Transcript
Line Scan Camera SK2048USD Manual (v. 7.2012)
Monochrome Line Scan Camera SK2048USD
• Robust input and output connections • Hot-pluggable • Ultimate in mobility
Interface:
2048 pixels, 14 µm x 14 µm, 15 MHz pixel frequency Camera
SK2048USD
Sensor Type
IL-P3-B
Pixel number
4
14 µm
Sensor width
14 µm
Active length
28.7 mm
Anti-Blooming
yes
Integration Control
yes
Shading Correction
no
Window Function (ROI)
yes
Pixel frequency
15 MHz
Line frequency max
14.1 kHz
Line frequency min
0.03 kHz
Integration time max
35 ms 1)
Integration time min
2 µs
Dynamic range
1:2500 (rms)
Spectral range
400 – 900 nm
Interface
3
14 µm x 14 µm
Pixel spacing
Video signal
2
2048
Pixel size
1 Monochrome line scan camera SK2048USD Interface: USB 2.0
monochrome 8/12-bit digital
Interface:
Voltage
USB 2.0
+5 V (300 mA)
Power consumption
1.6 W
Casing (W x H x D)
AU2 (65 x 65 x 73 mm)
Objective mount
M40x0.75 thread, with locking bridge for fixing focus and aperture
0.2 kg
Working temperature
with
2 Clamp set SK5102 3 Mounting bracket SK5105 4 Photo lens Nikon AF 1:1.4/f'=50 mm,
M40 x 0.75
Weight
1)
1
Single Line Sensor
USB 2.0
+5°C to +45°C
Longer exposure times are possible in trigger mode "exposure active".
Contents Section
SK2048USD
1. 2. 3. 4. 4.1 4.2 4.3
Page Section
Introducing the SK2048USD Camera Connections Hardware and Software Installation Camera Control and Measurements Camera Control and Synchronization Gain / Offset Adjustments Generating a 2D Image – Scanning a Surface
2 2 3 4 4 4 4
4.4 5. 6. 7. 8. 9.
Page
Anti-blooming Adjustment Sensor Performance Specifications Dimensions Line Scan Camera Fundamentals Warranty Accessories
5 6 9 10 12 12
Line scan cameras from Schäfter+Kirchhoff are supplied factory-preset for the particular application. If you are not familiar with line scan cameras, or their operation using the supplied software, then consult the glossary in Section 7. Line Scan Camera Fundamentals, p 10.
Kieler Str. 212, 22525 Hamburg, Germany
•
Tel: +49 40 85 39 97-0
•
Fax: +49 40 85 39 97-79
•
[email protected]
•
www.SuKHamburg.de
Line Scan Camera SK2048USD Manual (v. 7.2012)
1. Introducing the SK2048USD Line Scan Camera The line scan camera SK2048USD is designed for ultimate portability. The robustly attached dedicated connections enable external synchronization of the camera and the output of data to the USB 2.0 port of the computer, which also supplies power to the camera.
Once the camera driver and the SkLineScan® program have been loaded from the SK91USB-WIN CD then the camera can be parameterized. The integration time and thresholding parameters are stored permanently in the camera even after a power down or disconnection from the PC.
The USB 2.0 connection means that the camera is hotpluggable and, with the highly robust connection, provides the greatest degree of flexibility and mobility. The computer does not require a grabber board, allowing a laptop to be used when space or weight restrictions are also at a premium.
The oscilloscope display in the SkLineScan® program can be used to adjust the focus and aperture settings, for evaluating field flattening of the lens and for orientation of the illumination and the sensor (for further information, see Section 7. Line Scan Camera Fundamentals, p 10).
2. Connections The line scan camera SK2048USD has two robustly attached dedicated connections: BNC coaxial for external synchronization signals and USB 2.0 for supplying power, to program the camera parameters and for data collection.
The camera requires a USB 2.0 connection or better and is not backwards compatible with USB 1.1. The USB power supply should provide +5 V with a minimum current of 500 mA.
