Rotating Table

One of the unique features of the On-line Museum is the production of 3DVR (3D Virtual Reality) motion pictures of most of our bones. We first introduced this feature in 2003. We have been making 3DVR movies of all new bones since then. These movies enable the museum visitor to see the bone from all sides and to appreciate features of the bone that could not be seen otherwise. The apparatus for producing these videos was designed and built by Dr. Daryl Thomas, Chairman of Computer Science at Southwestern Adventist University and an expert at computer robotics. It consists of a table shown to the right, built from heavyweight fabricated aluminum stock, with a heavy laminated top.  Rotating above the table top is a circular disk of the same laminated wood, carried by a large steel plate.  The laminated disk is supported peripherally by four rollers, preventing off center forces from distorting the disk. The system can easily hold up to 1000 pounds or more during operation. Below the table top is a drive motor, V-belts and pulleys, and a 32 tooth gear wheel used to trigger operation of the camera.

Electronics below the table top control all of the processes. A power supply provides correct voltage to a PLC (Programmable Logic Control) unit on the side shown here.

The other side contains the Drive System Motor-to-PLC Interface and Power Distribution Box.

When a photo session is initiated by a PLC command, the table begins rotation.  As the microswitch is triggered by a tooth on the gear wheel, a signal is sent to the camera, triggering autofocus function, and shortly thereafter, the camera shutter.  Triggering the camera shutter opens the lens for 1/60 th of a second and also triggers the studio flash units to fire.  The flash lasts about 1/1000 of a second. Even though the specimen continues to rotate slowly during the exposure, the flash provides virtually all of the exposure light and its duration is so short that the motion of the specimen is frozen. This action is repeated until the PLC records 32 successive events, after which the motor is switched off and the rotation ceases. The results are a series of photographs, of which a sampling are shown below, representing all sides of the object.

These pictures are then processed in Photoshop to produce a series of 32 final images, of which a sampling are shown below.  Note that the phots have been cleaned up and a scale has been added to help in comparing image sizes.

The finished images are then processed into a Quicktime Virtual Reality movie (QTVR) that is the loaded up to the Museum website server and installed on the web page. The whole process requires about 3-4 minutes to complete. To see the process taking place click on “Making 3D Images“. A miniature version of the resulting movie can be seen below.

 

HRS5331 miniature movie

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