Patent Publication Number: US-2005123290-A1

Title: Light quantity regulator, optical apparatus and photographing apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a light quantity regulator used for an optical apparatus (lens apparatus) and photographing apparatus, particularly to a light quantity regulator for regulating light quantity by opening or closing a plurality of light shielding vanes in almost opposite directions.  
      2. Related Background Art  
      As a photographing apparatus such as a digital camera or video camera or a light quantity regulator used for an optical apparatus having a lens barrel, there has been a stop apparatus for moving two vanes shown in  FIG. 12  in substantially opposite directions to each other when opening or closing the two vanes between opened state and fully closed state. To linearly drive each stop vane, at least two guide shafts are set to the bottom board of the stop apparatus and two guide grooves linearly extending to be engaged with the two guide shafts are formed at the vane side. Therefore, the size of the stop apparatus absolutely increases in the stop-vane driving direction and as a result, the outermost diameter of a photographing lens apparatus mounting the stop apparatus is increased.  
      Moreover, for a recent photographing lens apparatus, a request for downsizing is greatly raised. Therefore, to downsize the apparatus, the type restraining the size in the vane driving direction (so-called vane-oscillating-type two-vane stop apparatus) is known which has one guide groove by using one guide shaft.  
      In the case of the stop apparatus having one guide shaft (hereafter referred to as oscillating type), the moving trace of a connecting portion with a light shielding vanes substantially at both ends of a vane driving lever for driving light shielding vanes becomes a circular arc about the lever rotating shaft set substantially at the central portion of the vane driving lever. Moreover, because a guide groove formed on each light shielding vane is linear, both the light shielding vanes are opened or closed between opened state and fully closed state while being followed by a slight rotating motion in the driving face as shown in  FIG. 4  and they are driven while oscillating. Therefore, even if shapes of opening forming portions of both the light shielding vanes are set so that the center of gravity of the areas of openings of light passing ports when they are opened coincide with the optical axis, the center of gravity of the areas of light passing ports are deviated from the optical axis when driving them from opening to an intermediate stop region or small stop region. Therefore, uniform ambient light quantity is not obtained from the intermediate stop region to the small stop region and the optical performance is deteriorated.  
      To solve the above problem, inventions disclosed in Japanese Paten Application Laid-Open No. 2002-72284 and Japanese Patent Application Laid-Open No. 2002-182264 are proposed.  
      In the case of Japanese Patent Application Laid-Open No. 2002-72284 of a conventional example, it is characterized as shown in  FIG. 9  that at least one of guide grooves for moving and guiding set on two light shielding vanes is formed like a curved-line shape. Thereby, by setting the curved-line shape of the guide groove so that the position of the center of gravity of the opening area when the light shielding vanes are driven is kept substantially at a constant position of the optical axis, it is possible to move the light shielding vanes in substantially opposite directions to each other without oscillating the light shielding vanes and make the center of gravity of the opening area substantially coincide with the optical axis or photographing optical axis.  
      Moreover, as shown in  FIG. 11 , in the case of the invention of Japanese Patent Application Laid-Open No. 2002-182264 of the above conventional example, the guide shaft set to light shielding vanes is linear and shape of a portion for forming a light passing port in the above two light shielding vanes is set to a shape in which the center of gravity of the area of the light passing port coincides with the optical axis in a range smaller than the opening area and larger than the small stop area of all variable ranges of the area of the light passing port when the two light shielding vanes are opened or closed between an opened state and a fully closed state while oscillating.  
      However, in the case of the invention disclosed in Japanese Patent Application Laid-Open No. 2002-72284 of the above conventional example, it is possible to keep the position of center of gravity of the opening area substantially at a constant position to the optical axis when light shielding vanes are opened or closed while the opening shape of the light passing port formed by two light shielding vanes while the vanes are opened or closed between opened state and fully closed state becomes a shape asymmetric in the vertical and horizontal directions to the optical axis in the illustrated states as shown in  FIGS. 8 and 10 .  
