Bernardino J. Buenaobra, National Institute of Physics, University of the Philippines, Diliman Campus, Philippines

Products used:
LabVIEW 7.0 Express ™
LabVIEW PID Toolkit™ for Windows
LabVIEW State Diagram Toolkit™
LabVIEW Math Interface Toolkit™
LabVIEW Simulation Interface Toolkit™
LabVIEW Picture Control Toolkit™
IMAQ Vision Toolkit 6.0™
Vision Builder 6.0™
PCIGPIB Interface card™
PCI6024E Multifunction card™
PCI6602 Counter Timer board™
PCI1411 Image Acquisition card™
NIDAQ 6.93 Drivers™
IMAQ™ Drivers

The Challenge:
To design and build a desktop Laser Scanning Microscope with a Wireless Virtual Instrumentation System enabling students, university faculty, research and laboratory personnel to acquire, share data over the air, share time slices for data acquisition and instrument control integrating LabVIEW‘s powerful communications features with wireless local area networking (WLAN) and Global System for Mobile Communications (GSM).

The Solution:
We use the Remote Panel connectivity and Web server feature of LabVIEW XP7 to connect virtually to a costumed designed motorized Laser Scanning Confocal Microscope via IEEE 802.11g wireless local area network to distribute shared control time, image files and data acquisition among remote users. Telecommunications for sending notifications was implemented via Siemens M20 GSM terminal module.

Abstract
A relatively expensive scientific instrument such as laboratory quality, Laser Confocal Microscope located at a research university could be readily shared remotely by users over cable by a LAN with certain defined privileges and security access to a dedicated IP address and server granted by a system administrator. The idea of a networked based instrument is extended here by the use of WLAN within an existing network layout of a laboratory floor to distances permitted by IEEE 802.11g wireless standard. Going further beyond and outside the laboratory that is from campus wide or from a city access to as distant as country wide research collaboration between universities, a GSM wireless communications solution could be employed wherever HSCSD, GPRS/EGRPS data quality service is available. At the instrument design level, integration of motion control, data acquisition and instrument control and advanced communications can be implemented in one single program by use of National Instruments hardware and software tools of LabVIEW Express 7.0, IMAQ Vision, NI-DAQ, and VISA-GPIB along with built-in advanced analysis packages and tool kits.

Overview of System Architecture
The system has been designed with the objective of connecting remote users with LabVIEW XP7 runtime engines running locally but accessing remotely by a Web Browser a main server panel from a single costumed designed remote instrument. First tested through an existing UTP version LAN connection in the laboratory it is extended to a wireless LAN connection (WLAN) by use an Access Point Hub as shown in figure 1 below:

Figure 1. Project MAEROL uses LabVIEW's Remote Panels over the Internet with Wireless LAN and GSM Module

In the same figure above, node computers are equipped with WiFi interface that are reachable well within unobstructed distance of 30-50 ft. with bandwidth as high as 54Mbps on a USB 2.0 port, this connection will enable instrument use virtually anywhere in the laboratory floor. In this implementation we use a subset from the university network which can allow certain accesses by permission to use a fixed and dedicated IP address, while a firewall maybe employed for security purposes. All remote users are privileged users with password identification issued by the laboratory. User notifications can be issued as SMS text messages by a GSM Modem which is serially programmed in NI VISA with string formatted AT-Commands Set, while JPEG image file transmission by email can be sent out to remote nodes with TCP/IP communication VIs’ already made possible in LabVIEW 6.1, 7.0. The above graphic shows the picture of the actual instrument, the front panel of the centrally located instrument (a Laser Scanning Microscope) and an email reception showing an attachment (www.yahoo.com email). The wireless facility can be easily extended to accommodate not just SMS text service from access outside the laboratory to a remote location which can be made possible by a dial-up connection through the local communications provider data quality grade channel such as a General Packet Radio Service (GRPS) or the enhanced version called EGRPS/EDGE, or via High Speed Circuit Switched Data channel (HSCSD) with a pre-paid Internet Service Provider (ISP).

Workings of the Remote Instrument System Design
At the front end, the university laboratory’s Laser Scanning Microscope has been upgraded and retrofitted with NI hardware, combining motion control, vision, instrument control and measurement hardware and software, including capability to send text messages via GSM communication module. Figure 2 is representative of this system design. In the subheadings that follow some description on the operation are discussed.


Figure 2. Remote Instrument System combines measurement, motion control,
vision, instrument control with GSM communications module

Data Acquisition, Analog I/O and Measurement
We designed an analog measurement system around National Instruments multifunction card PCI6024E hardware to implement 12-bit measurements of very slowly varying analog quantities usually present in electro-optics experiments. It was also used for the discrete control of temperature of specimen heater/cooler in closed loop PID control. One channel has been dedicated for temperature input reading and one channel for analog output for voltage driving a thermoelectric element cooler (Thorlabs TEC 3.6). We recover analog currents into a defined analog input signal channel configured by NIDAQ MAX this is a feedback signal from optical detection of a semiconductor Laser made available from the output of a GPIB enabled Laser controller. The low level signals are conditioned, converted to voltage by electronics, assembled and normalized internally in software to form a 2D array to correspond to picture element of which determines the amount of light intensity reflected from the sample surface at that point.

