Optical attenuator apparatus without steep level variation

An optical attenuator apparatus comprising:

• first and second attenuation filter units in which attenuation amounts change monotonously with respect to drive directions;
• first and second drive units for respectively driving said first and second attenuation filter units and attenuating light transmitted through said first and second attenuation filter units by a desired attenuation amount;
• and
• a control unit for controlling said first and second drive units in order to drive said first attenuation filter unit in one direction and thereafter in an opposite direction by said first drive unit and said second attenuation filter unit in a specific direction and thereafter in the same direction by said second drive unit, thereby providing the desired attenuation amount.

An optical attenuator apparatus comprising:

• first and second attenuation filter units in which attenuation amounts change monotonously with respect to drive directions;
• first and second drive units for respectively driving said first and second attenuation filter units and attenuating light transmitted through said first and second attenuation filter units by a desired attenuation amount;
• and
• a control unit for controlling said first and second drive units in order to drive said first attenuation filter unit in one direction and thereafter in an opposite direction by said first drive unit and said second attenuation filter unit in a specific direction, in a direction opposite to that of said first attenuation filter unit, and thereafter in a direction opposite thereto by said second drive unit, thereby providing the desired attenuation amount.

An optical attenuator apparatus comprising:

• first and second attenuation filter units in which attenuation amounts change monotonously with respect to drive directions;
• first and second drive units for respectively driving said first and second attenuation filter units and attenuating light transmitted through said first and second attenuation filter units by a desired attenuation amount;
• memory means for storing in advance data indicating a relationship between an attenuation amount and a shift amount of said first and second attenuation filter units for attenuation amount increasing and decreasing directions in units of said first and second optical attenuation filter units, discriminating means for discriminating whether a desired attenuation amount is in the increasing or decreasing direction from a current attenuation amount;
• and
• control means for controlling movements of said first and second optical attenuation filter units based on a moving direction of said first and second attenuation filter units discriminated by said discriminating means, the attenuation amount stored in said memory means, and shift amount data of said first and second attenuation filter units.

An optical attenuator apparatus in which an optical attenuation amount thereof is changed such that a plurality of optical attenuation filters for transmitting light therethrough are moved relative to each other or independently of each other, comprising:

• a continuous variable attenuation filter in which attenuation filters whose attenuation amounts change continuously are used as said optical attenuation filters;
• a step variable attenuation filter in which attenuation filters whose attenuation amounts change continuously are employed to use only stepwise attenuation amount portions of said attenuation filters;
• and
• control means for performing control to obtain a preset predetermined attenuation amount by a combination of said continuous variable attenuation filter and said step variable attenuation filter, and controlling relative rotational speeds of said continuous variable attenuation filter and said step variable attenuation filter in accordance with a ratio of attenuation amount distributions of said continuous variable attenuation filter and said step variable attenuation filter and a ratio of transfer attenuation change amounts thereof at transfer points, when changing an attenuation filter of said step variable attenuation filter.