JP2010145941A - Nd filter and light quantity control diaphragm using nd filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress decrease of light quantity passing through an opening due to a ND (neutral density) filter to the minimum when a diaphragm is opened while reducing an element for size increase in an imaging optical system and influence of warpage of the ND filter. <P>SOLUTION: The ND filter 26 attached to one of diaphragm blades 22, 23, comprises a filter part 26a for controlling transmitted light quantity and a filter part 26b which has light transmittance higher than that of the filter part 26a and about equal to that of a substrate. The filter part 26a is provided in a part of the filter part 26b and is formed to a triangle shape from one end part of the filter part 26b toward a facing another end part. When the diaphragm blades 22, 23 operate to make a diameter of a diaphragm aperture 29 smaller than the inside diameter of an opening 30 provided in a bottom board, the diameter of the diaphragm aperture 29 becomes a substantial diaphragm aperture diameter. When the diaphragm diameter becomes smaller than a prescribed value as shown in (c), the diaphragm aperture 29 is covered with the filter part 26a, and image degradation due to light diffraction produced by decrease in the diaphragm diameter is prevented. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an ND filter used in an optical apparatus such as a digital video or a digital still camera, and a light amount reduction device using the ND filter.

  In an imaging optical system such as a digital still camera and a digital video, a light amount diaphragm device that adjusts a light amount by changing an aperture diameter formed by a diaphragm blade is used.

  FIG. 10 is a configuration diagram of an imaging optical system such as a video camera or a digital still camera. A lens 1, a light amount diaphragm device 2, lenses 3, 4, 5, a low-pass filter 6, and a solid-state image sensor 7 are arranged from the front along the optical axis. The light quantity diaphragm device 2 includes diaphragm blades 8 and 9 and a diaphragm base plate 10, and an ND filter (Neutral Density) 11 for light quantity adjustment is bonded to the diaphragm blade 8.

  FIG. 11 shows a configuration of a conventional light quantity diaphragm device 2. The light quantity diaphragm device 2 enables the aperture diameter of the diaphragm aperture 12 to be changed by linearly driving two diaphragm blades 8 and 9 in opposite directions. With this operation, the amount of light passing through the aperture opening 12 can be adjusted.

  An ND filter 11 is integrally bonded and fixed to the diaphragm blade 8, and a part of the diaphragm opening 12 is covered with the ND filter 11. A straight line passing through the center O of the aperture opening in the direction orthogonal to the paper surface is the optical axis. Since the aperture 13 is provided in the diaphragm base plate 10 and its inner diameter is unchanged, even if the aperture diameter of the diaphragm aperture 12 is larger than the inner diameter of the aperture 13 as shown in FIG. As the aperture diameter, the diameter of the opening 13 is maximized. Further, as shown in FIG. 11B, when the aperture diameter of the aperture 12 is smaller than the inner diameter of the aperture 13, the diameter of the aperture 12 becomes a substantial aperture diameter.

  When the aperture diameter is reduced, a diffraction phenomenon of light passing through the aperture opening 12 is likely to occur. In order to remove the adverse effect of diffraction on the small aperture side, the ND filter 11 is attached to the aperture blade 8 and the light transmittance is decreased simultaneously with the reduction of the aperture diameter as shown in FIG. Thus, practically no aperture diameter smaller than the aperture diameter of the stop, which is a problem even in a wider luminance range, is achieved.

  As types of the ND filter 11, in addition to the uniform density type on the entire surface, a multi-density ND filter composed of a plurality of density regions disclosed in Patent Document 1, a gradation ND filter disclosed in Patent Document 2, and the like are known. Yes.

JP 2004-117718 A JP 2005-326687 A

  In the light quantity diaphragm device 2 described above, when an object to be photographed is dark, such as indoor shooting, the light quantity tends to be insufficient even when the diaphragm is opened, and the image quality of the photographed image tends to deteriorate.

  For this reason, it is preferable that the ND filter 11 is completely retracted from the aperture opening 13 when the aperture is opened to increase the amount of light passing through the aperture 13. However, in order to completely retract the ND filter 11 from the aperture opening 13, it is necessary to increase the opening / closing stroke of the aperture blade 8 to which the ND filter 11 is attached.

