JP5410473B2 - Optical member - Google Patents

Description

  The present invention relates to an optical member that is mounted on an imaging optical system such as a video camera or a still camera, and particularly prevents the generation of ghost light and flare light.

  In imaging optical systems such as video cameras and still cameras, a light quantity adjustment device is used to adjust the light quantity by changing the aperture diameter using a plurality of aperture blades. If the aperture diameter becomes too small, light diffraction will occur. Deterioration of optical performance due to the problem becomes 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.

  As shown in FIG. 16, there is a case where nothing is processed while the aperture edge 1a of the aperture blade 1 forming the aperture opening is cut. In this case, the scattered light spreading in the random direction is small among the light hitting the opening edge 1a, and the ghost light strengthened in the direction perpendicular to the surface of the opening edge 1a is increased on the imaging surface. . When such unnecessary reflection occurs inside the taking lens, halo light or ghost light is generated on the screen, and the image quality deteriorates.

  For this reason, ghost light or the like is suppressed by applying black paint on the inside of the lens barrel or on the surface of the aperture blade, or by devising the arrangement of the ND filter to be 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 hitting the edge of the edge of the aperture blade or the edge of the ND filter becomes harmful light.

  Conventionally, for example, as disclosed in Patent Document 1, all or part of the aperture end face of the diaphragm blade is provided with minute irregularities, and the light beam hitting 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 harmful light.

  Further, in Patent Document 2, by irregularly forming a plurality of stepped steps on the end face of the diaphragm blade, the light beam hitting 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.

  Further, Patent Document 3 discloses a light amount adjusting device in which an ND filter covering an opening is attached to an aperture blade, and the ND filter is provided with a plurality of density regions set to different uniform transmittances. The plurality of density regions of the ND filter are set so that the transmittance decreases sequentially from the inside to the outside of the opening, thereby avoiding image quality deterioration due to a small aperture state.

  In addition, part of the light that passes through the ND filter and enters the image sensor may be reflected by the surface of the image sensor or the surface of a cover glass, a crystal low-pass filter, an infrared cut filter, or the like and return to the subject side. . Then, the return destination is reflected again by the surface on the image sensor side of the ND filter and the surface on the object side, and the reflected light enters the image sensor to generate ghost light. As a countermeasure against this ghost light, Patent Document 4 proposes a light amount adjusting device in which an antireflection film is provided on the surface of the ND filter on the image sensor side.

  As the ND filter, there are known a type in which an organic dye or pigment that absorbs light is mixed into a transparent resin material and kneaded, and a type in which an optical thin film is deposited on the surface of a base film substrate. Yes. The advantage of the kneading type ND filter is that a filter with a constant concentration can be manufactured in large quantities at a low cost, but the rate of change in transmittance depending on the wavelength is larger than that of the vapor deposition type ND filter. Therefore, many of the ND filters used in the light amount adjusting device are of the vapor deposition type.

  For the vapor deposition type ND filter, a resin film having a low haze value indicating the transmittance of the material and a high light transmittance is used. Specifically, for example, a transparent plastic film such as polyethylene terephthalate, polycarbonate, acrylate, cycloolefin, polymethylpentene or the like with a light absorption film is known.

  If the transparent plastic film has a large haze value, the image deteriorates due to scattering, so a film having a small haze value is desirable. The reason for using a resin film for the ND filter is that it is light and easy to cut. The ND filter made of resin has a thickness of 50 to 300 μm, and a substrate of 100 μm is usually used.

  Since the ND filter uses a resin film as a base material, as shown in FIG. 17, when the edge 2a that is a cut surface of the ND filter 2 is not particularly processed, the light hitting the end face or the ridge line is reflected. And easy to penetrate. Thereby, there is little scattered light which spreads in a random direction, and it becomes easy to become ghost light strengthened in the vertical direction with the edge 2a.

Japanese Patent Laid-Open No. 5-281590 JP 2002-229095 A Japanese Patent Laid-Open No. 2-190833 JP 2000-36917 A

  As described in Patent Document 1, in the method of providing an uneven portion on the end face of the diaphragm blade, since the incident light is only distributed to the left and right with respect to the traveling direction, a certain degree of improvement can be expected. There is an outbreak.

