Lens unit

Abstract

To provide a lens unit with a lens assembled to a lens barrel by press-fitting, in which the positional accuracy of fixation of the lens to the lens barrel is heightened.SOLUTION: R denotes the maximum radius of a lens (lens radius). At the time of press-fitting, a vertical plane L3C1 does not contact an inner plane 10B11 for press-fitting in the entire range of the thickness direction, and the vertical plane L3C1 and the inner plane 10B11 for press-fitting directly contact in only a range from H5 to H4 (fitting section F). The length of the fitting section F along the thickness direction (direction of optical axis A) constitutes a fitting length Z. A region below H4 in a third outer circumferential lens surface L3C is made to be an inclined plane L3C2 inwardly inclined by an angle θ from the vertical direction and separated from the inner plane 10B11 for press-fitting. The preferable range of R / Z is 6.25≤R / Z≤25.0.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a lens unit in which a lens having at least an outer periphery made of a resin material is housed and fixed in a lens barrel.

Background Art

[0002] For example, as an optical system used in an imaging device mounted on an automobile, a surveillance camera, etc., a lens unit in which a plurality of lenses are arranged in the direction of the optical axis (the optical axis of the imaging device) from the object side to the image side (the imaging element side) is used. This lens unit is designed to favorably form an image of an object by visible light on the imaging element. For this reason, the positional relationship between the respective lenses, the positional relationship between each lens and the lens barrel, and the positional relationship between this lens unit and the imaging element are fixed with high precision, and it is required that no large load is applied to each lens.

[0003] Generally, while the lens barrel is made of a resin material, there are two types of materials for the lenses used: a resin material and glass. The former has low mechanical strength but is inexpensive, while the latter has high mechanical strength but is expensive. Also, for example, when the shape of the lens is an aspherical shape, the former is particularly less expensive than the latter. Also, since the coefficient of thermal expansion of the latter is smaller, in the case of a lens where thermal expansion particularly has an adverse optical effect, the latter is preferable. Also, from the viewpoint of not deteriorating the distortion of the lens and the lens barrel or the positional accuracy of the lens with respect to the lens barrel during temperature change, it is preferable that the coefficient of thermal expansion of the lens barrel and the coefficient of thermal expansion of the lens are close, and thus a resin material lens is preferable. Considering these points, it is determined which of the plurality of lenses is to be made of glass and which is to be made of a resin material.

[0004] Among these, in particular, a lens made of a resin material (plastic lens) is also press-fitted and fixed to a lens barrel made of a resin material. Also, a glass lens (glass lens) may be handled as a lens after being fixed to a lens holder made of a resin material. In this case, the entire lens holder may be regarded as the above-mentioned plastic lens and may be press-fitted and fixed to the lens barrel in the same manner.

[0005] Since plastic lenses are less hard than glass lenses, distortion is likely to occur during press-fitting. Also, generally, plastic lenses (including the above lens holders) are manufactured by molding a resin material using a mold. At this time, for example, fine unevenness is formed due to internal structures essential in the mold (such as boundary parts when combining a plurality of molds, gates into which the resin material before solidification is poured, etc.). At this time, the presence of such unevenness on the lens surface (the surface of the lens where light rays contributing to imaging enter or exit) directly affects the optical characteristics. Therefore, such unevenness is formed on the flange part formed around the lens surface or on the outer peripheral surface of the lens (flange part).

[0006] However, the upper and lower surfaces (the object side and the image side in the optical axis direction) of the flange part are used to fix the positional relationship between adjacent lenses, and the outer peripheral surface of the flange part (lens) is used to fix the positional relationship between this lens and the lens barrel. Therefore, in this case, such unevenness affects the positional accuracy of this lens.

[0007] In Patent Document 1, in consideration of such a situation, a technique for suppressing deterioration of positional accuracy due to the above-mentioned unevenness formed on a plastic lens by adjusting the shape on the inner surface side of the lens barrel is described. Thereby, in a lens unit in which a plurality of plastic lenses (including the case of combining a glass lens and a lens holder as described above) are fixed in a lens barrel by press-fitting, good optical characteristics can be obtained. The unevenness mainly considered in this case is the parting line formed corresponding to the boundary part between two molds.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Although the deterioration of the lens position accuracy due to parting lines and the like has been improved by the above-mentioned technology, it has been required to further increase these position accuracies in order to obtain better optical characteristics. Further, the requirements for this position accuracy also include improving the shape accuracy of the lens (no distortion). Therefore, it has become necessary to further suppress the occurrence of distortion, inclination with respect to the optical axis, and play in the lens depending on the positional relationship between the outer periphery of the lens and the inner surface side of the lens barrel that directly contacts therewith.

[0010] For this reason, it has been desired to further improve the positional accuracy of the press-fitted lens with respect to the lens barrel.

[0011] The present invention has been made in view of such a situation, and an object thereof is to improve the positional accuracy of fixing a lens with respect to a lens barrel in a lens unit in which the lens is press-fitted and incorporated into the lens barrel.

Means for Solving the Problems

[0012] The lens unit according to the present invention includes a plurality of lenses arranged in a direction along the optical axis and having a substantially circular shape perpendicular to the optical axis, and a cylindrical lens barrel made of a resin material and holding the plurality of lenses on the outside as viewed from the optical axis. At least one of the lenses is a press-fit lens fixed in a state of being in contact with a press-fit inner surface, which is a surface parallel to the press-fit direction along the press-fit direction parallel to the central axis of the lens barrel, on the inside of the lens barrel. On the outer peripheral surface of the press-fit lens facing the press-fit inner surface and made of a resin material, there is provided a vertical surface which is a surface parallel to the press-fit direction and a part of which in the press-fit direction is in direct contact with the press-fit inner surface, and an inclined surface which is adjacent to the vertical surface in the press-fit direction and is inclined from the press-fit direction so as to be separated from the press-fit inner surface. When the fitting length, which is the length of the fitting portion along the press-fit direction, is Z and the maximum radius around the optical axis of the press-fit lens is the lens radius R, it is in the range of 6.25 ≦ R / Z ≦ 25.0.

