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EDDI 01 Design Description Document

University of Rochester

Design Description Document

Eye Dominance Detection Instrument

Kara Lambson, Christopher Marsh, Zhengsheng Zhu, Yingxing Qian

Customer: Scott MacRaeEngineers: Kara Lambson, Christopher Marsh, Zhengsheng Zhu, Yingxing QianAdvisor committee: Len Zheleznyak

Document Number: 01

Revision Level:B

Date: 5/9/2015

This is a computer generated document and the electronic master is the official revision. This paper copy is authenticated for the following purpose only:

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A cellphone-based portable device that can quantitatively measure the eye dominance in human eyes.



ContentsProduct Requirement Document.................................................................................................................4

System Block Diagram.................................................................................................................................4

Optical Design..........................................................................................................................................4

Lens System.............................................................................................................................................6

Mechanical Housing for Optics................................................................................................................8

Phone and Application...........................................................................................................................11

Test Plan / Validation.................................................................................................................................13

Risk Assessment........................................................................................................................................14

Transition Plans.........................................................................................................................................14



Product Requirement Document (See digital document 01)

System Block Diagram1) An optical system to collimate on-screen stimulus onto eye. 2) Mechanical housing to hold optics and smartphone. 3) Software application on smartphone to display stimulus and process user input.

Optical Design

Overview:

The objects for our optical system are two separate stimuli that subtend 1 degree onto the retina corresponding to the right and left eye are displayed on the screen as shown in Figure 1. The diameter of the gratings must satisfy this condition in order to decrease the chance of binocular rivalry that would cause a "checkerboard" appearance rather than a uniform single grating orientation while viewing the stimulus. Each stimulus will display a sinusoidal pattern with 4 cycles of alternating dark and light bands.


O p ti c a l D e s ig n

H o u s in g

A p p lic a ti o n


Figure 1 – Stimulus pattern, the focus ring will subtend two to three degrees.

Figure 2 One Sinusoidal Cycle of Bright and Dark bands

The pixel density of the phone is 538 PPI, therefore the pixel size is 47µm. Since 8 pixels per cycle- which corresponds to one cycle of light and dark bands as seen in Figure 2- should suffice for a smooth sinusoidal pattern, then the stimulus should be about 32 pixels per 1 degree. The minimum focal length required was calculated to be 86mm, as shown in Equation 1 below.

Equation 1


f= htan (θ )

=

472µm

tan( 164° )

= 86 mm


While the minimum focal length can be 86 mm, we instead chose 150mm in order to allow more pixels for the stimulus to improve the appearance. The stimulus size was calculated using Equation 2 below where f is the desired focal length and the angle θ is the angle subtended onto the retina.

Lens System

EDDI consists of two 150mm focal length plano-convex N-BK7 lenses ordered from Edmund Optics. They are 1 inch in diameter, which required us to add a plastic ring of around 8.3mm around the lens to hold it in place in the 33.7mm diameter wide holder that already exists in the housing. The screen is placed at the focal length of the system to ensure that the light emerging comes out collimated. The collimated beam then enters the eye and focuses down onto the retina. The whole system from object to image can be seen in Figure 3. A zoomed in view of the lens and the eye is shown in Figure 4. 13:09:20

Plano-Convex Singlet and Eye Model Scale: 0.90 04-Mar-15

27.78 MM

Figure 3- Overall system ray trace from object on screen to image on retina


h=ftan (θ )=(150mm ) tan (1 ᵒ )=2.618mmEquation 2

EDDI 01 Design Description Document 13:04:47

Plano-Convex Singlet and Eye Model Scale: 3.60 04-Mar-15

6.94 MM

Figure 4 – Zoomed in ray trace and optics of EDDI



13:44:58

0.000,0.000 MM 0.00, 0.00

0.000,0.916 MM 0.00, 0.70

0.000,1.309 MM 0.00, 1.00

FIELDPOSITION

DEFOCUSING 0.00000Plano-Convex Singlet

.264E-01 MM

100% = 0.062385 RMS = 0.024262

04-Mar-2015

100% = 0.062442 RMS = 0.024300

100% = 0.062501 RMS = 0.024326

Figure 5 - Spot diagram showing the potential chromatic aberration of the image through the system.

