KR100972528B1 - Fisheye lens with replacible lens elements on the object side - Google Patents

Abstract

Provided is a fisheye lens that can replace some lens elements on the object side. The fisheye lens is a fisheye lens including a plurality of lens elements aligned in the optical axis direction, wherein the first barrel and the first barrel, to which some of the lens elements closer to an object are mounted, are detachable and the plurality of lenses And a second barrel on which the remaining lens elements of the elements are mounted. Such a fisheye lens is directly exposed to the outside without a separate transparent dome to obtain a high quality image, but if there is permanent contamination by environmental factors such as rain or dust or intentional damage by potential criminals, It is possible to easily replace only some of the lens elements on the object side, thereby minimizing the cost and time required for the maintenance of the imaging system.

Fisheye lens, barrel, front, body

Description

FISHEYE LENS WITH REPLACIBLE LENS ELEMENTS ON THE OBJECT SIDE}

The present invention relates to a fisheye lens, and more particularly to a fisheye lens capable of replacing some lens elements on the object side.

As social needs for safety increase, more and more security cameras are being installed. For example, in order to prevent accidents in reverse, the installation of rear cameras in automobiles is becoming more and more common.

1 shows an embodiment of an installation state of a rear camera for a vehicle according to the prior art. The rear camera 10 includes a camera body 11 including an image sensor (not shown) and an imaging lens 12 opposite the image sensor. The shape of the lens 12 is usually rotationally symmetric about the optical axis OA, and the sensor surface of the image sensor provided inside the camera body 11 is perpendicular to the optical axis OA. The image formed by the lens 12 is converted into an electrical signal in the image sensor, and then, through a signal wire (SW), an image display means such as a liquid crystal display (LCD) monitor or a digital video recorder (DVR) such as an automobile. Is transmitted to the image storage means.

The lens 12 itself is not usually made of a waterproof structure, and the gap between the lens fastening portion 13 and the camera body 11 which is coupled to the camera body is particularly vulnerable to moisture or rainwater. Therefore, the lens 12 and its surroundings are covered using a camera housing 14 as shown in FIG. 1 for waterproofing or the like. The camera housing 14 has a planar window 14a, which is aligned perpendicular to the optical axis OA, facing the lens 12, one end of which is firmly fixed to the camera body 11, An elastic component such as an O-ring is inserted between the 14a) and the housing 14 and between the camera body 11 and the housing 14 to be waterproof. In this structure, the lens 12 captures the external landscape through the planar window 14a mounted to the camera housing 14. The body 11 of the vehicle rear camera 10 is fixed to the vehicle body CB of the vehicle using camera fixing means 15 and 16 facing each other with the vehicle body CB interposed therebetween.

The planar window 14a provided in the housing 14 of the security camera 10 installed in a place where extreme environmental changes such as shock, vibration, high temperature and low temperature occur, such as a vehicle, is no longer an optical window in harsh conditions. It may be so severely damaged that it cannot function as), and scratches by rainwater, dust, sand wind, and rupture of the flat window 14a due to impact are sufficiently predictable. If the flat window 14a is damaged, the flat window 14a is removed from the camera housing 14 and replaced with a new flat window to minimize the maintenance cost and time of the rear camera.

2 shows a schematic structure of a conventional dome camera 20. The dome camera 20 is a type of security camera most widely used because of its relatively low cost and small size. In the dome camera 20 structure, the camera body 21 is mounted to the angle adjuster 23 fixed to the base 22 of the camera housing, and the angle adjuster 23 is fixed to the support 24 to rotate. do. The base end 22 is usually provided with fixing means (not shown) for fixing to the interior wall or ceiling. After fixing the dome camera 20 to the indoor wall or ceiling, the angle adjuster 23 may be rotated at an appropriate angle to align the optical axis OA of the security camera toward the observation (monitoring) area. After the alignment is completed, the transparent dome 25 may be fastened to the base end 22 to protect the camera body 21 from dust or moisture. In FIG. 2, reference numeral 26 denotes a lens, and reference numeral 27 denotes a lens coupling part fastened to the camera body 21.

Sometimes potential criminals deliberately compromise security cameras. For example, the dome may be broken by a strong impact using a hammer. In contrast, the base end 22 of the camera is made of hard metal using a die casting method, and the transparent dome 25 may be made of a polycarbonate (PC) material resistant to impact.

In addition to attempts to break the transparent dome 25, spray paint may be sprayed onto the surface of the transparent dome 25 to prevent the security camera from capturing images. As such, when the transparent dome 25 is damaged and a clear image is not obtained, only the transparent dome 25 may be replaced to obtain a clear image again. Therefore, instead of replacing the camera and the lens as in the embodiment of FIG. 1, it is possible to reduce the maintenance cost of the security camera by replacing only the inexpensive transparent dome 25.

On the other hand, there is a special kind of lens which is called a converter lens in the field of photography. References 1 to 3 show embodiments of such a conversion lens. The conversion lens refers to a lens that is detachably mounted on the front or rear surface of a master lens composed of a set to provide an effect of increasing or decreasing the angle of view. The conversion lens has been developed to reduce the inconvenience of having to carry several heavy lenses when it is expensive to have a standard lens, a wide-angle lens, and a telephoto lens separately. Such a conversion lens is an afocal lens mounted on a master (standard) lens and effectively converts an angle of view, and does not form an image by itself and does not have an aperture therein. In particular, FIG. 3A of Reference 1 illustrates a conversion lens mounted on an underwater camera and a meniscus lens that can be further mounted on the conversion lens to further expand the angle of view. In addition, many camera manufacturers provide conversion lenses that include one or more lens elements, and products that can produce a fisheye lens effect by installing the conversion lens are also commercially available.

Recently, interest in fisheye lenses has been increasing in various fields such as security, surveillance, entertainment, and robot driving. A fisheye lens generally refers to a lens having an angle of view of 160 ° or more and having a generally proportional ratio between an incident angle of incident light and an image height in an image plane. However, a true fisheye lens can be said to have a lens angle of 180 ° or more. The degree of difficulty of lens design differs significantly depending on whether the angle of view is 180 ° or more, and when the angle of view is 180 ° or less, at least six fisheye lenses are required to simultaneously obtain images in all directions, but the angle of view is 180 °. This is because only two fisheye lenses are needed.

Figure 3 shows the optical structure and the path of the light beam of the fisheye lens of the embodiment of the present invention shown in References 3 to 4. The fish-eye lens has an F-number of 2.8, an angle of view of 190 °, with a total of eight lens elements (E ₁₁ through E ₁₈ ), and a 1/2 inch or 1/3 inch CCD (charge coupled) device) Optimized for the sensor. The third lens element E ₁₃ and the fourth lens element E ₁₄ of this fisheye lens constitute a cemented doublet, and the fourth lens element E ₁₄ and the fifth lens element E ₁₅ An aperture S is located between, and an optical low pass filter F is located between the eighth lens element E ₁₈ and the sensor surface I of the image sensor.

The first to eighth lens elements E ₁₁ to E ₁₈ are all refractive lens elements and have two lens surfaces. For example, each of the first to eighth lens elements E ₁₁ to E ₁₈ has a lens surface on the object side and an lens surface on the image side. The upper lens surface of the third lens element E ₁₃ is identical to the object-side lens surface of the fourth lens element E ₁₄ . Accordingly, the first, third, fifth, sixth, and eighth of the fifteen first to fifteenth lens surfaces R ₁ to R ₁₅ of the first to eighth lens elements E ₁₁ to E ₁₈ . , The tenth, twelfth, and fourteenth lens surfaces R ₁ , R ₃ , R ₅ , R ₆ , R ₈ , R ₁₀ , R ₁₂ , and R ₁₄ may include first to eighth lens elements E ₁₁ to E _18. ), And the second, fourth, sixth, seventh, ninth, eleventh, thirteenth, and fifteenth lens surfaces R ₂ , R ₄ , R ₆ , R ₇ , R ₉ , R ₁₁ , R ₁₃ and R ₁₅ form the upper lens surface of the first to eighth lens elements E ₁₁ to E ₁₈ . Table 2 in Reference 4 shows the complete optical design for this lens.

