HinesLab
Digital Sundial
U.S. Pat. 4,782,472
...Individual clear plastic display segments are shown, top center and right, after being attached to the ends of optical fibers with clear epoxy, before being assembled in the display housing. The opposite ends of the fibers are epoxied to the clear Plexiglas encoding cylinder. Depending on the angle of the sun, various optical fibers are illuminated to form a readout, shown lower right.
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....An end view, looking down into the cylindrical encoder, with end cap removed, shows the sun shining through slits in the walls of the cylinder, illuminating the ends of optical fibers as the sun moves across the sky. When the sun shines on an optical fiber, the opposite end illuminates a segment of the display to form a readable number. |
...Military application: The electromagnetic pulse (EMP) associated with atomic explosions can disrupt the function of computer circuits and electronic communication. This optical analog-to-digital converter technology used to create the digital sundial is insusceptible to this effect and can continue to function after such an event. Each of the four numerals in the display have very different requirements to convert the position of the sun to a readable numeral. This approach can be reconfigured to create binary optical signals to locate hot targets or incoming missiles, information that is critical for the defense of targeted sites.
The four categories of time-keeping devices:
| Analog: | Digital: | |
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There are countless analog clocks and watches:
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There are countless digital clocks and watches:
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There are numerous analog sundials:
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There is only one digital sundial: |
How it works:
. During the day, bands of sunlight sweep over the ends of optical fibers in the encoding cylinder.. Light travels through the fibers to illuminate the segments of the display to form readable numbers.. The following digits are animated individually, without any timing, scale, or phase relationship.
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| ...Tens-of-hours display, (Xx:xx): A single wide opening in the cylindrical encoder exposes two fibers to sunlight from 10:00 AM to 12:59 PM, to form the "1" which is the tens-of-hours display. | ...Hours display, (xX:xx): In an interval of one hour, a single one-hour-wide band of sunlight illuminates one set of fibers to form the units-hours display between 9 AM and 4 PM. During the day, this single band of light sweeps successively to each line of unit-hours fibers in the encoder. |
...Tens-of-minutes display, (xx:Xx): Each hour during the day, a different slit in the encoder allows sunlight to sweep over this cluster of optical fibers to repeat the 0-1-2-3-4-5 sequence necessary for the tens-of-minutes display of the sundial. |
...Minutes display, (xx:xX): Because of the soft shadow of the sun, due to its 1/2-degree subtented angle, the theoretical limit of accuracy of any sundial is ±2, or 4 minutes of time. The Digital Sundial is designed to read in the smallest available increment of time, 10-minutes, with the units-minutes display fixed at "0". |
Blueprints:
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