JP2010256472A - Optical unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the occurrence of flare and ghost by effectively interrupting stray light due to light from a substantially lateral object side. <P>SOLUTION: An optical system includes: a lens group having a reflection refractive optical element LG2 and a lens group having an aperture diaphragm S disposed rather closer to the image side than the lens group. The reflection refractive optical element LG2 has a first face formed on the object side ahead, a second face formed on the image side and a third face formed on the whole peripheral surface between the first face and the second face. The first face includes a first transmission face formed around the optical axis and a first reflection face formed annularly in the periphery of the first transmission face and pointing the image side. The second face includes a second transmission face formed around the optical axis and a second reflection face formed annularly in the periphery of the second transmission face and pointing the object side ahead. The third face is a transmission face including an annular light shield member F formed of light shielding material in the vicinity of the aperture diaphragm S, and having an inside diameter larger than the inside diameter of the aperture diaphragm S and smaller than the inside diameter of the lens barrel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical unit having an optical element capable of observing a substantially lateral object simultaneously with observing a front object.

  Conventionally, an optical system for simultaneously observing a front object and a substantially lateral object, a lens barrel holding the optical system, a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor), etc. An optical unit including an image sensor is known. An example of such an optical unit is described in Patent Document 1. Note that “substantially side” includes not only the side of the optical system itself but also the diagonally forward and diagonally rear sides of the optical system.

As shown in FIG. 7, the optical unit described in Patent Document 1 includes a convex rotator mirror 24 after light LR _s from a substantially lateral object passes through a translucent housing 26. And is incident on the lens 28.

JP 2002-233494 A

However, in the optical unit having the configuration described in Patent Document 1, not all of the light reflected by the convex rotating mirror 24 is incident on the lens 28 like the light LR _s1 , but the light LR There is a case where it goes to the translucent housing 26 like _s2 . Such light LR _s2 is reflected on the inner surface of the translucent housing 26 and thus becomes stray light. When such stray light enters the lens 28 and reaches the image sensor 31, there is a problem that flare and ghost are generated.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to effectively block stray light caused by light from a substantially lateral object side, An optical unit capable of suppressing the occurrence of ghosts is provided.

  In order to achieve the above object, an optical unit of the present invention includes an optical system for observing a front object and a substantially lateral object, a lens barrel that holds the optical system, and an image sensor. The optical system includes: a lens group having a catadioptric optical element; and a lens group disposed on the image side of the lens group having the catadioptric optical element and having an aperture stop. The catadioptric optical element extends over the entire surface between the first surface formed on the front object side, the second surface formed on the image side, and the first surface and the second surface. A first transmission surface formed around the optical axis, and formed in an annular shape around the first transmission surface and facing the image side. A first reflection surface, and the second surface is a second transmission surface formed around the optical axis. A second reflection surface formed in an annular shape around the second transmission surface and facing the front object side, the third surface is a transmission surface, and in the vicinity of the aperture stop, An annular light shielding member that is formed of a light shielding material and has an inner diameter larger than the inner diameter of the aperture stop and smaller than the inner diameter of the lens barrel is provided.

  In the optical unit of the present invention, the light from the front object side is incident on the first transmission surface, and then is emitted from the second transmission surface to the image side. It is preferable that after entering the third surface, the light is sequentially reflected by the second reflecting surface and the first reflecting surface and emitted from the second transmitting surface to the image side.

  Further, in the optical unit of the present invention, a lens group having a negative refractive power is disposed on the object side in front of the lens group having the catadioptric optical element, and the optical unit is more than the lens group having the catadioptric optical element. The lens group disposed on the image side preferably has a positive refractive power.

  In the optical unit of the present invention, it is preferable that the aperture stop and the light shielding member are integrally formed.

  In the optical unit of the present invention, it is preferable that the outer peripheral surface is constituted by the outer peripheral surface of the barrel and the third surface.

  In the optical unit of the present invention, it is preferable that the imaging element is held by the lens barrel.

  In the optical unit of the present invention, the lens barrel includes an inner cylinder that holds a lens group disposed on the image side of the catadioptric optical element, and an outer cylinder that holds the inner cylinder, and It is preferable that the member is formed integrally with the inner cylinder.

