Installation and Equipment - Laser Scanning



Introduction

This page is dedicated to the Installation and Equipment of the Laser Scanning method used at Iowa State University. It includes a detailed information of each part of the setup with its corresponding manual. The installation of each part and common problems are also presented.

Camera Setup

IMG_4489.jpg

Parts

Camera Body

The camera body used in this setup is called Basler acA2500-14um and has a resolution of 2592 px x 1944 px. The camera requires a 3.0 USB port to communicate with a laptop. The camera comes with a software called 'pylon Viewer' which can be downloaded here. This software is not needed for this setup, but it helps to check the camera is working properly before connecting it to the setup. Another way to check this is to look if the green light at the back of the camera is on; if it is, the camera is connected to the computer.

For more details on the camera body, please visit here or get the manual here.

Camera Lens

The camera body does not come with a lens, so it needs to be bought separately. The lens used is called Lens Ricoh FL-CC2514-2M F1.4 f25 mm2/3 and its general specifications are:

Focal Length 25 mm
Horizontal Angle of View 20.0˚
Min. Object Distance 0.25 mm

The manufacturer's spec sheet can be found here.

Lens Filter

To reduce the contribution of the surrounding light, the camera has a bandpass filter lens with the same peak wavelength, 660 nm, as the laser. The lens filter used is called Edmunds #67-836 and has the same diameter, 25 mm, as the camera lens. However, the filter does not match perfectly into the lens of the camera. A strip of electronic surface mount resistor tape was placed to fill the gap between the lens ID and the filter OD.

The manufacturer's spec sheet can be found here, and the coating curve of the laser here.

Camera Tripod Mount

The camera's manufacturer offers a Tripod Mount Ace that helps attaching the camera to any surface or design. The details of this mount can be found here, and the drawing and dimensions here.

Tilt Stage

To facilitate the calibration of the camera, a Tilt Stage Metric was included to the setup. This stage allows the user to move slightly the camera in two directions, and it is easy to install under the camera tripod. The spec sheet is found here, and its drawing and dimensions here.

Recommendations (optional)

  • The camera body comes with a 3.0 USB port cable to connect it to the computer of only 1 meter long. This is an inconvenience since the camera will move across the entire length of the stave core (1.5 m). Also, the connector of the cable and the camera's body is very loose. When the camera moves, most of the time gets disconnected from the computer. A quick solution for both problem is a 5 m cable with a screw down connector.

  • Due to the precision of the measurements, it is very convenient to have different levels around the setup. For the particular case of the camera setup, a level was placed on top of the camera's body.

Installation

IMG_4590.jpg

The installation (connection) of all these parts is very straight forward as indicated in the figure above. The green square on top of the camera is the level. The silver plate under the body of the camera is the tripod mound. The tilt stage is below the tripod and attached to the metallic arm with the silver plate. The lens filter is not pictured in this photo, but it is located at the left end of the camera.

Preparing it for LabVIEW

The camera is setup by default to work with its own software and not with LabVIEW, but this can be adjusted. Once you have installed LabVIEW and the 'NI Vision Acquisition' package, connect the camera through a 3.0 USB port and open 'NI MAX.' This program should appear in your desktop. On the left side of the window, click the 'Devices and Interfaces' ARROW and a list will all the devices connected to your computer should appear. Select 'Baser acA2500-14 um "camX"' where X is any number selected by the program. You must be seeing a window just as the figure below; if you do not, you must have clicked on the words of 'Devices and Interfaces' and not the arrow. Please go back, and click on the arrow.

IMG_4489.jpg

There are three things you need to check to connect the camera correctly to LabVIEW.