The first and second lens elements E ₁₁ , E ₁₂ both have negative refractive power and negative meniscus lens elements with convex surfaces (lens surfaces R ₁ , R ₃ ) facing towards the object. ), The refractive index is 1.7 or more, and the Abbe number is 40 or more. The third lens element E ₁₃ is a positive meniscus lens element in which the convex surface (lens surface R ₆ ) faces upward, and has a refractive index of 1.7 or more and a Abbe number of 30 or less, which is relatively low. The fourth lens element E ₁₄ is a negative meniscus lens element with a convex surface (lens surface R ₇ ) facing upwards. The junction lens composed of the third lens element and the fourth lens element serves to correct a difference in refractive power according to the wavelengths of the first lens element E ₁₁ and the second lens element E ₁₂ . The fifth lens element E ₁₅ is a biconvex lens element, the sixth lens element E ₁₆ is a biconvex lens element, and the seventh lens element E ₁₇ and the eighth lens element E ₁₈ are biconvex. Lens element. Incident light originating from an object point on the object side (left side of the ground, not shown) is incident on the first lens surface R ₁ , which is a refractive surface of the first lens element E ₁₁ , thereby allowing the first to eighth lenses. Elements E ₁₁ -E ₁₈ and the optical low pass filter F sequentially pass and then converge to the sensor plane I.

4 and 5 illustrate an optical structure of a fisheye lens of the present invention consisting of eight lens elements E ₁₁ to E ₁₈ and a lens barrel B including a retainer (RT) and a spacer (SP). ) Shows the structure at a glance. In FIG. 4, the upper portion ('a' portion of the figure) shows the cross-sectional structure inside the barrel B based on the optical axis OA, and the lower portion ('b' portion of the figure) shows the outer circumference of the barrel B. see. 5 is a perspective view showing a cross-sectional structure inside the barrel.

The first to eighth lens elements E ₁₁ to E ₁₈ are sequentially arranged in the lens barrel B in the optical axis OA direction as shown in FIGS. 4 and 5, and the spacing between some lenses in the optical axis direction. In order to maintain the first to fourth spacers SP ₁ to SP ₄ are used. For example, the distance in the optical axis direction between the second lens element E ₁₂ and the third lens element E ₁₃ is defined by the first spacer SP ₁ , and thus the fourth lens element E ₁₄ and the fifth lens element. The distance in the optical axis direction between (E ₁₅ ), between the fifth lens element (E ₁₅ ) and the sixth lens element (E ₁₆ ), and between the seventh lens element (E ₁₇ ) and the eighth lens element (E ₁₈ ), respectively. It is stably held by the second spacer SP ₂ , the third spacer SP ₃ , and the fourth spacer SP ₄ . On the other hand, the first lens element E ₁₁ and the second lens element E ₁₂ are in edge contact with each other. Thus, no separate spacer is required between the first lens element E ₁₁ and the second lens element E ₁₂ . Meanwhile, in order to prevent the first lens element E ₁₁ from being detached from the lens barrel B, the retainer RT is used to fix the first lens element E ₁₁ to the barrel B. In addition, a first O-ring OR ₁ is used to prevent moisture from entering between the retainer RT and the lens barrel B. The second O-ring OR ₂ is used for waterproofing between the lens and the camera housing to which the lens is coupled. The first O-ring OR ₁ is located between the lens barrel B and the first lens element E ₁₁ and is mounted in a groove formed in the inner circumferential surface of the lens barrel B. The second o-ring OR ₂ is disposed between the upper side of the lens barrel B and the camera housing (not shown).

When such a fisheye lens is to be used for a rear camera or a dome camera, a problem inherent to the fisheye lens occurs. First, in order to obtain an external image having an angle of view of 180 ° or more using a fisheye lens, the camera barrel structure as shown in FIG. 1 cannot be used. This is because incident light with a large incident angle causes total reflection in a window having a planar structure. Thus, using a transparent dome as in the camera of FIG. 2 is the only realistic alternative. However, when the fisheye lens is placed in the transparent dome, light is reflected from the inner and outer walls of the transparent dome, which is an obstacle in obtaining a clear image. In particular, the problem is exacerbated when there is a strong direct light source outside.

However, when the transparent dome is not used in consideration of the reflection problem of light, a new problem arises in that the entire lens or the entire camera needs to be replaced when there is contamination or intentional damage caused by environmental factors. For example, if paint is applied to the first lens surface R ₁ of the first lens element E ₁₁ closest to the object side, or if scratches are caused by sand wind, only the first lens element E ₁₁ has a problem. Despite this, there is an economic loss to replace the entire lens.

[Reference 1] A. Inoue, "Wide converter lens system for both underwater and above-water use", US Pat. No. 6,654,179 (registration number), registered November 25, 2003.

[Reference Document 2] Lee, Hwan-Seon, "Wide-angle Converter Lens", Republic of Korea Patent No. 10-0585603 (registration number), May 25, 2006.

[Reference 3] N. Miyazawa, "Front converter lens", US Pat. No. 7,170,689 (registration number), registered January 30, 2007.

[Reference Document 4] Kwon Kyung-il, Milton Rykin, "Fisheye Lens", Korean Patent No. 10-0888922 (registration number), registration date March 10, 2009.

[Reference 5] G. Kweon, Y. Choi, and M. Laikin, "Fisheye lens for image processing applications", J. of the Optical Society of Korea, 12, 79-87 (2008).

The present invention allows the fisheye lens to be directly exposed to the outside without using a transparent dome to obtain an excellent image, and if damage occurs to the surface of the lens, the lens can be restored to its original state by replacing only some lens elements without replacing the entire lens. Provides a fisheye lens.

Fish-eye lens comprising a plurality of lens elements aligned in the optical axis direction according to an embodiment of the present invention, the first barrel is mounted to a portion of the lens element close to the object of the plurality of lens elements, the first barrel is detachable And a second barrel on which the remaining lens elements of the plurality of lens elements are mounted.

The portion of the lens element mounted to the first barrel is the first lens element closest to the object side, and the first lens element is the negative meniscus lens element with the convex surface facing towards the object.

The fisheye lens further includes a fixing part for preventing the second barrel from moving when the first barrel is attached to the second barrel fixed to the support.

According to another embodiment of the present invention, a fish-eye lens including a plurality of lens elements aligned in an optical axis direction may be coupled to a first barrel and a first barrel on which some lens elements closer to an object of the plurality of lens elements are mounted. And a second barrel on which the second lens barrel of the plurality of lens elements is mounted, and a barrel gap adjuster for adjusting a distance along the optical axis direction between the first barrel and the second barrel.

The present invention obtains a high quality image by directly exposing the fisheye lens to the outside without a separate transparent dome, the fisheye lens when there is permanent contamination by environmental factors such as rain or dust or intentional damage by potential criminals It is possible to easily replace only some lens elements on the object side, thereby minimizing the cost and time required for the maintenance of the imaging system.

According to the fisheye lens of the embodiment of the present invention, by detachably attaching to the second barrel the first barrel including some lens elements, for example, the first lens element closest to the object side, the first lens element may be damaged or damaged. In this case, only the first barrel needs to be replaced without replacing the entire lens, thereby simplifying installation, maintenance and repair. Moreover, it is not necessary to remove all the lenses from the camera, and unlike the camera using a flat window or the dome camera using a transparent dome, there is no optical degradation of the lens.

According to another embodiment of the present invention, by providing a barrel spacing adjuster connecting the first barrel and the second barrel to accurately maintain the gap between the lens elements mounted on the first barrel and the lens elements mounted on the second barrel. Can be.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 6 to 17.

(First embodiment)

6 is an exploded cross-sectional view of the fisheye lens 100 of the first embodiment of the present invention, Figure 7 is an assembled cross-sectional view. 6 and 7 show the mechanical structure of the entire lens including the lens element and the barrel of the fisheye lens of the first embodiment of the present invention.

