JP2005077616A - Photographic lens , lens barrel and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely shield reflected light at a lens edge which is an unwanted light, and reflected light, diffused light or refracted light in a plane chamfered section at the outer side in the radial direction from the edge. <P>SOLUTION: The edge generated at the boundary between the concave surface of a first lens included in a plurality of the lenses and a plane section on the outer side in the radial direction thereof, and the curved surface of the second lens adjacent thereto are brought into line contact, to determine the positions of the first lens and the second lens in their optical axis direction and a masking means extending at the external shape of the lens from the inner side in the radial direction, from the curved surface of the second lens with the first lens is arranged. The masking means is set as printing or painting. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photographing lens, a lens barrel, and a camera that can block harmful light and prevent occurrence of flare and the like, and can be applied to all types of cameras.

  Conventionally, in camera taking lenses, in order to prevent flare that is the cause of image contrast degradation, masks are placed in the gaps between lenses with different curvatures, or rectangular masks are used to shield unnecessary light. There are a lot of things. These are used as means for shielding light rays other than effective light rays and reducing internal reflection in the lens barrel as much as possible.

  As a specific example of the unnecessary light shielding means as described above, there is one in which a mask having a non-circular opening is inserted in front of the stop (see, for example, Patent Document 1). This is intended to shield unnecessary light by making the mask non-circular by using the fact that the effective ray height differs depending on the image height in front of the stop (subject side).

Japanese Utility Model Publication No. 6-64218

  On the other hand, in order to accurately determine the position in the optical axis direction between adjacent lenses in terms of the lens configuration, the boundary between the lens effective surface and the plane portion on the outer side in the radial direction on one side of one adjacent lens. In this case, an edge portion is formed, and this edge portion is brought into line contact with the curved surface of the other lens.

  Usually, a lens having an edge portion as described above has a flat surface outside the edge portion in the radial direction and is an optically unnecessary surface. Therefore, when light is incident on this plane portion, the incident light diffuses in the plane portion and becomes harmful light. In order to prevent such a problem, the flat surface is usually painted with an anti-reflection coating to prevent reflection. This painting is performed so as to hide the edge portion of the lens as much as possible, but the edge portion is not coated with paint well and is not painted. For this reason, the incident light is reflected at the edge portion, becomes harmful light, and may cause problems such as flare. Also, the coating applied to the rough rubbing surface is not completely shielded from light, and part of the light may be transmitted. The light that has passed through the rough rubbing surface is refracted and diffused, reaches the imaging surface, and causes flare light that spreads over the entire screen, causing problems.

  In the invention described in Patent Document 1, since the effective ray height of the optical surface immediately after the stop is almost circular, even if a rectangular mask along the effective ray is inserted into the gap of the lens, the edge portion of the lens Therefore, it is impossible to shield the reflected light and the transmitted light and diffused light from the flat portion, that is, the flat portion on the outer side in the radial direction following the edge portion, and a large image quality improvement effect cannot be obtained. Further, if it is attempted to block light at a position away from the edge portion, it is not possible to block light incident from outside the effective light beam, and therefore an image quality improvement effect cannot be expected. This is particularly a problem with zoom lenses that change the angle of view.

The present invention has been made to solve the above-described problems of the prior art, and the object of the invention described in each claim is as follows.
According to the first aspect of the present invention, the edge portion of the first lens included in the plurality of lenses and the curved surface of the second lens adjacent thereto are brought into line contact with each other, and the positions of the first lens and the second lens in the optical axis direction are brought into contact with each other. And by arranging a masking means from the inner side in the radial direction from the tangent to the first lens of the curved surface of the second lens to the lens outer shape, the reflected light at the edge portion, which is unnecessary light, and the edge portion The object is to reliably shield the reflected light, diffused light or refracted light at the flattening portion on the radially outer side.

  According to a second aspect of the present invention, one surface of the first lens is a concave surface, one surface of the second lens is a convex surface, and the concave surface of the first lens has a flat portion outside the effective diameter. The circular edge portion formed by the concave surface and the flat portion abuts on the convex surface of the second lens, thereby determining the positions of the first lens and the second lens in the optical axis direction, and masking means on the convex surface of the second lens. By providing, the object is to surely shield unnecessary light from reflection at the edge portion, reflection from the flat portion, and refracted light.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the masking means of the photographic lens is printed or painted, thereby reducing the positional deviation of the lens interval without increasing the number of parts, and optical. The object is to maintain the performance and provide an unnecessary light shielding effect.