Instrument Control
Local connection to the centralized and networked ancillary instrument is made possible by use of a National Instruments’ PCIGPIB interface card by a control system personal computer. The program is designed in such a way that the instrument control function is integrated with a single Graphical User Interface (GUI) on a user event drive front panel; where set-up initialization, internal clamps and alarms were all predetermined for safety purposes at the beginning; all these have been pre-programmed into the Laser Diode Controller (Melles Griot 06 DLD 105). The controller will have privileged control for power control and validations of commands and safety checks done by direct vision using a CCD camera (Hamamatsu Photonics Model C3057) equipped with a zoom lens, connected to a PCI1411 IMAQ card and by interrogations on the GPIB bus by a main UI.

Motion Control
Movement in the nanometer as small < 32nm per step (New Focus Picomotors) to submicron regime of < 0.05mm motor resolution (Thorlabs Multi-Axis Translation Stage) employed precision power drivers and specialized actuators made to match those control schemes available using in NI products. The seamless software integration for device driver development for a single and unified program synchronizing motion, low level signal acquisition and imaging, vision and instrument control has been easily achieved in LabVIEW utilizing advanced synchronization schemes as a design pattern for code development. Also, pulsed or otherwise continuous form of driving input for these specialized Electro-Optical and Opto-Mechanical devices has determined the use of National Instruments’ PCI6602 counter/timer board for the stage’s tilt control (Yaw, Pitch and Roll) axis. LabVIEW APIs’ and custom design control software from supplied VI libraries have been used for motion control in the programming of the X, Y and Z-axis DC-Servo motors (Faulhaber-Micromo) on a DCX-PCI100 Motion Control Board (Precision MicroControl Corporation). Tuning parameters obtained from motor datasheets such as coil resistance, inductance, and mechanical time constant and back-EMF can be used as input for Simulation and Math Toolkits to obtain initial values for Proportional, Integral and Derivative control gains.

Vision and Image Processing
Image construction and generation from low level signal acquisition is obtained by extensive use of LabVIEW Vision Utilities in combination with 2D Array processing and manipulations. An algorithm was devised for such purpose whereby an image frame is formed element by element by filling each row bins by normalized light intensity on a matrix which has programmed size in microns along Y-axis by X-axis which is set by the servos calibrated to have about 5.2nm per 1000 encoder pulse. By use of LabVIEW Picture Control VIs progressive one line scans generates an image in either BMP or JPEG format with or without false color information. Offline analysis of images were verified and validated by use reference photographs from Scanning Electron Microscope shots (SEM) and by use of National Instruments’ Vision Builder. Additional post processing was carried out using MatLAB’s Image Processing Toolbox to construct 3D surface profiles from 2D scans. An Image Acquisition (IMAQ) card PCI-1411 from National Instruments takes continuous shots for on-line monitoring of the experimental process that can be used for commands validation from LCD display of the Diode Laser Controller.

Communications via WLAN Internet and GSM Module
An option is added for remote users outside the laboratory floor or where the location does not permit wireless LAN connection. A serially programmable GSM Terminal Module (Siemens M20) or alternatively a Nokia 6150 hand phone with internal GSM modem could be used for transmit SMS messages for user notifications. A predefined message can be written on a designated front panel area also enabling user upon selection, to send a text message and/or a JPEG image scans to an email address when the Laser Microscope is done. Because of the current billing system for data quality channel over GSM networks by a commercial communications carrier a special subscription is needed for a SIM card to enable it to transmit over high speed channel called HSCSD, GRPS, and EDGE service current rates can be as low as 0.25 pesos/Kbytes download in the Philippines but has a flat recurring rate subscription. Depending on the handheld device this telecommunications capability could be implemented via extended HTML (XHTML by Nokia) by use of downloadable System Development Kits (SDK).

LabVIEW Software Implementation
We highlight below a screen shot of an example of a complete scan operation for a sample whose image size is 100X 100 pixels shown are both false color and gray scale image windows simultaneously. The panel allows the user of to select the displacement counts on the X-axis and Y-axis servos as well enabling the panel to send out communications notifications upon completion of a job through a mobile number and/or email address. This software made use of Queued Synchronization for timing data acquisition, motion control and vision. The Web Server configuration property has also been enabled to allow remote access.


Figure 3 Screenshot of MAEROL LabVIEW Software showing image generated in two simultaneous windows

Conclusion
LabVIEW software and National Instruments (NI) hardware products can easily be combined and integrated seamlessly with other traditional experimental instruments in a university laboratory setting, enabling them to be automated, remotely accessed and thus providing economical solution to data sharing and time slice control scheme. The advanced communications capability of LabVIEW can be extended to Internet and Wireless solutions.