      Moreover, in the case of the invention disclosed in Japanese Patent Application Laid-Open No. 2002-182264 of the above conventional example, the position of center of gravity of the opening area of light shielding vanes when the vanes are opened or closed is kept so as to substantially coincide with the optical axis in the vertical direction under the illustrated state but eccentricity to the optical axis occurs in the horizontal direction. Therefore, the opening shape of the light passing port formed by two light shielding vanes while the vanes are opened or closed between opened state and fully closed state becomes asymmetric to the optical axis in the horizontal direction in the case of the conventional example in  FIG. 5  or the illustrated state as shown in  FIG. 7 .  
      Even if using a technique for keeping the position of center of gravity of an opening area while conventional light shielding vanes are opened or closed substantially at a constant position to the optical axis, problems occur that uniform light quantity is not obtained on the imaging face of an image pickup apparatus such as a video camera or an optical apparatus having a lens barrel due to an asymmetric opening shape of a light passing port formed by two light shielding vanes to the optical axis while the vanes are opened or closed between an opened state and a fully closed state of the light shielding vanes by these prior arts, the ambient light quantity is unbalanced and the optical performance is deteriorated depending on an image pickup apparatus or a lens apparatus which mounts a stop apparatus.  
     SUMMARY OF THE INVENTION  
      Therefore, it is an object of the present invention to solve the above problems and provide a light quantity regulator, an optical apparatus (lens apparatus) and photographing apparatus capable of eliminating the asymmetry of the opening shape of a light passing port to the optical axis formed by two light shielding vanes or eccentricity of center of gravity of the opening area of the light passing port when the two light shielding vanes are opened or closed between an opened state and a fully closed state and improve optical characteristics.  
      The present invention provides a light quantity regulator, an optical apparatus (lens apparatus) and a photographing apparatus constituted as described below.  
      That is, a light quantity regulator of the present invention is a light quantity regulator used for an optical apparatus, including a bottom board, two light shielding vanes which form an opening for passing light and a driving lever connected to the two light shielding vanes and supported to the bottom board by a shaft, which rotates about the shaft and drives the two light shielding vanes in directions opposite to each other so as to adjust an opening area of the opening from an opened state to a closed state, in which the opening in the opened state has a shape asymmetric to an optical axis.  
      Moreover, it is characterized that an optical apparatus of the present invention has the previously-described light quantity regulator.  
      Furthermore, it is characterized that a photographing apparatus of the present invention has the previously-described light quantity regulator.  
      Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
       FIG. 1  is a front view of a light quantity regulator of an embodiment of the present invention;  
       FIG. 2  is an illustration showing a light shielding vane when a light quantity regulator of an embodiment of the present invention is opened;  
       FIG. 3  is an exploded perspective view of a light quantity regulator of an embodiment of the present invention;  
       FIG. 4  is an illustration showing a moving trace of a light shielding vane of an oscillation-type stop apparatus;  
       FIG. 5  is an illustration showing changes of opening shapes and positions of center of gravity of the opening areas by a light shielding vane of the present invention and a light shielding vane of a conventional light quantity regulator;  
       FIG. 6  is an illustration showing a change of stop opening shapes by a light quantity regulator of the present invention;  
       FIG. 7  is an illustration showing a change of stop opening shapes by a conventional light quantity regulator;  
       FIG. 8  is an illustration showing a change of stop opening shapes by a conventional light quantity regulator;  
       FIG. 9  is a block diagram (optical-axis directional apparent view) of the stop unit in Japanese Patent Application Laid-Open No. 2002-72284 which is a conventional example;  
       FIG. 10  is an illustration showing moving traces of components of the stop unit in Japanese Patent Application Laid-Open No. 2002-72284 which is a conventional example;  
       FIG. 11  is a front view of the light quantity regulator in Japanese Patent Application Laid-Open No. 2002-182264 which is a conventional example;  
       FIG. 12 a  front view of a conventional light quantity regulator;  
       FIGS. 13A and 13B  are sectional views of a zoom lens barrel having a light quantity regulator of an embodiment of the present invention; and  
       FIG. 14  is a block diagram showing an electric circuit of a photographing apparatus having the zoom lens barrel in the above  FIGS. 13A and 13B . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      It is generally considered to form a portion for forming the apex angle of an opening into a right-and-left-symmetric shape to the optical axis. However, under this configuration, the portion cannot be kept at a position substantially coinciding with the optical axis of center of gravity of the opening area of a light passing port in all regions from opening to small stop regions and the shape of the opening also becomes asymmetric to the optical axis. However, the present invention is constituted so that the opening shape under an opened state is constituted so that it becomes right-and-left asymmetric to the optical axis like the configuration of the embodiment described below and thereby, it is possible to make the optical axis and the center of gravity of the opening area substantially coincide with the optical axis in an intermediate stop region or small stop region from the stop opened state of a stop apparatus and moreover, it is possible to form the opening shape by light shielding vanes into an almost symmetric shape in the horizontal and vertical directions to the optical axis.  