The fisheye lens 100 includes a cover part (CP) facing toward an object and a main body (MB) facing upward. The front portion CP is the first barrel 110 and some lens elements mounted to the first barrel 110 of the plurality of lens elements E ₁₁ to E ₁₈ aligned in the optical axis direction of the fisheye lens 100. It includes. Some lens elements mounted on the first barrel 110 are at least one lens element comprising a first lens element E ₁₁ closest to the object side. In this embodiment, the first lens element E ₁₁ constitutes some lens element mounted on the first barrel. The body portion MB includes the second barrel 120, the remaining lens elements E ₁₂ to E ₁₈ except for some lens elements E ₁₁ mounted on the first barrel 110, and an aperture. . According to the exemplary embodiment of the present invention, when the first lens element E ₁₁ is mounted on the first barrel 110, the second barrel 120 includes the second to eighth lenses from the object side toward the image along the optical axis. Elements E ₁₂ to E ₁₈ can in turn be mounted. The optical structure of the first to eighth lens elements E ₁₁ to E ₁₈ may adopt the optical structure of the conventional fisheye lens shown in FIG. 3, and the optical performance of the fisheye lens 100 is described in Reference Documents 4 to 8. It may be identical to the performance of the fisheye lens shown in 5.

The first barrel 110 is provided with a first barrel fastening portion 111 so that the first barrel 110 and the second barrel 120 are detachable from each other, and the second barrel 120 has a second barrel fastening portion. 121a is provided. As an exemplary embodiment, as shown in FIGS. 6 to 9, the first barrel fastening portion 111 is implemented by a female screw formed on the inner circumferential surface of the first barrel 110, and the second barrel fastening portion 121a is It may be implemented by a male screw formed in the first region of the outer peripheral surface of the second barrel (120). However, the present invention is not limited thereto, and the shape and the fastening method of each fastening part may be variously modified.

The fisheye lens 100 is provided between a plurality of lens elements E ₁₁ to E ₁₈ to maintain a distance between neighboring lens elements and determine the position of the plurality of lens elements E ₁₁ to E ₁₈ . It may include at least one spacer, for example, first to fourth spacers 161 to 164. The lens elements E ₁₁ to E ₁₈ can be kept constant between them by these spacers 161 to 164 to achieve optimized optical performance.

Referring to FIGS. 6 and 7, the front part CP may include a first fastener that may be fastened to the first barrel fastener 111 to prevent the first lens element E ₁₁ from being separated from the first barrel 110. And retainer 151. For example, the first retainer 151 may be implemented as an annular male screw screwed to the first barrel fastening portion 111. Meanwhile, the body portion MB may include a second retainer 152 to prevent the second lens element E ₁₂ from being separated from the second barrel 120.

6 to 9, a first barrel gripping portion 112 is formed on an outer circumferential surface of the first barrel 110 such that the first barrel 110 of the fisheye lens 100 according to the first embodiment of the present invention is formed. It is possible to facilitate the coupling or disengagement of the second barrel (120). The first barrel gripper 112 may be implemented in the form of a protrusion or knurling provided on the outer circumferential surface of the first barrel 110. The user grips the first barrel holding portion 112 and the second barrel 120 formed on the first barrel 110 with both hands, respectively, so that the first barrel 110 and the second barrel 120 are easily coupled or combined. Can be released.

The front part CP may include at least one first barrel fixing screw fastening hole 113 formed in a direction perpendicular to the optical axis OA from the outer circumferential surface of the first barrel 110 to the first barrel fastening portion 111, and 1 further includes at least one first barrel fixing screw 114 fastened to the barrel fixing screw fastening hole 113. As shown in FIG. 7, when the first barrel fixing screw 114 is fastened to the first barrel fixing screw fastening hole 113 in a state in which the first barrel 110 and the second barrel 120 are coupled, The first barrel fixing screw 114 exerts a strong friction force on the second barrel coupling portion 121a inserted into the first barrel 110. Accordingly, the first and second barrels 110 and 120 are firmly engaged and relatively fixed, and the distance between the first lens element E ₁₁ and the second lens element E ₁₂ of the second barrel 120 is constant. Can be maintained.

In order to achieve the intended optical performance in the design, the body portion MB is formed of the second to eighth lens elements E ₁₂ to E ₁₈ arranged in sequence along the optical axis OA in the second barrel 120. The apparatus may further include first to fourth spacers 161 to 164 to maintain a predetermined interval. For example, the distance between the second lens element E ₁₂ and the third lens element E ₁₃ is stably maintained by the first spacer 161. Similarly, the distance between the fourth lens element E ₁₄ and the fifth lens element E ₁₅ is maintained by the second spacer 162 and the fifth lens element E ₁₅ and the sixth lens element E ₁₆ . The spacing of is maintained by the third spacer 163, and the spacing of the seventh lens element E ₁₇ and the eighth lens element E ₁₈ is maintained by the fourth spacer 164. In addition, in the present embodiment, the second spacer 162 is used as a fixed aperture.

The second retainer 152 is used to prevent the second lens element E ₁₂ , located at the outermost side of the second barrel 120 towards the object, from leaving the second barrel 120. In the example of FIGS. 6-7, the second retainer 152 is screwed into the second barrel 120 such that the second lens element E ₁₂ is fixed along the optical axis OA. However, the present invention is not limited thereto, and the second retainer may be coupled to the second barrel in various ways.

When the first barrel 110 and the second barrel 120 are screwed together and sufficiently tightened, the outer side of the second lens surface R ₂ of the first lens element E ₁₁ and the second retainer 152 as described above are secured. The first barrel 110 and the second barrel 120 are close to each other until the abutment. Referring to FIG. 7, in a state in which the first barrel 110 and the second barrel 120 are coupled, the first surface of the second retainer 152 may be partially connected to the upper lens surface of the first lens element E ₁₁ . In contact with the second surface abuts the side of the second lens element E ₁₂ (above the ground). In this way, the first lens element E ₁₁ and the second lens element E ₁₂ have an optimized spacing in the optical axis direction.

On the other hand, a fixing nut fastening portion 121b to which the fixing nut 140 is fastened is formed in a second region adjacent to the first region on the outer circumferential surface of the second barrel 120, and the second on the outer circumferential surface of the second barrel 120 is formed. The lens fastening part 121c is fastened to a lens holder (not shown) mounted to the camera in the third area upwardly adjacent to the two areas. The lens fastening portion 121c is fastened to a lens holder which is typically provided in a small board camera, and is usually formed of a 12mm male screw or 9mm male screw. In the embodiment of the present invention, the lens fastening portion 121c is implemented by Hitachi M12 male thread. This lens fastening portion corresponds to the screw portion of the lens holder (Lens holder) of the camera. Therefore, the lens fastening portion is coupled to the screw portion of the lens holder to maintain a constant distance between the lens and the image sensor I located inside the lens holder.

Meanwhile, the fixing nut fastening part 121b is used for fixing the fisheye lens 100 to the support 50 such as a wall as shown in FIGS. 7 and 9. That is, after forming the lens insertion hole 51 having a diameter sufficient to pass through the fixing nut fastening portion in the support 50 to which the fisheye lens 100 is to be installed, the fixing nut fastening portion 121b of the fisheye lens 100 is formed. ) Is inserted into the lens insertion hole 51 formed in the support 50 from the outside to the inside direction (from left to right on the basis of the drawing). Thereafter, when the fixing nut 140 corresponding to the fixing nut fastening part 121b is fastened from the inside of the support 50, the fisheye lens 100 is fixed in close contact with the support.

The fixing nut fastening part 121b may be implemented with a male screw, and the inner circumferential surface of the fixing nut 140 may be implemented with a female screw corresponding to the fixing nut fastening part 121b. A fixing nut gripping portion 142 is formed on an outer circumferential surface of the fixing nut 140 to easily hold and rotate the fixing nut 140 by hand. The fixing nut gripping portion 142 may be implemented as a protrusion or knurling formed in the optical axis direction on the outer circumferential surface of the fixing nut. In addition, at least one nut fastening hole 143 formed in a direction perpendicular to the optical axis OA through the outer circumferential surface of the fixing nut 140 and at least one nut fastening to the at least one nut fastening hole 143 are fixed. Screw 144 may be provided. Therefore, as shown in FIG. 7, when the nut fixing screw 144 is fastened to the nut fastening hole 143 in a state where the fixing nut 140 is fastened to the second barrel 120, the nut fixing screw 144 is provided. Applies a strong frictional force to the outer circumferential surface of the fixing nut fastening portion 121b. Therefore, the fixing nut 140 and the second barrel 120 are firmly engaged to be relatively fixed, and the fixing nut 140 may be prevented from being arbitrarily released from the second barrel 120.