[0013] In this configuration, by appropriately setting the length Z of the fitting portion, it is possible to improve the positional accuracy of the fixing of this press-fit lens with respect to the lens barrel, particularly in the radial direction around the optical axis, and it is also possible to easily perform the press-fit for fixing. As a result, in this lens unit, high imaging characteristics can be stably obtained. In particular, by using the lens radius which is easy to control with high precision as a reference, this setting is also easy.

[0014] Also, when the maximum thickness on the radially outer side of the press-fit lens as viewed from the optical axis is the flange thickness B, it may be in the range of 1.25 ≦ B / Z ≦ 12.5. This configuration can further enhance the above effects.

[0015] Also, in the press-fit lens, when the length of the vertical surface along the press-fit direction is Y, it may be set that Z ≦ Y / 2. In this case, by reducing the ratio of the fitting portion in the vertical surface, the press-fit operation becomes particularly easy.

[0016] Further, in the press-fitting lens, the lens center height, which is the midpoint between one lens surface and the other lens surface on the optical axis, may be within the range of the fitting portion in the press-fitting direction. In this case, the region between the two lens surfaces, which is the optically most important part of the press-fitting lens, is particularly strongly supported and fixed. Therefore, high imaging characteristics in this lens unit can be obtained particularly stably.

[0017] Further, the press-fitting lens is characterized by being made of a resin material. In this case, the press-fitting lens is a plastic lens entirely made of a resin material. In this case, the above configuration is particularly effective. Further, when looking at the fitting portion of the press-fitting lens from one side to the other side in the radial direction around the optical axis, the fitting portion may be configured to be densely filled with the resin material constituting the press-fitting lens. In this case, the distortion generated in the plastic lens during press-fitting can be made particularly small, and this press-fitting lens can be fixed particularly firmly to the lens barrel.

Advantages of the Invention

[0018] According to the present invention, in a lens unit in which a lens is press-fitted and incorporated into a lens barrel, the positional accuracy of fixing the lens to the lens barrel can be improved.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of the lens unit 1 according to the present embodiment, and FIG. 2 is a cross-sectional view taken along its optical axis A. Further, FIG. 3 is an exploded view of this lens unit 1.

[0021] In FIG. 2, the object (Ob) side is the upper side in the figure, the image (Im) side is the lower side in the figure, and the imaging element (not shown) is located at the lowermost part in the figure. Each of the lenses L1 to L6 is directly or indirectly fixed to the lens barrel 10. In FIG. 2, mainly the configuration for fixing each lens or between each lens and the lens barrel 10 is mainly described. Actually, a structure for fixing the positional relationship between the imaging element and the lens barrel 10 is also provided, but its description is omitted.

[0022] The imaging element is a two-dimensional CMOS image sensor, and each pixel is two-dimensionally arranged in a plane perpendicular to the optical axis A. In FIG. 2, a lens unit 1 in which the first lens L1 to the sixth lens L6 are fixed to the lens barrel 10 is configured. The lens unit 1 is configured to form an image of the visible light image of the imaging object on the imaging element (image plane) in a desired field of view and in a desired form.

[0023] In FIGS. 2 and 3, the first lens L1 provided on the side closest to the object (the upper side in the figure) is a fisheye lens, and mainly, the field of view of the imaging device etc. is determined by this. Closer to the imaging element side (Im side) than this, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are sequentially arranged. Each lens has a shape that is substantially symmetric around the optical axis A, and in particular, its lens surface (the surface of the lens where the light rays contributing to imaging are incident or exit) has a shape that is symmetric around the optical axis A. Also, a diaphragm 20 for restricting the light beam is provided between the third lens L3 and the fourth lens L4, and a thin film-like light shielding plate 21 for removing unnecessary light is provided between the second lens L2 and the third lens L3.

[0024] FIG. 4 is a perspective view seen from the object (Ob) side of the lens barrel 10. As shown in FIGS. 2 and 4, on the object (Ob) side of the lens barrel 10, a first accommodation part 10A which is a large-diameter cavity part with an inner peripheral surface that is substantially cylindrical is provided, and the image-side bottom surface of the first accommodation part 10A becomes a first placement part 11 that abuts against the first lens L1. An O-ring 30 is installed outside the first placement part 11 as seen from the optical axis A, as shown in FIGS. 2 and 3.

[0025] Also, in FIG. 4, on the image side (the lower side in the figure) than the first placement part 11, a second accommodation part (lens accommodation part) 10B which is a substantially cylindrical cavity part that is coaxial with the first accommodation part 10A and has a smaller diameter than the first accommodation part 10A is provided. In FIG. 2, the image-side bottom surface of the second accommodation part 10B becomes a second placement part 12 that abuts against the cemented lens L50. The central axes of the first accommodation part 10A and the second accommodation part 10B are made common and are equal to the optical axis A. Also, as will be described later, actually, the inner peripheral surface of the second accommodation part 10B is gradually and stepwise made smaller corresponding to each lens from the object side toward the image side. For this reason, as shown in FIG. 3, each lens etc. can be sequentially incorporated and fixed to the lens barrel 10 from the object side.

[0026] 4, 12 lens fixing ribs 10B1 (only five of which are shown in FIG. 4) are formed at equal intervals in the circumferential direction on the inner peripheral surface of the second housing portion 10B, which extend along the optical axis A and locally protrude toward the optical axis A. For this reason, when each lens is fixed to the lens barrel 10, the lens fixing ribs 10B1 are the portions where each lens and the lens barrel 10 actually abut in the radial direction around the optical axis A, and as described later, the radial position of each lens is restricted by the lens fixing ribs 10B1.

[0027] In FIG. 2, the object-side and image-side lens surfaces of each lens are appropriately curved (convex or concave) so that the lens unit 1 provides desired imaging characteristics.

[0028] Generally, there are two types of materials that constitute the lenses in such small imaging devices: glass and resin. The former has high mechanical strength but is expensive, while the latter has low mechanical strength but is inexpensive. In addition, since the thermal expansion coefficient of glass is smaller than that of resin, it is preferable to use glass lenses for lenses in which minute changes in shape and position caused by thermal expansion at high temperatures have a large effect on imaging characteristics (such as changes in focal position). For this reason, in order to achieve high performance and low cost for the lens unit 1, it is preferable to use glass only for lenses that are preferably made of glass, and use resin materials for the other lenses.

