JP2019179179A - Lens unit - Google Patents

Abstract

To provide a lens unit that, when lenses are built into a lens barrel by a press-fit method, reduces a pressure generated on the lens barrel and lenses and reduces backlash between the lens barrel and lenses after the press fit.SOLUTION: A lens unit 10 has a plurality of lenses 1 built into a resin lens barrel 2, and the plurality of lenses 1 include an intermediate lens group 1a press-fit into the lens barrel 2 and lenses 1b on both ends arranged on both sides in the optical axis direction of the intermediate lens group 1a and fastened to the inside of the lens barrel 2 with retainers 3.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lens unit used in a surveillance camera, an in-vehicle camera, and the like, and more particularly to a lens unit that performs press-fitting and fixing as means for incorporating and storing a lens in a lens barrel.

  In recent years, surveillance cameras and in-vehicle cameras have become widespread. Lens units installed in surveillance cameras and in-vehicle cameras (hereinafter referred to as in-vehicle cameras) have a wide range of usage environments and must be used in cold to tropical regions. Stable performance in the ambient temperature range is desired.

  The lens can be accommodated in the lens barrel by a method in which the outer diameter of the lens is made smaller than the inner diameter of the lens barrel and the lens is sandwiched using a presser ring (retainer) that is screwed from the opening of the lens barrel. A press-fit fixing method is adopted in which the outer diameter is made larger than the inner diameter of the lens barrel and is incorporated by applying pressure.

As the former presser ring, a method has been proposed in which a plurality of lenses are inserted into a lens barrel, fixed with an adhesive, and finally fastened to the presser ring (Patent Document 1).
On the other hand, the latter press-fitting method has a small number of parts and is a simple assembling method, but it is difficult to control the press-fitting amount. When the press-fitting amount is increased, a large load is generated on the lens, and the lens is distorted to deteriorate the optical performance. On the other hand, when the amount of press-fitting is reduced, loosening (playback) may occur in the fitting portion between the lens and the lens barrel due to the difference in linear expansion coefficient between the lens barrel and the lens material in a high temperature environment. In addition, when the environment is subject to vibration, the looseness between the lenses may become larger due to the combination of heat and vibration. For this reason, it has also been proposed to press-fit by providing a buffer portion between the lens and the lens barrel (Patent Document 2).

Furthermore, the method of adhering and fixing the lens to the lens barrel reduces the number of parts, but since many of the adhesives are UV-curing, the adhesive strength is reduced if the curing is insufficient, and there is a backlash. May occur. In addition, there is a possibility that the bonding is not performed evenly, or the components of the adhesive are vaporized and adhere to the lens to cause fogging.
On the other hand, in the press-fitting method using the buffer member, the number of parts cannot be suppressed, and as a result, the cost may increase.

  Therefore, there is a demand for a lens unit that reduces the pressure generated in the lens barrel and the lens when the lens is assembled into the lens barrel by the press-fitting method, and does not cause backlash after press-fitting even during vibration or in a high temperature environment.

JP 2009-244393 A Japanese Patent No. 6182380

  An object of the present invention is to provide a lens unit that reduces pressure generated in the lens barrel and the lens when the lens is assembled into the lens barrel in a press-fitting manner, and that does not cause backlash between the lens barrel and the lens after press-fitting. It is.

An embodiment of the present invention for solving the above problems has the following configuration.
(1) A lens unit in which a plurality of lenses are incorporated in a resin lens barrel, wherein the plurality of lenses are press-fitted into the lens barrel, and an optical axis direction of the intermediate lens group A lens unit comprising: both end lenses disposed on both sides and fastened in the lens barrel by a retainer.
(2) The lens unit according to (1), wherein the retainer is made of an elastic body.
(3) The inner peripheral surface of the lens barrel is formed with at least one projecting portion that protrudes into a string shape into the lens barrel and into which the incorporated intermediate lens group is press-fitted (1) or (2). The lens unit described.
(4) The lens barrel has a thick portion and a thin portion, and the thin portion has a recess formed in an outer peripheral surface of a region including a portion where the protruding portion is formed on the inner peripheral surface. The lens unit according to (3).
(5) The lens unit according to (3) or (4), wherein the protrusions are formed at predetermined intervals on the inner peripheral surface of the lens barrel.
(6) On the inner peripheral surface of the lens barrel, a protrusion is formed as a reference position where the periphery of one surface of the lens abuts when the lens is assembled from both ends of the lens barrel (3) to (5 The lens unit according to any one of the above.

