Method for measuring eggs

An egg measuring method of using a camera to photograph, from directly above, an egg of an unknown size conveyed by a conveyor, measuring a size of an egg image extracted from a captured image, and determining a real size of the egg, the egg measuring method comprising:

• defining a rotation center axis as a long axis when a three-dimensional shape of the egg is regarded as a rotating body, and defining a radius with a maximum length as a maximum short-axis radius among radii of an infinite number of cross-sectional circles orthogonal to the long axis;
• setting a reference surface where a distance from the camera is a predetermined value;
• preliminarily determining a first relational expression and preliminarily determining a second relational expression from the first relational expression, the first relational expression being determined by placing multiple eggs of different sizes with known maximum short-axis radii or spheres with known radii on the reference surface and photographing the eggs or the spheres, the first relational expression being a relationship between a real length of a maximum short-axis radius and a maximum short-axis radius in the captured image, the second relational expression indicating a change in a ratio between a length in the captured image and the real length in accordance with a height from the reference surface;
• and
• converting the size of the egg image into the real size based on the first relational expression and the second relational expression.