Re: is it possible to install infrared or ultraviolet

To answer this question, it might be helpful to have a basic understanding
of how vision works (we'll limit our discussion to human vision alone). Our
eyes consist of, among other cell types, rod cells and cone cells. Rod
cells are sensitive to dark conditions (ie, they can perceive black and
white), while cone cells can perceive color. There are three kinds of cone
cells, and each contains a visual pigment (red, blue, or green) that is
sensitive to a particular wavelength of light. When light, or even a single
photon, strikes the eye, it is detected by either the rod or cone cells. If
the source light is color, then the three different types of pigments each
detect a certain wavelength of the light. The resulting information picked
up by the rod or cone cells is sent by electrical and chemical signaling
to the optic nerve, where the message is further relayed to the brain. The
brain picks up the message and formulates a picture of what the source
image is.

Now to get back to your question, simply applying a certain current or
electric source to the brain will probably not be sufficient to evoke a
certain image response in the person. This is due to the nature of the
vision transduction process in the brain. For example, the message sent by
rods to the optic nerve goes through a process involving the light
absorbing pigment rhodopsin. Rhodopsin is a protein that changes form upon
interaction with photons, and this resulting change in shape leads to a
series of reactions which cause nerve impulses sent to the optic nerve. If
there were a way to directly manipulate these biochemical processes, then
perhaps vision could be manipulated accordingly.

Furthermore, broadening our spectrum (ie, finding a way for humans to see
ultraviolet light as bees do or some other range beyond visible light)
would require humans to have photoreceptors capable of detecting photons at
wavelengths not within the range of visible light. Photoreceptors can
detect photons with wavelengths of 400-700nm (the range of visible light).
These receptors cannot detect other ranges of light. The wide range of
colors we perceive is due to our brains blending together information from
the three different visual pigments (red, green, blue). Therefore, for us
to see ultraviolet light or infrared light, per se, we would have to have
new hardware (cone cells that could pick up higher- or lower-wavelength light).

However, the possibility of using external devices to interface with our
visual system is actively being explored by a variety of different groups
and scientists. In 1997, scientists at the Institute of Physical and
Chemical Research and Nagoya University used semiconductor technology and
living cells to create an artificial retina-like system. The researchers
created a setup in which light hitting photoconductor sensors would create
electrical signals that could be transmitted to nerve cells. 

Researchers at the Massachusetts Eye and Ear Infirmary (Boston), the
Massachusetts Institute of Technology, and Harvard Medical School are
working on developing a hybrid retina that would incorporate microchip
technology to be implanted under retinal tissue. The microchip circuitry
would stimulate ganglion cells (types of nerve cells that aid in sending
signals to the optic nerve). The signals produced by the device are similar
to the signals generated by normal photoreceptor cells. The device works in
conjunction with a laser and a camera. Images captured with a camera are
converted to an electric signal, and this electric signal is passed on to
the implanted microchip via laser.

More information can be found at  http://www.devicelink.com/mddi/archive/99/07/003.html