  According to the present invention, the intermediate lens group is incorporated in the lens barrel with a minimum press-fitting pressure, and is arranged on both sides in the optical axis direction of the intermediate lens group, and both end lenses are fastened in the lens barrel by the retainer. Therefore, the pressure generated in the lens barrel and the lens can be reduced. Furthermore, since the resin lens barrel can absorb the linear expansion associated with the environmental temperature change, the lens does not play due to the temperature change after the press-fitting.

It is a perspective view which shows the camera which has a lens unit which concerns on one Embodiment of this invention. It is sectional drawing of the lens unit shown in FIG. FIG. 2 is a cutaway perspective view of the lens unit shown in FIG. 1. It is a perspective sectional view showing the lens barrel of the lens unit shown in FIG. It is sectional drawing which shows the lens unit which concerns on another embodiment of this invention. FIG. 6 is a perspective view of the lens unit shown in FIG. 5.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a camera 100 including a lens unit 10 according to an embodiment of the present invention. The lens unit 10 includes a resin-made lens barrel 2 and a plurality of lenses 1 (first lens 11 to sixth lens 16) incorporated in the lens barrel 2.

  As shown in FIG. 2, the plurality of lenses 1 includes a second lens 12 to a fifth lens 15 (hereinafter referred to as an intermediate lens group 1a) and a first lens disposed on both sides in the optical axis direction of the intermediate lens group 1a. 11 and the sixth lens 16 (hereinafter each referred to as a double-ended lens 1b). The intermediate lens group 1a is press-fitted into the lens barrel 2 and incorporated. Both end lenses 1 b include a first lens 11 closest to the subject (object) and a sixth lens 16 closest to the image plane (sensor), and are fastened in the lens barrel 2 by the retainer 3.

  The material of the lens 1 is not specifically limited, For example, a glass lens, a thin glass lens, a resin lens etc. are used, It uses suitably combining according to a use. The number, diameter, thickness, etc. of the lenses 1 may be different from each other as long as they can be incorporated into the lens barrel 2.

  The lens barrel 2 is a resin-made cylindrical member that accommodates the lens 1 therein, and has openings at both ends on the object side and the image plane side.

  The lens barrel 2 is preferably designed by simulating the minimum necessary press-fit pressure (pressure generated in the lens in the direction perpendicular to the optical axis) that can hold the lens in the lens barrel in the operating environment temperature range. The press-fitting pressure is 20 to 70 MPa, more preferably 20 to 60 MPa. By setting the press-fitting pressure, adverse effects on the lens 1 are suppressed, and glass materials having different linear expansion coefficients can be used. The operating environment temperature range of the lens barrel 2 is −40 to + 105 ° C., more preferably −40 to + 125 ° C. This temperature range may also be applied to other members including the lens 1.

  The lens barrel 2 is made of resin from the viewpoint of ease of molding by injection molding (mold molding), lightness, and cost. For example, a polycarbonate (PC) resin or a polyphenylene sulfide (PPS) resin is preferable. In particular, PPS resin has high rigidity and strength and is preferably used. In order to obtain higher strength and lower linear expansion, for example, glass fibers may be mixed in the resin.

  As shown in FIGS. 2 and 3, the lens 11 and the lens 16 are attached to the end of the lens barrel 2 by the retainer 3. The retainer 3 is an annular member, and is attached to the object side and image plane side ends of the lens barrel 2 in parallel with the optical axis direction, and both ends of the first lens 11 and the sixth lens 16 at the end of the lens barrel 2. The lens 1b is fastened so as to be sandwiched between the lens barrels 2 respectively. The retainer 3 may not only hold the both end lenses 1 b but also hold the intermediate lens group 1 a in the inner direction of the lens barrel 2. That is, the second lens 12 and the fifth lens 15 with which both end lenses 1b abut can be pressed toward the inner side of the lens barrel 2. Further, the intermediate lens group 1a can hold the entire lens 1 when adjacent lenses are in contact with the interval ring 6 as will be described later.