  FIG. 12A shows a state in which a part of the ND filter 11 remains in the opening 12 when the diaphragm is opened. However, if the ND filter 11 is completely retracted from the diaphragm opening 13, FIG. As shown in b), the ND filter 11 needs to be retracted to the right in the drawing by the distance X. For this purpose, the diaphragm blade 8 to which the ND filter 11 is bonded is moved backward. In this case, the diaphragm blade 9 moves in a direction opposite to the diaphragm blade 8. As a result, a space for the increase Y of the moving distance of the diaphragm blades 8 is required for the light quantity diaphragm device 2, which results in an increase in the size of the diaphragm device.

  In addition, as shown in FIG. 13, the conventional ND filter 11 includes an example in which the tip of the ND filter 11 on the opening 12 side has an arc shape. However, the ND filter 11 produced by forming an inorganic hard film on a resin base material is likely to be warped due to changes in humidity and temperature, and the shape protruding from the opening portion 13 is easily affected by this. There is a risk of interference. For this reason, it is necessary to take measures such as providing a sufficient distance between the ND filter 11 and the diaphragm blade 9 facing the ND filter 11. As a result, the diaphragm device becomes thick and the production process becomes complicated. .

  An object of the present invention is to provide an ND filter that minimizes the reduction in the amount of light passing through the opening due to the ND filter when the diaphragm is opened while reducing the influence of the warping of the ND filter and the elements that increase the size of the imaging optical system. An object of the present invention is to provide a light quantity stop device using an ND filter.

  In order to achieve the above object, an ND filter according to the present invention includes a first light attenuator that attenuates the amount of transmitted light and a second light attenuator that transmits more light than the first light attenuator. In the ND filter, the first light attenuating part is formed in a part of the second light attenuating part so as to have a region that protrudes from one end to the other opposite end.

  In addition, the light quantity diaphragm device using the ND filter according to the present invention includes an aperture that allows light to pass through, a diaphragm blade that adjusts the amount of light that passes through the aperture, and light that passes through a diaphragm aperture formed by the diaphragm blade. The ND filter uses a first light attenuating unit for attenuating the amount of transmitted light, and a second amount of light transmitted through the first light attenuating unit is larger than that of the first light attenuating unit. It has a light attenuating part, and the 1st light attenuating part formed the field which became convex toward the other end which counters from a part of the 2nd light attenuating part. .

  According to the ND filter and the light quantity diaphragm device using the ND filter according to the present invention, the aperture is opened while suppressing the enlargement and the warpage of the ND filter without changing the density of the ND filter and the size of the minimum diaphragm diameter. It is possible to improve the image quality by increasing the amount of photographing at the time.

  The present invention will be described in detail based on the embodiment shown in FIGS.

  FIG. 1 is a configuration diagram of a light quantity diaphragm device using an ND filter according to the first embodiment. In FIG. 1A, the light quantity diaphragm device 20 is composed of diaphragm blades 22 and 23 and a drive arm 25 that rotates about a rotation shaft 24 and drives the diaphragm blades 22 and 23. The ND filter 26 is fixed with an adhesive 27.

  As shown in FIG. 1A, the ND filter 26 has a filter unit 26a that is a first light attenuating unit that adjusts the amount of transmitted light, and has a light transmittance higher than that of the first light attenuating unit and almost equal to the light transmittance of the substrate. And a second light attenuating filter 26b. The filter part 26a is provided in a part of the filter part 26b, and is formed in a triangular shape from one end part of the filter part 26b toward the other opposite end part. The light transmittance of the substrate used for the ND filter 26 is normally 80% or more, and the light transmittance of the filter portion 26b is about 80%.

  Assuming that the line extending through the aperture opening center O and extending in the operation direction of the ND filter 26 is the center line C of the ND filter 26, the boundary line of the filter unit 26a to the filter unit 26b is the two oblique sides of the triangle. The vicinity of the line C is the apex of the triangle.

  The aperture blades 22 and 23 are provided with linear guide holes 22a, 22b, 23a and 23b. These guide holes 22a, 22b, 23a, and 23b are guided by guide pins formed on the diaphragm base plate, and the diaphragm blades 22 and 23 move linearly in parallel with the center line C.

