SwissRanger SR-3000 Manual. Version 1.02 October, 2006

Transcription

1 SwissRanger SR-3000 Manual Version 1.02 October, 2006

2 2

3 History Date Version Name Description Approved V1.0 various V1.01 Tog - Scattering light Artifact - CSEM to MESA corrections - Web-Link adjustments V1.02 Tog Mounting instructions V1.03 JSP Quick guide for 3D demo 3

4 Table of contents 1 FOREWORD TARGET APPLICATIONS D-TOF MEASUREMENT PRINCIPLE SR-3000 DELIVERY PACKAGE SR-3000 DIMENSIONS SR-3000 MOUNTING INSTRUCTIONS SR-3000 BLOCK DIAGRAM SR-3000 TIMING Detailed SR-3000 Timing SR-3000 SYSTEM PARAMETERS Hardware Parameters System Performance Electrical Characteristics Environment Specifications SR-3000 SOFTWARE Drivers Sample Code Demo Software Matlab Package SR-3000 INTERFACE API Package Amplitude Threshold Integration Time Image Acquisition

5 11.5 X, Y, Z Data SOFTWARE DOWNLOADS Camera Configuration / Firmware Update API Package Demo Software Package for Windows2000/XP D Demo Software Quick-Start Guide Demo Software Package for Linux Demo Software Package for Mac OS X SR-3000 ARTIFACTS Light Scattering Multiple Reflections CONTACT ADDRESS

6 1 Foreword Figure 1: Photograph of the SR-3000 camera. Range cameras are expected to find many practical uses in manufacturing, safety, surveillance and security. In particular, compact solid-state range cameras are extremely appropriate for a wide range of applications. The present document gives an overview of the capability, the operation of the first product of a complete solid-state Time-Of Flight (TOF) range camera, developed by CSEM. Interestingly, it has already been demonstrated that, for a large range of illumination levels, the range accuracy is essentially only limited by the shot noise of the available light. Our theoretical understanding of TOF range cameras allows us to predict reliably the obtainable range resolution. Nevertheless, the practical use and suitability of this type of camera, for example in an industrial environment, typically require proceeding software and algorithms. 6

7 2 Target Applications Mobile Robotics: Navigation Machine Vision: Presence Check Gaming / PC peripherals Biometrics Men-Machine Interface People Counting Security Safety in Robotics Figure 2: Example of an application in biometrics. 7

8 3 3D-TOF measurement principle The 3D camera developed at CSEM is an imaging and distance-measuring device. It simultaneously delivers gray level images and the 3D information of the scene. With the default settings (i.e. a modulation frequency of 20 MHz), the non-ambiguity distance range is 7.5 meters. Distances up to 20 meters can however be measured using lower modulation frequencies. The camera can be read by a USB2.0 interface (USB1.1 also possible, but slows down the frame rate). The results of the distance-measuring process can be viewed as a color-coded image on a PC with a (lateral) spatial QCIF resolution (176x144 pixels). The depth accuracy is typically of the order of a few centimeters down to millimeter for advantageous scenarios. The distance accuracy depends on distance range, (the AC modulated) signal intensity and the DC background illumination. The distance measurement is based on the Time-Of-Flight (TOF) principle. A detailed discussion of the TOF principle and its present implementation in a silicon-based image sensor has been published, for example during the RIM Days. The paper can be downloaded from The SR-3000 camera is based on a 2-dimensional dedicated image sensor with a spatial resolution of 176*144 pixels manufactured in 0.6 micron CMOS / CCD technology. The camera is typically driven with an internal main frequency of 20 MHz, the emitted light being modulated at 20 MHz. The measured distance is proportional to (twice) the time needed for the light to travel from the camera to the object. In the present CW Figure 3: 4-times sampled incoming light signal. modulation scheme, a phase shift is actually measured, namely the phase shift between the outgoing signal (modulated illumination intensity) and the detected reflected signal. The reflected signal is sampled four times (samples A0, A1, A2, A3) in a period, each time phase-shifted by 90. In the following, the phase shift is computed according to equation 1. At the same time, the amplitude A can be calculated using equation 2. 8