  The method of fastening the retainer 3 to the lens barrel 2 is not particularly limited as long as no looseness occurs in the lens to be fastened. For example, screws are cut on the inner peripheral surface side of the retainer 3 and the outer peripheral surface sides of both ends of the lens barrel 2. And a method in which the retainer 3 and the lens barrel 2 are fitted and then screwed with a screw (not shown) from the outside.

  The retainer 3 is preferably formed of an elastic body in order to absorb linear expansion accompanying a change in environmental temperature with respect to the lens unit and to apply a stable pressing force in the optical axis direction. The two end lenses 1b can be pressed into the lens barrel 2 by the stress caused by the elastic deformation of the retainer 3, and can be fixed more reliably. For example, a metal material such as aluminum or a resin material such as PPS can be used. Further, the retainer 3 may be provided with a pressing portion (for example, a leaf spring) that presses the lenses 11 and 16 inward from the opening side.

  As shown in FIGS. 3 and 4, the inner peripheral surface of the inner surface of the lens barrel 2 where the intermediate lens group 1a to be press-fitted is incorporated is provided with a protrusion 5 for receiving the press-fitted lens, It is good to have a substantially circumferential shape (polygonal shape). The protrusion 5 protrudes in a string shape (D shape) in the lens barrel 2 in order to maintain the outer diameter of the press-fit lens 1. The protruding amount of the protruding portion 5 is preferably a protruding amount that does not block the light beam narrowed by the stop 4. The height of the protruding portion 5 in the protruding direction is 0.115 to 0.105 mm, and the thickness is preferably equal to or greater than the edge of the lens. Further, the larger the contact area between the protrusion 5 and the lens, the better. If the contact area is large, the stress is low and lens holding is ensured. If the contact area is small, the stress is large, and the protrusion 5 may be plastically deformed to cause lens play. .

  There is no need to provide the protrusions 5 over the entire circumference of the inner surface of the lens barrel 2, and at least one protrusion is sufficient to maintain the outer diameter of the lens 1, and more preferably, between the protrusions 5 on the inner peripheral surface. It is preferable to provide them at predetermined intervals. For example, it is preferable to provide three or four places at predetermined intervals so that the inner circumference of the lens barrel 2 is divided into three or four equal parts. In the case where the protrusions 5 are provided with a predetermined interval, even if the outer peripheral surface of the lens 1 and the protrusions 5 are in contact with each other, air is supplied between the outer peripheral surface of the lens 1 and the inner peripheral surface of the lens barrel 2. There is a gap through it. Therefore, the adjacent lenses 1 are not sealed, pressure can be released, and the shape of the lens barrel 2 can be further prevented from being deformed.

  The protrusion 5 is provided for each lens of the intermediate lens group 1a to be press-fitted, and the shape and installation location may be different depending on the diameter of the lens. The protruding portion 5 may be integrally formed with the lens barrel 2 by resin molding or the like, or another member may be attached to the lens barrel 2.

  As shown in FIG. 4, the lens barrel 2 has a thick portion 2a and a thin portion 2b in which the outer peripheral surface into which the intermediate lens group 1a is press-fitted differs in thickness corresponding to the outer diameter of the lens. . In this thin portion 2b, a recess 8 is formed on the outer peripheral surface of the region including the portion where the protruding portion 5 is formed on the inner peripheral surface of the lens barrel 2. The concave portion 8 can be provided by, for example, removing the outer peripheral surface of the lens barrel 2 in the region including the portion where the protruding portion 5 is formed. The recesses 8 are preferably made to correspond to the locations and the number of the protrusions 5 in the lens barrel 2.

