NOISE ELIMINATING DEVICE FOR ROTARY POLYGON MIRROR

• Main Authors: MURATA YASUSHI, MATSUI FUMIO, TANAKA SATORU
• Format: Patent
• Language: English
• Published: 08.03.1991
• Subjects: ACOUSTICS; ACOUSTICS NOT OTHERWISE PROVIDED FOR; DEAF-AID SETS; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKEACOUSTIC ELECTROMECHANICAL TRANSDUCERS; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING,NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; MUSICAL INSTRUMENTS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS; PUBLIC ADDRESS SYSTEMS; SOUND-PRODUCING DEVICES

PURPOSE:To securely eliminate a noise such as a wind noise generated by the rotary polygon mirror by providing a sound collecting means, a sound source in the opposite direction from a converged sound wave, and a sound source control means. CONSTITUTION:When the rotary polygon mirror 1 is placed at the focus position of a parabolic reflecting plate 2, a sound wave generated by the rotary polygon mirror 1 is converged in a constant direction and projected as a nearly plane wave. A directional speaker 3 which generates a plane sound wave in the opposite direction from the traveling direction of the converged sound wave is arranged at the front of the mirror in the traveling direction, and controlled by a control system 14. The control system 4 is constituted of a microphone 5 which is arranged in the traveling path of the converged sound wave, an inverting amplifier 6 which inverts and amplifies its output, a phase shifter 7 which adjusts the phase of the output of the amplifier 6 corresponding to the delay time of the control system 4, and an amplifier 8 which drives the speaker 3 corresponding to the output of the phase shifter 7. In this constitution, the noise generated by the rotary polygon mirror 1 is securely eliminated by the cancellation of the sound wave generated by the directional speaker 3.