  1. On the list under 'Devices and Interfaces,' right click on the camera and select 'Driver.' Two options should be available. The first one, 'Basler ace USB3 Vision Camera,' is used to connect the camera to its own software; the second option, 'NI-IMAXQdx USB3 Vision Device', allows it to be connected to all National Instruments (NI) programs including LabVIEW. A method to double-check if the camera is connected properly is to click on 'Snap' on the top of the window. A photo from the camera should appear at the center of the window. It is possible that the photo only shows a small fraction of the field of view (FoV) of the camera. To zoom out, right click on the image, select 'Viewer Tools' and then 'Zoom to Fit.' Warning: If LabVIEW and NI MAX are open at the same time, it creates at conflict on the camera. I will only work for one of the software and refuse to work with the other one. Just close one of the two.
  2. Right click again on the camera as in [1], and click on 'Rename...' and select a name for the camera. The default name should be 'cam0', but is highly recommended to change this name to avoid conflicts in the software with new devices. Make sure that whatever name you use for the camera is the same as the one used in your LabVIEW code.
  3. On the bottom of the window, select 'Acquisition Attributes' (or just click 'Snap as in [1]). Go to 'Pixel Format' and change it to 'Mono 12.' Then go to 'Output Image Type' and choose 'Grayscale (U16).'

Once all these conditions are met, the camera should be all setup for the experiment.

Laser

IMG_4489.jpg

A very specific laser called ProPhotonix DV-660-010-L41-S-45-S-B-2 was used in this setup. This laser has a peak wavelength of 660 nm as the lens filter subtracting the contribution of the surrounding light. The laser has a fan angle of 45˚ and creates 41 horizontal lines parallel to each other. The center line has a dot in its center that differentiates it from the rest of the lines. More information about all the specifications of this laser and any other laser with this company can be found here, and a more specific one to our laser here (this last link has a typo, the fan angle of the laser is 45, not 53). The laser classifies as a Class 3R type which is considered safe if handled carefully, with restricted beam viewing.

For the right performance of the laser, it needs to be connected to a power supply as indicated in the table below.

Wire Color Characteristic
Yellow TTL Signal (5.0V Max)
White TTL Ground
Blue Analogue Signal (3.3V Max)
Black Ground
Red 5.00V - 24.00 V

After the laser was connected to the metallic arm, and with the same purpose than in the camera setup, a level was place on top of the laser as indicated in the photo above. This helps when calibrating the laser with respect to the optical bench.

Laser Holder

In the photo of the laser above, the laser is covered by a metallic body. This structure was build to facilitate the installation of the laser to the metallic arm, and to secure the laser in a fixed position to avoid any kind of vibration while moving the setup. A tripod ball head was also included to help the laser move freely during the calibration, and then fixed the desired location. A level was placed on top of the laser as in the camera setup. The white screws on the side secure the laser to the holder, but allows the laser to change its height with respect to the optical bench if desired. This is very important since the bending and the pressurized test are done at different heights. Drawings and dimensions (in inches) can be found here.

Metallic Arm (holder)

In the experiment, the stave core does not move but lies on the surface of the optical bench. The camera and the laser in the opposite, do all the moving in the scan. Then, they need to be attached to the cart of the linear stage. A metallic arm was designed for this experiment to keep the camera and the laser secured and to avoid any vibration when the cart is moving. The dimensions of this arm, based on previous experiments, have the correct height where the camera needs to be to have the entire width of the stave core in its field of view. The drawings and dimensions of the metallic arm can be found here.

There are once important change from the drawings. The stave core has an extra rectangle in one of the sides called end of the stave card that makes it impossible for the stave core to be placed right next to the linear stage. The stave core is located about 8 cm away from the linear stage, creating enough space for the end of the stave card to be placed on the surface of the optical bench without touching the linear stage. As long as the position of the stave core is consistent, this is not a problem for the setup or the metallic arm; except that now the thread rods are 6 inches instead of 5 in.

Optical Bench

The optical bench has two parts. A breadboard where all the equipment is placed on it, and a vibration isolation stand that supports the breadboard and isolate it from vibration.

Breadboard

The breadboard used in this setup is a Vere 90-180-4-M-3-FM which is a 90 x 180 cm table with a 3 mm cover of ferromagnetic steel. It has a grid pattern every 25 mm in both directions specifically designed for M6 threads, and has a core thickness of 4 inches. More specifications and details about the breadboard can be found here.

Vibration Isolation Stand

The stand used was a Vere VITSVIC3A09018034LLC. Installation instructions can be found here.

Linear Stage

In the scanning, the stave core stays still in the surface of the optical bench while the camera and the laser, attached to the linear stage's cart, are moving. This linear stage has two main parts: the motor drive that moves the cart, and the linear slide where the cart moves. A list including all the parts (and quote) of the linear stage used in this experiment can be found here.