  Conventionally, when the intermediate lens group 1a is press-fitted into the lens barrel 2, since the rigidity of the lens barrel 2 is large, a large stress is generated due to the difference between the inner diameter of the lens barrel 2 and the outer diameter of the lens 1 to be press-fitted. However, by providing the concave portion 8, it is possible to relax the rigidity of the lens barrel 2 at the lens housing location and reduce the press-fitting pressure of the lens 1. In this way, a lens such as a resin lens or a thin glass lens, which has conventionally been subjected to a large load due to press-fitting and has been distorted to deteriorate optical performance, is press-fitted into the lens barrel 2 as the intermediate lens group 1a. Can do.

  The lens barrel 2 may have a reference position 9 and a spacing ring 6 in addition to the above.

  The diaphragm 4 is a thin plate member that is provided between the second lens 12 and the third lens 13 and controls the amount of light entering the lens by opening a predetermined aperture. The stop 4 includes an aperture stop that limits the amount of transmitted light and determines an F value that is an index of brightness, or a light blocking stop that blocks light that causes ghosts and aberrations. The diaphragm 4 may be in contact with the interval ring 6 or the third lens 13, which has the effect of maintaining the lens interval. The material of the diaphragm 4 is preferably made of metal from the viewpoint of durability and the like, and examples of the metal include stainless steel and aluminum, and stainless steel is preferable.

  The reference position 9 is a reference for lens arrangement when the intermediate lens group 1a is press-fitted into the lens barrel 2, and indicates a contact position of the lens surface where the lens is first arranged. In this embodiment, the reference position 9 is a substantially intermediate position (third position) of the entire lens in order to make a balance between the change amount of the lens 1 and the change amount of the lens barrel 2 with respect to the linear expansion of the lens barrel 2. It is preferable to provide it at a position between the lens 13 and the fourth lens 14. Providing the reference position 9 at a substantially intermediate position of the lens has an effect that the lens unit 10 can be made compact compared to providing the aperture position or one side of the entire lens. The reference position 9 may be appropriately changed according to the number and performance of the lenses, but distortion is less likely to occur when the number of lenses before and after the reference position 9 is the same.

  As shown in FIG. 4, the reference position 9 is located in the lens barrel 2 with the third lens contact reference surface 93 and the fourth lens contact reference surface 94 inclined to the image surface side and the object side, respectively. It is formed protruding from the mold. The third lens 13 and the fourth lens 14 are in contact with the third lens contact reference surface 93 and the fourth lens contact reference surface 94, respectively, and are held at appropriate positions. The inner peripheral surface of the reference position 9 is circular. The reason why the third lens contact reference surface 93 and the fourth lens contact reference surface 94 are inclined is to prevent internal reflection that affects the imaging, and This is because it is easy to pull out the mold during integral molding.

  Based on the reference position 9, the lens focal length variation caused when the environmental temperature changes from the low temperature side (−40 ° C.) to the high temperature side (125 ° C.) with respect to the reference temperature (about 20 ° C.) of the lens unit. Optical design is performed so that the expansion and contraction of the lens barrel 2 can be optically compensated. At this time, if the reference position 9 is arranged at a substantially intermediate position of the entire lens, it is possible to perform compensation design considering a smaller amount of change than setting the reference at the object side or the image side end. Therefore, the optical design of the lens unit is facilitated, and more stable optical performance can be obtained. For example, when the first lens 11 to the sixth lens 16 are installed in the lens barrel 2, first, the third lens 13 is first incorporated into the reference position 9 from the object side of the lens barrel 2, and the fourth lens 14 from the image plane side. Incorporate Next, it is preferable to incorporate the first lens 11 and the second lens 12 from the object side of the lens barrel 2 and the fifth lens 15 and the sixth lens 16 from the image plane side. At this time, the front group having negative refractive power including the first lens 11 and the second lens 12 includes the rear group having positive refractive power including the third lens 13 to the sixth lens 16, and the aperture stop 4 that is opened. It is composed of sandwiches. As described above, when an imbalance occurs in the length on the optical axis between the front group and the rear group in the entire lens, if the reference position 9 is provided at a substantially intermediate position of the entire lens, it occurs when the environmental temperature changes. The lens focal length variation and the expansion / contraction of the lens barrel 2 can be optically compensated, and the optical performance is stabilized. On the other hand, if the reference position 9 does not satisfy the above conditions, optical compensation may not be possible, and optical performance may deteriorate.

