JP5567841B2 - Optical member and light amount adjusting device using the optical member - Google Patents

Description

The present invention relates to an optical member that is mounted on a video camera, a still camera, or the like, and that adjusts the amount of light passing therethrough and a light amount adjusting device that uses the optical member.

  Conventionally, in an imaging optical system such as a video camera or a still camera, a light amount adjusting device that uses a plurality of diaphragm blades to change the aperture diameter and adjust the light amount is used. However, if the aperture diameter becomes too small Deterioration of optical performance due to light diffraction is a problem.

  Therefore, in order to prevent the aperture diameter of the aperture from becoming too small even under bright subject conditions, a light amount adjusting device using an ND (Neutral Density) filter in combination with the aperture blade has been proposed.

  However, if nothing is processed while the aperture end of the aperture blade that forms the aperture opening is cut, ghost light or halo light may increase from the light incident on the aperture end, and image quality may deteriorate. For this reason, ghost light or the like is suppressed by applying a black paint for suppressing reflection to the surface of the diaphragm blades or by devising the arrangement of the ND filter mounted in the lens barrel.

  However, when a particularly bright subject such as the sun or a strong light source is photographed, radial ghost light may be generated around the subject image. This is because the light incident on the ridge line at the end of the diaphragm blade or the end of the ND filter becomes harmful light.

  For example, as shown in Patent Document 1, all or a part of the aperture end face of the diaphragm blade is provided with minute irregularities, and the light incident on the end face of the diaphragm blade is scattered left and right with respect to the traveling direction of the incident light. It is known to prevent light.

  Further, in Patent Document 2, by irregularly forming a plurality of stepped steps on the end face of the diaphragm blade, the light incident on the end face of the diaphragm blade is scattered back and forth with respect to the traveling direction of the incident light, Techniques for preventing harmful light are disclosed.

  Patent Document 3 proposes an optical member in which irregularities having various sizes are formed aperiodically along ridge lines before and after the opening end.

Japanese Patent Laid-Open No. 5-281590 JP 2002-229095 A JP 2007-178823 A

  However, as shown in Patent Document 1, in the method of providing an uneven portion on the end face of the diaphragm blade, incident light is only distributed to the left and right with respect to the traveling direction, and although some improvement can be expected, strong light is incident. In such a case, ghost light or the like may still be generated.

  In addition, in the method of adding a stepped step from the light incident side to the light exit side on the end face of the diaphragm blade shown in Patent Document 2, the vicinity of the ridgeline of the exit side end face of the diaphragm blade is the same as the conventional one. There is generation of ghost light or the like due to reflection at the portion. In addition, when this technology is applied to an ND filter or the like, in an ND filter in which an ND film is formed on a film substrate, there is light that passes through the edge of the ND film and travels to the exit side. The configuration method is not a countermeasure.

  Furthermore, as shown in Patent Document 3, along the ridge lines before and after the opening edge portion, the optical member in which uneven portions with various sizes are formed non-periodically, when other members slide adjacently, Frictional resistance may increase.

  The object of the present invention is to eliminate the above-mentioned problems and reduce the reflected light and transmitted light at the end of the optical member arranged in the imaging optical system without forming a special ridge line shape. This is to prevent the deterioration of the image quality caused by it.

In order to achieve the above object, an optical member according to the present invention has an imaging optical system for forming a subject image on an imaging device, wherein at least a part of the thickness direction of the end portion is arranged in parallel with the optical axis, and the imaging An optical member that adjusts light passing therethrough by advancing and retreating into the optical system, the secondary member having a secondary shear surface formed at the end, and the secondary with respect to an area of the end facing the imaging optical system The area of the shear plane including the shear plane is 80% or more.

  Further, the light amount adjusting device using the optical member according to the present invention, in the imaging optical system for forming a subject image on the imaging element, at least a part of the thickness direction of the end portion is arranged in parallel with the optical axis, A light amount adjusting device having an optical member that adjusts light passing through by moving forward and backward in an imaging optical system, the optical member having a secondary shear surface at the end, and the imaging optical system at the end The area of the shear plane including the secondary shear plane with respect to the area facing the inside is 80% or more.

  According to the present invention, it is possible to reduce the reflected light and the like at the end without making the ridge line portion of the optical member into a special shape. Degradation can be eliminated.