When releasing or otherwise engaging the first barrel 110 from the second barrel 120 while the first barrel 110 and the second barrel 120 of the fisheye lens 100 are fixed to the support 50. Despite the fixing nut 140, the second barrel 120 may move or rotate together with the first barrel 110. In order to prevent the second barrel 120 from moving with the first barrel 110 as described above, one side of the upper side of the second barrel 120 in contact with the support as shown in FIGS. 8 and 9 (hereinafter, referred to as a support contact surface). It may be provided with a fixing portion (125).

6 to 9, the fixing part 125 may include at least one second barrel fixing screw fastening hole 123 formed in parallel with an optical axis OA on an upper side of the second barrel 120. And at least one second barrel fixing screw 124 fastened to the at least one second barrel fixing screw fastening hole 123. As illustrated in FIGS. 6 and 7, the second barrel fixing screw fastening hole 123 is formed at an interface between the second barrel fastening part 121a and the fixing nut fastening part 121b.

Referring to FIG. 9, at least one second barrel fixing screw which has a one-to-one correspondence with the second barrel fixing screw fastening hole 123 of the second barrel 120 around the lens insertion hole 51 formed in the support 50. Insertion hole 52 may be provided. When the second barrel fixing screw 124 is fastened to the second barrel fixing screw fastening hole 123, one end of the second barrel fixing screw 124 may protrude upward through the support 50. Therefore, when the fixing nut fastening portion 121b is inserted into the lens insertion hole 51, one end of the second barrel fixing screw 124 protruding upward may be inserted into the second barrel fixing screw insertion hole 52. have. Therefore, even if the first barrel 110 is rotated relative to the second barrel 120 to engage or disengage the first and second barrels 110 and 120, the second barrel 120 may be in the optical axis OA. Does not rotate around the center

6 to 9, the fixing part 125 includes a second barrel fixing screw fastening hole 123 and a second barrel fixing screw 124. However, the fixing part may be implemented in various forms. For example, a second barrel fixing rod and a second barrel fixing rod fastening hole may be implemented instead of the second barrel fixing screw. In such a case, the production cost can be reduced when the second barrel is to be produced by injection.

On the other hand, the fixing portion may be implemented in the form of a protrusion on the support contact surface of the second barrel. For example, a protrusion is formed on a support contact surface of the second barrel 120 in place of the second barrel fixing screw 124, and a protrusion is formed in the support 50 in place of the second barrel fixing screw insertion hole 52. An insertion hole may be formed so that the protrusion may be inserted into the groove. In a simpler way, an adhesive tape such as a double-sided tape may be applied to the support contact surface of the second barrel 120 without using the second barrel fixing screw 124 or the protrusion. In addition, a method of forming a rough surface on the support contact surface with sandpaper or the like to greatly increase the friction force between the contact surface of the second barrel and the support may be used. Alternatively, the second barrel fixing screw or the rod may be fastened to the second barrel in a vertical direction rather than in a direction parallel to the optical axis. In this case, the second barrel fixing screw fastening hole or the second barrel fixing bar fastening hole should be formed at a side perpendicular to the optical axis of the second barrel. As such, the fixing part serves to prevent the second barrel from moving along even if the first barrel is loosened or tightened, and the specific shape may be implemented in various forms.

According to the first embodiment, when the first lens element (E ₁₁ ) closest to the object side of the fisheye lens, in particular the first lens surface (R ₁ ) is damaged, only the front part needs to be replaced, not the entire lens, so maintenance Becomes very simple. In addition, there is an advantage that does not need to separate the second barrel 120 from the camera.

In the first embodiment of the present invention, in order to reduce the maintenance cost of the fisheye lens 100, that is, to reduce the number of lens elements replaced, the first lens element E ₁₁ closest to the object side of the plurality of lens elements E _11. ), Only the first lens element (E ₁₁ ) and the second lens element (E ₁₂ ) are mounted in the first barrel (110), considering only the structure of the fisheye lens. It is further preferred that the second barrel 120 is equipped with third to eighth lens elements E ₁₃ to E ₁₈ .

The first embodiment and the prior art of the present invention has the following differences. First, in a camera using a flat window as shown in FIG. 1 or a dome camera using a transparent dome as shown in FIG. 2, a flat window or a transparent dome does not affect the optical performance of the lens. In other words, in an ideal case, the same image may be obtained regardless of the existence of a planar window for protecting the lens 12 of FIG. 1 and a transparent dome 25 for protecting the lens 26 of FIG. In the case of the conventional converter lens, there is a difference in the angle of view with and without the converter lens, and the image can be obtained only with the master lens without the converter lens. As such, conventional planar windows, transparent domes, and converter lenses are only optional components, not essential components for obtaining images. Moreover, in the case of flat windows, transparent domes, there is no need for precise alignment with the lens. On the contrary, the first lens element E ₁₁ of the replaceable first barrel 110 in the fisheye lens 100 according to the embodiment of the present invention is an essential component for obtaining an image, and the first barrel 110 is provided. Some of the lens elements (including at least the first lens element) mounted therein and the remaining lens elements mounted on the second barrel 120 in the optical axis direction, the center position, the inclination angle, etc., are all within a predetermined error range. It must be aligned. For example, the error in the distance in the optical axis direction should be within 20 μm, the decentering from the center position within 7.5 μm, and the tilt angle of the lens element should be within 0.01 °.

(Second embodiment)

10 shows the shape of a lens comprising a plurality of lens elements and the path of the light rays according to an embodiment of the invention. The lens has an F-number of 2.8, an angle of view of 240 °, and a 1 / 2.5-inch charge coupled device (CCD) sensor. The image size corresponding to the incident angle of 120 ° is given as 1.848 mm so that the angle of view in all directions of the image captured by the camera using such an image sensor is 240 °.

The lens comprises a plurality of lens elements E ₂₁ to E ₂₉ and an aperture S which are divided into _first to third groups G ₁ to G ₃ . The first group G ₁ is composed of the first lens element E ₂₁ and the second lens element E ₂₂ from the object side, and the second group G ₂ is the third lens element E ₂₃ to the first. It consists of five lens elements E ₂₃ to E ₂₅ , and the third group G ₂ consists of sixth to ninth lens elements E ₂₆ to E ₂₉ .

The first to ninth lens elements E ₂₁ to E ₂₉ are all double-sided refractive lens elements, and the aperture S is located between the fifth lens element E ₂₅ and the sixth lens element E ₂₆ . . An optical low pass filter F, which is part of the components of the camera body covering the image sensor plane I, may be located between the ninth lens element E ₂₉ and the image sensor plane I. The role of the optical low pass filter (F) is to remove the moire effect in the image. 10 shows that the lens is designed in consideration of this optical low pass filter.

As described above, the first to ninth lens elements E ₂₁ to E ₂₉ are all refractive lens elements and have two lens surfaces. For example, the first lens element has a first lens surface R _{1 on} the object side and a second lens surface R _{2 on} the image side, and the second lens element E ₂₂ is It has a third lens surface R ₃ on the object side and a fourth lens surface R _{4 on the image} side, and the remaining lens elements also have a fifth lens surface R ₅ to a seventeenth lens surface R ₁₇ .

Incident light originating from an object point on the object side is incident on the first lens surface R ₁ , which is the refractive surface of the first lens element E ₂₁ , and the first to ninth lens elements E ₂₁ to E ₂₉ . After passing through the optical low pass filter F sequentially, it converges to the sensor plane I.