[0029] From this viewpoint, in this embodiment, the first lens L1 arranged closest to the object side is made of glass, which is resistant to scratches, since it is located on the outermost surface of the imaging device. In addition, the lenses adjacent to the aperture 20 (the third lens L3 and the fourth lens L4) are subject to significant changes in focal length due to temperature changes, so the fourth lens L4, which is one of them, is made of glass. The other lenses are made of an inexpensive resin material. However, the fourth lens L4 is actually fixed in the lens barrel 10 as a fourth lens body L40, which is housed and fixed in a lens holder 41 made of a resin material.

[0030] As the material of the lens barrel 10, crystalline plastics (polyethylene, polyamide, polytetrafluoroethylene) with excellent weather resistance are preferably used. On the other hand, the second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6 are made of amorphous plastics (such as polycarbonate) that are excellent in lens performance (light transmittance and moldability). Further, since the lens holder 41 is made of the same amorphous plastic as the third lens L3, etc., the fourth lens body L40 can be handled as a plastic lens similar to the third lens L3, etc. within the lens barrel 10.

[0031] Also, in FIG. 2, the fifth lens L5 and the sixth lens L6 are formed into a joined lens L50 joined and integrated by an adhesive including the lens surfaces. Therefore, actually, this joined lens L50 can be handled as a plastic lens similar to the third lens L3, etc. within the lens barrel 10.

[0032] That is, in the configuration of FIG. 2, the second lens L2, the third lens L3, the fourth lens body L40, and the joined lens L50 are handled as plastic lenses incorporated into the second housing portion 10B within the lens barrel 10.

[0033] Hereinafter, the lens surface on the object side of each lens is referred to as the first surface R1, and the lens surface on the image side is referred to as the second surface R2. Also, as the shape of the lens surface (convex curved surface or concave curved surface), the shape as viewed from the object side for the first surface R1 and the shape as viewed from the image side for the second surface R2 are respectively meant.

[0034] In FIG. 2, the first lens L1 is a negative lens in which the lens surface L1R1 on the object side is a convex curved surface and the lens surface L1R2 on the image side is a concave curved surface. On the upper surface side of the first lens L1, the lens surface L1R1 occupies almost the entire area. On the lower surface side (image side) of the first lens L1, outside the lens surface L2R2, a first lens lower surface L1A formed by a plane perpendicular to the optical axis A is provided. Also, the outermost peripheral portion of the first lens L1 constitutes a cylindrical first lens outer peripheral surface L1B centered on the optical axis A. Among these surfaces, the optically used ones are the lens surfaces L1R1 and L1R2, and the other surfaces are used to fix the first lens L1 to the lens barrel 10.

[0035] In FIG. 2, the upper end side of the lens barrel 10 is a first lens locking portion 13 bent toward the optical axis A (center) side so as to restrict the movement of the first lens L1 toward the object side. Also, the first lens lower surface L1A abuts against the first placement portion 11 of the lens barrel 10. Therefore, the positional relationship of the first lens L1 with respect to the lens barrel 10 in the direction of the optical axis A is determined by the first lens locking portion 13 on the object side (upper side in the figure), and is determined by the first placement portion 11 on the image side (lower side in the figure). At this time, an O-ring support surface L1C dug downward as viewed from the image side is formed on the radially outer side of the first lens lower surface L1A, and an O-ring 30 is provided between the O-ring support surface L1C, the inner peripheral surface of the first housing portion 10A, and the first placement portion 11, whereby the space between the first lens L1 and the lens barrel 10 is sealed. As shown in FIG. 4, actually, a plurality of convex portions (first lens placement convex portions 11A) are discretely provided on the first placement portion 11, similar to the lens fixing ribs 10B1 on the inner peripheral surface of the second housing portion 10B, and actually, the position of the first lens L1 on the image side is determined by the first lens placement convex portions 11A.

[0036] Also, the first lens outer peripheral surface L1B abuts against the inner peripheral surface of the first housing portion 10A in the lens barrel 10. Thereby, the positional relationship in the direction (radial direction) perpendicular to the optical axis A between the first lens L1 and the lens barrel 10 is determined. That is, with the above configuration, when the first lens L1 is fixed to the lens barrel 10, the positional relationship in the direction of the optical axis A and the radial direction between the first lens L1 and the lens barrel 10 is determined.

[0037] The second lens L2 is a negative lens with its object-side lens surface L2R1 being a convex curved surface and its image-side lens surface L2R2 being a concave curved surface. On the object side (the upper side in FIG. 2) of the second lens L2, outside the lens surface L2R1, there is provided a second lens upper surface L2A which is a plane perpendicular to the optical axis A and located on the image side (the lower side in FIG. 2) of the lens surface L2R1. On the image side (the lower side in FIG. 2) of the second lens L2, outside the lens surface L2R2, there is provided a second lens lower surface L2B which is a substantially flat surface perpendicular to the optical axis A.

[0038] The second lens outer peripheral surface L2C that constitutes the outermost periphery of the second lens L2 abuts against the inner peripheral surface of the second housing portion 10B (precisely the lens fixing rib 10B1). Therefore, the positional relationship between the second lens L2 and the lens barrel 10 in the radial direction is determined thereby.

[0039] Similar to the relationship between the first lens L1 and the first lens locking portion 13 in the lens barrel 10, the position of the second lens L2 on the object side in the direction of the optical axis A is determined by the second lens upper surface L2A being locked to the second lens locking portion 14 provided on the lens barrel 10 side.

[0040] The third lens L3 is a positive lens with its object-side lens surface L3R1 being a concave curved surface and its image-side lens surface L3R2 being a convex curved surface. On the object side (the upper side in the figure) of the third lens L3, outside the lens surface L3R1, there is provided a third lens upper surface L3A which is a substantially flat surface perpendicular to the optical axis A and located on the object side (the upper side in FIG. 2) of the lens surface L3R1. On the image side (the lower side in FIG. 2) of the third lens L3, outside the lens surface L3R2, there is provided a third lens lower surface L3B which is a substantially flat surface perpendicular to the optical axis A.