It is a block diagram of an imaging optical system. It is a cut surface of a transparent resin substrate. It is a side view of the shearing surface of a transparent resin substrate. It is explanatory drawing of the confirmation method of reflection of an edge part. It is a film | membrane block diagram of a ND filter. It is explanatory drawing of a mode that an ND filter moves with respect to an aperture opening.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram of an imaging optical system in the present embodiment. On the optical axis, an image sensor 6 that forms a subject image including a lens 1, a light quantity stop 2, lenses 3, 4, a low pass filter 5 provided with an AR coat 5a, a CCD, and the like are sequentially arranged. In the light quantity diaphragm 2, a pair of optical members 9 and 10 made of a synthetic resin material having a thickness of 50 to 125 μm are attached to diaphragm support plates 7 and 8 that can move forward and backward.

  The optical members 9 and 10 do not transmit light, but cooperate with each other to form a diaphragm aperture to change the amount of transmitted light. There are cases of optical filters that regulate the amount of transmitted light.

  In the imaging optical system, the optical members 9 and 10 are arranged so that at least a part of the thickness direction of the optical members 9 and 10 is parallel to the optical axis, and are advanced and retracted toward the optical axis, and function as a light quantity adjusting device. 2 is attached. In this embodiment, the two optical members 9 and 10 are used. However, these optical members may be composed of two or more or one.

  2A to 2C show a cut surface in a state where the transparent resin substrate 11 which is the base material of the optical members 9 and 10 is cut through a cutting blade such as a Victoria blade type, a Thomson blade type, or a Pinnacle blade type. The configuration of the cut surface varies depending on the sharpness of the cutting blade and the cutting conditions.

  FIG. 2A shows the state of the end face of the optical member made of the transparent resin substrate 11 facing the surface that restricts the passing light in the imaging optical system. The transparent resin substrate 11 has a PET film having a thickness of 75 μm, for example. The cutting surface which carried out the shearing process in the thickness direction with the cutting blade of Victoria blade type is shown.

  From the upper side of the drawing in which the cutting blade enters, the sword 12, the shear surface 13, the fracture surface 14, the secondary shear surface 15, and the flash 16 are formed in order, but the area of the sword 12 is the smallest and the fracture surface 14 is almost present. The cut surface when not doing is shown. This indicates that the transparent resin substrate 11 has been cut to the end because the tip of the cutting blade has an acute angle.

  In this cut surface, the depth 12 is several μm wide, and the fracture surface 14 is 1% or less with respect to the film thickness of 75 μm. Further, the area of the shearing surface 13 including the secondary shearing surface 15 is slightly more than 90% of the entire end surface portion.

  The relationship between the shearing surface 13 and the fracture surface 14 is determined mainly by the surface accuracy and clearance of the punch and die during normal pressing, but when cutting with a cutting blade as in this embodiment, the cutting blade It is determined by the state of the tip and the stress distribution of the material. By appropriately controlling these, the secondary shear surface 15 is generated on the cut surface, and as a result, the shear surface 13 is increased.

  FIG. 2 (b) shows the cut surface when the tip of the cutting blade is gradually worn out and changes over time to an obtuse angle, thereby pressing the transparent resin substrate 11. Compared with the cut surface of FIG. 2 (a), the area where the cutting blade enters tends to increase the area of the droop 12, and the transparent resin substrate 11 is torn from the middle of the cutting process, and a large fracture surface 14 is generated. To do.

  FIG. 2 (c) shows a cut surface by a cutting blade whose tip is further worn. When the cutting blade enters the transparent resin substrate 11, since the tip of the cutting blade is obtuse, a great deal of pressure is applied, and the area of the sword 12 becomes larger than that of FIG. Will occupy most of the cut surface.

  FIG. 3A shows the cut state shown in FIG. 2A, and FIG. 3B shows a side view of the end including the cut portion in the cut state shown in FIG. 2B. Both the droop 12 and the fracture surface 14 are formed so as to recede from the shear surface 13 to the substrate side by shearing. Further, in FIG. 3A, the secondary shear surface 15 is generated, and the fracture surface 14 is hardly present on the side of any one 12.

  When strong light is incident on the cut portion from the side 12 or the flash 16 side, the incident light is easily reflected by the side 12 or the fracture surface 14 in the case of the cut surface as shown in FIG. Normally, the surface of the optical member is subjected to an antireflection treatment such as an antireflection film that prevents the reflection of harmful light, but such an antireflection layer is destroyed on anybody or fractured surface. is there. In addition, when the optical member transmits light such as an optical filter, the thickness in the direction of the optical axis of the portion where the drooping surface or fracture surface is generated is larger than the thickness of the portion other than the vicinity of the end portion. getting thin. For this reason, the amount of light transmitted through this portion and emitted to the opposite side is larger than the amount of light emitted outside the vicinity of the end portion, and the vicinity of the end portion easily shines when viewed from the output side.