  An interval ring 6 is provided between the second lens 12 and the third lens 13 and the fourth lens 14 and the fifth lens 15 that are arranged with a space between them to maintain the distance between adjacent lenses. Also good. The spacing ring 6 is a member disposed in the lens barrel 2 and may be integrally formed with the lens barrel 2 or may be a separate member. The outer peripheral surface of the spacing ring 6 is in contact with the inner peripheral surface of the lens barrel 2. The spacing ring 6 is preferably made of metal because the amount of change with respect to temperature change is small and the rigidity is increased. The metal spacing ring 6 can ensure stable optical performance in a wide temperature range. Examples of the material of the spacing ring 6 include aluminum, titanium, magnesium, stainless steel, and alloys thereof, and the like. Aluminum is particularly preferable from the viewpoint of weight reduction and low cost. A diaphragm 4 is provided between the second lens 12 and the third lens 13 between the spacing ring 6 and the third lens 13.

  The fifth lens 15 and the sixth lens 16 may be a cemented lens (hereinafter referred to as a cemented lens). The cemented lens is preferably protected by disposing a fifth lens 15 having a smaller diameter than the sixth lens 16 on the object side so that stress in the optical axis direction due to temperature change does not act on the cemented surface. In addition, the fifth lens 15 and the sixth lens 16 are bonded together to improve the occurrence of chromatic aberration, and even when the number of lenses is increased, the influence of the deviation that occurs when the lenses are incorporated is reduced, that is, the sensitivity of incorporation is reduced. It can be designed to be lower. The cemented lens and the fourth lens 14 are preferably defined by a spacing ring 6.

  In the above description of the present invention, an optical system having a five-group, six-element configuration has been described as an example. However, the number of lenses and the configuration are not limited, and can be appropriately changed according to the application.

(Example)
In the description so far, the description has been based on the optical system of 6 elements in 5 groups. However, in this embodiment, 7 lenses in 7 groups (first lens 71 to 7 as shown in FIGS. 5 and 6). The lens unit 110 using the lens 77) and the lens barrel 20 was used to simulate the stress load applied to the lens and the lens barrel. Further, the incorporation reference position 9 in this embodiment is set between the second lens 72 and the third lens 73.

  As an example, a lens unit 110 shown in FIGS. 5 and 6 was prepared. The seven lenses 71 to 77 of the lens unit 110 are fastened to the second lens 72 to the sixth lens 76 (hereinafter referred to as the intermediate lens group 7 a) press-fitted into the lens barrel 20 and both ends of the lens barrel 20. A first lens 71 closest to the object side and a seventh lens 77 closest to the image sensor 99 (image surface side) (hereinafter referred to as a double-ended lens 7b). The intermediate lens group 7 a is respectively press-fitted and incorporated into the lens barrel 20, and the outer diameter is held by the string-like projecting portion 5 in the lens barrel 20. A spacing ring 6 is provided between the lenses of the intermediate lens group 7a to maintain the spacing between the lenses. A diaphragm 4 is installed at the rear end of the spacing ring 6 provided at the rear end of the second lens 72. When the lens 7 is assembled from both ends of the lens barrel 20 on the inner peripheral surface of the lens barrel 20, a reference position where the peripheral edge of one surface of the lens 7 is brought into contact with a substantially intermediate position of the entire lens 7. A protruding portion is formed. In the present embodiment, the protruding portion formed between the second lens 72 and the third lens 73 is the reference position 9. The image surface side peripheral edge of the second lens 72 is pressed against the reference position 9 via the interval ring 6 and the diaphragm 4, and the object side peripheral edge of the third lens 73 is directly in contact with the reference position 9. . On the other hand, the both end lenses 7 b are fastened by being sandwiched by the retainers 3 at both ends of the lens barrel 20. The lens barrel 20 increases in thickness from the object side to the image plane side, and has a thick portion 20a and a thin portion 20b.