  In addition, in the method of providing a stepped step on the end face of the diaphragm blade from the light incident side to the light exit side as 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.

  However, when this technique is applied to the ND filter, in the ND filter 5 in which the ND film 4 is pasted on the film substrate 3 as shown in FIG. 18, the light transmitted through the edge 4a of the ND film 4 and traveling toward the emission side Because it exists, the method of forming the steps in a staircase pattern is not a countermeasure. That is, when the ND filter 5 attenuates the light only slightly, the scattered light spreads in an irregular direction is small, and the light component due to the reflected light and the light component due to the transmitted light are on the edge of the ND filter 5 on the imaging plane. It is easy to become ghost light that is strengthened in the vertical direction.

  FIGS. 19A to 19C show the shape of the edge portion 6a of the ND filter 6 conventionally employed to be inserted into the opening portion of the diaphragm blade in order to adjust the amount of incident light, and the edge portion 6a. An angle is given to the edge portion of the light to regulate generation of ghost light or the like. However, when the illuminance of the subject is strong, it is not enough to eliminate ghost light and flare light just by giving an angle to the edge portion in this way, and it is not possible to ignore reflected light and further transmitted light at the end face. Can not.

  The object of the present invention is to eliminate the above-mentioned problems and prevent image quality deterioration due to reflected light and transmitted light at the edge line of the edge of the optical element that forms the opening of the imaging optical system or is located in the opening. It is to provide an optical member that can be used.

In order to achieve the above object, an optical member according to the present invention is an optical member in which an optical element is disposed in an imaging optical system that forms a subject image on the imaging element, and the optical element is an edge that forms an opening. A non-periodic concavo-convex part is formed along at least one ridge line of the edge and the edge that enters the opening, and the concavo-convex part protrudes along the optical axis of the imaging optical system .

  The optical member according to the present invention eliminates the generation of ghost light and flare light even when the edge of the optical element forms an opening or is disposed within the opening, and restricts the operation depending on the insertion position of the optical element. No need to consider.

  Further, even when the edge of the ND filter having a low density is disposed in the opening, it is possible to reduce the generation of ghost light and flare light. Furthermore, if irregular irregularities are formed on the end face, it becomes a further measure against harmful light.

It is a block diagram of an imaging device. 3 is a perspective view of a diaphragm blade according to Embodiment 1. FIG. It is a partial expansion perspective view of an aperture blade. It is operation | movement explanatory drawing of an aperture blade. 6 is a partially enlarged perspective view of an ND filter according to Embodiment 2. FIG. It is a partial expansion perspective view of another ND filter. It is explanatory drawing of a mode that an ND filter moves with respect to an aperture opening. It is operation | movement explanatory drawing of a ND filter. 6 is a partially enlarged perspective view of an ND filter according to Embodiment 3. FIG. It is a partial expansion perspective view of the ND filter of a modification. FIG. 9 is a configuration diagram of a diaphragm mechanism according to a fourth embodiment. It is a figure which shows a mode that an aperture blade moves with respect to a pupil diameter. 6 is a partially enlarged perspective view of an ND filter according to Embodiment 4. FIG. FIG. 10 is an operation explanatory diagram of an ND filter according to a fifth embodiment. It is a block diagram of the cutting blade for uneven | corrugated | grooved part formation. It is operation | movement explanatory drawing of the conventional aperture blade. It is operation | movement explanatory drawing of the conventional ND filter. It is operation | movement explanatory drawing of the conventional ND filter. It is a perspective view of the conventional ND filter.

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

  FIG. 1 is a configuration diagram of an imaging apparatus. In an imaging optical path, a lens 11a, an aperture mechanism 12, lenses 11b and 11c, a low-pass filter 13 provided with an AR coat 13a, and a solid-state imaging device 14 are sequentially arranged. The diaphragm mechanism 12 is made of a synthetic resin that can move opposite to the support plate 15 and is attached with two diaphragm blades 16 and 17 having a thickness of 50 to 125 μm as a pair.