Connections BNC:
input control using external synchronization signals
USB-A : connection with computer – supplying power (+5 V DC, >500 mA) and for data collection
BNC
USB BNC
USB
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Cable lengths: 1.7 m
Line Scan Camera SK2048USD Manual (v. 7.2012)
3. Hardware and Software Installation 1. Connect the power supply. 2. Attach USB connector to a Windows PC (XP SP3 or above). 3. The Hardware Assistant will look for a USB device driver. 4. P lace the SK91USB-WIN CD in the computer. The driver will be installed and the setup for the SkLineScan program starts automatically. 5. F ollow the dialog instructions and finish the installation of SkLineScan. 6. Once installed, start SkLineScan. -T he About dialog confirms that the "SK2048USD" camera is ready for use and the oscilloscope display window of the camera signal will open. - If the camera is not identified correctly then the driver installation must be attempted again.
The oscilloscope display facility of the SkLineScan program is responsive in real-time, and the zoom function can be used to highlight an area of interest. The oscilloscope display is ideally suited for parameterizing the camera, for evaluating object illumination, for focussing the image or for aligning the line scan camera correctly.
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Line Scan Camera SK2048USD Manual (v. 7.2012)
4. Camera Control and Measurements 4.1 Camera Control and Synchronization
4.3 Generating a 2D Image – Scanning a Surface
The camera SK2048USD has a maximum line frequency of 14.10 kHz and the programmable range for the exposure period is 0.07 ms up to 35.0 ms.
A two-dimensional image is generated by moving the object or the camera. The direction of the translation movement must be orthogonal to the sensor axis of the CCD line scan camera. To obtain a proportional image with the correct aspect ratio, a line synchronous transport with the laterally correct pixel assignment is required.
• Open the 'USB Camera Control' dialog from the SkLineScan program. • The adjustment range is defined by the left vertical slider and any changes are immediately visible in the oscilloscope signal display. • The button 'Default' sets the integration time at the minimum exposure period. The camera now works with the maximum line frequency. At shorter integration times than 0.07 ms, the 'Integr.Ctrl Status' automatically switches to 'Active' (Shutter mode).
The optimal object scan rate is calculated from:
•
WP VO = where VO WP fL ß S FOV
= = = = = =
fL
ß
object scan velocity pixel width line frequency magnification sensor length Field Of View
magnification = sensor length / Field Of View.
•
VO fL =
ß
S
v
WP
v
Pixel 1 CCD Sensor
V
Mode 0: Internal synchronization by the camera. Each line is acquired and the next scan is started automatically on completion of the previous line scan (free run mode). Mode 1: External camera synchronization. Each line scan is started by an external trigger (TTL) which determines the line frequency. The exposure time is constant and must be programmed prior to the first line scan. The TTL period must be longer than the exposure period. The TTL clock does not affect the integration time. Mode 3: The camera exposure period is started by a software operation. Mode 4: External synchronization is as for mode 1, but the falling edge of the trigger clock starts a new exposure period immediately (Restart-Reset-Mode). The minimum integration time in mode 4 is 0.07 ms. Mode 4 requires the use of the Integration Control function by the camera, which precludes the use of the shutter function.
If the velocity of the object carrier is not adjustable then the line frequency of the camera must be adjusted to provide an image with the correct aspect ratio, where:
VO
4.2 Gain / Offset Adjustments
Object structure V
Customized settings for gain or offset can be programmed using the SkLineScan software: 1. Offset: After blocking all light reaching the line sensor, bring the video signal near to 0 using the Offset slider. The line signal should be just visible above the baseline.
W v
P
v
FOV V
V
2. Gain: Fully illuminate the sensor and move the gain slider to provide maximum clipping of the signal (255 or higher).
Example: Object scan velocity for a given FOV and line frequency for the line scan camera SK2048USD
For cameras with two channel sensors, the 'B'-slider is activated automatically. The intensities of even and odd pixels are adjusted to provide the smallest deviations in signal. Page
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Pixel size Line frequency S FOV
= 14 µm = 7 kHz = 28.7 mm = 90 mm
VO
= 0.014 mm * 7000 / ( 28.7 / 90) s = 307.3 mm/s
Line Scan Camera SK2048USD Manual (v. 7.2012)
4.4 Anti-blooming Adjustment The optimum anti-blooming effect and greatest dynamic range for the camera are obtained when the output voltage of the camera is at ~90% of the saturation voltage VSAT.