Parts

Motor Drive

The motor drive used is a PCM4826E IDEA Drive. It connects to the computer with a USB port (not 3.0 USB port needed) and has to be connected to a power supply. Specifications and general information for this motor drive and others can be found here.

Linear Slide

The linear slide used in this experiment is the Haydon Kerk WGS06K-M0100-A03. The slide is a WGS (Wide Guide Screw) type that uses sliding plane bearings on a low profile aluminum guide rail that keeps the motion smooth throughout the travel distance. It has a length of 1.5 m, and can be connected to the optical bench with M4 threads through holes in the English system. More details and information can be found here.

Note: At ISU, the linear stage does not match the optical bench perfectly, since the optical bench uses the metric system and M6 threads. A solution was found by increasing the diameter of the screw holes of the linear stage to match the size of M6 threads, and to match the screws holes in the metric system. Only three threads are used to hold the linear stage on the optical bench. For the future, it will be better to have both, linear stage and optical bench, on metric system.

Installation

The instructions for the installation can be found in page 10 of the motor drive's manual (here). Most of what is need it for the correct installation is described in that page except for what the pins indicated in the figure are. In the table below, these pins and their corresponding cable is listed.

Pin 1 / A Red
Pin 2 / A bar Red / White
Pin 3 / B Green / White
Pin 4 / B bar Green

In addition, the linear stage requires a power supply. The total number of power supplies used in this setup is three: one for the linear stage, one for the fan and one for the laser.

Software

The linear stage comes with its own software called IDEA Drive Software and it can be downloaded here. In the same way as the camera, this software cannot be opened at the same time that the Laser Line Detector code. This software is useful in particular for checking that the linear stage is working correctly. Once the software has been opened, select stepper and enter 57H43-.05 for the motor part number, none for select drive auto, single for select comm mode, and any desired option for measurement units. The manual for this software can be found here.

Placing Linear Stage on Optical Bench

The linear stage should sit flat on the surface of the optical bench; however, this is not possible because a part of the motor is lower than the bottom of the linear slide when it is connected. To avoid this, the linear slide is placed at one edge of the table where the motor can be hanging in the air, but the entire linear slide lies on the surface. This can be observed in the drawings on pages two and three of the metallic arm's document.

Placing Stave Core in Setup

As mentioned before, the stave core was intended to be placed right next to the linear stage, but this is not possible because the presence of the end of the stave card. However, the solution is very simple. Instead of placing the stave core against the linear stage, a space of about 8 cm is left between those two enough for the card to not touch the linear stage. An aluminum bar with screw holes in the middle was placed on the optical bench between the stave core and the linear stage. Its purpose is to keep any stave always at the same distance from the linear stage, then the calibration of the laser and camera is based on this position of the stave.

There is also important to mentioned that the stave core has some white (plastic) connectors that do not let the stave core to lay on one of its surfaces which is necessary for the pressurized test. For solve this, the stave should be placed close to an edge of the optical bench so when the stave has the white connectors down they lay outside the table but the rest of the stave core is safely on the surface of the optical bench. When the stave core is in the other side, the white connector do not interference since they are pointing up.

Fan

When the linear stage is running even at small currents (500 mA), the motor's temperature heats up many degrees raising one side of the linear stage until a maximum temperature is reached. This effect creates a bias in the data, but can be easily prevented by having a fan close to the motor to keep it cool. Keep the fan out of the optical bench to avoid any vibration in the setup.

LabVIEW and NI Vision Acquisition Software

The 'Laser Line Detector' code has been programmed to work only with the 32-bit version of LabVIEW, and not for the 64-bit one. Please select this option while installing LabView. Instructions on how to install LabVIEW can be found here.

The same code requires an extra package called NI Vision Acquisition that needs to be bought separately. This package helps the camera talk to the camera as input data, and it usually comes with 3 installations. Information on how to install LabVIEW can be found here.

Bearing Supports

For the bending test, the stave core needs to be supported in very specific points that changes depending on the setup used. For this, and taking also into consideration the height of the white (plastic) connector of the stave core, seven bearing holders were made with plastic in a 3D printer, each one with a steel ball. The position of these holders can be adjusted to meet the expected location. The drawings can be found here.

