Optical simulation system for brain waves detection & measurements

Optical simulation system Optical simulation system for brain waves detection for brain waves detection

& measurements & measurements

Mid-term presentationMid-term presentation

Performed by:Performed by: Yevgeny Yevgeny SafovichSafovich

Pilnick NadavPilnick NadavSupervised by:Supervised by: Hen Hen BroodneyBroodney

Problem DefinitionProblem Definition

Measure eye vision quality Measure eye vision quality objectivelyobjectively

The vision should be measured (almost) The vision should be measured (almost) without cooperation of the person being without cooperation of the person being examinedexamined

SolutionSolution

Use PC to transmit series of images Use PC to transmit series of images of different colors at certain of different colors at certain frequencies in front of the patient frequencies in front of the patient (as a stimulation) (as a stimulation)

Use Electronic device to measure Use Electronic device to measure brain waves caused by change of brain waves caused by change of visionvision

Conclude regarding to the patient’s Conclude regarding to the patient’s vision abilities vision abilities

RequirementsRequirements

ImagesImages 3 pairs of colors:3 pairs of colors:

Blue, YellowBlue, Yellow Green, RedGreen, Red Black, WhiteBlack, White

Each pair has its own “blank” color: the Each pair has its own “blank” color: the average of the colors in the pairaverage of the colors in the pair

Steps frequency: 0.5Hz – 10Hz, resolution 1HzSteps frequency: 0.5Hz – 10Hz, resolution 1Hz dx = The delta between the Monitor dx = The delta between the Monitor

output and the electrical pulse output. output and the electrical pulse output. 0.5ms < dx < 1.5ms0.5ms < dx < 1.5ms

DefinitionsDefinitions Screen Refresh RateScreen Refresh Rate Vertical Blank Interval (VBI)Vertical Blank Interval (VBI)

DirectDrawDirectDraw Primary SurfacePrimary Surface Front BufferFront Buffer Back BuffersBack Buffers FlipFlip

Performance counterPerformance counter

Begin

End

Solution AlgorithmSolution Algorithm

Computer

Monitor

Video Card

Human

Brain Wavesmeter

Operator

* The red interfaces should be synchronized

TimingTiming

Computer

MonitorVideoCard

HumanBrain Waves

meter

Operator

t

t1b t3 t4t2 t5

• 0.5ms < |t5 – t3| < 1.5ms

• |t4 – t3|- We suppose this time does not matter and is taken care of by the “Brain Waves meter”

• |t3 – t2|- We suppose this interval is negligible

• |t2 – t1b| - The major problem of the project, discussed below

• |t5 – t1a| - A problem discussed below

t1a

Timing: focusTiming: focus

Ta = VBI beginTa = VBI begin Tb = FlipTb = Flip Tc = Flip Critical timeTc = Flip Critical time Td = Flip EndTd = Flip End Te =t1a = Out pulse sentTe =t1a = Out pulse sent Tf = t5 = Out pulse received (~ t1d)Tf = t5 = Out pulse received (~ t1d) Tg = t2 = VBI endTg = t2 = VBI end

Ta TgTb TfTc Te

Time

Screen

FrontBuffer

Td

Feasibility TestingFeasibility Testing

Testing Screen Sync.:Testing Screen Sync.: The goal is to ensure that the new The goal is to ensure that the new

image is shown at the screen ‘at the image is shown at the screen ‘at the moment’ the Pulse is sent to the parallel moment’ the Pulse is sent to the parallel port.port.

Testing Pulse delay:Testing Pulse delay: The goal is to ensure that the time The goal is to ensure that the time

between sending the pulse and between sending the pulse and receiving (Tf – Te), is negligible receiving (Tf – Te), is negligible Roundtrip delay

testing

Synchronization SolutionSynchronization Solution Build two Surfaces in DirectDrawBuild two Surfaces in DirectDraw

Front (Primary Surface)Front (Primary Surface) Back (Attached Surface)Back (Attached Surface)

Use windows priority mechanism to give Use windows priority mechanism to give maximum priority to the process (Real-Time) maximum priority to the process (Real-Time) and worker thread (Critical)and worker thread (Critical)

Use DirectDraw to determine VBI begin(t1b)Use DirectDraw to determine VBI begin(t1b) Use DirectDraw to Flip the SurfacesUse DirectDraw to Flip the Surfaces Use Parallel port in order to send output Use Parallel port in order to send output

PulsePulse Use performance counter to ensure we did Use performance counter to ensure we did

not miss the Flip critical time (t1f)not miss the Flip critical time (t1f)

Project Blocks DiagramProject Blocks Diagram

Parallel port InterfaceVideo

Interface

Run-time Module

Parallel port Wrapper (DLPortIO)

VideoInterface Wrapper

(DirectDraw)

DatabaseModule

Configuration module

Main applicationModule

StatisticsStatistics

Min Max Min Max Min Max Min Max Min Max6.15E-05 0.003998 1.84E-05 2.46E-05 3.63E-05 3.63E-05 0.00506 0.005082 0.105072 0.1050940.000389 0.004321 1.9E-05 2.32E-05 3.66E-05 3.66E-05 0.00505 0.005069 0.105062 0.1050830.00276 0.00669 1.79E-05 2.51E-05 3.58E-05 3.58E-05 0.005062 0.005081 0.105075 0.105094

0.002691 0.006626 1.9E-05 2.4E-05 3.63E-05 3.63E-05 0.00506 0.005083 0.105072 0.105095

Pulse EndVBI Start Flip End VBI End Pulse Start

The next run assumed pulse delay is 5 ms.The next run assumed pulse delay is 5 ms.The application collects maximum and The application collects maximum and minimum timesminimum times

Implicitly neglected the time it takes for the pulse to Implicitly neglected the time it takes for the pulse to be received (Tf-Te). Experiments showed Maximum be received (Tf-Te). Experiments showed Maximum time of ~0.04 ms time of ~0.04 ms RoundTripRoundTrip. .

Conclusions:Conclusions: We did not miss a single sync.We did not miss a single sync. Most Extreme results show 32.7 microsecond Most Extreme results show 32.7 microsecond

difference (~5.05 ms , ~5.08 ms). Way below difference (~5.05 ms , ~5.08 ms). Way below requirementsrequirements

Application screensApplication screens Main screenMain screen

Application screensApplication screens Menu optionsMenu options

Colors pairsColors pairs

Element type Element type

Page layoutPage layout

Application screensApplication screens Page configurationPage configuration

Application screensApplication screens OptionsOptions

Appendix 1Appendix 1DirectDrawDirectDraw

Interface IDirectDraw7Interface IDirectDraw7 ::WaitForVerticalBlank(…)::WaitForVerticalBlank(…)

Interface IDirectDrawSurface7Interface IDirectDrawSurface7 ::Flip(…)::Flip(…)