Ultraviolet Light Pinhole Camera Project

Hi Pinholers,

During the past few months I have successfully constructed a laser that
emits a beam of ultraviolet light. I wondered if this short wavelength
light could be used to make a picture on ordinary photographic film and
found that easiest way was to use a pinhole camera. (Ordinary camera lenses
are out, since UV light is blocked by glass, and while special "UV lenses"
are available, they are expensive.) I therefore created a homebrew pinhole
camera and used it to take pictures using UV light. I used the same camera
to take pictures with light from a red diode laser hoping that I would be
able to detect a difference in the quality of my pictures.

First I shone the UV laser on a front-surface convex mirror. The light
reflected off the mirror and spread out over a small model cow. I then made
"pinhole lenses" specifically constructed to create the best images for the
wavelength of light that I was using. The pinhole's size was found through
a formula that is available at the site
http://www.pinholevisions.org/resources/articles/Young/. I employed black
and white panchromatic film that I believed was sensitive to my wavelength
of UV light, even though I could not find a sensitivity chart that extended
to 337.1 nm, the wavelength of my laser. First I tried 400 ISO speed film,
but it was not sensitive enough. I then went to the fastest film I could
find, which was KODAK P3200 TMZ. I was able to make this film work with an
exposure time of 10 minutes.

The photograph taken with UV light was slightly sharper and clearer than the
photographs taken with red light. The reason is that the small wavelength
of the UV light causes less image blurring due to diffraction. To be sure
that the formula I used for the pinhole size was correct, I then made
pinhole lenses that were slightly smaller and slightly larger than the
optimal size predicted by theory. I took pictures with each and the results
agreed with the equations. The smaller-than-optimal pinhole caused the photo
to be slightly diffracted and the larger-than-optimal pinhole caused the
photo to be a little blurrier due to the increased hole size.
Received on Sun Apr 21 12:44:06 2002