  In the optical unit according to the present invention, the lens barrel is preferably formed of a light shielding material.

  Furthermore, in the optical unit of the present invention, it is preferable that the outer diameter of the light shielding member substantially coincides with the inner diameter of the lens barrel.

  ADVANTAGE OF THE INVENTION According to this invention, the optical unit which can interrupt | block the stray light resulting from the light from the substantially side object side effectively, and can suppress generation | occurrence | production of a flare and a ghost can be provided.

1 is a schematic diagram illustrating an optical unit according to Example 1. FIG. It is a schematic diagram which shows the catadioptric optical element contained in the optical system of the optical unit shown by FIG. 6 is a schematic diagram illustrating an optical unit according to Embodiment 2. FIG. 10 is a schematic diagram illustrating an optical unit according to Example 3. FIG. 10 is a schematic diagram illustrating an optical unit according to Example 4. FIG. 10 is a schematic diagram illustrating an optical unit according to Embodiment 5. FIG. It is a schematic diagram which shows the conventional optical unit.

  Hereinafter, embodiments of the present invention will be described in detail.

  First, the optical unit according to Example 1 will be described in detail with reference to FIG.

  This optical unit includes an optical system composed of three lens groups, an annular light shielding member inserted into the optical system, an imaging element on which an image is formed on the imaging surface by the optical system, and those optical systems And a light shielding member and a lens barrel for holding the image sensor.

  Next, an optical system included in this optical unit will be described.

This optical system is composed of a first lens group LG ₁ having negative refractive power, a second lens group LG _2, and a third lens group LG ₃ having positive refractive power in order from the front object side. ing. Incidentally, the third lens group LG ₃ has an aperture stop S.

Of the light incident on the optical system, light from the front object side enters the first lens group LG ₁ , the second lens group LG ₂ , and the third lens group LG ₃ in this order. On the other hand, light from the substantially object side is incident on the second lens group LG ₂ and the third lens group LG ₃ in this order.

  Further, this optical system is configured to be a retrofocus type optical system for both light from the front object side and light from the substantially object side. By taking such a configuration, the observation angle of view can be increased.

The first lens group LG ₁ is configured by the lens L ₁₁ is a plano-concave lens with a concave surface facing the image side.

The second lens group LG ₂ is configured, in order from the front-object side, a lens L ₂₁ is a reflective refractive optical element, a cemented lens of a lens L ₂₂ is a negative meniscus lens having a convex surface directed toward the front-object side Has been. Incidentally, the catadioptric optical element means an optical element that utilizes a light reflecting action and a refractive action.

The third lens group LG ₃ includes, in order from the front object side, a lens L ₃₁ that is a flat lens, a lens L ₃₂ that is a plano-convex lens with a convex surface facing the image side, a lens L ₃₃ that is a biconvex lens, The lens L ₃₄ is a concave lens, the lens L ₃₅ is a biconvex lens whose surface on the image side is aspheric, and L ₃₆ is a flat lens. Incidentally, the front-object side of the lens L ₃₁ is integrally with the lens L _31, the aperture stop S is provided. Further, a lens L ₃₃ and the lens L ₃₄ is a biconcave lens, are joined constitute a cemented lens.

Here, at the same time the lens L ₂₁ is a reflective refractive optical element for performing detailed description of the observation of the front object and the object of the approximately lateral with reference to FIG.

The lens L ₂₁ has a first surface L ₂₁ a, a second surface L ₂₁ b, and the third surface L ₂₁ c, and the first mounting portion L ₂₁ d, and a second attachment portion L ₂₁ e ing.

The first surface L ₂₁ a is formed on the object side in front of the lens L ₂₁ . The first surface L ₂₁ a is formed in an annular shape around the first transmission surface L ₂₁ a ₁ that faces the image side and the first transmission surface L ₂₁ a ₁ that is formed around the optical axis. And a first reflecting surface L ₂₁ a ₂ .

The second surface L ₂₁ b is formed on the image side of the lens L ₂₁ . The second surface L ₂₁ b is formed in an annular shape around the second transmission surface L ₂₁ b ₁ facing the front object side and the second transmission surface L ₂₁ b ₁ formed around the optical axis. Second reflecting surface L ₂₁ b ₂ .