  As shown in FIG. 3A, when the secondary shear surface 15 is provided on the cut surface, the wholly 12 becomes smaller. Further, the fracture surface 14 does not exist on the flash 16 side, and the reflection of light at the ridge line portion becomes extremely small. At the same time, even when the optical member transmits light such as an optical filter, the amount of light transmitted near the end as shown in FIG. 3B does not increase.

  In order to realize the optimum cut surface as shown in FIG. 2A, the cutting blade is managed and frequently subjected to polishing, etc., so that the mold is frequently adjusted, the cutting blade and the film There is a manufacturing method in which a protective film is sandwiched between substrates and cut.

  Further, when the secondary shearing surface 15 is generated in the normal press working, the life of the mold is adversely affected. However, when the resin substrate 11 is processed with a cutting blade as in the object of this embodiment, it is particularly large. There is no problem.

  In order to observe the degree of reflection of light at the end portions of the optical members 9 and 10 having the cut surface shown in FIG. 2A, light is applied from one side to place the end portions 21 in the same direction as shown in FIG. To observe visually. As a result, strong reflection and light entering and exiting from the end portion 21 were not recognized. In addition, when the optical member is an optical filter, the ridge line portion is also illuminated by the transmitted light near the end portion as a result of observing the end portion visually from the direction opposite to the direction in which light is applied contrary to FIG. The phenomenon was not observed.

  When incorporated in a video camera as shown in FIG. 1 as an imaging device, light that has once passed through the imaging device is reflected by the imaging device 6 and reenters the optical members 9 and 10. However, no matter what side of the optical member or flash side of the optical member 6 is directed to the image pickup device 6 side, no harmful ghosts or flares are generated, and good results are obtained. Even if the optical member was an optical filter, the same result was obtained for the reason described above.

  Furthermore, when not only the area in the optical axis direction of the shear surface 13 including the secondary shear surface 15 but also the length is 80% or more of the total length in the optical axis direction of the end portion of the optical member, a more preferable result is obtained. It was.

  In the second embodiment, under the same conditions as in the first embodiment, the cutting edge tip state and protection are performed so that the area of the shear surface 13 including the secondary shear surface 15 is about 80% of the entire area. The thickness of the film was adjusted.

  The cut surface was in the same state as in Example 1, and the secondary shear surface 15 was observed. As a result of observing this in the same manner as in Example 1, it was almost the same as Example 1 including the case where it was incorporated in a video camera, and good results were obtained.

  Further, as Comparative Example 1, under the same conditions as in Example 1, the tip state of the cutting blade and the thickness of the protective film were adjusted so that the area of the shear surface 13 was about 60%. At this time, the fracture surface 14 was about 25% of the entire surface, the cut surface was in the same state as in FIG. 2B, and the secondary shear surface 15 was not observed.

  As a result of observation by the same method as in the first embodiment, when the end portion 21 shines stronger than in the first embodiment and is incorporated in an imaging device as a video camera, harmful ghosts and flares may occur depending on the state of the subject. Was recognized.

  As Comparative Example 2, the tip state of the cutting blade and the thickness of the protective film were adjusted so that the area of the shearing surface 13 was about 35% under the same conditions as the previous examples. At this time, the fracture surface 14 was about 50% of the entire surface, the cut surface was in the same state as in FIG. 2B, and the secondary shear surface 15 was not observed.

  Then, as a result of observation by the same method as in Example 1, when the end 21 shines stronger than in Comparative Example 1 and is incorporated as an imaging device in a video camera, harmful ghosts and flares are generated depending on the state of the subject. Was recognized.

  As Comparative Example 3, the tip state of the cutting blade and the thickness of the protective film were adjusted so that the area of the shearing surface 13 was about 35% under the same conditions as the previous examples. The fracture surface at this time was about 75% of the whole, the cut surface was in the same state as in FIG. 2C, and the secondary shear surface 15 was not observed.

  As a result of observation by the same method as in Example 1, when the end portion 21 shines stronger than in Comparative Example 2 and is incorporated as an imaging device in a video camera, harmful ghosts and flares are generated depending on the state of the subject. Was recognized.