1
1 Line scan signal with centrally enhanced illumination and sharply rising signal edges. Integration time tA= 0.158 ms. 2 Over-exposure caused by a long integration time (tA = 0.533 ms). The blooming effect is increased at the sensor when overadjusting the blooming control voltage (low VA). The shapes of the signal are distorted. 3 The blooming control voltage limits the output signal of the sensor to about 90% of the saturation voltage VSAT. The antiblooming technique is active. Even with a longer integration time (tA = 0.806 ms), the signal edge positions from 1 are preserved.
2
3
Dynamic range
Oscilloscope signal display of the CCD line scan signal obtained from a barcode illuminated with incident light
The blooming control voltage VA is factory preset for optimum anti-blooming and should only be altered in exceptional circumstances P3 The electronics of the USD camera series already support the blooming control possibilities of the sensor and are factory preset at ~90% of the saturation level VSAT to provide the greatest dynamic range for the camera with the optimum level of anti-blooming protection. The saturation load is regulated by the blooming control voltage VA. Higher values of VA increase the anti-blooming protection but at the expense of the dynamic range of the camera, as the apparent saturation level VSAT is increasingly attentuated. The anti-blooming effect is switched off completely at zero voltage VA. The maximum output voltage of the sensor reaches the saturation level VSAT.
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The anti-blooming control voltage VA is adjusted using the trimmer P3: < anticlockwise – raises VA for greater anti-blooming protection but reduces dynamic range > clockwise – lowers VA and reduces anti-blooming protection >> fully clockwise – anti-blooming is off
The trimmer P3 is accessed from the front of the camera after the lens has been removed and is factory preset at ~90% of VSAT. To prevent maladjustment of the line scan camera, the P3 adjustment should be monitored under sufficient illumination while observing the oscilloscope display of the line scan signal on the computer screen.
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Line Scan Camera SK2048USD Manual (v. 7.2012)
5. Sensor Performance Specifications Manufacturer: Dalsa Type:
IL-P3-B 2048
Data source:
Dalsa Linear Sensor Document 03-036-00187-09
Pin-out and Dimensions
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Line Scan Camera SK2048USD Manual (v. 7.2012)
Block Diagram and Typical Performance Data
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Line Scan Camera SK2048USD Manual (v. 7.2012)
Performance Specifications
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Line Scan Camera SK2048USD Manual (v. 7.2012)
6. Dimensions Line scan cameras with USB interface
Ø 65
CCD line scan camera, digital
61.5
M40x0.75
2.5 6 12.7
Casing group: Lens thread: Distance to sensor: Input control: Data/power interface:
Ø 42
41.7
Pixel No.1
M3 (4x) CCD sensor
Depth 6.5 mm
BNC
19.5
2
3
4
36
68.5
1
Clamp set SK 5102
M3
Camera type: USD series with 512, 1024 or 2048 pixels 1 CCD line scan camera, digital Lens thread M40x0.75 mounted on: 2 Clamp set SK5102 3 Camera mount SK5105 4 Lens 5 Locking bridge (aperture and focus)
Mounting bracket SK5105
10
Clamp
5
USB
AU2 M40x0.75 19.5 mm BNC USB-A
10
for digital and analog cameras Order Code: SK5105
Cylinder screw DIN 912-M3x12
6
Warp resistant construction for mounting a CCD Line Scan Camera
3.5
36
16.5
40
63
70
42 Ø
41.7
M4 50.3
20
6.5
to lock the CCD Line Scan Camera at an arbitrary rotation
Ø3.3
1/4" 20G
M3
Clamp set SK5102 (set of 4)
50
66
15
Ø4.3
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Line Scan Camera SK2048USD Manual (v. 7.2012)
7. Line Scan Camera Fundamentals Line scan cameras from Schäfter+Kirchhoff are supplied factory-preset for the particular application, with optional accessories and appropriate software – for parameterization of the camera or for optimizing signal acquisition. The advantages and constraints of the technology are described below and some essential aspects of sensor alignment, lens focussing and signal optimization are presented.
7.1 Features and Characteristics
GigE SK7500GTO
Pixel 1 CCD Sensor
Object structure
A charge-coupled device is a linear array designed for moving discrete electrical charges from one element of the array to the next by successively applying a voltage to each element in turn. The discrete charge packets emanating from the end of the linear array are converted into a voltage and digitized for further transmission. A line scan signal is produced by moving the object to be imaged in a trajectory perpendicular to the camera sensor. By synchronizng data acquisition, high frequencies and resolutions are achieved. The choice of line scan camera is primarily determined by the customer application requirements, which influence sensor length, pixel number and line scan frequency – see Imaging Definitions, below.