The third surface L ₂₁ c is a cylindrical transmission surface formed over the entire circumferential surface between the first surface L ₂₁ a and the second surface L ₂₁ b.

The first attachment portion L ₂₁ d is formed between the first reflecting surface L ₂₁ a ₂ and the third surface L ₂₁ c. The first mounting portion L ₂₁ d has a cylindrical surface L ₂₁ d ₁ centered on the optical axis and an annular surface L ₂₁ d ₂ substantially perpendicular to the optical axis, thereby forming a stepped shape. It has become.

The second attachment portion L ₂₁ e is an annular surface formed between the second reflecting surface L ₂₁ b ₂ and the third surface L ₂₁ c and substantially perpendicular to the optical axis.

The first reflective surface L ₂₁ a ₂ and the second reflective surface L ₂₁ b ₂ are formed by vapor deposition. Specifically, for example, after the first transmission surface L ₂₁ a ₁ is masked in the same shape as the first transmission surface L ₂₁ a ₁ , mirror coating is applied to the entire first surface L ₂₁ a, Thereafter, the mask is peeled off. If such a method is used, since the masked portion is not mirror-coated, the first transmission surface L ₂₁ a ₁ can be used as the transmission surface even after the first reflection surface L ₂₁ a ₂ is formed.

The lens L ₂₁ is attached to the lens barrel at the first attachment portion L ₂₁ d and the second attachment portion L ₂₁ e.

  Next, the lens barrel that holds the optical system, the light shielding member, and the image sensor will be described with reference to FIGS. 1 and 2. In the drawing, only the imaging surface IP is shown for the imaging device.

This barrel is composed of a first barrel T ₁ and a second barrel T ₂ .

The first lens barrel T ₁ holds the first lens group LG ₁ and the second lens group LG ₂ . More specifically, the first lens barrel T ₁ holds the first lens group LG ₁ therein. The first barrel T ₁ is on the image side, it is attached a first attachment portion L ₂₁ d of the lens L ₂₁ is a reflective refractive optical element, holding the lens L _21. That is, a part of the inner peripheral surface of the first lens barrel T ₁ is in contact with the peripheral surface of the lens L ₁₁ . Further, a part of the inner peripheral surface of the first lens barrel T ₁ and the image side surface are in contact with the first mounting portion L ₂₁ d.

On the other hand, the second lens barrel T ₂ holds the second lens group LG ₂ , the light shielding member F, the third lens group LG _3, and the image sensor. More specifically, the second barrel T ₂ are, in the end surface on the object side of the front, by attaching a second attachment portion L ₂₁ e of the lens L ₂₁ is a reflective refractive optical element, holding the lens L ₂₁ ing. Further, the second lens barrel T ₂ holds a lens L ₂₂ therein. That is, a part of the inner peripheral surface of the second lens barrel T ₂ is in contact with the peripheral surface of the lens L ₂₂ . Further, the front-object side surface of the second barrel T ₂ is in contact with the second attachment portion L ₂₁ e.

As described above, in the optical unit of the present embodiment, the lens L ₂₁ that is a catadioptric optical element is provided with an attachment portion for attaching to the lens barrel, and the lens L ₂₁ that is a catadioptric optical element is directly attached to the lens barrel. ing. Therefore, the optical unit of the present embodiment does not need to be provided with a holding member larger than the diameter of the lens of the optical system unlike the conventional optical unit, and the entire apparatus can be downsized compared to the conventional optical unit. .

The first lens barrel T ₁ and the second lens barrel T ₂ are formed such that their outer peripheral surfaces substantially coincide with the outer peripheral surface of the third surface of the lens L ₂₁ . The outer peripheral surface of the optical unit is formed by these surfaces.

  Next, the annular light shielding member F inserted into the optical system will be described with reference to FIGS. 1 and 2.

  The annular light shielding member F is disposed on the object side of the aperture stop S. Further, the inner diameter of the light shielding member F is formed to be larger than the inner diameter of the aperture stop S.

The light shielding member F is made of a light shielding material. Further, the outer diameter of the light shielding member F is formed such that the inner diameter substantially matching the second barrel T _2, is fitted into the second barrel T ₂ so there is no gap, the light shielding adhesive It is fixed by.