  The drive arm 25 is rotated by the rotational motion transmitted to the rotary shaft 24 from a drive motor (not shown). The aperture blades 22 and 23 are provided with long holes 22c and 23c, and the drive arm 25 is provided with drive pins 28a and 28b. The drive pin 28a is fitted into the long hole 22c, and the drive pin 28b is fitted into the long hole 23c. Match.

  When the drive arm 25 rotates as shown in FIG. 1 (b), the drive pins 28a and 28b move the diaphragm blades 22 and 23 in opposite directions, and the diaphragm aperture formed by the diaphragm blades 22 and 23. The size of the opening diameter of 29 changes.

  With this operation, the amount of light passing through the aperture opening 29 can be adjusted, and a straight line passing through the center O of the aperture opening in the direction orthogonal to the paper surface becomes the optical axis. Since the inner diameter of the circular opening 30 provided in the diaphragm base plate does not change, even if the aperture diameter of the diaphragm opening 29 is larger than the inner diameter of the opening 30, the substantial diaphragm opening diameter is The diameter becomes the maximum.

  Further, when the aperture diameter of the aperture opening 29 is smaller than the inner diameter of the opening portion 30, the diameter of the aperture opening 29 becomes a substantial aperture aperture diameter. When the aperture diameter becomes smaller than a predetermined value as shown in FIG. 1C, the aperture opening 29 is covered with the filter portion 26a of the ND filter 26, and an image due to diffraction of light generated when the aperture diameter becomes smaller. Deterioration is prevented.

  2A shows a light amount diaphragm 20 using the ND filter 26, and FIG. 2B shows a conventional diaphragm apparatus using the ND filter 11. As shown in FIG. If the operation stroke of the diaphragm blades 22 and 23 is reduced in order to reduce the size of the light quantity diaphragm device 20, even if the diaphragm blades 22 and 23 fully open the opening 30, the conventional rectangular shape shown in FIG. A part of the ND filter 11 is exposed in the opening 30. The hatched portion represents the filter portion of the ND filter 11 that covers the opening 30 in the fully open state.

  By adopting the shape shown in FIG. 2A as in this embodiment, the area covering the opening 30 when the filter portion 26a of the ND filter 26 is open is smaller than that of the conventional ND filter 11. I understand that On the other hand, in the ND filter 26, even when the aperture diameter is reduced to the same minimum aperture diameter as the conventional type as shown in FIG. 2C, the entire area of the aperture opening 30 can be covered with the filter portion 26a.

  Here, the shape of the aperture opening 29 is determined by the inner edge portions 22d, 22e, 23d, and 23e of the apertures 29 of the aperture blades 22 and 23 as shown in FIG. Accordingly, the filter portion 26a of the ND filter 26 is formed on the opening direction side on the opening direction side with respect to the inner edge portions 22d and 22e of the diaphragm blade 22 and on the diaphragm direction side of the filter portion 26a with the inner edge portions 23d and 23e of the diaphragm blade 23. It is desirable to make the shape close to the inner edge shape. Furthermore, it is more preferable to form in a shape that can completely cover the minimum aperture diameter.

  However, the shape of the filter portion on the aperture direction side and the shape of the inner edge portion do not have to be completely the same shape, and in the filter portion 26a of the ND filter 26 as shown in FIGS. However, it has an arcuate convex shape on the aperture direction side from the outside. Alternatively, as shown in FIG. 3C, the effect of the present invention can be obtained even when the rectangular shape is convex toward the aperture direction.

  The filter part 26a is supported and fixed widely by the inner edge parts 22d and 22e of the aperture blade 22 by a filter part 26b having a high light transmittance and a large area. For this reason, the influence of the curvature by humidity or a temperature change can be reduced rather than the filter part 26a being independently exposed in convex shape by the aperture opening 30 side. Therefore, interference with the light quantity diaphragm 20 and its peripheral members can be reduced, and as a result, the apparatus can be reduced in size and thickness.

  As a material of the ND filter 26, a material in which an ND film 32 is formed on a transparent substrate 31 as shown in FIG. 4 is generally used. The material of the transparent substrate 31 used in the ND filter 26 is not particularly limited, but a material having transparency and mechanical strength is preferable, and film-like PET (polyethylene terephthalate) is mainly used. In addition, PEN (polyethylene naphthalate), polycarbonate, polyimide resin, norbornene resin, polystyrene, polyvinyl chloride, polyarylate, polysulfone, polyethersulfone, polyetherimide, acrylic resin, and the like are used. Further, the thickness of the transparent substrate 31 is desirably as thin as possible from the viewpoint of reduction in size and weight while maintaining the rigidity as the ND filter 26. Specifically, the thickness is preferably 300 μm or less, more preferably 50 to 100 μm.