Other custom features can be chosen, such as specialized or filtered illumination, choice of color or monochrome line sensors as well as type of interface, with either GigE VisionTM, Gigabit Ethernet, LVDS, CameraLink® or USB 2.0 interfaces available for data output. The oscilloscope display facility of the supplied software is responsive in real-time, and the zoom function can be used to highlight an area of interest. The oscilloscope display is ideally suited for parameterizing the camera, for evaluating object illumination, for focussing the image or for aligning the line scan camera correctly – see Section 7.2 Alignments and Adjustments.
Our considerable experience in line scan camera design and software production allows us to get the best possible imaging performance within the constraints of the technology. Potential problems are simply designed out – or an intrinsic constraint is tuned away – according to circumstance. For example, illumination over-exposure of the sensor causes blooming and signal blur or loss, from charge leakage across pixels. Blooming can be either designed out (antiblooming) or cut by reducing the integration time or lens aperture.
A line scan camera 2D area scan can easily be performed by simply specifying the number of line scans to be integrated.
Similarly, gain and offset tuning can increase signal-to-noise ratios, while shading correction negates any problems of pixel variability, lens vignetting or inhomogeneous illumination, whether initially present or not.
• Exposure Period and Integration Time
• Pixel and Line Scan Frequencies
• Optical Resolution
The illumination cycle of a line scan sensor, of a particular length and number of pixels, for a set period of time is designated the exposure period.
The pixel frequency for an individual sensor is the rate of charge transfer from pixel to pixel and its ultimate conversion into a signal. The minimum exposure period of a sensor is the minimum time required for the read-out of a whole line scan and is dependent on the maximum pixel frequency and the number of pixels (plus a sensor-dependent overhead of passive pixels).
The optical resolution of a line scan camera is determined primarily by the number of pixels in the linear sensor and secondarily by their size and spacing, the inter-pixel distance.
Imaging Definitions
Within a single exposure period, the integration time is the duration designated for signal accumulation of charges by the sensor. In continuous mode, the next exposure cycle is simply begun at the time of read-out of the previous exposure and, so, the durations of exposure period and integration time are identical. Cameras with integration control are capable of curtailing the integration time within an exposure period (emulating a shutter mechanism).
The line scan frequency is inversely proportional to exposure period. During the time the charges from a finished line scan are read out, the next line scan is being exposed. Thus, the minimum exposure period determines the maximum line scan frequency.
Currently available line scan cameras have up to 12 000 pixels, ranging from 4 to 14 µm in size and spacing, for sensors up to 56 mm in length and line scan frequencies up to 83 kHz. During a scanning run, the effective resolution perpendicular to the line scan camera is determined by the velocity of the scan and by the line scan frequency, i.e. the number of line scans per second.
Data Reduction and Acquisition Acceleration • Thresholding (B/W cameras only)
• Region of Interest
GigE SK7500GTF-XB
The thresholding process generates a binary signal from the gray scale data, with values below the threshold yielding 0 and those above yielding 1. Only the pixel addresses of the location and threshold transition (from high→low or low→high) are transmitted, reducing data throughput. Thresholding is particularly appropriate for measuring widths or edge positions, by simply masking the required pixel addresses.
A freely programmable window (region of interest, ROI) can be applied to the line sensor so that only the pixel information within the ROI can reach the memory. By only illuminating these ranges, data volume and data processing is accelerated for both line and area scan acquisitions. Constraint: the ROI memory allocation must be divisible by 8. Page
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Line Scan Camera SK2048USD Manual (v. 7.2012)
7.2 Alignments and Adjustments Sensor Alignment For linear illumination sources, rotating the line sensor results in asymmetric vignetting. The camera and illumination optics can be aligned optimally by monitoring the object illumination using the oscilloscope display. Sensor and optics rotated in apposition A and aligned B .