[0041] The third lens outer peripheral surface L3C that constitutes the outermost periphery of the third lens L3 abuts against the inner peripheral surface of the second housing portion 10B (precisely the lens fixing rib 10B1). Therefore, the positional relationship between the third lens L3 and the lens barrel 10 in the radial direction is determined thereby.

[0042] The light shield 21 is installed between the second lens L2 and the third lens L3. At this time, the annular light shield 21 is sandwiched between the second lens lower surface L2B of the second lens L2 and the third lens upper surface L3A of the third lens L3. For this reason, the second lens lower surface L2B and the third lens upper surface L3A are shaped such that the positional relationship in the optical axis A direction between the second lens L2 and the third lens L3 is determined when they come into contact with each other, and the light shield 21 is sandwiched between a part of them.

[0043] The fourth lens (glass lens) L4 is made of glass, and is a positive lens in which the lens surface L4R1 on the object side is a convex curved surface and the lens surface L4R2 on the image side is a convex curved surface. As described above, the fourth lens L4 is housed in the lens barrel 10 in a state of being press-fitted and fixed to the lens holder 41 made of a resin material to form an integrated fourth lens body L40. That is, the fourth lens L4 is treated as a lens in the same manner as the second lens L2 and the third lens L3 made of a resin material in a state of being the fourth lens body L40.

[0044] On the object side (the upper side in FIG. 2) of the fourth lens body L40, a substantially flat fourth lens body upper surface L40A that is perpendicular to the optical axis A and is located on the object side of the lens surface L4R1 is provided on the lens holder 41 outside the radial direction of the fourth lens L4, and the fourth lens body upper surface L40A abuts against the third lens lower surface L3B on the image side of the third lens L3. Also, on the image side (the lower side in FIG. 2) of the fourth lens body L40, a substantially flat fourth lens body lower surface L40B that is perpendicular to the optical axis A and is located on the image side of the lens surface L4R2 is provided on the lens holder 41 outside the radial direction of the fourth lens L4.

[0045] Further, the fourth lens body outer peripheral surface (outer peripheral surface) L40C, which is the surface constituting the outermost periphery of the fourth lens body L40, abuts against the inner peripheral surface of the second housing portion 10B (specifically, the lens fixing rib 10B1). For this reason, the positional relationship in the radial direction between the fourth lens body L40 and the lens barrel 10 is determined thereby.

[0046] The aperture 20 is installed between the third lens L3 and the fourth lens body L40. At this time, the annular aperture 20 is sandwiched between the lower surface L3B of the third lens L3 and the upper surface L40A of the fourth lens body. Therefore, the lower surface L3B of the third lens and the upper surface L40A of the fourth lens body are shaped such that their contact determines the positional relationship in the optical axis A direction between the third lens L3 and the fourth lens body L40, and the aperture 20 is sandwiched between a part of them.

[0047] The fifth lens L5 is a negative lens with its object-side lens surface L5R1 being a concave surface and its image-side lens surface L5R2 being a concave surface. The sixth lens L6 is a positive lens with an outer diameter smaller than that of the fifth lens L5, its object-side lens surface L6R1 being a convex surface, and its image-side lens surface L6R2 being a convex surface. The fifth lens L5 and the sixth lens L6 are set to form the joint lens L50 on the most image side by fitting their opposing lens surfaces and joining them with a thin adhesive layer.

[0048] On the object side of the joint lens L50 (the fifth lens L5), outside the radial direction of the lens surface L5R1, a joint lens upper surface L5A, which is a plane that contacts the lower surface L40B of the fourth lens body in the fourth lens body L40, is provided. Also, on the image side of the joint lens L50 (the fifth lens L5), outside the radial direction of the lens surface L6R2, a joint lens lower surface L5B, which is a plane perpendicular to the optical axis A, is provided. The joint lens lower surface L5B contacts the second placement portion 12. Also, inside the second placement portion 12 on the joint lens lower surface L5B, a stepped portion (engagement structure) L5C, which is concave toward the object side, is provided. Correspondingly, on the sixth lens L6, a stepped portion (engagement structure) L6A, which is convex toward the object side, is provided, and the stepped portion L5C and the stepped portion L6A engage with each other. That is, in the joint lens L50, the lens surface L5R2 of the fifth lens L5, the stepped portion L5C, the lens surface L6R1 of the sixth lens L6, and the stepped portion L6A are fixed in a fitted state, thereby determining the positional relationship between the fifth lens L5 and the sixth lens L6 in the optical axis A direction and the radial direction.

[0049] Also, the joining lens outer peripheral surface L5D, which is the surface constituting the outermost periphery of the joining lens L50 (the fifth lens L5), abuts against the inner peripheral surface of the second housing portion 10B (specifically, the lens fixing rib 10B1 described above). Therefore, the positional relationship in the radial direction between the joining lens L50 and the lens barrel 10 is determined thereby.

[0050] Thus, between the second lens L2, the third lens L3, the fourth lens body L40, and the joining lens L50, the upper and lower surfaces on the radially outer side of the lens surfaces between the lenses adjacent in the stacking direction abut against each other, whereby the positional relationship in the optical axis A direction between these lenses is fixed. On the other hand, among these, the object-side position of the second lens L2, which is the most object-side, in the optical axis A direction is restricted by the second lens locking portion 14, and the image-side position of the joining lens L50, which is the most image-side, in the optical axis A direction is restricted by the second mounting portion 12. Therefore, with the above-described structure, the positions of the second lens L2, the third lens L3, the fourth lens body L40, and the joining lens L50 in the optical axis A direction with respect to the lens barrel 10 can be determined.

[0051] In the above example, the upper and lower surfaces used for fixing each lens were substantially flat surfaces perpendicular to the optical axis A. However, similar to the first lens mounting convex portion 11A in the first mounting portion 11 described above, locally formed convex portions may be appropriately provided on these upper and lower surfaces.

