Project Objectives
Concisely list and prioritize the project objectives and constraints
High Priority Objectives
Obtaining an accurate measurement of the distance between the orbital rim and front of the eye
Eye safety: Classification of lasers and their effects on skin and eye
Geometric constraint: Placement of sensor between corner of eye and bridge of nose
Accuracy: Reading of distance within 0.25 mm error
Second Priority Objectives
Making device fit different facial structures
Use of optical light source
Laser and scanner having a parallel relationship
Sensitivity of sensor to ambient light
Constant light intensity from emitter
Other Constraints and Issues
Adding additional sensing components
Having all components in one compact frame
Light and portable
WOW Design Solution
With these constraints, we suggested a device that utilized a sensor on the inner side of the eye, near the nose, and a laser or infrared emitter on a horizontal slider. Once the sensor picked up the laser or infrared signal, the device would know that the slider had moved past the cornea, and the distance the slider had traveled could be calculated. This WOW design solution created a few more constraints, however. This design means that we must be careful about what type of sensing equipment we use to avoid damage to the eye.
Risk Reduction Strategy
List areas of risk and strategy that will be used to eliminate risk really in the design process.
4 sets of 5 trial measurements to establish grounds for possible systematic error when using existing device
The 4 results were compared the doctor's data of 17.85 mm
Results: Consistent, but varied from person to person
Values changed when looking at different angles as well as from patient posture.
Remaining Concerns
Light and Sensor Method
Finding a sensor that fits size design constraints
Run trials with non-acrylic eye models
Other Measurement Methods
Research ultrasonic proximity sensors
Angle sweep vs Linear slide
Addressing Systematic Error
Problems with multiple users
Different application to patient's orbital bone
Incorporate ears, forehead, using bubble levels
Intermediate Milestones
Light and Sensor Method
Finding a sensor that fits size design constraints
Run trials with non-acrylic eye models
Other Measurement Methods
Research ultrasonic proximity sensors
Angle sweep vs Linear slide
Addressing Systematic Error
Problems with multiple users
Different application to patient's orbital bone
Incorporate ears, forehead, using bubble levels