Next, a path followed by light incident on the optical system of the optical unit will be described with reference to FIGS. 1 and 2. Of the light incident on the optical system of the optical unit, the light LR _f incident from the front object side first passes through the lens L ₁₁ . Then, the light LR _{f that} has passed through the lens L ₁₁ is incident on the first transmission surface L ₂₁ a ₁ of the first surface L ₂₁ a of the lens L ₂₁ . Thereafter, the light LR _f incident on the first transmitting surface L ₂₁ a ₁ is incident to be output lens L ₂₂ from the second transmitting surface L ₂₁ b ₁ of the second surface L ₂₁ b of the lens L _21. The light LR _f emitted from the lens L ₂₂ passes through the lens L ₃₁ , the lens L ₃₂ , the lens L ₃₃ , the lens L ₃₄ , and the lens L ₃₅ in this order, and enters the image sensor. Thereby, an image of a front object is formed on the imaging surface IP of the imaging element.

On the other hand, of the light incident on the optical system of the optical unit, the light LR _S incident from the substantially object side first enters the third surface L ₂₁ c of the lens L ₂₁ . The light LR _S incident on the third surface L ₂₁ c is reflected to the object side by the second reflecting surface L ₂₁ b ₂ of the second surface L ₂₁ b of the lens L ₂₁ . Thereafter, the light LR _S reflected by the second reflecting surface L ₂₁ b ₂ is reflected to the image side by the first reflecting surface L ₂₁ a ₂ of the first surface L ₂₁ a of the lens L ₂₁ . Further, thereafter, the light LR _S reflected by the second reflective surface L ₂₁ a ₂ is incident on and emitted lens L ₂₂ from the second transmitting surface L ₂₁ b ₁ of the second surface L ₂₁ b of the lens L ₂₁ . Lens L ₂₂ light LR _S emitted from passes through the lens L _22, the lens L _31, the lens L _32, the lens L _33, the lens L _34, a lens L ₃₅ in order, enters the imaging device. Thereby, an image of a substantially lateral object is formed on the imaging surface IP of the imaging device.

Thus, the optical unit of the present embodiment, a configuration using the lens L ₂₁ is a reflective refractive optical element, observed in front of the object at the same time, the approximately lateral optical system capable of performing observation of objects Therefore, the generation of stray light in the optical system can be suppressed as compared with the conventional optical unit. That is, the light shielding member F formed of a light shielding material is disposed in the third lens group LG ₃ disposed on the image side of the second lens group LG ₂ including the lens L ₂₁ that is a catadioptric optical element. Therefore, stray light generated on the object side with respect to the light shielding member F hardly reaches the imaging surface IP, and as a result, flare and ghost can be effectively reduced.

  Next, the optical unit according to Example 2 will be described in detail with reference to FIG. The configuration of the optical system in the optical unit of the present embodiment, the shape of the catadioptric optical element, the shape of the light shielding member, the configuration of the lens barrel, and the optical path followed by the light incident on the optical system are the same as those of the optical unit of the first embodiment. Since they are substantially the same, members having substantially the same configuration are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 3, the optical unit is arranged such that the light shielding member F is between the lens L ₃₁ closest to the object side of the third lens group LG ₃ and the lens L ₃₂ on the image side. . Even if configured in this way, the same effects as those of the optical unit of Embodiment 1 can be obtained.

  Next, the optical unit according to Example 3 will be described in detail with reference to FIG. The configuration of the optical system in the optical unit of the present embodiment, the shape of the catadioptric optical element, the shape of the light shielding member, the shape of the first lens barrel, and the optical path followed by the light incident on the optical system are the same as in the first embodiment and the embodiment. Since the optical unit is substantially the same as the optical unit of Example 2, members having substantially the same configuration are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 4, the second lens barrel T ₂ ′ constituting the lens barrel of the optical unit has an inner shape, and the inner diameter of the portion holding the light shielding member F is larger than the inner diameter of the image side. As shown in FIG.