[0052] When actually manufacturing the lens unit 1 having the structure shown in FIG. 2, as shown in FIG. 3, with the aperture stop 20 and the light shield 21 sandwiched as described above, the joining lens L50, the fourth lens body L40, the third lens L3, and the second lens L2 are sequentially press-fitted into the second housing portion 10B from the object side, and then the structure below the second lens L2 is fixed using the second lens locking portion 14. After that, the first lens L1 may be fixed to the first housing portion 10A as described above.

[0053] In this case, the radial positional relationship between each lens (lens body) and the lens barrel 10 is greatly influenced by the above-mentioned press-fitting situation. At this time, in the configuration of FIG. 2, the press-fitting is performed from the object side toward the image side in the direction of the optical axis A. That is, the press-fitting direction is parallel to the optical axis A (or the central axis of the lens barrel 10). Alternatively, not only the position of each lens (lens body) in the radial direction but also the deviation (tilt) of the optical axis A direction of each lens (lens body) from the ideal case is influenced by this press-fitting situation. In the cross-section of FIG. 2, the lens fixing rib 10B1 is on the left side in the figure, and the portions where the positional relationship between the outer peripheral surface of each lens (lens body) and the inner peripheral surface of the second housing portion 10B (the above-mentioned lens fixing rib 10B1) should be considered are shown as region X2 (second lens L2), region X3 (third lens L3), region X4 (fourth lens body L40), and region X5 (joined lens L50).

[0054] FIG. 5 is a view showing an enlarged view of the situations of regions X2 to X5 in FIG. 2. Here, the inner diameter of the second housing portion 10B is set to gradually decrease step by step toward the image side, and correspondingly, the outer diameter of each lens (lens body) is set to gradually decrease toward the image side. Here, the press-fitting direction P is the vertical direction (downward) in the figure and is parallel to the optical axis A. Also, the press-fitting direction P is also the thickness direction of each lens. As an example, FIG. 6 is a diagram schematically showing an enlarged view of the contact situation between the third lens L3 and the inner surface (lens fixing rib 10B1) of the second housing portion 10B. Although the detailed situations are different for other lenses (lens bodies), the basic structure is the same as that of FIG. 6. That is, the second lens L2, the third lens L3, the fourth lens body L40, and the joined lens L50 are all press-fitted lenses that are press-fitted and fixed to the lens barrel 10. Note that in FIGS. 5 and 6, the unevenness in the lenses and the lens barrel is emphasized for description, and the scale is different from the actual one.

[0055] In FIG. 6, R is the distance from the optical axis A (the center of the third lens L3) to the outer periphery, which is the maximum radius (lens radius) of the lens. H1 and H2 are the heights of the upper surface L3A and the lower surface L3B of the third lens, respectively, and the interval between H1 and H2 is the flange thickness B.

[0056] As shown in FIG. 5, the inner surface that abuts against each lens of the second housing portion 10B is formed along the vertical direction (the direction of the optical axis A) for each corresponding lens. Similarly, on the outer peripheral surface of each corresponding lens, a surface formed along the vertical direction is provided. With such a structure, each lens can be press-fitted and fixed to the second housing portion 10B. In FIG. 6, among the inner surface (the surface of the lens fixing rib 10B1) of the second housing portion 10B, a press-fitting inner surface 10B11 protruding toward the optical axis A side (the right side in the figure) along the vertical direction (the direction of the optical axis A) so as to be able to directly abut against the third lens L3 is provided.

[0057] On the other hand, when the entire outer peripheral surface of the lens is uniformly formed along the vertical direction over the thickness direction and brought into contact with the press-fitting inner surface 10B11, it becomes substantially extremely difficult to perform the press-fitting operation. For this reason, as shown in FIG. 6, the outer peripheral surface L3C of the third lens L3 is a vertical surface L3C1 partially formed along the vertical direction only in the range of H3 (<H1) and H4 (>H2). This point is the same as the technique described in Patent Document 1.

[0058] However, here, during press-fitting, the vertical surface L3C1 does not abut against the press-fitting inner surface 10B11 over the entire region in the thickness direction (the direction of the optical axis A). The vertical surface L3C1 and the press-fitting inner surface 10B11 directly abut only in the range from H5 (the upper end of the press-fitting inner surface 10B11) to H4 (the lower end of the vertical surface L3C1) (the fitting portion F). The length along the thickness direction (the direction of the optical axis A) of the fitting portion F is the fitting length Z. Therefore, if the length (the length between H3 and H4) of the vertical surface L3C1 in FIG. 6 is Y, then Z≦Y<B.

[0059] When only considering simply fixing the third lens L3 firmly to the lens barrel 10, it is obvious that increasing the fitting length Z is effective. However, it is also obvious that when Z is increased, the press-fitting operation becomes difficult. In particular, each lens is required to be accurately fixed at the position shown in FIG. 2 in the direction of the optical axis A, but there are cases where it is fixed before reaching this position during press-fitting (making further press-fitting difficult). Therefore, there is an appropriate range for the fitting length Z.

[0060] When the fitting length Z or the length Y of the vertical surface L3C1 is made smaller than the flange thickness B in this way, as shown in FIG. 6, the region on the outer peripheral surface L3C of the third lens below H4 (the side that becomes the tip during press-fitting) is inclined inward by an angle θ from the vertical direction (the direction of the optical axis A) to form an inclined surface L3C2 that is separated from the inner surface 10B11 for press-fitting. This is effective for facilitating the press-fitting operation.

[0061] Also, by providing the inclined surface L3C2 in this way or setting Z < B, similar to the technique described in Patent Document 1, the parting line that is inevitably formed when molding the lens can be formed on the inclined surface L3C2 that is in a region other than the vertical surface L3C1 (the fitting portion F). Thereby, the adverse effect of the parting line on the positional accuracy of the lens can be eliminated.

[0062] On the other hand, when the inclined surface L3C2 is provided in this way, there is a possibility that the third lens L3 inclines by up to θ from the optical axis A during press-fitting. Therefore, it is necessary to consider preventing such an inclination during press-fitting. This influence depends on the lens radius R described above. When R is large, this influence is small, and when R is small, this influence becomes large. Also, the third lens L3 made of a resin material deforms slightly during press-fitting, but the absolute amount of this deformation is larger when the lens radius R is large. That is, the ease of press-fitting also depends on the lens radius R.