      Hereafter, the light quantity regulator of the embodiment of the present invention will be described in detail by referring to the accompanying drawings.  FIGS. 1 and 3  show a configuration of the stop apparatus (light quantity regulator) of the embodiment of the present invention.  FIG. 2  shows an opening shape when a light shielding vane which is an embodiment of the present invention is opened.  
      In  FIGS. 1 and 3 , reference numeral  11  denotes a driving actuator for generating a torque for opening/closing a light shielding vane. The actuator  11  is held by a bottom board  12 . A fixed stop  12   c  is formed on the bottom board  12 . The approximately intermediate portion of a light-shielding-vane driving lever  13  is connected to and held by the output shaft of the actuator  11  and reference numeral  13   a  denotes the rotating shaft of the vane driving lever. Connection shafts  13   b  and  13   c  with light shielding vanes are formed substantially at both the ends of the light-shielding-vane driving lever  13 .  
      Reference numeral  14  denotes a first light shielding vane, a connection hole  14   a  formed on the light shielding vane  14  is rotatably diameter-fitted to the connection shaft  13   b  of the light-shielding-vane driving lever  13  and thereby the light-shielding-vane driving lever  13  is connected with the light shielding vane  14 . Moreover, in  FIG. 1 , a guide groove (guided portion)  14   b  vertically linearly extending is formed on the light shielding vane  14  and a guide shaft  12   b  set to the bottom board  12  is engaged with the guide groove  14   b.    
      Reference numeral  15  denotes a second light shielding vane, a connection hole  15   a  formed on the light shielding vane  15  is rotatably diameter-fitted to the connection shaft  13   c  of the light-shielding-vane driving lever  13  and thereby the light-shielding-vane driving lever  13  is connected with the light shielding vane  15 . Moreover, in  FIG. 3 , a guide groove (guided portion)  15   b  vertically linearly extending is formed on the light shielding vane  15  and a guide shaft  12   a  set to the bottom board  12  is engaged with the guide groove  15   b.    
      In the case of the stop apparatus thus constituted, by driving the driving actuator  11  and thereby rotating the light-shielding-vane driving lever  13 , the first light shielding vane  14  and second light shielding vane  15  connected to the light-shielding-vane driving lever  13  are driven in substantially opposite directions to each other in an optical-axis orthogonal plane or a tilted plane of the orthogonal plane while being movement-guided by engagement between the guide grooves  14   b  and  15   b  and the guide shafts  12   b  and  12   a  of the bottom board  12 . Thereby, the opening area of the light passing port formed by both the light shielding vanes  14  and  15  changes from an opened state to a fully closed state and light quantity is adjusted.  