As the ND film 32 formed on the transparent substrate 31, a light absorption layer and an antireflection layer for adjusting the light transmittance are formed by any film forming means such as vacuum deposition, sputtering, ion plating, ink jet, and printing. To do. FIG. 4 is a schematic configuration diagram showing an example of the configuration of the ND filter 26 in which an ND film is formed by vacuum deposition. The first to eighth layers are composed of alternating layers of aluminum oxide (Al ₂ O ₃ ) and titanium oxide (TiOx), and the outermost layer is composed of an antireflection layer made of magnesium fluoride (MgF ₂ ). The number of layers and the material are not particularly limited.

  FIG. 5 is a schematic view of a vacuum deposition apparatus for manufacturing an ND filter. A rotation dome 42 is provided in the vapor deposition chamber 41, and a vapor deposition jig 43 holding the substrate 31 of the ND filter 26 is set on the rotary dome 42. During film formation, the rotating dome 42 rotates around the rotation shaft 44 in order to make the substrate temperature and the film thickness of the deposited film uniform. Further, materials for each layer constituting the ND film 32 are prepared, such as aluminum oxide for the vapor deposition source 45a, titanium oxide for the vapor deposition source 45b, and magnesium fluoride for the vapor deposition source 45c.

  When the vapor deposition process starts, the inside of the vapor deposition chamber 41 is maintained in a vacuum state, and the vapor deposition jig 43 is heated to a predetermined temperature. When the pressure and temperature reach predetermined values, the vapor deposition source 45a is heated as the first layer of the ND film 32, the vapor deposition material is evaporated, and the vapor deposition film is formed on the substrate 31 set in the vapor deposition jig 43. A predetermined thickness is formed. Thereafter, the deposition source 45 is switched as necessary to form a multilayer film.

  The transparent substrate 31 is set in a vapor deposition jig 43 as shown in FIG. 6A, and an opening is formed on the substrate 31 in the shape of the filter portion 26a of the ND filter 26 as shown in FIG. 6B. The deposited vapor deposition mask 46 is held. In this state, the ND film 32 is formed on the transparent substrate 31 in the shape of the filter portion 26a as shown in FIG. When the formation of the ND film is completed by the above procedure, the ND filter 26 can be obtained by cutting into an ND filter shape as shown in FIG.

  FIG. 7 shows an ND filter and a light quantity stop device according to the second embodiment. The ND filter 26 according to the second embodiment has two types of density regions, that is, a high density part filter part 26a that is a first light attenuation part and a low density part filter part 26c that is a second light attenuation part. ing.

  The darker the ND filter 26, the more the transmitted light can be attenuated, so that the minimum aperture diameter of the stop can be increased by that amount, and the influence of diffraction by the small stop can be reduced. However, on the other hand, when there are portions where the filter portions 26a and 26c are present in the opening 29 and portions where the filter portions 26a and 26c are not present, there is a possibility that unevenness in the amount of light called shading may occur due to the density difference.

  Therefore, in the second embodiment, the ND filter 26 is provided with a filter portion 26a used in a small-aperture state and a filter portion 26c having a lighter density than that, thereby eliminating an abrupt density difference. As in the first embodiment, the filter portion 26a has a convex shape in the vicinity of the center line C of the ND filter 26 on the diaphragm direction side of the outside thereof. In the ND filter 26 of the second embodiment, as in the first embodiment, the ND film 32 is formed on the filter portion 26a, and then the substrate 31 is turned over to form another ND film 32 on the entire back surface. can get.

  Also in the second embodiment, the filter portion 26a is formed in a part of the filter portion 26c having a higher light transmittance and a larger area, and the filter portion 26c is widely supported by the inner edge portions 22d and 22e of the aperture blade 22. It is fixed. For this reason, it is possible to reduce the influence of warping as in the first embodiment.

