P13541: Eye Tracker
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Detailed Design

Table of Contents

Expectations

Our main objective is to gain your approval of the designed system and move forward into building and testing of our system.

Prototyping, Engineering Analysis, Simulation

Engineering Analysis

Camera (Logitech C510)

The Logitech C510 is an HD webcam that has a maximum frame rate of 30 FPS. The resolution of the camera is 1280x720 pixels which is enough to capture a good image of the eye. The maximum frame rate of the camera is the ideal value in specification six. This camera's infrared filter can be removed without much difficultly; instructions are available online to do this. The camera is also fairly priced at $60. This is the cheapest webcam found that meets the specification for frame rate, has a removable IR filter, and that we believe to be of high enough resolution.

A more detailed analysis of the resolution can be found here:

WorkingDocuments/Camera Resolution Validation.pdf

Tablet (Nexus 10)

The tablet must have a rear facing camera, and must run android. Additionally, the tablet must have a usb port for interfacing with the camera. The software on the tablet must not have restrictions on modification that can not be bypassed. The Nexus 10 has a rear-facing camera, and runs a version of android that is very friendly to software modification. Additionally, the Nexus 10 has a dual-core processor with fast cores. (As opposed to a quad core processor with slower cores) A simple adapter can be connected to the micro usb port on the Nexus 10 to allow the normal usb plug that the camera has to be connected. Finally, the Nexus 10 is cheaper than many other similar tablets, leaving more room in our budget for other components. Two HD (720p) videos can be written at 19.39 Mbits per second (this is the bitrate HDTV uses), which is equal to 2.42 MB/s. The average bandwidth of storage on a tablet is 7.75 MB/s. This gives us plenty of bandwidth for our purposes.

Infrared LEDs

Conversion of mW/cm^2 to mW/Sr

Sr=A/R^2

Maximum intensity for prolonged exposure is 10mW/cm^2. Remote eye trackers can function at 1mW/cm^2, so that intensity should work for our system.

Operating Range: 24in – 8.5in with 17in as the ideal normal

1mW/cm^2

Max Norm Min
R(in) 24 17 8.5
R(cm) 60.9 43.18 21.59
R^2(cm^2) 3708.81 1864.51 466.13
Intensity(W/Sr) 3.708 1.865 .466
The above table shows the ideal intensities for the functional range of the device. The value of R is the distance the tablet is from the user's face. Each row is the calculation of the intensity in W/Sr based on the intensity being 1mW/cm^2 at the given value of R.

10mW/cm^2

Max Norm Min
R(in) 24 17 8.5
R(cm) 60.9 43.18 21.59
R^2(cm^2) 3708.81 1864.51 466.13
Intensity(W/Sr) 37.088 18.645 4.661
The above table shows the calculations for the max intensity for prolonged exposure to infrared light at each distance. The intensity of the minimum range should not be exceeded in the design of the infrared illumination system.
SFH 4550-EW
The infrared LED chosen was the SFH 4550-EW from Osram. The intensity of the light is between 630 and 1250mW/sr and generally falls closer to 1100mW/sr. There will be two sets of three LEDs used together to illuminate the eyes. This insures that the intensity of the IR light will be strong enough to illuminate the eye and low enough to prevent any harm. The LEDs have a half angle of emission of 3 degrees. At the normal distance this will create a circle with a diameter of 1.78 inches on the face. With two sets of LEDs positioned correctly a good portion of the face can be covered allowing for tilting of the tablet.