Mechanical Housing for Optics

We 3D printed an extension piece to allow for a longer focal length lens to fit in the housing since the original housing as seen in Figure 6 is too short to meet the minimum focal length requirement with a length of 70mm. We extended it in order to meet (and go beyond) the 8 pixel per cycle requirement. With the extension, the housing accommodates 150 mm focal length lenses. The altered housing schematic is shown in Figure 6.



Figure 6 – Altered housing schematic using 3D printing.

We first broke the original housing apart and measured their dimensions. We then used CREO® to model the extension part as shown in Figure 8. Finally we used MakerBot® Replicator 2 3D printer to print the extension and reassembled the housing as shown in Figure 10.

Figure 7 – The original housing can be taken apart, it is held together through a plastic clamp.



Figure 8 – 3D modeling of the clamp. The lower two pictures show the parts used to assemble the housing.

Additionally, we also used XYZ 3D printer to print the lens mounting shown in Figure 9. Its inner diameter matches the lens’ diameter.

Figure 9 Lens Mounting (Red)

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Figure 10 Assembled Housing

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Phone and Application The application for EDDI will run on the LG 3G, pictured in Figure 11. It runs Android 5.0 Lollipop and features Bluetooth 4.0. This particular model also relocates many of the side buttons, such as power and volume rocker to the back of the phone. This is particularly useful because the housing will surround the sides of the phone and leaves the back exposed. Thus allowing for more functionality while the phone is in the housing. There is also a mouse peripheral, which features horizontal and vertical scrolling, primary, secondary, and tertiary buttons.

The next page features a flowchart showing the pages and processes the user should face while interacting with the application.

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Figure 11 - This image displays the phone and mouse model used for EDDI


Table 1 – EDDI Application UI Design

The repository for the Android code can be accessed via following link:https://github.com/Crostiphex/EDDI.git

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https://github.com/Crostiphex/EDDI.git


Test Plan / ValidationThe test plan consists of multiple parts:

1. Test the proof of concept (POC) After 3D printing was completed and the lenses obtained, the initial tests with the android application was carried out by developers.

2. Test the prototype

After EDDI was assembled, it was tested on voluntary test subjects to measure the degree of eye dominance. Attention was paid to aspects of weight, ease of operation on patients, time to complete one measurement, and the overall accuracy of the test. The number of data sets is inversely correlated to error in the result. A 15-minute long test has enough number of data sets but takes too long. A shorter version of the test takes 5 minutes.

Risk Assessment

Currently, the largest amount of risk with the design involves with shortening the test. The original test length is 15 minutes. One minute for each contrast value. The test takes data gathered and fits a sigmoidal curve to it. The more data, i.e. more test time, the more precise the fitted curve. To make the test shorter we can collect less data, which means the fit isn’t as accurate to the person and hence neither is his/her dominance index. Theoretically, three points should be enough to get a good fit, but through testing with members of the team, it is found that five points gives a reliable dominance index value. Using three points is sufficient for suggesting a person is left- or right-eye dominant, rather than a quantitative value.

Transition PlansWe will deliver our prototype- which includes the smartphone and housing- to our customer, Dr. Scott MacRae, who will then decide whether to begin clinical testing or to further improve the device. Right now, the whole test will be about five minutes minimum in length. However, it is expected of the current procedure to be shorter in the sacrifice of accuracy for better efficiency in a clinical setting. It is also possible that the device could be made of metal instead of plastic to improve the appearance and make it more marketable, which would probably increase the weight and should be taken into consideration by the customer. Moreover, to further validate the accuracy of the device, measurements should be taken on multiple subjects and their results should be compared as the tests are getting shorter.

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