  FIG. 2 is a perspective view of the diaphragm blade 16 according to the first embodiment. The opening edge 16a of the diaphragm blade 16 cooperates with the opening edge of the diaphragm blade 17 to form a substantially diamond-shaped diaphragm opening on the imaging optical path. To do. FIG. 3 is an enlarged perspective view of the opening edge portion 16a. Along the ridge lines 16b and 16c before and after the opening edge portion 16a, uneven portions having various sizes and aperiodicity are formed by a minute sawtooth shape. Yes. The irregular concavo-convex portions form concavo-convex portions having a height of about 0.5 to 10 μm. A similar concavo-convex portion is also provided on the ridgeline of the opening edge portion 17a which is a pair of the diaphragm blades 17.

  In the diaphragm blades 16 and 17 configured as described above, when the incident light beam hits the opening edge portions 16a and 17a, variously depending on the uneven portions provided on the ridge lines 16b, 16c, 17b and 17c as shown in FIG. Reflects in any direction. By making the diffusion direction in the ridge lines 16b, 16c, 17b, and 17c irregular, the directivity of the reflected light is weakened and the light is diffused, so that the ghost light can be weakened. Further, among the ridge lines 16b, 16c, 17b, and 17c, since the diffusion effect is particularly great in the ridge lines 16b and 17b on the light incident side, the uneven portions may be provided only on the ridge lines 16b and 17b.

  If this uneven portion has periodicity, the reflected light may interfere and strengthen each other, but by making the uneven portions of the ridge lines 16b, 16c, 17b, and 17c non-periodic as in this embodiment, the reflected light Interference can be weakened.

  In addition, about the end surface in opening edge part 16a, 17a, you may make it a rough surface and may provide the irregular uneven | corrugated groove | channel which is mentioned later.

  FIG. 5 shows an edge portion 21a of the ND filter 21 having a predetermined light transmittance according to the kneading type, vapor deposition type or the like of the second embodiment, and along the ridge lines 21b and 21c before and after the edge portion 21a of the ND filter 21. As with the diaphragm blades 16 and 17, a non-periodic uneven portion is provided. These irregular irregularities form various irregularities of 0.5 to 10 μm substantially continuously. In addition, uneven grooves 21e having various heights are formed in the thickness direction of the edge surface 21d orthogonal to the ridge lines 21b and 21c.

  In addition, as shown in FIG. 6, this uneven | corrugated groove | channel 21e can also be formed toward the direction orthogonal to the thickness direction of the edge surface 21d of the ND filter 21, ie, a direction parallel to the ridgelines 21b and 21c.

  The ND filter 21 is inserted and used in a diaphragm opening formed by two diaphragm blades 16 and 17 in order to adjust the amount of incident light. FIGS. 7A to 7C are explanatory diagrams when the ND filter 21 is moved for light amount adjustment. A diamond-shaped diaphragm opening 22 is formed by the operation of the diaphragm blades 16, 17, and the ND filter 21 is driven separately from the diaphragm blades 16, 17. Even if the area of the diaphragm opening 22 is constant, the ND filter 21 can adjust the light quantity.

  7A shows a state in which the ND filter 21 is retracted from the aperture opening 22, FIG. 7C shows a state in which the ND filter 21 covers the aperture opening 22, and FIG. 7B shows an edge 21a of the ND filter 21. The state which has appeared in the aperture opening 22 is shown.

  When the ND filter 21 is operated in this way, it is not necessary to extremely reduce the size of the aperture 22 by the aperture blades 16 and 17, and image deterioration due to small aperture diffraction can be prevented. As shown in FIG. 7B, when the edge portion 21 a of the ND filter 21 is inserted into the aperture opening 22, the light rays hit the ridge lines 21 b and 21 c of the ND filter 21 as shown in FIG. 8. At this time, if the ridge lines 21b and 21c have serrated minute irregular irregularities, the light rays are reflected in various directions, and ghost light can be reduced.

