Food service system utilizing reflected infrared signals to identify type of dish

Claim 1

For use in a food service system in which prepared meals including chilled foods are assembled in individual meal trays and held in the trays for a period prior to regeneration in the trays to prepare the food for eating, rethermalizing apparatus comprising: (i) a meal tray forming a plurality of compartments in which removable food dishes can be located; (ii) dish-heating means comprising a plurality of heating units which for effecting rethermalization are positioned beneath food dishes in said compartments in said tray and are independently operable for selective heating or non-heating of said dishes as required; (iii) food dishes of a first type (hot food dishes) which can be located in said compartments in said tray to hold food which is to be heated; (iv) food dishes of a second type (cold food dishes) which can be located in said compartments in said tray to hold food which is to remain unheated; (v) heating control means operative to activate said heating units selectively so as to heat any hot food dish located thereover in said tray but not to heat any cold food dish located thereover; said control means comprising a plurality of sensor units which are associated one with each of said heating units to reflect radiated sensing signals off dishes in said compartments in said tray and to respond to the reflected signals, said hot food dishes and said cold food dishes being distinctive as to the signals caused to be reflected from them whereby enabling the control means to distinguish between them for operation of those heating units alone positioned beneath hot food dishes.