A
B
Integration Time and Aperture Optimization The line scan signal is optimum when the signal from the brightest region of the object corresponds to 95% of the maximum gain. Full use of the digitalization depth (255 at 8-bit, 4096 at 12-bit) provides an optimum signal sensitivity and avoids over-exposure (and blooming). The range of intensity distribution of the line scan signal is affected by the illumination intensity, the aperture setting and the camera integration time. Conversely, the aperture setting influences the depth of field as well as the overall quality of the image and the perceived illumination intensity. A
camera signal exhibiting insufficient gain: A the integration time is too short as only about 50% of the B/W gray scale is used.
B
ptimized gain of the camera signal after O increasing the integration time, by a factor of 4, to 95% of the available scale.
A
B
Gain / Offset and Shading Correction Cameras are shipped prealigned with gain and offset factory settings, although they can be customized using the SkLineScan software. A Offset. After blocking all light reaching the line sensor, the video signals are adjusted to zero using the offset sliders. The line signal should be just visible at the bottom of the oscilloscope display. B Gain. The sensor is fully illuminated and the gain sliders adjusted to provide a close to maximum signal intensity (255 for 8-bit or 4095 for 12-bit) and superimposed signals for each camera or RGB channel. C
Shading Correction. Shading correction,
white balance or flat-field compensation are all related techniques that automatically compensate for any variation in pixels, lens vignetting or inhomogeneity in the illumination, etc, whether initially present or not. All lenses show some vignetting as a function of the field angle (collectively, the relationship between sensor and focal lengths and magnification). Hence, even with homogeneous object illumination, the image signal intensity decreases with increasing image height.
B
C A
A reference signal for shading correction, for example, is obtained by taking an image of a diffuse white surface, followed by algorithmic compensation of each pixel to provide a maximum overall intensity. Many alternative solutions are available, such as using the R, G and B gain sliders directly to superimpose the individual channels. Corrected parameter settings can be stored within the non-volatile memory of the camera and are retained for subsequent use even after a complete shutdown.
Lens Focussing The oscilloscope display can also be used to focus a line scan camera system by using the variations in edge steepness at dark/bright transitions – observed as modulations in the zoomed line scan signal. Initial focussing is performed with a fully opened aperture (smallest depth of field and largest sensitivity to focus adjustment). The integration time can also be reduced to provide a sufficiently sensitive, low amplitude signal. A
Out of focus: edges are indistinct, signal peaks blurred with low density modulation
B
ptimal focus: dark-bright transitions have O sharp edges, highly modulated signal peaks with high frequency density variations
B
A
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Line Scan Camera SK2048USD Manual (v. 7.2012)
9. Accessories
8. Warranty This manual has been prepared and reviewed as carefully as possible but no warranty is given or implied for any errors of fact or in interpretation that may arise. If an error is suspected then the reader is kindly requested to inform us for appropriate action.
Mounting bracket SK5105
Order Code Warp-resistant construction for mounting the line scan camera
Clamp set SK5102
Order Code to lock the line scan camera in desired position (set of 4)
The circuits, descriptions and tables may be subject to and are not meant to infringe upon the rights of a third party and are provided for informational purposes only.
Mounting Console SK5105-2
Order Code for indirect mounting of the line scan camera via the extension tube, suitable for extension tube larger than 50 mm, for example with macro lens.
The technical descriptions are general in nature and apply only to an assembly group. A particular feature set, as well as its suitability for a particular purpose, is not guaranteed.
Software: SK91USB-WIN * Order Code SK91USB-LX ** SkLineScan operating program with oscilloscope display and scan function for setting camera parameters via USB
The warranty period for the CCD line scan camera when used for the purpose for which it was intended is 24 months. The warranty is immediately void on inappropriate modification, use or damage.
Operating systems: * Windows XP/2000, ** Linux
EC Declaration of Conformity
Lenses: • high resolution enlarging and macro lenses • high speed photo lenses • lenses with additional blocking bridge for locking of focus and aperture setting
This product satisfies the requirements of the EC directive 89/336/EEG as well as DIN EN 61326.
SK2048USD
Adapter: Lens adapter AOC-... • for fitting photo lenses onto the CCD line scan camera Focus adapter FA22-... • for fitting enlarging or macro lenses
Kieler Str. 212, 22525 Hamburg, Germany
•
Tel: +49 40 85 39 97-0
•
Fax: +49 40 85 39 97-79
•
[email protected]
•
www.SuKHamburg.de
