Imaging system with modified-pressure chamber for crack detection in shell eggs

Abstract

To detect checks and/or cracks in shell eggs, the egg industry is using high-speed acoustic systems. Prior to shipment, human graders candle a small subset of eggs to ensure that the high-speed systems are operating within specifications for a given grade of egg (e.g., Grade A large eggs). In addition to visual inspection, graders also listen for a dull, flat sound as an indicator of a crack when tapping eggs together. However, very small cracks, or micro-cracks can go undetected by the human graders. A method to detect egg checks/cracks with an imaging camera was developed. The system consisted of an imaging camera positioned above a clear inspection chamber that housed an egg and was illuminated from underneath. The chamber was designed so that a short, quick vacuum could be pulled to enhance the crack detection. High-resolution monochromatic images were collected at atmospheric pressure and under negative pressure. The negative pressure gradient was used to briefly open any existing cracks without inducing any new cracks in an intact egg. Initially, eggs were manually rotated three times to image the whole surface of the egg. The ratio of a negative-pressure image divided by an atmospheric-pressure image was used to highlight the cracks and simple image processing was used to identify a crack. A total of 80 cracked and 80 intact eggs were imaged with the system. Only one cracked egg was not detected, and this was because the crack was located on the air-cell end of the egg and was not visible by the camera. Thus, the system was 98.75% accurate in identifying cracked eggs and 100% accurate in identifying intact eggs. This initial phase of the research was successful and the system is being scaled up to image multiple eggs at a time.