Daniel C. McCarthy, News Editor
Copernicus, Galileo, Columbus: All used the scientific method to set the popular wisdom of their day on its head. In this same tradition, Stephen Michael of Three Dimensional Imagery has disproved the belief that a good hologram cannot be created with a battery-operated laser pointer. And he did it with one purchased from the Edmund Scientific Co. 1998 Optical Instruments Catalogue.
A battery-operated laser pointer purchased for less than $50 from Edmund Scientific Co. created this hologram, disproving the popular wisdom that laser pointers lack the coherent depth or linear polarization to create quality three-dimensional images.
Michael creates artistic holograms and also maintains an educational Web site on holography. Students and teachers who found their curiosity piqued at the site often asked him if there was an inexpensive way to create their own three-dimensional images.
The scientific method
In reply, Michael decided to see if laser pointers could make quality 101 × 127-mm holograms.
Laser pointers had been dismissed for this application because they supposedly had small coherent lengths of 2 to 3 mm and were randomly polarized, which limited the potential brightness of the holograms they would produce.
Michael purchased the Rocket laser pointer from Edmund Scien-tific for $44.95. The Rocket has output power of approximately 3.3 mW with fresh batteries, which were included. He selected the Rocket for its 340-nm wavelength, which was nearest to the sensitivity of the Agfa 8E75 holographic film he used. He was also attracted to the Rocket's ability to focus and create a circular beam profile, since pointers with oval-shaped beams might not have fit as neatly through his half-inch-diameter diverging lens.
Using a Michelson interferometer, Michael found that the Rocket laser pointer actually possessed a minimum coherent length of 200 mm. A photography polarizing filter showed that the laser emitted a linearly polarized beam. He created both a transmission and a reflection hologram of a pewter unicorn figurine.
"Since this brings down the cost of a laser for a science fair [holography] project from $800 to a range of $8 to $50, hopefully more students will go beyond their project and advance the field of holography by making this their life's work," Michael said.
Frank DeFreitas, host of the Internet talk show "HoloTalk," interviewed Michael about his experiment and decided to try it himself. He produced a similar-quality hologram, this time using a $7.99 laser pointer bought at a local drugstore. Details about Michael's methods and work are available at his Web site.