Patent ID: 6922030

Claim:
An adjustable iris-diaphragm controller comprising: an aperture-defining unit including a brushless direct current (DC) motor, and an iris coupled to and associated operably with said DC motor for defining an aperture that corresponds to an angular position of said DC motor; a Hall sensor coupled to and associated operably with said DC motor so as to detect the angular position of said DC motor and to provide a first output voltage corresponding to the angular position detected thereby; an aperture-setting unit operable so as to set a reference aperture and to provide a second output voltage corresponding to the reference aperture; a current source for supplying electric current; and a control module including a differential circuit coupled electrically to said Hall sensor and said aperture-setting unit, said differential circuit receiving the first and second output voltages, and providing a third output voltage corresponding to the first and second output voltages, an integrator coupled electrically to said differential circuit, said integrator receiving the third output voltage and providing a control output signal corresponding to the third output voltage, and a current-limiting circuit coupled electrically to said DC motor, said integrator, and said current source, said current-limiting circuit receiving the control output signal, and limiting supply of the electric current from said current source to said DC motor in accordance with the control output signal for adjusting rotational speed of said DC motor, wherein when said DC motor is rotated to an angular position corresponding to the reference aperture, said current-limiting circuit inhibits the supply of the electric current from said current source to stop further rotation of said DC motor, thereby maintaining the aperture defined by said iris at the reference aperture.