  According to a fourth aspect of the present invention, in the photographing lens according to any one of the first to third aspects, the first lens and the second lens are disposed in a second lens group located behind the stop. Therefore, it is possible to shield unnecessary light outside the effective light beam height behind the stop, which is a shape close to a circle, and to shield unnecessary light that could not be shielded in front of the stop in the past. And

  According to a fifth aspect of the present invention, in the photographing lens according to the fourth aspect, since the first lens group before the stop is a negative lens group, unnecessary light outside the effective light beam can be easily incident on the stop. An object of the present invention is to make it possible to shield unnecessary light incident on the diaphragm without being shielded earlier.

  According to a sixth aspect of the present invention, in the photographic lens according to any one of the first to fifth aspects, the zoom can be changed by moving at least one lens group, thereby reducing a field angle. Sometimes, it is intended to shield light incident outside the edge portion from unnecessary light that cannot be shielded by a mask limited to a high effective light beam height with a large angle of view. To do.

  According to a seventh aspect of the present invention, a lens capable of preventing a decrease in contrast due to the influence of flare and obtaining a high-quality image by using the photographing lens according to any of the first to sixth aspects for a lens barrel. The purpose is to obtain a lens barrel.

  An object of the present invention is to obtain a camera capable of obtaining a high-quality image by using the lens barrel according to claim 7 for the camera.

  According to a first aspect of the present invention, there is provided a photographing lens constituted by a plurality of lenses, the edge portion of the first lens included in the plurality of lenses and the curved surface of the second lens adjacent thereto. Are in line contact with each other, and the positions of the first lens and the second lens in the optical axis direction are determined, and between the first lens and the second lens, the tangent to the curved first lens of the second lens The most important feature is that a masking means is arranged from the radially inner side to the lens outer shape.

  According to the first aspect of the present invention, by being configured as described above, it is possible to reliably shield unwanted light from reflection at the edge portion, refracted light, and reflection from outside the edge portion, and refracted light. Can do.

  According to the second aspect of the present invention, one surface of the first lens is a concave surface, one surface of the second lens is a convex surface, and the concave surface of the first lens has a flat portion outside the effective diameter. The circular edge formed by the concave surface and the flat surface abuts on the convex surface of the second lens to determine the positions of the first lens and the second lens in the optical axis direction, and the masking means is provided on the convex surface of the second lens. Therefore, it is possible to reliably shield unnecessary light, such as reflection at the edge portion, reflection at the flat portion, and refracted light.

  According to a third aspect of the present invention, in the photographic lens according to the first or second aspect, by printing or painting the masking means, the positional deviation of the lens interval is reduced without increasing the number of parts. In addition, the optical performance can be maintained, and an unnecessary light blocking effect can be provided.

  According to a fourth aspect of the present invention, in the photographing lens according to any one of the first to third aspects, the first lens and the second lens are disposed in a second lens group located behind the stop. Thus, it is possible to block unnecessary light outside the radial direction from the effective light beam height behind the stop, which is a shape close to a circle, and to block light that cannot be blocked in front of the stop.

  According to a fifth aspect of the present invention, in the photographing lens according to the fourth aspect, the first lens group before the stop is a negative lens group, so that unnecessary light outside the effective light beam is likely to enter the stop. Therefore, it is impossible to block light before the stop, and unnecessary light incident on the stop can be blocked by the stop.

  According to a sixth aspect of the present invention, in the photographing lens according to any one of the first to fifth aspects, when the angle of view is small by changing the magnification by moving at least one lens group. Among the unnecessary light that cannot be shielded by the mask limited to the height of the effective light beam having a large angle of view, it is possible to shield the light incident on the outer side in the radial direction from the edge portion.

  According to the seventh aspect of the invention, by using the photographing lens according to any one of the first to sixth aspects for a lens barrel, it is possible to prevent a decrease in contrast due to the influence of flare, and a high-quality image can be obtained. The obtained lens barrel can be obtained.