9 Table 1: Basic time-of-flight calculations c( τ 3) c( τ1) ϕ = atan c( τ 0) c( τ 2) 1 2 [ C( τ ) C( τ )] + [ C( τ ) C( )] A = τ 2 The SR-3000 sensor is controlled as a so-called 1-tap sensor. This means that in order to obtain distance information, four consecutive exposures have to be performed. Fast moving targets in the scene may therefore cause errors in the distance calculations. The computed offset and amplitude allow a comparison and finally a qualification of the measured distance even at camera level. The SR-3000 camera is controlled by an FPGA, whose registers may be changed through the USB interface. This allows for the selection of different settings. 9

10 4 SR-3000 Delivery Package Hardware o 3D-TOF SR-3000 Camera o Power Supply with cable o USB cable Software o Drivers for Windows o Visualization Demo Software for Windows2000 / XP o Drivers for Linux / Mac OS X o Visualization Demo Software for Linux / Mac OS X (ready in Q1, 2005) o Source Code Console Program for Camera Operation in C++ o Source Code Data Visualization Program in C++ SR-3000 Camera Manual Figure 4: Hardware delivery package. 10

11 R15 MESA Imaging AG October, SR-3000 Dimensions M Ø 16 A A R2.5 R2 ( 29.3 ) (13 ) 42.3 Ø 12.7 A-A /4"-20 Fotogewinde Figure 5: Camera drawing. 11

12 6 SR-3000 Mounting Instructions The SR-3000 can be mounted using the two M4 threads on the backside of the SR-3000 camera. The maximal penetration depth of the screws is < 5 mm. The camera can also be fixed using the standard ¼ photo thread. Again, the maximal screw length is < 5 mm (see Figure 5). In order to avoid interfering signal directly reflected by the pedestal the camera is mounted on, the SR-3000 has to be fixed in such a way that direct reflection is avoided. Figure 7 illustrates the mounting instruction to avoid direct reflection from the camera pedestal Note: Make sure that during all operation conditions, the air slits on the top and bottom of the SR-3000 camera are kept free in order to guarantee a constant airflow through the SR-3000 camera (see Figure 6). Figure 6: Air flow through the SR-3000 camera a) b) Figure 7: Mounting instruction to avoid direct reflections; a) wrong mounting, b) ideal mounting. 12

13 7 SR-3000 Block Diagram The SR-3000 camera comprises: 1. Camera solid aluminum casing 2. High speed demodulation imager 3. Built-in high-speed near-infrared illumination unit 4. Built-in optical band-pass filter for daylight rejection 5. Built-in high speed lens 6. Camera electronics 6.1. USB communication board 6.2. Built-in image processing board Figure 8 illustrates the different modules of the SR-3000 camera / Figure 8: Block diagram of the camera 13

14 8 SR-3000 Timing In order to determine the impinging sine wave for each pixel, four sampling operations are executed. For that reason, in total four consequent integration cycles have to be performed. The image request from the PC directly loads the on-camera saved data to the PC. 8.1 Detailed SR-3000 Timing The implemented timing schedule looks as sketched in Figure 9. Figure 9: Timing schedule of the SR

15 9 SR-3000 System Parameters 9.1 Hardware Parameters ILLUMINATION Parameter Ratings Units Conditions Number of LEDs 55 - Modulation Frequency 20 MHz Total Emitted Optical Mean Power during Integration 1 20 MHz room temperature Peak Wavelength 850 room temperature Bandwidth FWHM 35 room temperature Emission Angle ±25 room temperature LENS Parameter Ratings Units Conditions Focal length 8 mm Aperture diameter 5.7 mm Mounting thread M12x ELECTRONICS The camera architecture is based on a modular PCB setup. In total, four PCBs are implemented in the camera. The boards are stacked onto each other. All boards have the same dimensions, except the illumination Module. The four boards are named: Illumination Module (ILM) Sensor Head Module (SHM) Image Processing Module (IPM) Communication Interface Module USB (CIM-USB) The ILM contains 55 LEDs and their high-power driver electronics. It is directly connected to SH boards through a stacking socket. The SHM controls the sensors and converts the raw sensor output signals into digital data values. The IPM processes the data from the SH and performs the distance and amplitude calculation as well as additional signal processing tasks.. The CIM-USB ensures the USB2.0 interface to the computer. Furthermore, it contains the power supplies. 15