Table 1 shows the complete optical design for the fisheye lens shown in FIG. 10. In Table 1, the units of radius and thicknesses are millimeters.

surface number group element surface radius thickness index Abbe number glass object infinity infinity One G ₁ E ₂₁ R ₁ 29.901 2.690 1.7724 49.61 E-LASF016 2 R ₂ 10.669 6.230 3 E ₂₂ R ₃ 33.255 1.490 1.7724 49.61 E-LASF016 4 R ₄ 5.072 4.350 5 G ₂ E ₂₃ R ₅ -16.511 4.140 1.7845 25.68 E-SF11 6 E ₂₄ R ₆ -5.754 1.080 1.7199 50.23 E-LAK10 7 R ₇ 9.090 1.940 8 E ₂₅ R ₈ -185.184 3.000 1.6199 36.26 E-F2 9 R ₉ -7.886 9.390 10 S S infinity 1.560 11 G ₃ E ₂₆ R ₁₀ 10.180 1.950 1.7014 41.17 E-BASF7 12 R ₁₁ -5.125 0.270 13 E ₂₇ R ₁₂ -4.107 0.980 1.8049 25.43 E-SF6 14 R ₁₃ 10.730 0.170 15 E ₂₈ R ₁₄ 38.840 2.170 1.6203 60.29 E-SK16 16 R ₁₅ -5.094 0.200 17 E ₂₉ R ₁₆ 8.228 2.070 1.6030 60.67 E-SK14 18 R ₁₇ -24.347 1.976 19 F F R ₁₈ infinity 3.000 1.5167 64.10 E-BK7 20 R ₁₉ infinity 1,000 21 I I R ₂₀ infinity

10 and Table 1, the first lens element E ₂₁ is a negative meniscus lens element with a convex surface facing towards the object. In other words, the first lens surface R ₁ of the first lens element E ₂₁ is a convex surface facing toward the object, and the second lens surface R ₂ is a concave surface facing upward. The first radius of curvature of the lens surface (R ₁₎ it is 29.901mm, and the center of a circle matching the first lens surface (R ₁₎ is located at the right side (that is, sangjjok) relative to the first lens surface (R ₁₎ . Therefore, in the center of this circle a first lens surface (R ₁₎ a vertex (vertex) on the facing direction - hereinafter referred to as a first lens surface direction of the vector (R ₁₎ - is the direction toward the object side, a side. Here, the vertex means an intersection point between the lens surface and the optical axis. The second is the radius of curvature of the lens surface (R ₂₎ is 10.669mm, the located on the right side with respect to the second lens surface (R ₂₎ a second lens surface (R ₂₎ center of the circle also matching. Therefore, the direction vector of the second lens surface R ₂ also faces toward the object from above. Such a lens element is referred to as a Meniscus lens element when the direction vector of the lens surface on the object side of an lens element coincides with the direction vector of the upper lens surface.

Meanwhile, since the radius of curvature of the first lens surface R ₁ is 29.901 mm and the radius of curvature of the second lens surface R ₂ is 10.669 mm, the first lens element E ₂₁ measures the lens element parallel to the optical axis. The thickness of is thicker at the edge than the center. The first lens element E ₂₁ is therefore a lens element with negative refractive power. Putting these facts together, the first lens element E ₂₁ is a negative meniscus lens element with the convex surface facing towards the object. Similarly, the second lens element E ₂₂ having the third lens surface R ₃ and the fourth lens surface R ₄ is also a negative meniscus lens element whose convex surface faces toward the object.

Meanwhile, the third lens element E ₂₃ and the fourth lens element E ₂₄ form a cemented doublet. The third lens element E ₂₃ has a fifth lens surface R ₅ on the object side and a sixth lens surface R ₆ on the image side, and the fourth lens element E ₂₄ has a sixth lens surface on the object side. (R ₆ ) and the seventh lens surface (R ₇ ) on the upper side. The third lens element E ₂₃ and the fourth lens element E ₂₄ share a sixth lens surface R ₆ due to the nature of the bonded lens. Physically, the upper lens surface of the third lens element E ₂₃ and the object-side lens surface of the fourth lens element E ₂₄ are processed to have the same curvature and then bonded using optical cement.

The fifth lens surface R ₅ of the third lens element E ₂₃ is an upwardly convex surface, and the sixth lens surface is shared between the third lens element E ₂₃ and the fourth lens element E ₂₄ . (R ₆ ) is also a convex surface facing upwards, and the radius of curvature of the fifth lens surface (R ₅ ) is -16.511 mm, and the radius of curvature of the sixth lens surface (R ₅ ) is -5.754mm, with the center portion edged. It is a thicker meniscus lens element, so that the third lens element E ₂₃ has a positive refractive power, in aggregate, the third lens element E ₂₃ has a positive meniscus lens with a convex surface facing upwards. Element.

On the other hand, the fourth lens element E ₂₄ has a sixth lens surface R ₆ and a seventh lens surface R ₇ . The sixth lens surface R ₆ is a concave surface facing toward the object side, and the seventh lens surface R ₇ is a concave surface facing upward. Therefore, the direction vector of the sixth lens surface R ₆ and the direction vector of the seventh lens surface R ₇ face each other. Such lens elements are referred to as bi-concave lens elements. Amphipathic lens elements always have negative refractive power.

The fifth lens element E ₂₅ has an eighth lens surface R ₈ and a ninth lens surface R ₉ . The eighth lens surface R ₈ is a convex surface facing toward the object, and the ninth lens surface R ₉ is a convex surface facing upward. Therefore, the direction vector of the eighth lens surface R ₈ and the direction vector of the ninth lens surface R ₉ face opposite to each other. Such lens elements are referred to as bi-convex lens elements. Biconvex lens elements always have positive refractive power.

The sixth lens element E ₂₆ positioned between the fifth lens element E ₂₅ and the aperture S has a tenth lens surface R ₁₀ and an eleventh lens surface R ₁₁ . The tenth lens surface R ₁₀ is a convex surface facing toward the object, and the eleventh lens surface R ₁₁ is a convex surface facing upward. The sixth lens element E ₂₆ is thus a biconvex lens element. Likewise the seventh lens element E ₂₇ is a biconvex lens element and the eighth lens element E ₂₈ and the ninth lens element E ₂₉ are biconvex lens elements.

Lens configurations, such as the glass composition and thickness of the spherical lens elements, are given in Table 1, and all optical glasses were selected from glass of Hikari. For example, the first lens element E ₂₁ is a high refractive glass with a refractive index of 1.7724 and an Abbe number of 49.61. Hikari (Hikari) product having such refractive index and optical characteristics closest to Abbe's number has the trade name "E-LASF016". The second to ninth lens elements E ₂₁ to E ₂₉ are also assumed to use Hikari's optical glass. However, such a design can be easily changed to suit the characteristics of products of other companies such as Schott or Hoya.

The lens elements belonging to the first group G ₁ are mainly introduced for the purpose of converting the incident angle of incident light and all have negative refractive power. High refractive index is required to greatly change the angle of incidence, and relatively high Abbe's number is required to reduce the variation with wavelength. In the present embodiment, both the first lens element E ₂₁ and the second lens element E ₂₂ belonging to the first group G ₁ have negative refractive power, the refractive index is 1.7 or more, and the Abbe number is 40 or more. to be. Such a high refractive index is necessary to obtain a sufficient angle of view without the lens surface being close to the hemisphere, and a relatively high Abbe number is necessary to reduce the variation according to the wavelength. In addition, the first lens element E ₂₁ and the second lens element E ₂₂ may be embodied as negative meniscus lens elements whose convex surfaces are directed toward the object. In particular, since the first lens element must convert the incident angle of incident light having an incident angle of 90 ° or more to 90 ° or less, it is inevitably implemented as a negative meniscus lens having a convex surface facing toward the object. However, the second lens element E ₂₂ is not necessarily implemented as a negative meniscus lens because it has the purpose of converting light rays having an angle of incidence of 90 ° or less into light rays having a smaller angle of incidence. (plano-concave lens element) or biconcave lens element (biconcave lens element) can be implemented in any lens form having a negative refractive power.

The third to fifth lens elements E ₂₃ to E ₂₅ belonging to the second group G ₂ have a main role of compensating for the difference in refractive power according to the wavelength of the lens elements of the first group. The above-mentioned junction lens is included, and a lens element having an Abbe number of 30 or less and a lens element having an Abbe number of 40 or more are used together in the junction lens. In the present embodiment, the third lens element E ₂₃ has a positive refractive power, the refractive index is 1.7 or more and the Abbe number is 30 or less. The fourth lens element E ₂₄ has a negative refractive power, and has a refractive index of at least 1.7 and an Abbe number of at least 40. The third lens element E ₂₃ and the fourth lens element E ₂₄ constitute a joint lens. The fifth lens element E ₂₅ is a lens element introduced for further chromatic aberration correction, and is a biconvex lens element having positive refractive power, having a refractive index of 1.6 or more and an Abbe number of 40 or less.