  FIG. 8 shows an ND filter and a light quantity stop device according to the third embodiment. The ND filter 26 of the third embodiment has a filter part 26a that is a high-density part that is a first light attenuating part and a plurality of light transmittances that are second light-attenuating parts, and the density changes stepwise. And a filter unit 26d having a density change. For this reason, the effect of preventing unevenness in the amount of light due to the density difference is further increased, and the density of the filter portion 26a can be further increased. As a result, the minimum aperture diameter can be increased and the influence of light diffraction by the small aperture can be reduced.

  In the ND filter 26 according to the third embodiment, the filter portion 26a has a convex shape in the vicinity of the center line C of the ND filter 26 on the diaphragm direction side from the outside thereof as in the first embodiment. The filter unit 26d whose density gradually changes from the filter unit 26a also has a density distribution so as to follow the convex shape of the filter unit 26a.

  Further, as a modification of the third embodiment, a gradation density changing unit in which the density of the filter unit 26d is continuously changed can be used. In this way, the effect of preventing unevenness in the amount of light due to the density difference is further enhanced, and a high-quality image can be obtained.

  Also in the third embodiment, the filter portion 26d is widely supported and fixed to the inner edge portions 22d and 22e of the diaphragm blade 22, and therefore, the influence of warpage can be reduced as in the previous embodiment.

  As shown in FIG. 9A, the ND filter 26 having the filter portion 26d whose concentration continuously changes is spaced from the transparent substrate 31 on the vapor deposition jig 43 by the frame 47, as shown in FIG. It is obtained by setting the vapor deposition mask 46 shown in b) to form a film. On the substrate 31, a filter part 26a and a filter part 26d are formed as shown in FIG. 9C, and the ND filter 26 is obtained by cutting the filter part 26d as shown in FIG. 9D.

It is a block diagram of the light quantity aperture device to which the ND filter of Example 1 was attached. It is the block diagram which compared the light quantity diaphragm device and the conventional light quantity diaphragm apparatus. It is a block diagram of the example of a shape of the light quantity aperture apparatus of Example 1. FIG. It is a block diagram of an ND filter. It is a block diagram of a vacuum evaporation system. It is explanatory drawing about the preparation methods of ND filter. It is a block diagram of the light quantity diaphragming apparatus of Example 2. It is a block diagram of the light quantity diaphragming apparatus of Example 3. FIG. 10 is an explanatory diagram illustrating a method for producing an ND filter according to Example 3. It is the schematic of the imaging optical system which uses an ND filter and a light quantity aperture device. It is a block diagram of the conventional light quantity aperture apparatus. It is a block diagram of the light quantity diaphragm | throttle device of the state which retracted | removed the light attenuation part of the conventional ND filter completely from the opening part. It is a block diagram of the light quantity aperture apparatus which attached the ND filter of the other conventional shape.

Explanation of symbols

22, 23 Diaphragm blade 26 ND filter 26a-26d Filter part 29 Opening 30 Opening part 31 Transparent substrate 32 ND film

Claims (6)

  An ND filter having a first light attenuator that attenuates the amount of light transmitted therethrough and a second light attenuator that transmits a larger amount of light than the first light attenuator, wherein the first light attenuator is An ND filter, wherein a region that protrudes from one end portion to the other end portion that faces the part of the second light attenuating portion is formed.   The ND filter according to claim 1, wherein the second light attenuator has a light transmittance of 80% or more.   3. The ND filter according to claim 1, wherein the first light attenuating unit continuously changes in light transmittance.   3. The ND filter according to claim 1, wherein the first light attenuating unit includes a plurality of regions having different light transmittances.   A light quantity diaphragm device using an opening for transmitting light, a diaphragm blade for adjusting the amount of light passing through the opening, and an ND filter for attenuating light passing through a diaphragm opening formed by the diaphragm blade, The ND filter includes a first light attenuating unit that attenuates the amount of light transmitted therethrough and a second light attenuating unit that transmits a larger amount of light than the first light attenuating unit. A light quantity stop device using an ND filter, characterized in that a part of the second light attenuating part is formed with a region that protrudes from one end to the other opposite end.   6. The ND filter according to claim 5, wherein at least a part of the first light attenuating portion is exposed to the opening when the aperture blade is configured to fully open the opening. Light quantity diaphragm device.