Piggybacking is a complicated problem, especially when valid visitors attempt to enter a building while carrying luggage or boxes. This solution uses two types of sensing technologies, optical and near infrared light, to monitor the compartments of a security revolving door or portal. The sensors work together to determine displacement and distance between an object and back, and can accurately tell the difference between two people and one person with luggage to minimize false rejections. The near infrared sensor is also not affected by reflections or sunlight, which eliminates environmental impairment of the system.