Lens elements belonging to the second group G ₂ and lens elements belonging to the third group G ₃ are distinguished by an aperture S. FIG. Lens elements belonging to the third group G ₃ are necessary to form a clear real image on the image sensor surface and have a positive refractive power as a whole. In this embodiment, the third group G ₃ is composed of sixth to ninth lens elements E ₂₆ to E ₂₉ . In particular, the sixth lens element E ₂₆ closest to the object side of the third group G ₃ and the ninth lens element E ₂₉ closest to the image have positive refractive power.

FIG. 11 shows the modulation transfer function characteristics in the visible light region of the fisheye lens of FIG. 10 and has a resolution of about 0.2 or more at 100 line pairs / millimeter. On the other hand, Fig. 12 shows that the peripheral light quantity ratio of this fisheye lens is almost close to one. In general, if the ambient light ratio is 0.6 or more, it is considered to be good, so the ambient light ratio of this fisheye lens is very excellent. Meanwhile, the left graph of FIG. 13 shows a field curvature of the fisheye lens shown in FIG. 10, and the right graph shows a calibrated distortion. From this graph, it can be seen that the maximum correction distortion is 6% or less. In other words, this lens implements an equidistant projection method fairly faithfully.

Another major characteristic of the lens is its overall length, i.e. the distance from the vertex of the first lens plane to the image plane I, 49.656 mm, which is relatively small. It also has a sufficient back focal length, so there is no inconvenience in industrial use.

Last but not least, the manufacturing tolerances are good. The lens of this embodiment has nine lens elements, and there are a total of 17 lens surfaces. In addition, a number of spacers and barrels are used to keep these lens elements precisely spaced as defined in Table 1. Since such lens elements and spacers must be mechanically processed, it is impossible to manufacture them accurately and without errors as designed. That is, there is some error. However, since Table 1 is a design that is optimized to have a given characteristic, if the design and the error has a degree of degradation occurs. In addition, depending on the lens design, the range of processing error that causes a certain amount of performance degradation is different. Good design results in relatively small degradation in performance even with large machining errors.

The manufacturing tolerances available with current production techniques vary among lens manufacturers, but general manufacturing tolerances are almost common. For example, the thickness tolerance is 20 µm, and the manufacturing tolerance of the radius of the lens surface is Newton ring 3 fringe. In this way, even if manufactured in the general manufacturing tolerances can be produced at low cost if the performance degradation is not large. However, if you try to produce a production tolerance smaller than the general production tolerances in order to reduce the performance degradation or defective rate, the production may be difficult or impossible, even if possible, the production cost is high, and mass production may be difficult. Therefore, a design that does not have sufficient manufacturing tolerances, even if it satisfies all desirable optical and mechanical properties, is not a good design.

The fisheye lens shown in FIG. 10 is a design that is good enough to maintain the failure rate at a general level even when fabricated with a general manufacturing tolerance. Such manufacturing tolerances can be identified through a process called tolerance analysis. If you have a complete lens design as shown in Table 1, you can easily check using a lens design program such as Zemax.

Figure 14 shows the mechanical structure of the fisheye lens of the second embodiment of the present invention. The front portion CP of the fisheye lens 200 includes the first barrel 210 and some lens elements mounted to the first barrel 210 of the plurality of lens elements E ₂₁ -E ₂₉ . The lens element mounted on the first barrel 210 comprises a first lens element E ₂₁ closest to the object side. The body portion MB may include the remaining lens elements (for example, the second lens element to the ninth lens element E ₂₂ to E ₂₉ ) except for some lens elements mounted on the second barrel 220 and the first barrel 210. A stop (not shown) and a barrel spacing adjuster 230. The stop may be disposed between the fifth lens element E ₂₅ and the sixth lens element E ₂₅ as shown in FIG.

The barrel spacing adjuster 230 is positioned between the two barrels 210 and 220 when the first barrel 210 and the second barrel 220 are coupled to adjust the gap between the two barrels. The first barrel 210 may be detachable from the barrel spacing controller 230, and the barrel spacing controller 230 may be detachable from the second barrel 220. To this end, the first and second barrels 210 and 220 and the barrel gap adjuster 230 are provided with fastening means, respectively. As an exemplary embodiment, as shown in FIGS. 14 to 17, the front part CP includes a first barrel fastening part 211 formed on an inner circumferential surface of the first barrel 210, and a first barrel fastening part. Reference numeral 211 is implemented with a female screw. The second barrel 220 includes a second barrel coupling portion 221a formed in the first region of the outer circumferential surface thereof, and the second barrel coupling portion 221a is implemented with a male screw. In addition, the barrel spacing adjuster 230 includes an outer fastening portion 231a formed on the outer circumferential surface and an inner fastening portion 231b formed on the inner circumferential surface, and the outer fastening portion 231a and the inner fastening portion 231b are male and female threads, respectively. Is implemented. The outer fastening part 231a is screwed with the first barrel fastening part 211, and the inner fastening part 231b is screwed with the second barrel fastening part 221a. According to the degree of fastening the inner fastening portion 231b of the barrel spacing adjuster 230 with respect to the second barrel fastening portion 221a of the second barrel 220, The distance in the optical axis direction can be adjusted. On the other hand, the first barrel fastening portion 211 of the first barrel 210 is fastened to the outermost fastening portion 231a of the barrel gap adjuster 230 to the maximum depth. However, the first barrel fastening portion 211, the second barrel fastening portion 221a, the outer fastening portion 231a, and the inner fastening portion 231b are not limited to the above examples, The shape and the fastening method may be implemented in various modifications capable of fastening and positioning.

Fish-eye lens 200 is provided between a plurality of lens elements (E ₂₁ ~ E _29), to maintain the spacing between adjacent lens elements and determine the location of a plurality of lens elements (E ₂₁ ~ E ₂₉₎ At least one spacer, such as first to fifth spacers 261 to 265. The lens elements E ₂₁ to E ₂₉ can be kept constant by these spacers 261 to 265 to achieve optimized optical performance. In addition, first to fourth retainers 251 to 254 are used to prevent lens elements from leaving the first to second barrels.

Referring to FIGS. 14 and 15, the front portion CP may include a first fastener that may be fastened to the first barrel fastening portion 211 to prevent the first lens element E ₂₁ from being separated from the first barrel 210. It may further include a retainer 251. The first retainer 251 is screwed to the first barrel fastening portion 211.

The first barrel 210 further includes a first barrel grip 212. 14 to 17, a first barrel gripping portion 212 is formed on an outer circumferential surface of the first barrel 210 to facilitate coupling or disengagement of the first barrel 210 and the barrel spacing adjuster 230. can do. Preferably, the first barrel gripping portion 212 is implemented in the form of a projection or knurling provided on the outer peripheral surface of the first barrel (210).

As shown in FIGS. 14 and 15, the second barrel 220 may include the second through fifth lens elements E ₂₂ through E ₂₅ of the second through ninth lens elements E ₂₂ through E ₂₉ . ) Is mounted on the front second barrel 220A and the sixth lens elements E ₂₆ to E ₂₉ so that one end of the object is inserted into the front second barrel 220A. 220B). The front second barrel 220A and the rear second barrel 220B may be manufactured and assembled separately.

In the front end second barrel 220A, the distance between the second lens element E ₂₂ and the third lens element E ₂₃ is stably maintained by the first spacer 261. Since the third lens element E ₂₃ and the fourth lens element E ₂₄ constitute a bonded lens, a separate spacer is not required between the third lens element E ₂₃ and the fourth lens element E ₂₄ . The distance between the fourth lens element E ₂₄ and the fifth lens element E ₂₅ is stably maintained by the second spacer 262.

The distance between the sixth lens element E ₂₆ and the seventh lens element E ₂₇ in the rear second barrel 220B is maintained by the fourth spacer 264, and the seventh through ninth lens elements E ₂₇ to E ₂₉ are maintained by the fifth spacer 265. The upper inlet cross-sectional area of the rear second barrel 220B is designed to be smaller than the cross-sectional area of the ninth lens element E ₂₉ so that the ninth lens element E ₂₉ is not separated from the rear second barrel 220B. In order not to affect the optical performance, the upper inlet of the trailing second barrel 220B is designed to be wider than the opening of the ninth lens element E ₂₉ .