Further, an ND film 31 in which Al ₂ O ₃ films 31 a and Ti _x O _y films 31 b as shown in FIG. 5 are alternately laminated on the transparent resin substrate 11 as described above, and an MgF ₂ film 31 c is laminated on the uppermost layer. ND filter 32 for adjusting the amount of transmitted light in the visible wavelength region is prepared. The ND film 31 may be formed at any step before or after the transparent resin substrate 11 is cut.

  FIGS. 6A to 6C are explanatory diagrams of the ND filter 32 that is used by being inserted into a diaphragm opening formed by two optical members 9 and 10 in order to adjust the amount of incident light. The rhomboid diaphragm opening 33 is formed by the operation of the optical members 9 and 10, and the ND filter 32 is driven separately from the diaphragm opening 33. Even if the area of the diaphragm opening 33 is constant, the ND filter 32 The amount of light can be adjusted.

  6A shows a state in which the ND filter 32 is retracted out of the aperture opening 33, FIG. 6B shows a state in which the edge 32a of the ND filter 32 is located in the aperture opening 33, and FIG. c) shows a state in which the ND filter 32 covers the aperture opening 33.

  When the ND filter 32 is operated in this manner, it is not necessary to extremely reduce the size of the aperture opening 33, and image deterioration due to small aperture diffraction can be prevented.

  As shown in FIG. 6B, when the edge 32 a of the ND filter 32 is inserted into the aperture opening 33, the light beam enters the edge 32 a of the ND filter 32. At this time, as the droop 12 of the edge portion 32a is reduced and the angle of the ridge portion is made as close as possible to 90 degrees, the reflection of the light beam is reduced and the ghost light can also be reduced.

  Furthermore, if the concentration of the ND film 31 is high, the transmitted light can be attenuated, so that ghost light and flare light due to regularly transmitted light components hardly occur.

  However, if the concentration of the ND film 31 is low, more light components are transmitted and ghost light and flare light are likely to be generated. However, the light incident on the edge 12 of the edge 32a is re-reflected in the direction of the image sensor. Will not cause any problems.

  In particular, in recent years, an ND filter 32 having a gradation in which the filter density continuously increases as the distance from the edge 32a is considered in consideration of a density drop or a transmission phase difference.

  The ND filter 32 having this gradation is a vapor deposition type filter, and the concentration decreases toward the edge 32a. As the edge 32a is approached, the attenuation of light decreases, so that the amount of transmitted light increases and the back surface reflection is also affected. Therefore, the reflectance of light is relatively high and ghost light and flare light are likely to occur.

  That is, as the edge 32a is approached, in the case of the ND filter 32 having gradation, ghost light and flare light are particularly likely to occur near the edge 32a. However, this can be solved by eliminating the drool 12 at the edge 32a of the ND filter 32, that is, by bringing the angle of the corner closer to 90 degrees.

DESCRIPTION OF SYMBOLS 1, 3, 4 Lens 2 Light quantity stop 5 Low-pass filter 6 Image pick-up element 7, 8 Support plate 9, 10 Optical member 11 Transparent resin substrate 12 Drain 13 Shear surface 14 Fracture surface 15 Secondary shear surface 16 Beam 32 ND filter 33 Aperture opening Part

Claims (5)

An optical system that adjusts the light passing therethrough by moving the thickness direction of at least a part in a state parallel to the optical axis in the imaging optical system that forms a subject image on the imaging device and moving back and forth in the imaging optical system. The member has a secondary shearing surface formed at the end, and the area of the shearing surface including the secondary shearing surface with respect to the area of the end facing the imaging optical system is 80% or more. An optical member characterized by the above.   The shearing surface including the secondary shearing surface has a length of 80% or more with respect to the length of the end portion of the end portion facing the imaging optical system in the optical axis direction. The optical member according to claim 1.   3. The optical member according to claim 1, wherein the optical member is an ND filter that is made of a base material of a transparent resin substrate and adjusts a transmitted light amount in a visible wavelength region that passes therethrough.   An optical system that adjusts the light passing therethrough by moving the thickness direction of at least a part in a state parallel to the optical axis in the imaging optical system that forms a subject image on the imaging device and moving back and forth in the imaging optical system. A light amount adjusting device having a member, wherein the optical member has a secondary shearing surface at the end, and an area of the shearing surface including the secondary shearing surface with respect to an area of the end facing the imaging optical system Is a light amount adjusting device characterized by being 80% or more. A camera provided with the optical member according to any one of claims 1 to 3 or the light amount adjusting device according to claim 4 in an imaging optical system.

Images