As described above, since the portion that holds the light shielding member F inside the lens barrel is formed in a stepped shape, this optical unit has a light shielding member F that can generate stray light on the object side of the light shielding member F due to an assembly error or the like. and through the gap between the lens barrel, not incident to the third lens group LG ₃ and the image pickup device located on the image side of the light shielding member F. For this reason, generation | occurrence | production of flare and a ghost can be reduced more effectively. Also, the assembly of the optical unit is facilitated.

  Next, the optical unit according to Example 4 will be described in detail with reference to FIG. The configuration of the optical system in the optical unit of the present embodiment, the shape of the catadioptric optical element, the shape of the first lens barrel, and the optical path followed by the light incident on the optical system are almost the same as those of the optical units of Embodiments 1 to 3. Since they are the same, members having substantially the same configuration are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 5, the second lens barrel T ₂ ″ constituting the lens barrel of the optical unit includes an outer tube T ₂ ″ ₁ and an inner tube T ₂ held inside the outer tube T ₂ ″ _1. “It consists of _two . The inner cylinder T ₂ ″ ₂ is integrally formed with a light shielding member F on the end surface on the object side. The inner cylinder T ₂ ″ ₂ and the light shielding member formed integrally therewith are provided. Each of F is made of a light shielding material.

Thus, the light shielding member F is formed integrally with the inner cylinder T ₂ ″ ₂ that holds the third lens group LG _3. As a result, this optical unit is generated on the object side of the light shielding member F. stray light, the gap between the shielding member F and the inner tube T _{2 "2} which can be the assembly error or the like does not enter into the third lens group LG ₃ and the image pickup device located on the image side of the light shielding member F. For this reason, generation | occurrence | production of flare and a ghost can be reduced more effectively. Also, the assembly of the optical unit is facilitated. Further, the third lens group LG _3, it is possible to assemble separately from the other lens groups, it is easy knitting center adjustment assembly and the optical system of the optical unit.

In the present embodiment, "the outer tube T _2" second barrel T ₂ has been constructed by ₁ and its outer tube T _{2 "1} in the tube T ₂ is held within the" ₂ The second lens barrel T ₂ ″ of the optical unit of the present embodiment is not limited to such a configuration, and may be configured by three or more members.

  Next, the optical unit according to Example 5 will be described in detail with reference to FIG. The configuration of the optical system in the optical unit of the present embodiment, the shape of the catadioptric optical element, the shape of the first lens barrel, and the optical path followed by the light incident on the optical system are almost the same as those of the optical units of Embodiments 1 to 4. Since they are the same, members having substantially the same configuration are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 6, the second lens barrel T ₂ ′ ″ constituting the lens barrel of this optical unit is located between the position where the light shielding member F is held and the position where the third lens group LG ₃ is held. An aperture stop S is integrally formed. Further, the second lens barrel T ₂ ″ ″ is formed such that the inner diameter on the object side is larger than the inner diameter on the image side than the integrally formed aperture stop S.

Thus, the aperture stop S is formed integrally with the second lens barrel T ₂ ″ ″. Thereby, in this optical unit, the stray light generated on the object side with respect to the light shielding member F is imaged more than the light shielding member F from the gap between the light shielding member F and the second lens barrel T ₂ ″ ″ caused by an assembly error or the like. not incident to the third lens group LG ₃ or the imaging element on the side. For this reason, generation | occurrence | production of flare and a ghost can be reduced more effectively. Also, the assembly of the optical unit is facilitated. Further, the third lens group LG _3, it is possible to assemble separately from the other lens groups, it is easy knitting center adjustment assembly and the optical system of the optical unit.

  In addition, this invention is not limited to these examples, The various combinations of the said Example are also included in this invention.

  In the above embodiment, the optical system capable of simultaneously observing a front object and a substantially lateral object is composed of three lens groups, but is provided in the optical unit of the present invention. The optical system is not limited to these examples, and may be constituted by two lens groups or four or more lens groups.

  Further, the lenses constituting the lens group of the optical system provided in the optical unit of the present invention are not limited to the shapes and the number of sheets shown in the above embodiments, but various optical elements including catadioptric optical elements. Systems are also included.

  Although not arranged in the above embodiment, a low-pass filter with an IR cut coat, a CCD cover glass, or the like may be arranged between the optical system and the image sensor.