  According to the eighth aspect of the present invention, a camera capable of obtaining a high quality image can be obtained by using the lens barrel according to the seventh aspect of the present invention for the camera.

Hereinafter, embodiments of a photographing lens, a lens barrel, and a camera according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view along an optical axis showing an embodiment of a photographing lens according to the present invention and a lens barrel using the photographing lens. In this embodiment, when used, the lens barrel can be extended to widen the distance between the lens groups. The mode shown in the figure is a mode when not in use, that is, when stored, and the lens barrel is reduced so that the interval between the lens groups is narrowed. Further, this embodiment is a zoom lens, that is, a photographic lens and a lens barrel capable of zooming, and a first lens group 3 and a second lens group 2 for zooming and a third lens group for focusing. 4 is configured. These lens groups are arranged in the above order from the subject side, and an image sensor 6 is arranged behind the third lens group 4. A subject image can be formed on the image sensor 6 by each of the lens groups with the lens barrel extended.

  The photographing lens and the lens barrel are assembled on the basis of the lens barrel base 1. The lens barrel base 1 is fixed to a camera (not shown) on one side, and a fixed cylinder 9 is fixed to the other side. On the outer periphery of the fixed cylinder 9, a cam cylinder 8 is fitted between the lens barrel base 1 and the fixed cylinder 9 in the optical axis direction. Accordingly, the cam cylinder 8 is rotated around the optical axis by being rotated by a drive source (not shown) or by manual operation in a state where movement in the optical axis direction is restricted. The cam cylinder 8 is provided with a first group cam groove for determining the position of the first lens group 3 and a second group cam groove for determining the position of the second lens group 2. The first lens group 3 and the first lens group 2 are held by respective lens holding cylinders, and are movable in the optical axis direction together with the respective lens holding cylinders.

  A first group driving pin and a second group driving pin are fixed to the holding cylinders of the first lens group 3 and the second lens group 2, and each driving pin is fitted into a guide groove and a cam groove described later. The lens holding cylinders are supported so as to be movable in the optical axis direction. The fixed tube 9 is provided with a guide groove extending in the optical axis direction for moving the first lens group 3 and the second lens group 2 in the optical axis direction without rotating. As described above, the first group driving pin and the second group driving pin are fitted in these guide grooves, but the first lens group 3 and the second lens group 2 receive urging forces in opposite directions by the springs. Each drive pin is pressed against and engaged with the accuracy surface of the cam groove. Further, the outer diameter of each holding cylinder holding the first lens group 3 and the second lens group 2 is fitted to the inner diameter of the fixed cylinder 9, and the first lens group 3 and the second lens group 2 are tilted with respect to the optical axis. It is suppressed. With the configuration described above, when the cam cylinder 8 rotates, the first lens group 3 and the second lens group 2 move in the optical axis direction without rotating while creating the required positional relationship in the optical axis direction. In addition, zooming can be performed. The second lens group 2 is provided with a shutter unit 5 having a function of a shutter that moves integrally with the second lens group 2 and a diaphragm.

  On the other hand, the third lens group 4 is held by a lens holding cylinder, and this lens holding cylinder is arranged to be movable in the optical axis direction. A stepping motor 7 is disposed in a space formed inside the fixed cylinder 9 and outside the image sensor 6 in a direction in which an output shaft extends in parallel with the optical axis. A lead screw 7 a is provided on the output shaft of the stepping motor 7, and a nut is screwed into the lead screw 7 a, and this nut is engaged with the holding cylinder of the third lens group 4. Therefore, the third lens group 4 moves in the optical axis direction independently of the first lens group 3 and the second lens group 2 while being fitted to the main shaft and the sub shaft by driving the stepping motor 7, It is the composition which focuses on.