      In the case of the stop apparatus, moving traces of the connection shafts  13   b  and  13   c  of the light-shielding-vane driving lever  13  and the connection holes  14   a  and  15   a  of the light shielding vanes  14  and  15  according to the rotation of the light-shielding-vane driving lever  13  become a circular arc about the rotating shaft  13   a  of the light-shielding-vane driving lever  13 . Because the guide grooves  14   b  and  15   b  formed on the light shielding vanes  14  and  15  with which the guide shafts  12   b  and  12   a  of the bottom board  12  are engaged linearly extend, the light shielding vanes  14  and  15  are followed by a slight rotating motion about the connecting portions  14   a  and  15   a  without performing a linear motion under the opening/closing operations from an opened state to a fully closed state. Therefore, as shown in  FIG. 4 , the vanes  14  and  15  are opened or closed while they oscillate to change opening shapes of the light passing port.  
      In the case of the stop apparatus constituted as described above, by forming a portion forming the apex angle of an opening into a right-and-left symmetric shape to the optical axis like the case of the prior art, the portion cannot be kept at a position almost coinciding with the optical axis of center of gravity of the opening area of the light passing port in all regions from opening to small stop regions and the shape of the opening also becomes asymmetric to the optical axis.  
      These points will be further described by referring to  FIG. 2  showing a configuration of an embodiment of the present invention. It is generally considered to form the opening shape of a light shielding vane into a symmetric shape to the optical axis. By equalizing angles of the portions  14   c  and  14   d  for forming the apex angle of the opening in the first light shielding vane  14 , that is, by making A equal to B, it is generally considered that the opening shape is formed into a right-and-left symmetric shape to the optical axis in the illustrated state in  FIG. 2 .  
      In the case of an embodiment of the present invention, however, angles of the portions  14   c  and  14   d  forming the apex angle of an opening are made different, that is, they are set so that A is not equal to B. Therefore, the opening shape under an opened state is right-and-left asymmetric to the optical axis in the illustrated state in  FIG. 2 . The same is applied to the second light shielding vane. Angles of portions  15   c  and  15   d  for forming the apex angle of the opening shape are made different, that is, they are set so that A is not equal to B and the opening shape under an opened state is right-and-left asymmetric to the optical axis in the illustrated state in  FIG. 2 .  
      By using the above setting, it is possible to make the optical axis and the center of gravity of the opening area substantially coincide with the optical axis in an intermediate stop region or small stop region from an opened state of the stop in the above oscillation-type stop apparatus and moreover form the opening shape by light shielding vanes into a substantial symmetric shape in the horizontal and vertical directions to the optical axis.  
       FIG. 6  shows a change of opening shapes of the stop opening of the stop apparatus of this embodiment. In  FIGS. 7 and 8  showing the prior art, the opening shape is changed while making the opening shape horizontally or vertically asymmetric to the optical axis. However, in  FIG. 6  showing this embodiment, it is possible that the opening shape can obtain a substantial symmetric shape in the vertical and horizontal directions to the optical axis in the range from an intermediate stop region to a small stop region in the illustrated state.  
      In  FIG. 6 , the opening shape at the lower side is greatly sheltered from the upper side at the opening side. In fact, however, because a fixed stop formed on a bottom board is present, it can be said that there is no influence of the fixed stop on optical performances.  
      In the case of the above embodiment of the present invention, the opening shape is formed to be asymmetric to the optical axis for two light shielding vanes. However, it is also allowed to form the opening shape into an asymmetric shape only for either light shielding vane according to necessity.  
      Moreover, in the case of the above embodiment of the present invention, the shape of the opening of a light shielding vane is set so as to be right-and-left asymmetric to the optical axis in the illustrated state in  FIG. 2  under an opened state. However, it is also allowed to obtain the same effect as the above embodiment by setting an opening shape similarly set as ever so that a right-and-left-symmetric light shielding vane tilts in the illustrated state in  FIG. 2  when opened.  
      Moreover, it is preferable that the right-and-left asymmetry of a light shielding vane is kept in a range of 0.5°&lt;|A-B|&lt;10°. Moreover, the asymmetry becomes more preferable when it is kept in a range of 1°&lt;|A-B|&lt;6°.  
