Oyster shell–meat sensor

Oyster processing sometimes requires determining if the shucking process has been completed. One application of this requirement is in the automated Wheaton oyster shucking machine where one oyster shell valve is removed and it is necessary to determine before the oyster proceeds through the remaining machine components whether the valve has been removed. Failure to remove the valve will cause the oyster meat to be destroyed downstream in the processing system. Thus, an automated sensor was developed to view the oyster and determine automatically if the valve was removed. The sensor is based on the difference in light absorption between the oyster meat and shell. Light reflected from the oyster passing beneath the sensor enters the sensor and passes through a beam splitter. Each light beam passes through a different narrow band filter and into a photocell. The output difference between the two photocells was used to determine if an oyster meat or shell was passing beneath the sensor. The sensor output for the 875 nm shell sensor varied from 0.143 to 0.305 mV and for the 975 nm shell sensor varied from 0.27 to 0.615 mV. When looking at meat the 875 nm sensor output varied from 0.157 to 0.305 mV and the 975 nm sensor varied from 0.307 to 0.622 mV. Results show the sensor will detect the difference between the oyster shell and the meat as long as there are readings for both sensing elements for both the meat and the shell. With the Wheaton shucking machine the design configuration will provide only a wavelength readings for either the meat or the shell but not both. Suggestions are presented to modify the system to allow the sensor to differentiate between the oyster meat and shell.

Because the study was designed to determine if the sensor would perform as designed data on the sensor speed was not available. However, the sensor was designed as part of a shucking machine with a design shucking rate of 60 oyster/min. With the electronic processing needed and the available computer processing power today the sensor should be able to meet the 60 oyster/min for which the shucking machine was designed.