  In the above embodiment, the third surface of the catadioptric optical element has a shape in which the front object-side diameter and the image-side diameter substantially coincide with each other. Alternatively, a shape having a larger image side diameter or a shape having a smaller image side diameter than the front object side diameter may be used. Here, the diameter on the front object side means the diameter in the plane perpendicular to the optical axis at the position on the most front object side on the third surface, and the diameter on the image side means the third surface. The diameter in the plane perpendicular to the optical axis at the position closest to the image side.

  Moreover, in the said Example, although the 1st reflective surface and the 2nd reflective surface are formed by the vapor deposition method, the formation method is not limited to said method.

  In the above embodiment, the light shielding member is disposed on the most object side or the image side of the lens on the most object side in the third lens group. It is not limited to the position. In order to enhance the effect of suppressing flare and ghost, it is preferable that the third lens group is disposed at a position closer to the object side than the most image side lens.

F light shielding member IP imaging surface LG ₁ first lens group LG ₂ second lens group LG ₃ third lens group LR _f , LR _S , LR _S1 , LR _S2 light L ₁₁ , L ₂₁ , L ₂₂ , L ₃₁ , L _{32 , L 33, L 34, L} 35, L 36, 28 lens L ₂₁ a first surface L ₂₁ a ₁ first transmitting surface L ₂₁ a ₂ first reflective surface L ₂₁ b second surface L ₂₁ b ₁ second transmission Surface L ₂₁ b ₂ second reflecting surface L ₂₁ c third surface L ₂₁ d first mounting portion L ₂₁ d ₁ cylindrical surface L ₂₁ d ₂ annular surface L ₂₁ e second mounting portion S aperture stop T ₁ first one barrel _{T 2, T 2 ', T} 2 ", T 2''' the second barrel T _{2" 1} outer tube T _{2 "2} inner cylinder 24 convex rotation body mirror 26 translucent enclosure 31 imaging element

Claims (9)

In an optical unit comprising an optical system for observing a front object and a substantially lateral object, a lens barrel holding the optical system, and an image sensor,
The optical system includes a lens group having a catadioptric optical element, and a lens group disposed on the image side of the lens group having the catadioptric optical element and having an aperture stop,
The catadioptric optical element is formed over the entire peripheral surface between the first surface formed on the front object side, the second surface formed on the image side, and the first surface and the second surface. A third surface, and
The first surface includes a first transmission surface formed around the optical axis, and a first reflection surface formed in an annular shape around the first transmission surface and facing the image side,
The second surface includes a second transmission surface formed around the optical axis, and a second reflection surface formed in an annular shape around the second transmission surface and facing the front object side,
The third surface is a transmission surface;
An optical device comprising an annular light shielding member formed of a light shielding material in the vicinity of the aperture stop and having an inner diameter larger than the inner diameter of the aperture stop and smaller than the inner diameter of the lens barrel. unit. Light from the front object side is incident on the first transmission surface and then emitted from the second transmission surface to the image side.
The light from the substantially object side is incident on the third surface, is then sequentially reflected by the second reflecting surface and the first reflecting surface, and is emitted from the second transmitting surface to the image side. The optical unit according to claim 1. A lens group having negative refractive power is disposed on the object side in front of the lens group having the catadioptric optical element,
3. The optical unit according to claim 1, wherein the lens group disposed on the image side of the lens group having the catadioptric optical element has a positive refractive power.   4. The optical unit according to claim 1, wherein the aperture stop and the light shielding member are integrally formed. 5.   The optical unit according to any one of claims 1 to 4, wherein an outer peripheral surface is constituted by the outer peripheral surface of the lens barrel and the third surface.   The optical unit according to claim 1, wherein the imaging element is held by the lens barrel. The lens barrel includes an inner cylinder that holds a lens group disposed on the image side of the catadioptric optical element, and an outer cylinder that holds the inner cylinder.
The optical unit according to any one of claims 1 to 6, wherein the light shielding member is formed integrally with the inner cylinder.   The optical unit according to claim 7, wherein the lens barrel is made of a light shielding material.   9. The optical unit according to claim 1, wherein an outer diameter of the light-shielding member substantially coincides with an inner diameter of the lens barrel.

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