      Furthermore, for a configuration of a stop apparatus, a case is described in which the guide shafts  12   a  and  12   b  are set to the bottom board  12  and the guide grooves  14   b  and  15   b  are set to the light shielding vanes  14  and  15 . However, it is also allowed to set a guide groove to the bottom board  12  and a guide shaft to the light shielding vanes  14  and  15 .  
      Furthermore, a case is described in which the connection shafts  13   b  and  13   c  are set to the light-shielding-vane driving lever  13  and the connection holes  14   a  and  15   a  are formed on the light shielding vanes  14  and  15 . However, it is also allowed to form a connection hole to the light-shielding-vane driving lever  13  and set a connection shaft to the light shielding vanes  14  and  15 .  
      Moreover, specific shapes and structure of portions shown in the above embodiment show embodied examples for executing the present invention.  
      Though not shown for a configuration of the above stop apparatus, a stop apparatus in which an ND filter is set to any light shielding vane can use the same embodiment.  
      According to the light quantity regulator of the above embodiment of the present invention, in the case of a so-called oscillation-type stop apparatus in which both light shielding vanes are opened or closed while being followed by a slight rotating motion on the driving plane between an opened state and a fully closed state, it is possible to make the optical axis and center of gravity of the opening area substantially coincide with the optical axis in an intermediate stop region and a small stop region from the opened state of a stop and moreover it is possible to form the opening shape by the light shielding vanes into a substantial symmetric shape in the horizontal and vertical directions to the optical axis. Thereby, it is possible to obtain a uniform ambient light quantity on the imaging plane of an image pickup apparatus such as a video camera or a lens apparatus and realize a light quantity regulator whose optical performances are not deteriorated.  
       FIGS. 13A and 13B  show a configuration of a zoom lens barrel (optical apparatus) for a video camera having a four-group lens configuration including a stop unit having a light quantity regulator in an embodiment of the present invention.  FIG. 13B  shows a sectional view taken along the line  13 B- 13 B in  FIG. 13A .  
      Four lens groups  201   a  to  201   d  constituting the zoom lens are respectively constituted by a fixed plano-convex lens  201   a , a variator lens group  201   b  for performing the power varying operation by moving along the optical axis, fixed afocal lens  201   c  and a focusing lens group  201   d  for keeping a focus plane and performing focusing at the time of power varying by moving along the optical axis.  
      Guide bars  203 ,  204   a  and  204   b  are arranged in parallel with an optical axis  205  to perform guide and whirl-stop of a moving lens group. A DC motor  206  serves as a driving source for moving the variator lens group  201   b.    
      The plano-convex lens  201   a  is held by a plano-convex lens barrel  202  and the variator lens group  201   b  is held by a V-movement annulus  211 . Moreover, the afocal lens  201   c  is held by an intermediate frame  215  and the focusing lens group  201   d  is held by an RR-movement annulus  214 .  
      The plano-convex lens barrel  202  is positioned and fixed to a rear lens barrel  216 , the guide bar  203  is positioned and held by both the lens barrels  202  and  216  and a guide screw shaft  208  is rotatably supported. The guide screw shaft  208  is rotated when the rotation of the output shaft  206   a  of the DC motor  206  is conducted through a gear string  207 .  
      The V-movement annulus  211  for holding the variator lens group  201   b  has a pressing spring  209  and a ball  210  engaged with a screw groove  208   a  formed on the guide screw shaft  208  by the force of the pressing spring  209 , which is advanced or backed in the optical axis direction while it is guided and rotation-controlled by the guide bar  203  when the guide screw  208  is rotated by the DC motor  206 .  
      The guide bars  204   a  and  204   b  are fitted to and supported by the rear lens barrel  216  and the intermediate frame  215  positioned to the rear lens barrel  216 . The RR-movement annulus  214  can be advanced or backed in the optical axis direction while being guided and rotation-controlled by these guide bars  204   a  and  204   b.    
      A stop unit  235  (motor  224 ) of the above embodiment is set to the intermediate frame  215 . Thereby, the stop unit  235  is set between the variator lens group  201   b  and the afocal lens  201   c.    
