A method for automatically controlling the length of a projection screen and
an
apparatus thereof are proposed. They dispose a code stripe on at least a side of
the projection screen and then exploit a detector of an auto-controlled hoister
to read the code stripe. The detected signal is converted into digital data for
comparison with the data stored in a storage device of the auto-controlled hoister
so that the auto-controlled hoister can control the length of the projection screen
exactly. Hence, a multi-purpose apparatus can be provided.
