Developing a Remote-Controlled Laser Projection System with NI LabVIEW, Machine Vision, and Data Acquisiton

Author(s):
Hoo Hean Ee - Nanyang Technological University

Industry:
University/Education

Products:
Vision, LabVIEW

The Challenge:
Developing a low-cost laser projection system that can easily create, store, and project stunning laser images without complex operational requirements.

The Solution:
Implementing a LabVIEW-based vision and data acquisition system using National Instruments IMAQ hardware and DAQ card.

We needed to create a projection system that we could control remotely for use in areas such as project presentation, special functions, and product seminars. By using NI Vision software and hardware, we can capture images of the object using the PCI 1411, single channel color image acquisition board, and an analog camera. The system then extracts the shape of the image using a Rake function supported in the NI Vision Development Module. After resizing and inverting the shape of the image, the system sends the data to the DAQ card PCI 6025E to control the laser galvanometer in order to project the laser image.

High-Performance Hardware
We chose to use the NI 6025E low-cost, 12-bit DAQ devices with E Series technology because deliver high-performance and reliable data acquisition in a wide range of applications. With these, we receive up to 200 KS/s, 12-bit performance on 16 single-ended analog inputs. These devices feature digital triggering capability, as two 24-bit, 20 MHz counter/timers and eight digital I/O lines. The NI 6025E also features two analog outputs.

The NI 1411 series plug-in image acquisition products work compatibly with analog video input from standard color or monochrome cameras. These devices come with easy-to-use image acquisition driver software. Unlike multimedia “frame grabbers,” the NI 1411 series features increase image acquisition throughput and processing, such as on-the-fly color conversion to HSL and partial image acquisition with programmable region of interest.

The canon VC-C3 Web-cam features:
· One-quarter inch CCD, 4760,000 pixels for high-quality images
· High-performance 10x power zoom
· High-speed precision camera head movement
· Preset function, featuring a programmable preset we can store in the camera’s memory

We designed our system, the CATWEAZLE LC II, for use with an external laser source up to 5 W output power in the range of 400-700 nm wavelengths. It works at a selectable source of 115 VAC or 230 VAC in normal dry ambient at a room temperature of max 30 degrees Centigrade. The system features:
· All solid-state and very compact design
· Continuous-wave output
· High beam quality and high stability

The VMM-D1 Shutter Driver and the VMM-T1 Shutter/Driver Timer include:
· An addressable RS-232 input. We can daisy chain eight units together via the RS-232 input and the user can select an address for each unit at the rear panel.
· A LOCAL/REMOTE switch which effectively “disconnects” all input signals from the controller allowing the user to manually control the shutter without having to remove the signals from the BNC input or the terminal strip located at the front panel. We also disable RS-232 signals in the LOCAL position.

The Melles Griot filter binder system is protective and convenient. Double-pocketed vinyl pages hold one 50 mm x 50 mm (or smaller) filter and the corresponding spectrophotometer or microdensitometer curve. We can assemble individual pages, complete with filters and curves, into our filter binders for convenient storage. The filter pocket location alternates on each page to facilitate stacking.

Software with a GUI Interface
We developed the software to control the image capture and the laser projection operations.

The left top and bottom panel displays the captured vertical and horizontal axis by the Web-cam. The two axis results combine together to form the processed result and project in the center of the panel. In this way, we can check the accuracy of the image captured to determine its suitability for laser image projection.

The preview frames panel displays the current selected laser image according to the frame number. The user can save the current image in the frame by pressing “save” button or the user can also load a particular image in the desire frame by pressing the “load” button. There are a total of 10 frames built into the software, and the user can, according to his taste, insert any image of his choice into the “frames” according to the frames number.

Easily Capture of Laser Images
We employed a standard procedure to generate the laser image of an object. While grating lines project onto the surface of the object, the Canon color Web-cam captures each grating phase simultaneously. After all required gratings are projected and captured, the program begins a process of image filtering and laser shape calculations. The final laser image then displays in the form of predefined laser pattern by using a green laser.

We developing dditional software and interfaces for remote image control and generation, save/load functions, and pattern displaying. LabVIEW features built-in grating line function that we used to generate the required grating lines. We prefer computer-controlled grating lines because we can alter them at will, and can precisely manipulate the phase and create intensity variation. Additionally, we created an interface for camera focusing, simultaneous grating projection, and visibility of the user interface.

Precise Image Capturing and Processing
We used a color Web-cam to capture the image of the object. We can capture one consecutive image using LabVIEW functions and save it in the image buffers. Out of this, we can use the images for laser processing. We then convert the image formats in the buffers to luminance format using the convolution operation. We perform edge detection on the original image to produce a gradient intensity image.

We perform edge detection by projecting light onto the object, and determining the area where light reflects. Using a black cloth eliminates the background of the object. We convert the images we capture to pixel form, which is the numerical representation from 0 to 255. We then compare the real-time image with other image with gratings separately. We then send the compared images out for processing.
The calculation of the laser image coordinates requires images of the gratings on the object-captured though horizontally and vertically. With our system, we can obtain the final result of the processed laser image coordinates from the raw data.

In order to generate a laser image, we had to project the laser source on to the laser x-y scanner. For our project, we based the laser image on the rotation of the x and y-axis mirrors on the laser scanner. Using a galvanometer attached on to the laser scanner, we can obtain the desired laser image on to the screen in the form of a shape of a green laser.

However, generating a laser image is not sufficient. It would be disappointing to see only a still, unedited image, because it fails to show the “life” of the laser image. With our built-in “frames” function, made possible with the use of NI software and hardware, we created multiple laser images that animate the projected laser image. To facilitate editing of the laser image, we added features in the graphical user interface (GUI) for user interaction, such as frame editing and sorting.

Meeting Our System Goals
Using National Instruments software and hardware, we easily built a low-cost laser projection system with remote-control features to create, store, and project edited laser images without complex operational requirements.

For more information, contact:
Hoo Hean Ee
Nanyang Technological University
Electrical & Electronic Engineering Dept
Blk 102 #06-16
Jalan Rajah 321102, Singapore
hooheanee@pmail.ntu.edu.sg
Tel: 67904527

Browse All Case Studies »