  FIG. 2 shows the positions of the lens groups and the outermost effective rays (upper ray, lower ray, principal ray) of the photographing lens according to the embodiment in the wide state with a wide angle of view. FIG. 3 shows the position of each lens group in the tele state with a narrow angle of view and the outermost effective rays (diagonal, upper ray, lower ray, principal ray) of the photographing lens. Here, a specific lens configuration of each lens group will be described. The first lens group 3 includes, in order from the subject side, a negative meniscus lens 12, another negative meniscus lens, and a biconvex lens, and the first lens group 3 as a whole has a negative refractive power. . The second lens group 2 includes, in order from the subject side, a biconvex lens, a biconcave lens 10 bonded to this lens, a biconvex lens 11, and another biconvex lens. The third lens group 4 is composed of one positive meniscus lens. In FIG. 2, reference numeral 14 indicates an image plane. The imaging surface 14 is an imaging surface of the image sensor 6 in the example of FIG. The individual lenses are hereinafter displayed as a first lens, a second lens,... Counting from the subject side. However, the first lens and the second lens in the embodiment do not necessarily match the first lens and the second lens described in the claims.

  The fifth lens 10 in the second lens group 2 has a concave surface on the image plane side, and has a chamfered portion radially outward from the effective lens surface. The sixth lens 11 disposed behind the fifth lens 10 has a convex surface on the object side, that is, the object side, and these two lenses 10 and 11 are formed by the concave surface of the fifth lens 10 and a flat portion. The circular edge portion and the convex curved surface of the sixth lens 11 are in line contact with each other, so that the positions in the optical axis direction of the above-mentioned column drawings 10 and 11 are positioned with high accuracy.

  A cover 13 having a rectangular opening is disposed in front of the first lens 12, and the opening of the cover 13 is in a range that does not block the outermost effective light beam. As shown in FIG. 2, light having a larger angle than the outermost effective light is blocked by the cover 13 at the wide end, and unnecessary light is rarely incident on the photographing lens. On the other hand, at the telephoto end, as shown in FIG. 3, the angle of the outermost effective light beam is small, and the light beam having a larger angle enters the first lens group without being blocked.

  As described above, the second lens group 2 is provided with the shutter unit 5 having the functions of a shutter that moves integrally with the second lens group 2 and an aperture. In FIGS. 2 and 3, this shutter unit is represented as a diaphragm 5a. Most of the unnecessary light rays incident on the first lens group are shielded by the diaphragm 5a. However, since the first lens group has a negative refractive power as a whole, the exit angle becomes smaller than the incident angle, and the diaphragm 5a. It is easier to enter. On the tele side, since the distance between the first lens group and the second lens group is short, the lens arrangement is such that more unnecessary light is easily incident thereon. The effective light beam that has entered through the stop 5a has a substantially circular diameter immediately after the stop 5a, and the effective light beam diameter is almost the same even if the angle of view is different. Unnecessary rays can be blocked by the diaphragm 5a.

  FIG. 4 is a ray diagram when a ray having a larger incident angle than the outermost effective ray enters in the tele state. Some of the light rays incident on the second lens group reach the flattening portion and the edge portion of the fifth lens 10. Conventionally, the flattening portion is provided with a sanitization 15 (see FIG. 5) for shielding light, and the unnecessary light beam is shielded by the sanitization 15. However, in the case of a strong light beam, it passes through the sanitization 15, refracts at the flattening portion, and reaches the imaging surface 14. Further, since the flattening portion is not an optical surface, it is a rough rubbing surface. However, due to the effect of the diffusion plate, the flattened portion that is a rough rubbing surface scatters unnecessary incident light at the flattened portion as shown in FIG. 5 and reaches the imaging surface. Similarly, the incident light also diffuses at the edge portion as shown in FIG. 5 and reaches the imaging surface. Since the unnecessary light spreads and enters the entire imaging surface, the captured image generally has a reduced contrast and becomes a flare image with a whitish fog, which degrades the captured image quality. Therefore, these flares must be eliminated.

  Therefore, as shown in FIG. 6, the present invention includes a plurality of lenses, and the edge portion of the fifth lens 10 included in the plurality of lenses and the curved surface of the sixth lens 11 adjacent thereto are in line contact with each other. In the photographing lens in which the positions of the lenses 10 and 11 in the optical axis direction are determined, an edge portion is formed on the convex surface of the sixth lens 11 in order to shield the transmitted light of the flattening portion of the lens 10 and the irregular reflection of the edge portion. The masking means 16 shields light from the radially inner side to the lens outer shape. More specifically, the surface of the fifth lens 10 on the sixth lens 11 side is a concave surface, and the surface of the sixth lens 11 on the side facing the fifth lens 10 is a convex surface. On the concave surface side of the fifth lens 10, there is a flat portion that continues to the concave surface outside the effective diameter. Therefore, the fifth lens 10 has a circular edge centered on the lens optical axis at the boundary between the concave surface and the flat surface, and this edge is in contact with the convex surface of the sixth lens 11. Masking means 16 is provided from the inside in the radial direction from the abutting portion to the lens outer shape.