[0063] Also, in FIG. 6, when the third lens L3 is viewed from one side (e.g., the left side) in the radially outer (horizontal) direction, depending on its height, there are cases where the resin material forming the third lens L3 is continuously formed without gaps toward the other side (e.g., the right side), and cases where there are portions where the resin material is missing toward the opposite side. In FIG. 6, an example of the former height is indicated by arrow K1, and an example of the latter height is indicated by arrow K2. At the height of arrow K2, due to the concave shape of the lens surface on the image side, a portion where the resin material is missing as viewed from the radially outer side is generated. The uppermost part of the range corresponding to arrow K1 (the densely filled region) has a height of H7 (= H3) in this third lens L3, and the lowermost part of the range corresponding to arrow K1 has a height of H8, which is the point where the image-side surface of the third lens L3 is most recessed. That is, the region outside the range from height H7 to H8 is the densely filled region. On the other hand, other regions, for example, the region below H8, are the sparsely filled regions corresponding to the above arrow K2.

[0064] When the third lens L3 is fixed by the press-fitting inner surface 10B11, the lens is less likely to be distorted during press-fitting when the above densely filled region is brought into contact with the press-fitting inner surface 10B11 compared to the case where the sparsely filled region is brought into contact.

[0065] Taking the above points into consideration, by adjusting the parameters shown in FIG. 6 and determining the relationship, particularly the shape of the outer peripheral surface of the lens (plastic lens) and the press-fitting inner surface 10B11, it becomes possible to firmly fix the lens to the lens barrel 10 without distortion. Here, for this purpose, experiments were conducted using a dummy plastic lens and a dummy lens barrel. The results will be described below.

[0066] Here, multiple types of lens radii R, flange thicknesses B, and fitting lengths Z in FIG. 6 were set, and the situation during press-fitting was examined. Here, the lens radius R was in the range of 1.5 mm to 6 mm, the flange thickness B was in the range of 0.1 mm to 3.5 mm, and the fitting length Z was in the range of 0.1 mm to 0.5 mm (< the range of the flange thickness B). Note that the lens radius R in the actually used lens unit is typically in the range of 5 mm to 7 mm.

[0067] Figure 7(a) shows, in this case, the press-fitting situations when changing the lens radius R and the fitting length Z, classified into three types: ○ (no problem), △ (some problems but applicable), and × (problematic and not applicable). Here, the flange thickness B was set to 2.5 mm. When the fitting length Z was as small as 0.1 mm, regardless of the lens radius R, play (including inclination) of the lens occurred after press-fitting, so it was marked as ×. When the fitting length Z was 0.2 mm, press-fitting was slightly difficult when the lens radius R was 1.5 mm, so it was marked as △; when the lens radius R was 2.5 mm or 3.5 mm, there was no problem at all, so it was marked as ○; when the lens radius R was 5 mm, slight play that did not cause a problem occurred in some cases, so it was marked as △; when the lens radius R was 6 mm, play occurred, so it was marked as ×.

[0068] When the fitting length Z was 0.3 mm, press-fitting was difficult when the lens radius R was 1.5 mm, so it was marked as ×; when the lens radius R was 2.5 mm, 3.5 mm, or 5.0 mm, there was no problem at all, so it was marked as ○; when the lens radius R was 6 mm, slight play that did not cause a problem occurred in some cases, so it was marked as △. When the fitting length Z was 0.4 mm, press-fitting was difficult when the lens radius R was 1.5 mm, so it was marked as ×; when the lens radius R was 2.5 mm, press-fitting was slightly difficult, so it was marked as △; when the lens radius R was 3.5 mm, 5.0 mm, or 6.0 mm, there was no problem at all, so it was marked as ○. When the fitting length Z was 0.5 mm, press-fitting was difficult when the lens radius R was 1.5 mm or 2.5 mm, so it was marked as ×; when the lens radius R was 3.5 mm, 5 mm, or 6.0 mm, press-fitting was slightly difficult, so it was marked as △.

[0069] From these results, as described above, press-fitting is difficult when the fitting length Z is large, and play becomes large when the fitting length Z is small. Also, while press-fitting becomes easier as the lens radius R increases, play is also more likely to occur, and as the lens radius R increases, the appropriate range of the fitting length Z shifts toward the larger Z side. Further, as described above, the influence of the lens tilt is smaller when R is larger. For this reason, as an index indicating this situation, the ratio of the lens radius R / fitting length Z is appropriate. Fig. 7(b) shows this ratio corresponding to each item in Fig. 7(a).

[0070] From these results, it is estimated that the preferable range of R / Z is 6.25 ≦ R / Z ≦ 25.0, including the ranges of 〇 and △ in Fig. 7(a). That is, a lens with R / Z within this range can be stably and firmly fixed to the lens barrel without play. Also, setting R / Z below this upper limit value contributes to reducing the lens size without excessively increasing the lens radius R while maintaining Z within an appropriate range. From this perspective, within the above range, the range corresponding to 〇 in Fig. 7(a), 8.33 ≦ R / Z ≦ 17.50 is particularly preferable.

[0071] Similarly, Fig. 8(a) shows the press-fitting situation when changing the flange thickness B and the fitting length Z. Here, the lens radius R was set to 3.5 mm. Here, when the fitting length Z was as small as 0.1 mm, press-fitting was difficult when the flange thickness B was 0.1 mm, so it was marked with ×, when the flange thickness B was 0.5 mm, there was no problem at all, so it was marked with 〇, and when the flange thickness B was 2.5 mm or 3.5 mm, play (including tilt) of the lens occurred after press-fitting, so it was marked with ×. When the fitting length Z was 0.2 mm, there was no problem at all when the flange thickness B was 0.5 mm or 2.5 mm, so it was marked with 〇, and when the flange thickness B was 3.5 mm, play of the lens occurred after press-fitting, so it was marked with ×.