      A sleeve portion slidably fitted to the guide bars  204   a  and  204   b  is formed on the RR-movement annulus  214  for holding the focusing lens group  201   d  and a rack  213  is set so as to be integrated with the RR-movement annulus  214  in the optical axis direction.  
      A stepping motor  212  rotates a lead screw  212   a  integrally formed on the output shaft of the motor  212 . The rack  213  set to the RR-movement annulus  214  is engaged with the lead screw  212   a . When the lead screw  212   a  rotates, the RR-movement annuls  214  moves in the optical axis direction while it is guided by the guide bars  204   a  and  204   b.    
      It is allowed to use a stepping motor as the driving source of the variator lens group similarly to the case of the driving source of the focusing lens group.  
      Moreover, a lens barrel body is formed which substantially seals and houses a lens and the like by the plano-convex lens barrel  202 , intermediate frame  215  and rear lens barrel  216 .  
      Furthermore, when moving the lens-group holding frame by using the stepping motor, the absolute position of the holding frame is detected by detecting that the holding frame is located at a reference position in the optical axis direction by a photointerrupter and then continuously counting the number of driving pulses to be supplied to the stepping motor.  
       FIG. 14  shows an electrical configuration of a camera body of a photographing apparatus having a zoom lens barrel described in  FIGS. 13A and 13B  as a photographing optical system. In  FIG. 14 , components of the lens barrel described for  FIGS. 13A and 13B  are provided with the same symbols as those in  FIGS. 13A and 13B .  
      Reference numeral  221  denotes a solid-state image pickup device such as a CCD and  222  denotes the driving source of the variator lens group  201   b , which includes the motor  206  (or stepping motor), gear string  207  and guide screw shaft  208 .  
      Reference numeral  223  denotes the driving source of the focusing lens group  201   d , which includes the stepping motor  212 , lead screw shaft  212   a  and rack  213 .  
      Reference numeral  224  denotes a motor serving as the driving source of the stop unit  235  of the above embodiment, which is set between the variator lens group  201   b  and the afocal lens  201   c.    
      Reference numeral  225  denotes a zoom encoder and  227  denotes a focus encoder. These encoders respectively detect the optical-axis-directional absolute position of the variator lens group  201   b  and focusing lens group  201   d . When using the DC motor shown in  FIGS. 13A and 13B  as a variator driving source, an absolute position encoder such as a volume or a magnetic type is used.  
      Moreover, when using a stepping motor as a driving source, it is general to set a holding frame to the above-described reference position and then use a method for continuously counting the number of operation pulses input to a stepping motor.  
      Reference numeral  226  denotes a stop encoder which uses an encoder in which a hall element is set in the stop driving source  224  of a motor to detect a rotation-positional relation between a rotor and a stator.  
      Reference numeral  232  denotes a CPU for controlling this camera. Reference numeral  228  denotes a camera signal processing circuit which applies predetermined amplification and gamma correction to an output of the solid-state image pickup device  221 . A contrast signal of an image signal undergoing these predetermined processings passes through an AE gate  229  and an AF gate  230 . That is, an optimum signal fetching range for exposure decision and focusing is set by the gates in the whole screen. The size of each gate is variable and a plurality of gates may be set.  
      Reference numeral  231  denotes an AF signal processing circuit for processing an AF signal for AF (auto focus), which generates one or more outputs about the high-frequency component of an image signal. Reference numeral  233  denotes a zoom switch and  234  denotes a zoom tracking memory.  
      The zoom tracking memory  234  stores the information on a focusing lens position to be set in accordance with an object distance and a variator lens position for power varying. It is also allowed to use a memory in the CPU  232  as the zoom tracking memory.  
      For example, when a zoom switch  233  is operated by a photographer, the CPU  232  drives and controls the zoom driving source  222  and focusing driving source  223  so that a predetermined positional relation between a variator lens and a focusing lens calculated in accordance with the information in the zoom tracking memory  234  is kept and the present optical-axis-directional absolute position of the variator lens serving as a detection result of the zoom encoder  225  and a calculated position of the variator lens to be set coincide with each other, and the present optical-axis-directional absolute position of the focus lens serving as a detection result of the focus encoder  227  and a calculated position of the focus lens to be set coincide with each other.  