16 9.1.4 OPTICAL FILTER Parameter Ratings Units Conditions CWL typical 870 nm FWHM typical 80 nm SENSOR Parameter Ratings Units Conditions Number of active Pixels 176 x QCIF Demodulation Frequency (default) 20 MHz Dynamic Range Modulated Light 70 db Background light suppression 400 W/m 2 corresponds to 50% of / µm ability the maximal sun light Pixel Size 40 x 40 µm System Performance Parameter Ratings Units Conditions Best Case Standard Deviation < MHz Modulation Non-ambiguity Range 750 cm Depth resolution of central Pixel 1 Distance [m] Frame Rate [Hz] Resolution [mm] Electrical Characteristics Parameter Ratings Units Conditions Power supply 12±5% VDC Typical power consumption 12 W Depends on integration time Maximal power consumption 18 W Drawing of Power Supply Connector: (not compatible with SR2!) 0V DC (GND) + 12V DC DC Connector Manufactor TCO: Typ - K-0135A Distributor Compona: Best. Nr Acquisition at room temperature; target with 90% reflectivity, 20 MHz modulation frequency 2 At full frame 16

17 9.4 Environment Specifications Parameter Min max Units Storage Temperature Range C Operating Temperature Range 0 50 C Background illumination W/m 2 /µm 3 Corresponds to 50 % of the maximal sun light power condition 17

18 10 SR-3000 Software 10.1 Drivers Drivers are available for Windows2000/XP, for Linux and MacOSx WINDOWS2000/XP INSTALLATION 1) Download the most recent SwissrangerSetupX.X.X.X.exe drivers from and execute it (Note: You need to be administrator to install it!). 2) Plug in thesr-3000 camera. 3) Execute the steps described in the Swissranger.chm help file, section Driver installation. 4) Start the demo program (Make sure you have connection to http! See note below). Note: At the first call to the SR-3000 dll-function, the camera specific calibration file (*.xml) is automatically downloaded from the http server and stored at the right location on: C:\Program Files\CSEM\Swissranger\firmware If at the start-up the camera-specific xml-file is neither available in this folder nor can be downloaded via http, a warning message will appear. If this can not be fixed contact the distributor to get this file Sample Code Some very simple sample code is also contained in the driver package. libusbsrtester is a very simple console test application that shows how to open the driver, setup the camera, acquire images and close the driver. It acts also as a function test of the camera. SwissrangerSampleGui is a simple Win32-application that acquires and displays data on Windows Demo Software WINDOWS2000/XP Plug and Play point cloud visualization Visualization of distance and amplitude On-line settings change File sequence storage 18

19 LINUX Please check out: Matlab Package The complete Matlab interface is described in the Swissranger.chm help file that is installed with the driver. Note: To make all the functions available to Matlab under Windows, following path must be added at the end to the Matlab search path: (Matlab->Set Path...) C:\Program Files\CSEM\Swissranger\matlab\swissranger C:\WINDOWS\system32 To have an overview and further details about the implemented m-functions call help swissranger from Matlab or read the Swissranger.chm help file. 19

20 11 SR-3000 Interface The camera transmits its data trough a USB2.0 interface to the computer. However, the camera interface can be complemented in the future with the following standards: Ethernet 10/100M CAN Bus (for control data flow only) Camera Link Please contact info@swissranger.ch, for the availability of other interfaces than USB API Package The camera is delivered with an API package that provides functions to setup the camera, to acquire and to process distance images. Below the most important interface functions are described. The complete and detailed API is described in the Swissranger.chm help file that is installed with the driver Amplitude Threshold Setting the amplitude threshold, noisy pixels can be filtered. The amplitude determines the amount of emitted light that is reflected back on the pixel. Therefore, it represents a means to qualify the measurements for each pixel. All pixels, that do no reach a higher amplitude values as given in this register are filtered and set to 0. The amplitude threshold can be set with the API-function SR_SetAmplitudeThreshold( ). Figure 10 shows the effect of setting the amplitude threshold filter and filtering out all pixels with an amplitude considered as being g too small. a) b) Figure 10: Example of the setting a high amplitude threshold: a) the threshold is set to 0, therefore no distance is filtered. b) The threshold is set to a high value. All dark blue pixels are considered not having reflected enough light to be considered. 20