Calibration Tool

Once the entire setup is running, it needs to be calibrated before taking any measurements as indicated in the section Calibration. For consistency and practical reasons, a calibration tool specifically design for the project was made of aluminum. The dimensions of the calibration tool are shown here.

Pressurizing System

To pressurized the stave core, these five things are required:

  1. A sealed stave core.
  2. Dry Nitrogen reservoir that can be pumped into the stave.
  3. A pressure gauge that controls the follow of dry nitrogen that goes into the stave core. The gauge has to be able to get to 5 PSI which is the maximum pressure that is usually applied in the experiment.
  4. A hose connecting the stave core and the pressurizing system. A connector for the hose and the stave core is also needed.
  5. Once the stave core is attached to the pressurizing system through the hose, it should not be touched to avoid any change on the position of the stave core. However, after the stave core has been pressurized, it holds an internal pressure even when the gauge has been turn off; this is caused because the stave core is sealed. To avoid this, a toggle lever bleeder off valve was included in the system to allow to open the connection and remove the internal pressure of the stave core without disconnecting it from the pressure system.

Sealing the Stave Core

For the pressurized test, it is required to be able to apply an internal pressure of 5 PSI to the stave core. In places where the facing and the honeycomb structure are not properly glued together, the pressure should push the surface of the stave creating a 'bump.' If the stave core is not completely sealed, because there is one or more leaks, the dry nitrogen will not pressure the surface making the flaws invisible to the experiment. Therefore, the sealing process of the stave core is crucial to the correct performance of this method. It is recommended to look for any kind of leak in the stave core, and if found, glue them with epoxy. A detailed report of the most common places where leaks can be found can be seen here.

Major updates:
-- CarlosMiguelVergelInfante - 2017-02-16

Topic attachments
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GIFgif 2120_Metric_Tilt_Platform.gif r1 manage 18.7 K 2017-02-16 - 23:07 CarlosMiguelVergelInfante  
PDFpdf 3D_Pro_Laser.pdf r1 manage 686.7 K 2017-02-17 - 18:25 CarlosMiguelVergelInfante  
PDFpdf Ace_USB_3_0_Users_Manual.pdf r1 manage 5389.5 K 2017-02-16 - 02:21 CarlosMiguelVergelInfante  
PDFpdf Bearing_support.pdf r1 manage 44.4 K 2017-02-20 - 22:35 CarlosMiguelVergelInfante  
PDFpdf Haydon_Kerk_WGS06_Motorized_Linear_Slide_v2.pdf r1 manage 1390.3 K 2017-02-22 - 06:20 CarlosMiguelVergelInfante  
PDFpdf IDEA_Drive_Software_User_Manual.pdf r1 manage 931.7 K 2017-02-27 - 23:59 CarlosMiguelVergelInfante  
JPEGjpg IMG_4485.jpg r1 manage 1089.0 K 2017-02-17 - 00:29 CarlosMiguelVergelInfante  
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PDFpdf Laser-SpecSheet.pdf r1 manage 513.1 K 2017-02-17 - 18:25 CarlosMiguelVergelInfante  
PDFpdf Laser__camera_carriage_support.pdf r1 manage 103.1 K 2017-02-22 - 05:36 CarlosMiguelVergelInfante  
PDFpdf Laser_mount.pdf r1 manage 78.7 K 2017-02-21 - 23:18 CarlosMiguelVergelInfante  
PDFpdf Q-24447-MCS_Haydon_Quote.pdf r1 manage 37.3 K 2017-02-22 - 06:20 CarlosMiguelVergelInfante  
PDFpdf Sealing_Stave.pdf r1 manage 792.6 K 2017-02-21 - 00:21 CarlosMiguelVergelInfante  
JPEGjpg SetupCameraLabVIEW.jpg r1 manage 62.7 K 2017-02-17 - 00:45 CarlosMiguelVergelInfante  
PDFpdf Stave_calibration_plate.pdf r1 manage 33.7 K 2017-02-17 - 22:14 CarlosMiguelVergelInfante  
PDFpdf VITSVICxxxx.pdf r1 manage 128.9 K 2017-02-21 - 23:12 CarlosMiguelVergelInfante  
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