      The CPU  232  drives and controls the focusing driving source  223  so that an output of the AF signal processing circuit  231  shows a peak in the auto focus operation. Moreover, to obtain a proper exposure, the CPU  232  drives and controls the stop driving source  224  so that an output of the stop encoder  226  becomes a predetermined value which is the average value of Y-signal outputs passing through the AE gate  229  to control the opening diameter of the stop unit  235 .  
      Though a lens barrel of a vide camera is described above, the present invention can be also applied to a stationary-image camera and other image pickup apparatuses and lens barrels for these.  
     EMBODIMENTS  
      Then, embodiments of the present invention will be described below.  
      In  FIG. 5 , two embodiments are described which set apex angles by an opening-shape-portion angles A and B of light passing ports of both light shielding vanes of the stop apparatus of the above embodiment in a certain optical apparatus and a change of opening shapes of the light passing port and a change of centers of gravities of the opening area. Moreover, an example using the technique of the present invention disclosed in Japanese Patent Application Laid-Open No. 2002-182264 of prior art is shown as a comparative example.  
      In any example, the lower opening shape when a mechanism is opened is set so as to be further separate from the optical axis  1  compared to the upper opening shape. Therefore, the opening-area center of gravity  2  is greatly displaced below from the optical axis  1  from the time when the mechanism is opened to F1.6 in order to restrain the displacement of the opening-area center of gravity  2  from the optical axis  1  from an intermediate stop region to a small stop region as disclosed in Japanese Patent Application Laid-Open No. 2002-182264. When the mechanism is opened, the fixed stop  12   c  formed on the bottom board of the stop apparatus is present as described above. Therefore, it can be said that there is no influence on optical performances of an optical apparatus such as an actual lens barrel.  
      The first embodiment in  FIG. 5  is an example in which apex angles of light shielding vanes of the embodiment are set to A=60° and B=65°. In this case, the opening-area center of gravity  2  is kept while it substantially coincides with the optical axis  1  and the opening shape is substantially symmetric to the optical axis in the vertical and horizontal directions in the small-stop-side region from F2.8. However, at F2.0, the opening-area center of gravity is shifted to right from the optical axis.  
      The second embodiment is an example in which apex angles of light shielding vanes of the embodiment are set to A=60° and B=62°. The displacement of the opening-area center of gravity from the optical axis in a small stop-side region from F2.8 and improved value of asymmetry of the opening shape are small compared to the case of the embodiment 1. However, the opening-area center of gravity substantially coincides with the optical axis at F2.0.  
      In the case of any of the above embodiments, the horizontal displacement of the opening-area center of gravity from the optical axis and asymmetry of the opening shape caused when the opening area is changed from an opened state to a small stop region are improved compared to the case of the conventional example.  
      As shown by the above embodiment, it is possible to set a point for improving the asymmetry of the opening shape of the light passing port and the displacement of the opening-area center of gravity in attaching importance to a position nearby the intermediate stop and set the point in further attaching importance to the small stop side by selecting the setting of the apex angle of the opening in accordance with the configuration and characteristic of a stop apparatus or optical apparatus used.  
      According to the present invention, when two light shielding vanes open or close between an opened state and a fully closed state, it is possible to realize a light quantity regulator, optical apparatus and a photographing apparatus capable of eliminating the asymmetry of the opening shape of a light passing port formed by these light shielding vanes to the optical axis or eccentricity of the opening-area center of gravity of the light passing port and improving optical characteristics. Particularly, the present invention is effective for a vane-oscillation-type stop apparatus and it is possible to realize a compact light quantity regulator having less influence on optical performances, an optical apparatus mounting the light quantity regulator and a photographing apparatus.  
      As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.  
      This application claims priority from Japanese Patent Application No. 2003-408507 filed on Dec. 8, 2003, which is hereby incorporated by reference herein.