  In addition, since the ND filter 21 made of a resin film generally has a thickness of 50 to 300 μm, when the illuminance of the subject is strong, only ridges 21b and 21c of the ND filter 21 are provided with minute sawtooth-shaped uneven portions. Then, the ghost light and the flare light are not sufficiently eliminated. That is, since the reflected light and transmitted light on the edge surface 21d of the ND filter 21 cannot be ignored, providing the sawtooth-shaped uneven groove 21e also on the edge surface 21d as described above weakens the directivity of the reflected light, More effective in eliminating flare light.

  FIG. 9 shows a perspective view of the ND filter 31 of the third embodiment. In the vapor deposition type ND filter 31 in which the ND film 33 is attached to the back surface of the transparent film substrate 32, the ridge line 33 a that is the edge of the ND film 33 is provided with an uneven portion. In this case, the amount of light that passes through the ND filter 31 is larger in the ND film 33 when the concentration is low, and ghost light and flare light are likely to be generated.

  When the light beam strikes the ridge line 33a of the ND film 33, the light beam is scattered in various directions by the sawtooth-shaped minute irregular irregularities formed on the ridge line 33a. As shown in FIG. 9, when the concentration of the ND film 33 is high, the transmitted light is attenuated, so that ghost light and flare light due to regularly transmitted light components hardly occur.

  However, as shown in FIG. 10, when the concentration of the ND film 33 is low, the transmitted light component increases and ghost light and flare light are likely to be generated. However, the light is scattered in an irregular direction by the ridge line 33a. There is no.

  In the present embodiment, by making the diffusion direction of the ridge line 33a of the ND film 33 of the ND filter 31 irregular, the directivity of the transmitted light is weakened and the light is diffused, so that the intensity of the ghost light is reduced. Can do.

  FIG. 11 shows the diaphragm mechanism 12 according to the fourth embodiment. The ND filter 41 is driven integrally with the diaphragm blade 17. That is, in the diaphragm mechanism 12 that drives the two diaphragm blades 16 and 17 facing each other and adjusts the amount of incident light, a substantially trapezoidal ND provided with minute sawtooth irregular irregularities on the ridgeline of the edge 41a. A filter 41 is attached to the diaphragm blade 17. Further, the ridgelines of the opening edge portions 16a and 17a of the diaphragm blades 16 and 17 are also provided with the minute and irregular uneven portions as described above.

  FIG. 12 shows a state in which the diaphragm blade 17 and the diaphragm blade 16 with the ND filter 41 move for light amount adjustment. 12A shows a state in which the diaphragm blades 16 and 17 are retracted outward from the pupil diameter, FIG. 12C shows a state in which the ND filter 41 covers the diaphragm opening 22, and FIG. ) In the middle state. In the fourth embodiment, as shown in (a) and (b), ghost light can be reduced in the diaphragm mechanism 12 having an operation state in which the ND filter 41 partially shields the pupil diameter or the diaphragm opening 22.

  In the fourth embodiment, the directivity of the reflected light is weakened by making the diffusing directions of the ridge line of the ND filter 41 and the ridge lines of the diaphragm blades 16 and 17 irregular, and the directivity of the ghost light is weakened and the light is Since it diffuses, its strength can be weakened. Further, as the ND filter 41 of the fourth embodiment, a filter with a gradation in which the filter density continuously increases as the distance from the edge 41a is considered in consideration of a density drop and a transmission phase difference.

  The ND filter 41 having this gradation is a vapor deposition type, and as shown in FIGS. 13A and 13B, the concentration of the ND filter 41 decreases toward the edge 41a. The ridge lines 41b and 41c of the edge portion 41a are provided with minute serrated irregular irregular portions, and the end surface 41d is also provided with serrated irregular grooves 41e. Thereby, the directivity of reflected light is weakened, and ghost light and flare light are effectively eliminated.

  In the case of the gradation ND filter, the attenuation of light decreases as it approaches the edge, so that the amount of transmitted light increases and the back surface reflection also affects, so the light reflectance is relatively high. Furthermore, the closer to the edge of the gradation ND filter, the easier it is to generate ghost light and flare light. That is, in the case of a gradation ND filter in which the amount of light transmitted increases as it approaches the edge, ghost light and flare light are likely to be generated near the edge, but the ridges 41b and 41c of the ND filter 41 and the end surface 41d It is eliminated by the uneven groove 41e.

