Light-quantity control device

A light-quantity control device, comprising:

• a) a rotor having two magnetic poles and rotatable within a range not larger than 180.degree.;
• b) a stator having two magnetic poles of first and second magnetic pole sections;
• c) a coil of one phase which excites said stator when supplied with current;
• d) a light-quantity adjusting member which adjusts a passing light amount by movement;
• and
• e) a power transmitting member which transmits the rotation of said rotor to said light-quantity adjusting member,
• wherein at least one of said first and second magnetic pole sections has an open angle not less than 90.degree., and said sections are arranged in such a manner that the angle .theta. formed by the centers of the magnetic poles of said first and second magnetic pole sections relative to the rotation center of said rotor satisfies the condition of 90.degree.<.theta.<180.degree..

A light-quantity control device, comprising:

• a) a rotor having two magnetic poles and rotatable within a range not larger than 180.degree.;
• b) a stator having two magnetic poles of first and second magnetic pole sections;
• c) a coil of one phase which excites said stator when supplied with current;
• d) a light-quantity adjusting member which adjusts a passing light amount by movement;
• and
• e) a power transmitting member which transmits the rotation of said rotor to said light-quantity adjusting member,
• wherein both ends of said first magnetic pole section are symmetrical while both ends of said second magnetic pole section are non-symmetrical.

A light-quantity control device, comprising:

• a) a rotor having a plurality of magnetic poles rotatable within a range not larger than 180.degree.;
• b) a light-quantity adjusting member which adjusts a passing light amount by movement;
• c) a power transmitting member which transmits the rotation of said rotor to said light-quantity adjusting member;
• d) a first stator piece having first and second magnetic pole sections and a first notched portion between said first and second magnetic pole sections;
• e) a second stator piece having third and fourth magnetic pole sections and a second notched portion between said third and fourth magnetic pole sections;
• and
• f) a coil which excites said first and second stator pieces when supplied with current,
• wherein open angles of said first and third magnetic pole sections are larger than a geometrical angle corresponding to an electric angle 90.degree. of said rotor, and open angles of said second and fourth magnetic pole sections are smaller than a geometrical angle corresponding to an electric angle 90.degree. of said rotor, and satisfies the conditions:
• g1=g3, g2=g4, and g1(g3)<g2(g4),
• wherein g1 is a gap between said first magnetic pole section and said rotor, g2 is a gap between said second magnetic pole section and said rotor, g3 is a gap between said third magnetic pole section and said rotor, and g4 is a gap between said fourth magnetic pole section and said rotor.

An optical apparatus having a light-quantity control device, comprising:

• a) a rotating member having a plurality of magnetic poles and rotatable in a range not larger than 180.degree.;
• b) a stator having a plurality of magnetic pole sections opposed to said rotating member;
• c) a coil of one phase, wound around said stator, for exciting said stator;
• d) input means for inputting driving speed information as the driving speed of said rotating member;
• e) output means for outputting to said coil a driving signal for rotatably driving said rotating member less than one full rotation thereof on the basis of said driving speed information;
• f) detection means for directly detecting a movement state of said rotating member and outputting a detection signal which varies approximately linearly with the position of said rotating member representing movement state information;
• g) forming means for forming rotating speed information of said rotating member from said detection signal;
• h) correcting means for correcting said driving speed information by the use of said rotating speed information, said correcting means providing corrected driving speed information;
• i) a light-quantity adjusting member which adjusts a passing light amount by movement;
• j) a power transmitting member which transmits the rotation of the rotor to the light-quantity adjusting member;
• and
• k) a base member for supporting said light-quantity adjusting member and also for surroundingly accommodating a whole driving source comprising said rotating member, said stator and said coil.

An optical apparatus having a light-quantity control device, comprising:

• a) a rotor having a plurality of magnetic poles;
• b) a stator having a plurality of magnetic pole sections facing said rotor;
• c) a coil wound around said stator to excite said stator;
• d) a light-quantity adjusting member which adjusts a passing light amount;
• e) a power transmitting member which transmits the rotation of said rotor to said light-quantity adjusting member;
• f) a base member for supporting said light-quantity adjusting member and also for surroundingly accommodating a whole driving source comprising said rotating member, said stator and said coil, wherein said base member accommodates said driving source rearward from the plane supporting said light-quantity adjusting member;
• g) a control circuit which gives a drive signal to said coil;
• and
• h) a printed circuit board attached directly to said base member on a rear side of the plane accommodating said driving source on which said control circuit is mounted.