[0072] When the fitting length Z was 0.3 mm, it was marked with ○ because there was no problem at all when the flange thickness B was 0.5 mm, 2.5 mm, or 3.5 mm. When the fitting length Z was 0.4 mm, it was also marked with ○ because there was no problem at all when the flange thickness B was 0.5 mm, 2.5 mm, or 3.5 mm. When the fitting length Z was 0.5 mm, it was marked with × because it was difficult to press-fit when the flange thickness B was 0.5 mm, and it was marked with ○ because there was no problem at all when the flange thickness B was 2.5 mm or 3.5 mm.

[0073] From these results, as described above, it is difficult to press-fit when the fitting length Z is large, and the play becomes large when the fitting length Z is small. However, the larger the flange thickness B is with respect to the fitting length Z, the easier the press-fitting becomes, but the play is also more likely to occur. As the flange thickness B increases, the appropriate range of the fitting length Z shifts to the larger Z side. For this reason, as an index indicating this situation, the ratio of the flange thickness B / fitting length Z is appropriate. Figure 8(b) shows this ratio corresponding to each item in Figure 8(a).

[0074] From these results, it is estimated that the preferable range of B / Z is 1.25 ≤ B / Z ≤ 12.5, including the ranges of ○ and △ in Figure 8(a). That is, a lens with R / Z within this range can be stably and firmly fixed to the lens barrel without play. Also, setting B / Z to be less than this upper limit value contributes to reducing the flange thickness B without excessively increasing it while maintaining Z within an appropriate range, that is, to thinning the lens and the lens unit. Among the above ranges, 5.00 ≤ B / Z ≤ 8.33 had the least play and was also easy to press-fit. In Figure 8(a), when the fitting length Z = flange thickness B (= 0.1 mm, 0.5 mm), it corresponded to the case where the inclined surface L3C2 was not provided, and in both cases, it was difficult to press-fit. This shows that providing the inclined surface L3C2 is effective during press-fitting.

[0075] Note that the flange thickness B << lens radius R, and the setting of the lens radius R can be performed with higher precision and more easily than the setting of the flange thickness B. For this reason, it is preferable to perform the setting of R / Z as described above preferentially over B / Z.

[0076] In the above example, the third lens L3 which is a plastic lens has been described. Similarly, the same configuration is effective for the second lens L2 which is also a plastic lens. Further, for the fourth lens body L40, at least its outer peripheral surface L40C is similarly made of a resin material, so it is the same. Furthermore, not limited to the case where a glass lens and a resin material lens holder are combined like the fourth lens body L40, as long as the lens has an outer peripheral surface made of a resin material, it is the same. For the cemented lens L50, it is substantially the fifth lens L5 that is press-fitted, and the same is effective for the fifth lens L5 as well.

[0077] Also, in the relational expression of the above B / Z range, only the relationship between the cob thickness B and the fitting length Z is defined. On the other hand, the length Y (distance between H3 and H4) of the vertical surface L3C1 and the fitting length Z have a relationship of Z ≦ Y. Here, since the relationship among Y, Z, and B is Z ≦ Y < B, when the cob thickness B is sufficiently large, after taking a large Y, the above B / Z range can be realized. In this case, the ratio of Z / Y can be made small, that is, the portion that becomes the fitting portion F on the vertical surface L3C1 can be reduced. Thereby, the press-fitting operation of the lens can be facilitated. Specifically, it is preferable to set Z ≦ Y / 2.

[0078] Also, as described above, supporting the region (dense filling region) corresponding to the arrow K1 in FIG. 6 is less likely to cause distortion of the lens during press-fitting than supporting the region (sparse filling region) corresponding to the arrow K2. Therefore, in the optical axis A direction, it is more preferable that the fitting portion F is included in such a dense filling region. Also, in this case, since the fitting portion F uniformly exists from one side to the other side in the radial direction with respect to the lens barrel, this lens can also be firmly fixed to the lens barrel.

[0079] In FIG. 6, the third lens L3 is shown in which the lens surface on the object side is concave and the lens surface on the image side is convex. However, in a lens (for example, the fifth lens L5) in which both lens surfaces on both sides are concave, since the densely filled region is narrow, this influence is significant. Here, the so-called "sparse filling" and "dense filling" mean, as shown in FIG. 6, the case where there is a portion without the resin material due to the shape of the lens and the case where there is no such portion, respectively, and do not mean the density state of the resin material during molding, for example.

[0080] Also, in the lens, optically the most important is the lens surface on the object side, the lens surface on the image side, and the region therebetween. Therefore, it is preferable that this region is included in the fitting portion F and securely fixed in the direction of the optical axis A. From this viewpoint, in FIG. 6, it is preferable that the height H9, which is the intermediate height (lens center height) between the lens surface L3R1 and the lens surface L3R2, is included in the fitting portion F.

[0081] Regarding such settings other than Y, Z, and B, depending on the shape of the lens, there are cases where the setting is possible and cases where the setting is impossible. Therefore, such settings can be appropriately selected according to the shape of the lens.

[0082] (Main features of this embodiment) The features of this embodiment are briefly summarized as follows. (1) This lens unit 1 includes a plurality of lenses (L1 to L6) arranged in a direction along the optical axis A and having a substantially circular shape perpendicular to the optical axis A, and a cylindrical lens barrel 10 made of a resin material and holding the plurality of lenses on the outside when viewed from the optical axis A. At least one of the lenses is a press-fitted lens (e.g., the third lens L3) fixed in a state of being in contact with a press-fitting inner surface 10B11, which is a surface parallel to the press-fitting direction P in the lens barrel 10. On the third lens outer peripheral surface L3C of the third lens L3, which faces the press-fitting inner surface 10B11 and is made of a resin material, a vertical surface L3C1, which is a surface parallel to the press-fitting direction P and a part of which in the press-fitting direction P is in direct contact with the press-fitting inner surface 10B11, is defined as a fitting portion F, and an inclined surface L3C2, which is adjacent to the vertical surface L3C1 in the press-fitting direction P and is inclined from the press-fitting direction P so as to be separated from the press-fitting inner surface 10B11, is provided. When the fitting length, which is the length of the fitting portion F along the press-fitting direction P, is Z, and the maximum radius around the optical axis A of the third lens L3 is the lens radius R, the range is 6.25 ≦ R / Z ≦ 25.0.