21 11.3 Integration Time The integration time can be set by register 20. It controls the exposure time for one of the four acquired images and can be varied from 200 µs to 51.2 ms in steps of 200 µs, whereas the value 0 corresponds to an integration time of 200 µs and 255 of 51.2 ms. The integration time can be set with the API-function: SR_SetIntegrationTime(,intTime). The integration time is then (1+ inttime)* 200 µs Image Acquisition The camera transmits 16 bit distance and amplitude data. The distance is in spherical coordinates with values from 0x0000 to 0xffff that represent a distance from 0 m to 7.5 m. The data is acquired with the API-function SR_Acquire( ). The memory of the images can be inquired with the functions SR_GetImage(,index) where index 0 refers to a 16bit distance image and index 1 refers to a 16bit amplitude image X, Y, Z Data The spherical distance data can be transformed into carthesian coordinates with the API-functions: SR_CoordTrfXXX() 21

22 12 Software Downloads The following documents / packages can be downloaded from the website API Package o SwissRanger dll o C++ Source Code Console Program Simple Data Visualization Program o Libusb Drivers o Help Files o Matlab Demo Files o Calibration Toolbox Demo Software Package for Windows 2000/XP (*.exe file) Visualization Program for Linux Visualization Program for Mac OS X FAQ Camera configuration files 12.1 Camera Configuration / Firmware Update At every start-up of the camera, the camera is configured through the USB port. The customer can always download the latest firmware update from the web. The camera configuration is set through the USB port API Package The latest API package is available on the net. It helps to ensure an easy interfacing of the SwissRanger camera for customers using various operation systems. The API package includes: SwissRanger DLL C++ source code o Console program o Simple Data Visualization Program Libusb drivers Help Files Matlab Demo Files 22

23 12.3 Demo Software Package for Windows2000/XP The Demo software for Windows2000/XP aims at the first plug-and-play visualization of the data acquired by the SR-3000 camera. Figure 11: Snap shot of the demo software for Windows 2000/XP. 23

24 12.4 3D Demo Software Quick-Start Guide Init Cam Start / Stop Amplitude Threshold Integration Time Auto Initializes the camera Starts/Stops capturing Distance quality threshold Integration time Highest possible integration time Sqrt Scaling Stretch Uses the square root of the amplitude for amplitude display Histogram equalization of amplitude Sets the size of the points when in point list display mode Cut off distance in the display Scales the view in depth Shift the origin in the z-axis Scales the color bar Sets the color offset of the color bar Display 3D Median Filer Oscillate Number of Frames Start Export Main display on/off Median filtering of distance data Oscillates the view by xx degrees Number of frames to be streamed Starts the memory stream Exports normalized distance, normalized lateral values & and amplitude as ASCII Right click in the main display window to pop-up the menu Solid Wire Frame Point List Color Amplitude Display distance as surface Display distance as wires Display distance as point cloud Uses a color map as overlay Uses amplitude as overlay Export dxf Export stl Export point cloud Uses amplitude as overlay DXF export of current frame Binary STL export of current frame ASCII export 24

25 For any updates on the demo program, please check out: Demo Software Package for Linux Please check out: Demo Software Package for Mac OS X Please check out: 25

26 13 SR-3000 Artifacts 13.1 Light Scattering Light scattering occurs in the camera s internal optical path. Since not all of the impinging light is absorbed by the imager, a portion is reflected by the imager. This reflected light can be again reflected by e.g. the optical lens back to other pixels on the sensor. Of course, this artifact mainly affects the distance values of those pixels that do not get much of modulated energy from the direct optical light. Figure 12 illustrates this light scattering effect schematically. Figure 12: Schematic drawing illustrating the light scattering artefact. 26

27 13.2 Multiple Reflections All LEDs on the SR-3000 camera are perfectly synchronized and all the pixels acquire the image simultaneously. Multiple paths might occur in the scene. As illustrated on Figure 13, the light projected from Point A reflects directly to the camera on path 1 as well as on path 2. This artifact can mainly be observed by acquiring corners. Figure 13: Illustration of a scenario with multiple reflections. 27

28 14 Contact Address MESA Imaging SA Badenerstrasse Zürich - Switzerland - phone fax support@swissranger.ch 28