Drawings, Schematics, Flow Charts, Simulations

System Detailed Block Diagram

Infrared Circuit Simulation

Graph of Infrared Circuit Simulation

Monte Carlo Simulation

Printed Circuit Board of Infrared Circuit

Mount Schematics

Mount Parts

public/Photo Gallery/Mount Pieces.jpg

Bill of Material (BOM)

public/Photo Gallery/BOM Update.png

Test Plans

public/Photo%20Gallery/test_IR_LED.png

public/Photo%20Gallery/test_calibration.png

public/Photo%20Gallery/test_camera.png

public/Photo%20Gallery/test_tablet.png

Risk Assessment

ID Risk Item Effect Cause Likelihood Severity Importance Action to Minimize Risk Resolution Owner
Describe the risk briefly What is the effect on any or all of the project deliverables if the cause actually happens? What are the possible cause(s) of this risk? L*S What action(s) will you take (and by when) to prevent, reduce the impact of, or transfer the risk of this occurring? If it exists, what has been a resolution to the risk? Who is responsible for following through on mitigation?
1 Choosing incorrect software library option Lose time because we will have to go back to try other option Inexperience among members 2 3 6 Research software options thoroughly M.Kelly B.Wideman
2 Limited time available Failure to complete the project on time Imagine RIT brings sooner deadline; Scheduling conflicts among members 2 2 4 Meetings involve only pertinent members T.Podrasky M.Krenzer H.Pichardo B.Wideman M.Kelly
3 Poor library support available More workload for the Computer Engineers in the group; More time needed to accomplish goal Using a different platform 2 2 4 Make sure there is library support before making final decisions B.Wideman
4 Camera field of view not capturing the eye Inaccurate functionality Improper interfacing between camera and tablet 2 2 4 Use facial recognition software; Alert user that they are out of camera's field of view M.Krenzer H.Pichardo
5 Lack of previous eye tracking experience by group members Improper design None of the team members have used eye trackers before 3 1 3 Research of eye tracking by members Research and meetings with eye-tracking experts T.Podrasky M.Krenzer H.Pichardo B.Wideman M.Kelly

Resolved Risks

ID Risk Item Effect Cause Likelihood Severity Importance Action to Minimize Risk Resolution Owner
1 Interface from camera to tablet may be complicated and may require additional hardware More time consumption; Additional items attached to tablet Camera may not be readily compatible with tablet 2 2 4 Research interface as soon as possible Chose a camera that had a USB interface and it is compatible with Linex M.Krenzer H.Pichardo
2 Lead times on components/tablet Less time with devices Some parts can be sold out 2 2 4 Find alternative sources for parts; Order parts early Most of the primary components have been purchased T.Podrasky
3 Processing power of tablets within our budget could be inadequate Going over budget Components needed are expensive 1 2 2 Finding good deals for components Already bought the most powerful tablet we could have T.Podrasky
4 Could damage camera when removing the IR filter Camera could become unusable Scratching the sensor during filter removal 1 2 2 Follow online instructions very carefully; build up motor skills Sensor was not scratched in removal H.Pichardo
5 The tablet may not adequately power the webcam and the IR Leds on its own The camera or IR LED circuit may not work correctly; Tablet may drain too quickly; IR LED circuit would need an external battery pack The USB interface from the tablet may not output enough power 1 2 2 Test the system early Tested early and plenty of power from USB M. Krenzer
6 Algorithmic Latency in processing imagery The device may not function in real time; Failure to meet customer needs High processing power required by algorithms 2 1 2 Consider benchmarks on algorithms Tablet was fast enough M. Kelly
7 Lack of mechanical engineering expertise Inability to properly mount components to tablet No mechanical engineer assigned 3 1 3 Seek mechanical help if needed; Use a clip; Possibly use a 3D printer to create mounts Sought assistance from Mechanical Engineers T.Podrasky
8 Processing power of tablet could be inadequate Poor performance Poor software optimization 1 3 3 Make software more efficient Tablet had enough processing power M.Kelly B.Wideman
9 Camera may not focus correctly Eyetracking may not work as intended Camera's effective resolution is lost 2 3 6 Test and modify filtered camera as needed Refocused camera after IR filter removal H.Pichardo
10 Camera may not correctly filter visible light Extra reflection on user would detriment eyetracking Replacement filter may not be as effective as needed 3 2 6 Use two layers of film when reapplying light filter Developed film pieces properly filtered visible light H.Pichardo

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