The second retainer 252 is used to prevent the second lens element E ₂₂ from escaping from the shear second barrel 220A. The second retainer 252 is screwed to the second barrel 220 such that the second lens element E ₂₂ is fixed along the optical axis OA from the object side upward. A third retainer 253 is used at the object-side inlet of the rear second barrel 220B so that the sixth lens element E ₂₆ mounted on the rear second barrel 220B is not separated from the rear second barrel 220B. Do not. The third retainer 253 may be used as a fixed aperture. To this end, the inner diameter of the third retainer 253 is designed to fit the F-number of the fixed aperture. The gap between the fifth lens element E ₂₅ and the rear second barrel 220B is stably maintained by the third spacer 263. On the other hand, the fourth retainer 254 is used so that the rear second barrel 220B is not separated from the front second barrel 220.

In the second region of the outer circumferential surface of the second barrel 220, that is, the object-side region of the outer circumferential surface of the front second barrel 220A, a fixing nut fastening part 221b to which the fixing nut 240 is fastened is formed. The fixing nut fastening part 221b is used for fixing the fisheye lens 200 to the support 50 as shown in FIGS. 15 and 17. That is, after forming the lens insertion hole 51 having a diameter sufficient to pass the fixing nut fastening portion 221b to the support 50 to install the fisheye lens 200, the fixing nut of the fisheye lens 200 The fastening part 221b is inserted into the lens insertion hole 51 formed in the support 50 from the outside inward direction. Thereafter, when the fixing nut 240 corresponding to the fixing nut fastening part 221b is fastened from the inside of the support 50, the fisheye lens 200 is fixed to the support.

A lens fastening portion 221c is formed at a third region of the outer circumferential surface of the second barrel 220, that is, at the outer circumferential surface of the rear second barrel 220B, to be coupled to a lens holder (not shown) mounted to the camera. The lens fastening portion 221c is fastened to a lens holder which is typically provided in a small board camera, and is usually formed of a 12mm screw or a 9mm screw. In an embodiment of the present invention, the lens fastening portion 221c is implemented by Hitachi M12 screws. The lens fastening part 221c may be coupled to the screw part of the lens holder in correspondence to the screw part of the lens holder of the camera to maintain a constant distance between the lens and the image sensor I located inside the lens holder. .

The fixing nut fastening part 221b may be implemented with a male screw, and the inner circumferential surface of the fixing nut 240 may be implemented with a female screw corresponding to the fixing nut fastening part 221b. A fixing nut gripping portion 242 is formed on an outer circumferential surface of the fixing nut 240 to easily hold and rotate the fixing nut 240 by hand. The fixing nut gripping portion 242 may be a protrusion or knurling formed in the optical axis direction on the outer circumferential surface of the fixing nut 240. The fixing nut 240 is fastened to at least one nut fastening hole 243 and at least one nut fastening hole 243 formed in a direction perpendicular to the optical axis OA from its outer circumferential surface to the fastening nut fastening portion 221b. At least one nut fixing screw 244 is further included. Therefore, as shown in FIG. 15, when the nut fixing screw 244 is fastened to the nut fastening hole 243 in a state where the fixing nut 240 is fastened to the second barrel 220, the nut fixing screw 244 is fixed. Applies a strong friction force to the outer circumferential surface of the fixing nut fastening portion (221b). Therefore, the fixing nut 240 and the second barrel 220 are firmly engaged with each other to be relatively fixed, and the fixing nut 240 can be prevented from being arbitrarily released from the second barrel 220.

In the state where the fisheye lens 200 is fixed to the support 50, the second barrel 220 may be used even when there is a fixing nut 240 when disengaging or otherwise engaging the first barrel 210 from the second barrel 220. ) May move together with the first barrel 210. As such, the fixing part 225 is provided on an upper side of the second barrel 220 to prevent the second barrel 220 from moving together with the first barrel 210.

In the second embodiment illustrated in FIGS. 14 to 17, the fixing part 225 may include at least one second barrel fixing screw fastening hole 223 formed in parallel with the optical axis OA on the upper side of the second barrel 220. And at least one second barrel fixing screw 224 fastened to the at least one second barrel fixing screw fastening hole 223. As shown in FIG. 15 and FIG. 16, the second barrel fixing screw coupling hole 223 is formed at the interface between the second barrel coupling portion 221a and the fixing nut coupling portion 221b.

Referring to FIG. 17, a plurality of second barrels are fixed around the lens coupling part insertion hole 51 of the support 50 so as to correspond to the position of the second barrel fixing screw fastening hole 223 of the second barrel 220. The screw insertion hole 52 is provided. When the second barrel fixing screw 224 is fastened to the second barrel fixing screw fastening hole 223, one end of the second barrel fixing screw 224 protrudes upward. Therefore, when the fixing nut fastening portion 221b is inserted into the lens insertion hole 51, one end of the second barrel fixing screw 224 protruding upward is inserted into the second barrel fixing screw insertion hole 52. Therefore, even if the first barrel 210 is rotated relative to the second barrel 220 to engage or disengage the first and second barrels 210 and 220, the second barrel 220 may be inclined to the optical axis OA. Does not rotate around the center

The barrel gap adjuster 230 that adjusts the gap between the first barrel 210 and the second barrel 220 in the optical axis direction includes an outer fastening portion 231a and an inner fastening portion 231b, and has a ring shape. May have The barrel spacing adjuster 230 may further include an adjuster gripping portion 232. Referring to FIGS. 14 to 17, an adjuster gripping portion 232 is formed on an outer circumferential surface of the barrel gap adjuster 230 to facilitate coupling or disengaging of the barrel gap adjuster 230 and the first barrel 210. have. The adjuster gripping portion 232 may be implemented in the form of a protrusion or knurling provided on the outer circumferential surface of the barrel spacing adjuster 230. Accordingly, the user grips the first barrel gripper 212 formed on the first barrel 210 and the regulator gripper 232 formed on the barrel gap adjuster 230 with both hands, respectively, so as to hold the first barrel 210 and the barrel gap. The regulator 230 may be coupled or disengaged.

The barrel spacing regulator 230 is fastened to at least one regulator fixing screw fastening hole 233 and a regulator fixing screw fastening hole 233 formed in a direction perpendicular to the optical axis OA from the outer circumferential surface to the inner fastening part 231b. It further includes at least one adjuster fixing screw 234. Therefore, as shown in FIG. 14, when the regulator fixing screw 234 is fastened in a state in which the second barrel 220 and the barrel spacing regulator 230 are coupled, the fixing screw fixing part 234 may have a second barrel ( A strong friction force is applied to the second barrel fastening portion 221a formed at 220. Therefore, the second barrel 220 and the barrel gap adjuster 230 may be firmly engaged to be relatively fixed.

The distance between the first lens element E ₁₁ disposed in the first barrel 110 and the second lens element E ₁₂ disposed in the second barrel 120 according to FIGS. The spacing is maintained by the second retainer 152 in contact with both the first and second lens elements E ₁₁ , E ₂₂ . Accordingly, when the first lens element E ₁₂ and the second retainer 152 are rubbed and worn, when the first barrel 110 and the second barrel 120 are repeatedly engaged or disengaged. It is difficult to keep the gap between E ₁₁ ) and the second lens element E ₁₂ constant. For example, when retaining the first barrel, the second retainer may be released together by friction. On the other hand, referring to FIG. 15, the first lens element E ₂₁ does not contact the second lens element E ₂₂ and the second retainer 252, and therefore, the first barrel 210 and the second barrel 220. It is possible to prevent the occurrence of friction during repeated coupling or disengagement of).

Referring to FIG. 15, the spacing t ₂ of the first lens element E ₂₁ and the second lens element E ₂₂ must be kept constant in order to achieve optimal optical performance. However, due to manufacturing tolerances, the second to ninth lens elements E ₂₁ to E ₂₉ , the second retainer 252, the first to fifth spacers 261 to 265, the rear second barrel 220B, and the like. The spacing in the direction of the optical axis OA may have any error. When such an error accumulates, a large error may occur in the distance between the first lens element E ₂₁ and the second lens element E _{22 which} are not in direct contact, and the optical performance of the lens may be greatly degraded.