  FIG. 14 shows an ND filter 51 of Example 5, in which an ND film 53 is deposited on a film substrate 52. The ridge lines 51b and 51c of the edge 51a of the ND filter 51 are ridges protruding from the end face 51d, and a non-periodic concavo-convex portion is formed on the ridges.

  Since the film base 52 is transparent, when light that passes through the ND filter 51 is also considered, it is effective to eliminate ghost light and flare light by forming concave and convex portions on the ridge lines 51b and 51c that are convex. It is. Further, the end face 51d of the ND filter 51 is provided with a concave / convex groove 51e.

  Thus, by using the ridges 51b and 51c as ridges and providing the ridges on the ridges, the scattered light spreading further in the random direction increases and the ghost light decreases.

  In each embodiment of the present invention, by making the light diffusion direction irregular at the end face of the diaphragm blade or (and) the end face of the ND filter, the directivity of the light transmission and reflection components is weakened, and the ghost light is scattered. Therefore, the intensity of ghost light can be weakened. In the case of a resin film ND filter, light is transmitted as compared with a diaphragm blade having high light shielding properties. Therefore, the ridge line has a convex shape, so that the transmission distance is longer. Therefore, the amount of light that causes ghost light and flare light. Can be expected to reduce.

  On the other hand, the depth of the concavo-convex part is equal to that of one side of the minimum aperture so that the fluctuation of the incident light quantity caused by the concavo-convex shape is within the tolerance range of the set light quantity without adopting a special structure. Desirably smaller than the length.

  In addition, the unevenness | corrugation formation in the said Example can be formed with a press etc. FIG. For example, as shown in FIGS. 15 (a) and 15 (b), the cutting blades 61 and 62 are processed by saw-tooth or staircase shape and press-molded, or after the press-cut processing, the irregularities are processed with a file or the like. be able to.

11a to 11c Lens 12 Diaphragm mechanism 13 Low-pass filter 14 Solid-state imaging device 15 Support plate 16, 17 Diaphragm blade 21, 31, 41, 51 ND filter 22 Diaphragm opening 32, 52 Film base material 33, 53 ND film

Claims (13)

An optical member in which an optical element is arranged in an imaging optical system that forms a subject image on a photographing element, and the optical element is formed on at least one ridge line of an edge forming an opening and an edge entering the opening. A non-periodic uneven portion is formed along the optical member, and the uneven portion protrudes along the optical axis of the imaging optical system .   The optical member according to claim 1, wherein the uneven portion is provided with unevenness of various sizes in a sawtooth shape.   The optical member according to claim 1, wherein a non-periodic concavo-convex groove is formed on an end face of the edge of the optical element, and the direction of the concavo-convex groove is directed in a direction different from the ridge line direction.   The optical member according to claim 1, wherein a non-periodic concavo-convex groove is formed on an end face of the edge of the optical element, and the direction of the concavo-convex groove is directed in the same direction as the ridge line direction.   The optical member according to claim 3 or 4, wherein the concave and convex grooves are provided in various sizes in a sawtooth shape.   The optical member according to any one of claims 1 to 5, wherein the optical element is a diaphragm blade, and a plurality of diaphragm blades are operated to form the opening by the edge.   The optical member according to any one of claims 1 to 5, wherein the optical element is an optical filter, and the edge portion is inserted into the opening.   The optical member according to claim 1, wherein the optical element is an optical filter having a diaphragm blade that forms the opening by the edge and the edge that enters the opening.   The optical member according to claim 8, wherein the diaphragm blades and the optical filter operate independently.   The optical member according to claim 8, wherein the optical filter operates together with one of the diaphragm blades.   The optical member according to any one of claims 7 to 10, wherein the optical filter is an ND filter having a light attenuating film on at least one surface of a transparent plastic film.   11. The optical filter according to claim 7, wherein the optical filter is a gradation ND filter having a light attenuation characteristic in which the light transmittance continuously changes, and having a light transmittance lowered as the distance from the edge portion increases. The optical member according to claim 1. An imaging apparatus comprising the optical member according to any one of claims 1 to 12 in an optical system.