best results when objects are viewed at largedistances (i.e. ∞). This is due to the paraxial lens displacement described in Section 4.6.3.
11.2 Radiometric calibration software
The calibration software shipped with the Pentacam system can be used to convert digitalnumbers to radiometric units. The software applies Equation 7, which is simply Equation 3solved for L.
[7]L = DN −DFG $ f/#R
2 $ ETR
Dimensional analysis of Equation 7 shows that L will have the same radiometric units as thesource used to calculate the gain image (G).
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The radiometric calibration software is started by selecting ‘Calibration’ under the Pentacamheading on the Envi toolbar (see Figure 39). Once started, the pop-up shown in Figure 42appears asking the user to enter the exposure time and f/# of the image undergoing calibration.
.
Figure 42. Exposure time and f/# inputs.
The exposure time and f/# entered represent ETn and f/#n as described in Equations 4 and 5.
Once the user has entered the appropriate exposure time and f/#, the software prompts the user toenter an image cube with units in DNs. The pop-up used to facilitate this process is shown inFigure 43.
.
Figure 43. DN pop-up.
Next, the software requires the user to input a gain image. The gain image is generated by usinga source of know radiance. Gain images have been shipped with the system (on the CD) but it isgood practice to recalibrate (calculate new gain images) on a regular basis or if any of the opticalhardware changes (lens, filters, etc.). The gain image pop-up is shown in Figure 44.
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.
Figure 44. Gain image file selection pop-up.
The final input required by the software is a dark field image. The dark field should be collectedusing the same (camera) gain, offset, and exposure time as the DN image. The dark field pop-upis shown in Figure 45.
.
Figure 45. Dark field file selection pop-up.
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After the dark field image is selected and the software calculates the radiance cubes, the user isasked to save the calibrated images using the pop-up seen in Figure 46.
.
Figure 46. Image cube save pop-up.
Notice that the default file name for the radiance cube is derived from the current time, currentdate, camera name, and ‘rad’ for radiance. The default file extension is ‘fla.’ However, both thename and file extension can be changed by the user.
In addition to the radiance cube, the calibration software creates a header file (file extension‘hdr’) containing information about the radiance cube and the input images. Table 16 lists theinformation contained in the header file created with the radiance cube. Notice that the headercontains information about the radiance data, as well as, the images used by the ENVI to createthe radiance images.
Table 16. Contents of radiance cube header file.
DN file name & locationcamera gain, offset, & exposure time# of images (bands)
start & end capture timesdark field file locationcreation timecamera name & numberdark field file namecreation date
Field Data (Flight Settings)Lab Calibration DataRadiance Cube
12 INSTALLING THE PENTACAM SOFTWARE ON ADDITIONAL COMPUTERS
The Pentacam software is fully installed and operational on the laptop shipped with the system.However, it is possible to install the software on additional computers.
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Installing the software is straightforward. The CD shipped with the system contains a foldercalled ‘Pentacam Software.’ The contents of this folder contain all of the necessary componentsneeded to run the software, including the camera driver. Therefore, all the user must do to usethe software is copy the ‘Pentacam Software’ folder to the C drive on the new computer. Afterthe software is copied and the system is connected via USB, the user must install the driversusing the process outline in Section 3
.
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13 PENTACAM MULTISPECTRAL SENSOR SPECIFICATION SHEET
GPS, AHRS (optional)Auxiliary equipmentEach camera separately setGain, offset, exposure7.0 fps (USB limited)Frame rate (max)Synchronized (all cameras)Image captureUser selectedSpectral bandsInterchangeable, F or C mountLensesAzimuth, elevation, rotationBoresight adjustmentMultispectralImaging5# of cameras
Features
MonochromeCMOS type10 bits Resolution500 fps (CMOS alone)Max frame rate TrueSNAP (electronic shutter)Exposure control19.67 mmDetector diagonalCMOSDetector type1,280 × 1024, 12 µmDetector resolution, pixel size
Detectors
Blue (450), Green (525), Red(650), IR1 (800), IR2 (900)Central wavelength (example), nm
CustomFilter holders4 mm × 50.8 mm × 50.8 mm Allocated volume (up to)Between optics and CMOSPosition
Bandpass filters
Radiometric calibrationImage co-registrationCamera alignment / boresightingGPS / AHRS data capture and time synch to imageryCamera control via USB (live preview, data capture, camera setting)Software
Side or down lookingSensor mount8.6 kgMass (no lenses)10.0 in (254 mm)Height13.1 in (333 mm)Width12.9 in (328 mm)Length
Mechanical
USBImage transferExternalSupply location5 AmpsMax current 5 VDCSupply voltage
Electrical
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