In order to solve such a problem, in the present embodiment, the interval between the first barrel 210 and the second barrel 220 is adjusted using the barrel gap adjuster 230 to adjust the second to ninth lens elements E ₂₂ to. E ₂₉ ) cumulative tolerances up to. That is, considering the cumulative tolerance and the length of the second retainer 252 in the optical axis OA direction, the first lens element E ₂₁ and the second lens element E ₂₂ are predetermined intervals along the optical axis OA. The barrel spacing adjuster 230 is rotated in a clockwise or counterclockwise direction with respect to the second barrel 220. After the relative rotation of the barrel spacing controller 230 with respect to the second barrel 220, when the regulator fixing screw 234 is fastened to the regulator fixing screw fastening hole 233, the barrel spacing controller 230 and the second barrel 220. Is firmly interlocked. Then, when the first barrel 210 is screwed to the barrel spacing adjuster 230 until the first barrel 210 no longer rotates, the first lens element E ₂₁ and the second lens element E ₂₂ . Can maintain the spacing in the designed optical axis direction.

Preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the detailed description and the embodiments of the present invention are merely exemplary, and it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

Since the fisheye lens of the embodiment of the present invention can easily replace some lens elements including the first lens element closest to the object side, an excellent image can be obtained by directly exposing the lens to the outside without using a separate transparent dome. When the lens surface is damaged, only some of the lens elements can be replaced to restore the optimum state quickly and at low cost.

1 is a conceptual diagram of an installation state of a rear camera for a vehicle according to the prior art.

2 is a conceptual diagram of a dome camera according to the prior art.

3 is a view showing the optical structure and the path of the light ray of the fisheye lens according to the prior art.

4 is a view showing a barrel structure of a fisheye lens according to the prior art.

5 is a partial cutaway perspective view of a fisheye lens according to the prior art;

6 is a cross-sectional view of the front portion separated from the fisheye lens of the first embodiment of the present invention.

7 is a cross-sectional view of the front portion coupled to the fisheye lens of the first embodiment of the present invention.

8 is an exploded perspective view of a fisheye lens of a first embodiment of the present invention;

9 is an exploded perspective view of the fisheye lens of FIG. 8 further comprising a support and a retaining nut;

10 is a view showing the optical structure and the path of the light beam of the fisheye lens of the second embodiment of the present invention.

11 is a graph showing modulation transfer function characteristics of a fisheye lens of a second exemplary embodiment of the present invention.

12 is a graph showing the ambient light quantity ratio of the fisheye lens of the second embodiment of the present invention.

FIG. 13 is a graph illustrating image curvature and correction distortion of a fisheye lens according to a second exemplary embodiment of the present invention. FIG.

14 is a cross-sectional view of a front part separated from the fisheye lens of the second embodiment of the present invention;

15 is a cross-sectional view of the front portion coupled to the fisheye lens of the second embodiment of the present invention.

16 is an exploded perspective view of a fisheye lens of a second embodiment of the present invention;

17 is an exploded perspective view of the fisheye lens of FIG. 16 further comprising a support and a retaining nut;

<Description of the symbols for the main parts of the drawings>

CP: front

MB: Body

100: fisheye lens of the first embodiment

110: first barrel

120: second barrel

125: fixed part

140: fixing nut

200: fisheye lens of the second embodiment

210: first barrel

220: second barrel

225: fixed part

230: barrel spacing adjuster

240: fixing nut

Claims (26)

A fisheye lens comprising a plurality of lens elements aligned in the optical axis direction, A first barrel on which some lens elements of the plurality of lens elements close to an object side are mounted; A second barrel, to which the first barrel is detachable, to which the remaining lens elements of the plurality of lens elements are mounted; The portion of the lens element mounted to the first barrel is the first lens element closest to the object side, The first lens element is a fisheye lens element with a convex surface facing towards the object. delete According to claim 1, The fisheye lens further comprises a fixing portion for preventing the second barrel from moving when detaching the first barrel to the second barrel fixed to the support. The method of claim 3, The fixing part and at least one second barrel fixing screw fastening hole formed on one surface of the second barrel in contact with the support; And at least one second barrel fixing screw fastened to the at least one second barrel fixing screw fastener. The method of claim 3, The fixing part and at least one second barrel fixing rod fastening hole formed on one surface of the second barrel in contact with the support; And at least one second barrel fixing rod which is fastened to the at least one second barrel fixing rod fastening hole. The method of claim 3, The fixing part is a fish-eye lens made of a protrusion formed on one surface of the second barrel in contact with the support. According to claim 1, The first barrel includes a first barrel fastening portion formed on the inner peripheral surface thereof, The second fish barrel includes a second barrel fastening portion formed in a first region of its outer circumferential surface and fastened to the first barrel fastening portion. The method of claim 7, wherein The first barrel fastening portion is a female screw, and the second barrel fastening portion is a male screw. The method of claim 7, wherein The fisheye lens, At least one first barrel fixing screw fastening hole penetrating the outer circumferential surface of the first barrel in a direction perpendicular to the optical axis; And at least one first barrel fixing screw coupled to the at least one first barrel fixing screw fastening and in contact with the second barrel fastening. delete delete delete delete According to claim 1, The first barrel further comprises a first barrel gripping portion formed on the outer circumferential surface, fisheye lens. delete According to claim 1, A fixing nut fastening portion formed in a second region of an outer circumferential surface of the second barrel; The fisheye lens further comprises a lens fastening portion formed in a third region of the outer circumferential surface of the second barrel. A fisheye lens comprising a plurality of lens elements aligned in the optical axis direction, A first barrel on which some lens elements of the plurality of lens elements close to an object side are mounted; A second barrel, to which the first barrel is detachable, to which the remaining lens elements of the plurality of lens elements are mounted; The fisheye lens further comprises a fixing portion for preventing the second barrel from moving when detaching the first barrel to the second barrel fixed to the support. 18. The method of claim 17, The fixing part and at least one second barrel fixing screw fastening hole formed on one surface of the second barrel in contact with the support; And at least one second barrel fixing screw fastened to the at least one second barrel fixing screw fastener. 18. The method of claim 17, The fixing part and at least one second barrel fixing rod fastening hole formed on one surface of the second barrel in contact with the support; And at least one second barrel fixing rod which is fastened to the at least one second barrel fixing rod fastening hole. 18. The method of claim 17, The fixing part is a fish-eye lens made of a protrusion formed on one surface of the second barrel in contact with the support. 18. The method of claim 17, The first barrel includes a first barrel fastening portion formed on the inner peripheral surface thereof, The second fish barrel includes a second barrel fastening portion formed in a first region of its outer circumferential surface and fastened to the first barrel fastening portion. The method of claim 21, wherein the fisheye lens, At least one first barrel fixing screw fastening hole penetrating the outer circumferential surface of the first barrel in a direction perpendicular to the optical axis; And at least one first barrel fixing screw coupled to the at least one first barrel fixing screw fastening and in contact with the second barrel fastening. 18. The method of claim 17, The first barrel further comprises a first barrel gripping portion formed on the outer circumferential surface, fisheye lens. 18. The method of claim 17, A fixing nut fastening portion formed in a second region of an outer circumferential surface of the second barrel; The fisheye lens further comprises a lens fastening portion formed in a third region of the outer circumferential surface of the second barrel. A fisheye lens comprising a plurality of lens elements aligned in the optical axis direction, A first barrel on which some lens elements of the plurality of lens elements close to an object side are mounted; A second barrel, to which the first barrel is detachable, to which the remaining lens elements of the plurality of lens elements are mounted; The first barrel further comprises a first barrel gripping portion formed on the outer circumferential surface, fisheye lens. A fisheye lens comprising a plurality of lens elements aligned in the optical axis direction, A first barrel on which some lens elements of the plurality of lens elements close to an object side are mounted; A second barrel, to which the first barrel is detachable, to which the remaining lens elements of the plurality of lens elements are mounted; A fixing nut fastening portion formed in a second region of an outer circumferential surface of the second barrel; The fisheye lens further comprises a lens fastening portion formed in a third region of the outer circumferential surface of the second barrel.

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