Ania Warczyk, Alia Durrani, Shivani Shah, Dan Maxwell, Timothy Chen.

Optical Imaging  Technique used in neuroscience for detection of brain activity  Uses changes in deflection of incident light to infer hemodynamic activity

Problem Statement  Design a small wireless camera for optical imaging of the cortex which allows free movement of animal being tested

Primary Objectives  Make a design with these criteria:  Scalable to fit on the head of a monkey  Small and lightweight  Wireless potential  High resolution and well depth  Providing direct, even lighting

Performance Criteria  Desired resolution: 512 x 512  Desired frame rate: 300 fps  Well depth: 12 bits  Must run continuously: 5 minutes  Must not impede movement of animal: ~300 grams  Maximum wireless frame rate: 10 fps  Maximum cable frame rate: 30 fps  USB is the only way to get 300 fps  Eventually, wireless frame rate: 100 fps  Not before 3 years

Solution Descriptions  Current method: Large Camera  Design 1: PillCam  Design 2: Lensless Setup  Design 3: Beam Splitter Setup

Current Method: Large Camera

PillCam: Hypothesis  PillCam design proves a small self-contained wireless camera can be constructed 2 cm

PillCam: Synthesis  Diagram of our design based on PillCam concepts

PillCam: Performance  Failure with this approach, therefore must try new design  Illumination is uneven and inconsistent  No adjustable focus  Fixed lens to chip distance (S2)  Microfabrication with expensive custom parts  Proprietary information  To mediate these obstacles:  Need microcontrollers for lens and chip  $$$$$$

Lensless Setup: Hypothesis  Can putting lens in contact with membrane on cortical surface eliminate the need for optics?

Lensless Setup : Synthesis (Done with different illumination techniques) Slide with thin slices of pig liver Solid piece of liver tissue imaged through glass cover slip

Lensless Setup: Performance Liver slide with transmitted light Liver slide with reflected light Liver tissue with reflected light Liver tissue with transmitted light

Lensless Setup: Resolution Test Image of 1mm grid taken without a lensImage of 1mm grid taken with a lens

Lensless Setup: Performance  Failure of this approach, therefore must try new design  Low resolution  Illumination issues  Transmitted light does not work for bulk tissue  Reflected light requires moving CCD chip away from tissue surface  To mediate these obstacles:  Can implant fiber optic to illuminate from within

Beam Splitter Setup: Hypothesis  Beam splitter can provide direct illumination with conventional optical techniques in an onboard approach

Beam Splitter Setup: Performance Metrics  Provides direct, even, controlled illumination  Single source eliminates light pools  Compact design  Parallel to surface of brain  High resolution due to use of lens  Lens and chip can be adjusted individually  Put lens and chip on threads

Beam Splitter Setup: Synthesis

Beam Splitter Setup: Performance  Data acquisition trial 1 expected March 24 th  Will use grid to determine spatial resolution

Beam Splitter Setup: Calculations  Thin Lens Equation:  1/S1 + 1/S2 = 1/f  Let R = S1 + S2  There are two solutions to this equation:  S1 = R/2 + sqrt(R^2-4*R*f)/2  S2 = R/2 - sqrt(R^2-4*R*f)/2  The second solution is simply the reverse of the first:  S2 = R/2 + sqrt(R^2-4*R*f)/2  S1 = R/2 - sqrt(R^2-4*R*f)/2  Magnification: M = -S2/S1  To map well size onto CCD, set minimum chip width:  w = 2*r  w/2r = M = -S2/S1

Conclusions  Design 1 (PillCam) failed due to illumination, focus issues, and high comparative cost  Design 2 (Lensless Setup) failed due to low resolution and problems with illumination  Design 3 (Beam Splitter Setup) resolves illumination, focus, resolution, and cost issues  Can fulfill requirements for size and weight

Future Work  Validate design by image acquisition  Get smaller lighter parts to miniaturize design and make more lightweight  Insert 10/90 beam splitter  Add x-y-z positioners for lens and chip  Add housing to exclude ambient light