[0083] In this configuration, by appropriately setting the length Z of the fitting portion F, it is possible to improve the positional accuracy of the fixation, particularly in the radial direction around the optical axis A, of the third lens L3, which is taken as an example, with respect to the lens barrel 10, and also to easily perform the press-fitting for fixation. As a result, in this lens unit 1, high imaging characteristics can be stably obtained. In particular, by using the lens radius R, which is highly accurate and easy to control, as a reference, this setting is also easy.

[0084] (2) When the maximum thickness on the radially outer side of the press-fitted lens (e.g., the third lens L3) when viewed from the optical axis A is the flange thickness B, the range is 1.25 ≦ B / Z ≦ 12.5. This configuration can further enhance the above-described effects.

[0085] (3) In the press-fitted lens (e.g., the third lens L3), when the length of the vertical surface L3C1 along the press-fitting direction P is Y, Z ≦ Y / 2. In this case, by reducing the ratio of the fitting portion F in the vertical plane L3C1, the press-fitting operation becomes particularly easy. (4) In the press-fitting lens (e.g., the third lens L3), the lens center height H9, which is the midpoint between the first surface L3R1 and the second surface L3R2 on the optical axis A, is within the range of the fitting portion F in the press-fitting direction P. In this case, the region between the two lens surfaces, which is the optically most important part of the third lens L3, is particularly strongly supported and fixed. For this reason, high imaging characteristics in this lens unit 1 can be obtained particularly stably.

[0086] (5) The press-fitting lens (e.g., the third lens L3) is made of a resin material. In this case, the press-fitting lens is a plastic lens entirely made of a resin material. In this case, the above configuration is particularly effective. (6) When the fitting portion F in the press-fitting lens (e.g., the third lens L3) is viewed from one side to the other side in the radial direction around the optical axis A, the fitting portion F is tightly filled with the resin material constituting this press-fitting lens. In this case, the distortion generated in the plastic lens during press-fitting can be made particularly small, and this press-fitting lens can be fixed particularly firmly to the lens barrel 10.

[0087] As long as a lens (lens body) whose outer peripheral surface is made of a resin material is used, the number and configuration of the lenses used are arbitrary. Also, for example, when a plurality of plastic lenses are used, the above configuration may be applied only to some of the plastic lenses.

[0088] Although the present invention has been described based on embodiments and their modifications, it should be understood by those skilled in the art that these embodiments are illustrative, and various modifications are possible for combinations of their respective components, etc., and such modifications are also within the scope of the present invention.

Explanation of Reference Numerals

[0089] 1 Lens Unit 10 Lens Barrel 10A First Accommodating Portion 10B Second Accommodating Portion 10B1 Lens Fixing Rib 10B11 Press-Fitting Inner Surface 11 First Placing Portion 11A First Lens Placing Protrusion 12 Second Placing Portion 13 First Lens Locking Portion 14 Second Lens Locking Portion 20 Diaphragm 21 Light Shield 30 O-Ring 41 Lens Holder A Optical Axis F Fitting Portion Im Image (Side) L1 First Lens L1A First Lens Lower Surface L1B First Lens Outer Peripheral Surface L1C O-Ring Support Surface L2 Second Lens L2A Second Lens Upper Surface L2B Second Lens Lower Surface L2C Second Lens Outer Peripheral Surface L3 Third Lens L3A Third Lens Upper Surface L3B Third Lens Lower Surface L3C Third Lens Outer Peripheral Surface L3C1 Vertical Surface L3C2 Inclined Surface L4 Fourth Lens (Glass Lens) L5 Fifth Lens L5A Bonded Lens Upper Surface L5B Bonded Lens Lower Surface L5C, L6A Step Portion (Engagement Structure) L5D Bonded Lens Outer Peripheral Surface L40 Fourth Lens Body L40A Fourth Lens Body Upper Surface L40B Fourth Lens Body Lower Surface L40C Fourth Lens Body Outer Peripheral Surface L50 Bonded Lens Ob Object (side) P Pressing direction R1 First surface R2 Second surface

Claims

1. A plurality of lenses arranged in a direction along the optical axis and having a substantially circular shape perpendicular to the optical axis, A cylindrical lens barrel made of a resin material and holding the plurality of lenses on the outside as viewed from the optical axis, A lens unit comprising: At least one of the lenses is a press-fitted lens fixed in contact with a press-fitting inner surface, which is a surface parallel to the press-fitting direction inside the lens barrel, along the press-fitting direction parallel to the central axis of the lens barrel, On the outer peripheral surface of the press-fitted lens that faces the press-fitting inner surface and is made of a resin material, A vertical surface that is a surface parallel to the press-fitting direction and a part of which in the press-fitting direction is in direct contact with the press-fitting inner surface is defined as a fitting portion, An inclined surface that is adjacent to the vertical surface in the press-fitting direction and is inclined from the press-fitting direction so as to be separated from the press-fitting inner surface, Is provided, When the fitting length, which is the length of the fitting portion along the press-fitting direction, is Z, and the maximum radius around the optical axis of the press-fitted lens is the lens radius R, 6.25 ≦ R / Z ≦ 25.0 The lens unit is characterized in that it is in the range of.

2. When the maximum thickness on the radially outer side of the press-fitted lens as viewed from the optical axis is defined as the flange thickness B, 1.25 ≦ B / Z ≦ 12.5 The lens unit according to claim 1, characterized in that it is in the range of.

3. In the press-fitted lens, when the length of the vertical surface along the press-fitting direction is Y, the lens unit according to claim 1 or 2, characterized in that Z ≦ Y / 2.

4. In the press-fitted lens, the lens center height, which is the midpoint between one lens surface and the other lens surface on the optical axis, enters within the range of the fitting portion in the press-fitting direction. The lens unit according to claim 1 or 2, characterized in that.

5. The lens unit according to claim 1 or 2, characterized in that the press-fitted lens is made of a resin material.

6. When the fitting portion of the press-fitted lens is viewed from one side to the other side in the radial direction around the optical axis, the lens unit according to claim 5, characterized in that the fitting portion is densely filled with the resin material constituting the press-fitted lens.

Images