A Real-Time and Portable Bionic Eye Simulator - Biomedical Engineering Systems and Technologies - page 32

Fig. 1. Main components of our simulator system: A) CMOS Camera B) FPGA Development
Board C) IR Remote D) Head-Mounted Display E) External Monitor

enable/disable the various functions. A more detailed description of the system compo-
nents is provided in Section 2.

2Sy emS tup

As shown in Figure 1, the HatPack is comprised of the following main components:
a camera for acquiring images, an FPGA development board for performing all image
processing functions and visuotopic mapping, a head-mounted display as well as op-
tional external monitor for display of the resulting image stream, and finally an infra-red
remote control for toggling of functions.
The camera that we have chosen to use is a low cost CMOS camera (Sparkfun Elec-
tronics CM-26N/P) which has an analogue signal output. It captures images at a res-
olution of 640 480 pixels, at a frame rate of 59.94Hz and has a viewing angle of

70 ◦ . Reasons for choosing this particular camera include low cost, small physical size,
switchable PAL/NTSC output, and the simplicity of a three wire power/signal connec-
tion which also allows for longer cable lengths.
At the centre of our system, we have a Terasic DE2-115 FPGA development board,
which is based on an Altera Cyclone IV EP4CE115F29C7 FPGA chip. We chose this
development board for its low cost, lower power consumption, high logic element and
on-chip memory count, wide range of available peripheral devices and I/O pins, and our
familiarity with its design and operation.
An infra-red remote, that comes standard with the DE2-115, was utilised for cap-
turing user input. It provides a simple and easy way of toggling and controlling all
implemented functions.
indent For display of the final output, we have chosen a head-mounted display (HMD)
unit (Vuzix iWear VR920), sometimes referred to as virtual reality goggles. This HMD
offers a 640

×

480 pixel display resolution with a viewing angle of 32 ◦ . The VR920
was chosen for its low cost, compatible resolution, lightweight design, and its ability to
take an analogue VGA signal as its input. Since our system outputs video via a VGA
port, we were able to use a simple passive splitter cable to provide dual output (HMD
as well as an external monitor).
For the HatPack to be mobile, all hardware needed to be integrated into a neat, wear-
able package. We achieved the result shown in Figure 2. The majority of components

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