  The masking means 16 may be formed by printing or painting. By doing so, the film thickness of the masking means 16 is reduced and the variation in film thickness is reduced, so that the positional deviation in the optical axis direction between the fifth lens 10 and the sixth lens 11 can be reduced, and the optical performance is high. Can be maintained.

In the claims, in order to relatively specify two adjacent lenses, one lens is a first lens and the other lens is a second lens. The first lens in the claims corresponds to the fifth lens 10 in the illustrated embodiment, and the second lens in the claims corresponds to the sixth lens 11 in the illustrated embodiment.
In the illustrated embodiment, the first lens and the second lens described in the claims are disposed in the second lens group, and the second lens group is located behind the diaphragm 5a, that is, on the image plane side. Thus, the above-described effects are obtained.

  With the configuration described above, the masking means 16 can block the transmitted light at the lens flattening portion and the irregularly reflected light at the edge portion of the incident unnecessary light with a simple configuration. It is possible to reduce flare that is a cause of a decrease in contrast of a captured image while maintaining optical performance by reducing positional deviation in the optical axis direction.

  The photographing lens according to the present invention refers to a portion composed of optical elements such as a lens, a diaphragm, and a masking means, and the lens barrel refers to a lens device including the photographing lens and a lens barrel that holds the photographing lens. Say.

  The lens barrel according to the present invention can be used for all kinds of cameras, and thereby, a high-quality photographic image with high contrast and low flare can be obtained. Incidentally, the embodiment of the photographing lens and the lens barrel shown in FIG. 1 is an example provided with an image sensor 6 for a digital camera or a video camera. Can be applied to camera.

It is sectional drawing along the optical axis which shows embodiment of the imaging lens concerning this invention, and a lens barrel. FIG. 3 is an optical arrangement diagram showing the position of each lens group in the wide state and the outermost effective light beam in the photographing lens. FIG. 3 is an optical layout diagram showing the position of each lens group in the tele state and the outermost effective light beam in the photographing lens. It is a light ray diagram when a light ray having a larger incident angle than the outermost effective light ray enters in the telephoto state in the photographing lens. It is a light ray figure which shows the mode of the permeation | transmission of the light in the plane part of one lens, and the light scattering in an edge part. It is a light ray figure which shows a mode that the masking means in this invention shields the said light transmission and light scattering.

Explanation of symbols

2 Second lens group 3 First lens group 4 Third lens group 5 Shutter unit 5a Aperture 10 First lens 11 Second lens 16 Masking means

Claims (8)

A photographic lens composed of a plurality of lenses,
The edge portion of the first lens included in the plurality of lenses and the curved surface of the second lens adjacent thereto are in line contact, and the positions of the first lens and the second lens in the optical axis direction are determined,
A photographic lens, characterized in that masking means is arranged between the first lens and the second lens from the inside in the radial direction from the tangent to the curved first lens of the second lens to the lens outer shape.   One surface of the first lens is a concave surface, and one surface of the second lens is a convex surface. The first lens has a flat portion outside the effective diameter on the concave surface side, and the concave surface of the first lens The position of the first lens and the second lens in the optical axis direction is determined by the circular edge portion formed at the boundary of the flat portion contacting the convex surface of the second lens, and masking means is provided on the convex surface of the second lens. The photographic lens according to claim 1, wherein the photographic lens is provided.   3. A photographic lens according to claim 1, wherein the masking means is formed by printing or painting.   4. The photographing lens according to claim 1, wherein the first lens and the second lens are disposed in the second lens group, and the second lens group is located behind the stop.   5. The photographic lens according to claim 4, wherein there is a first lens group before the stop, and the first lens group is a negative lens group.   6. The photographing lens according to claim 1, wherein zooming is performed by moving at least one lens group.   7. A lens barrel using the photographing lens according to claim 1. 8. A camera using the lens barrel according to claim 7.

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