  When the lens 7 was attached to the lens barrel 20, a stress was applied so that the deformation amount (press fit amount) was 0.015 mm. In the embodiment, the lens 7 is an optical glass lens, and the lens barrel 20 is made of PPS resin, and the protrusion 5 is integrally formed on the inner surface. The retainer 3 is made of PPS resin, and the spacing ring 6 is made of aluminum alloy. Further, each diameter of the lens 7 and each contact area of the lens 7 to the inner peripheral surface of the lens barrel 2 and the protruding portion 5 are as shown in Table 1. Here, the contact area means the area of the portion where the outer peripheral portion (edge) of the lens 7 is press-fitted into the protruding portion 5, and differs depending on the outer diameter of the lens 7 and the thickness of the lens edge.

  As shown in FIG. 6, a region including a thin portion 20 b in which the protruding portion 5 is formed on the inner peripheral surface is formed on the outer peripheral surface of the lens barrel 20. The concave portion 8 formed in this region is for controlling the press-fitting amount due to the difference in the outer diameter of the lens 7 press-fitted into the lens barrel 20, and includes a portion where the protruding portion 5 is formed on the inner peripheral surface. Three locations on the outer peripheral surface of the region are arranged at the front and rear of the thin portion 20b so that the thickness is 0.75 to 0.85 mm thinner than the outer peripheral surface (thick portion 20a) of the other lens barrel 2 according to the outer diameter of the lens 7. Are formed at three locations in the circumferential direction of the lens barrel 20. The results are shown in Table 1.

In the lens unit of the example, the stress applied to the lens and the lens barrel was reduced when the lens was press-fitted, so that the lens and the lens barrel were not broken or damaged.
Furthermore, as shown in Table 1, by providing the recessed portion 8 in the thin portion 20b on the outer peripheral surface of the protruding portion 5, the thin portion 20b has a thinner structure, and the rigidity of the lens barrel 20 in the lens housing portion is reduced. Therefore, it was found that the force per contact area of the intermediate lens group 7a press-fitted into the lens barrel 20 is suppressed, and variation in the force applied to the lens 7 can be further suppressed.

  The lens unit according to the embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various improvements and improvements can be made. For example, the lens unit of the present invention is not limited to vibration resistance, and does not generate backlash between the lens barrel and the lens even with respect to temperature changes. It can also be suitably used for equipment in which a large temperature change occurs in the lens or the lens barrel due to the heat.

DESCRIPTION OF SYMBOLS 1 Lens 1a Intermediate lens group 1b Both end lens 2 Lens barrel 2a Thick part 2b Thin part 3 Retainer 4 Diaphragm 5 Projection part 6 Space ring 8 Concave part 9 Reference position 10 Lens unit 7 Lens 7a Intermediate lens group 7b Both end lens 20 Mirror Tube 100 Camera 110 Lens unit

Claims (6)

A lens unit in which a plurality of lenses are incorporated in a resin lens barrel,
The plurality of lenses includes an intermediate lens group press-fitted into the lens barrel, and both end lenses disposed on both sides in the optical axis direction of the intermediate lens group and fastened in the lens barrel by a retainer. Lens unit characterized by   The lens unit according to claim 1, wherein the retainer is made of an elastic body.   3. The lens unit according to claim 1, wherein at least one projecting portion is formed on an inner peripheral surface of the lens barrel so as to project into a string shape in the lens barrel and into which the incorporated intermediate lens group is press-fitted. The lens barrel has a thick part and a thin part,
The lens unit according to claim 3, wherein the thin portion has a recess formed on an outer peripheral surface of a region including a portion where the protruding portion is formed on an inner peripheral surface.   The lens unit according to claim 3 or 4, wherein the protrusions are formed at predetermined intervals on an inner peripheral surface of the lens barrel.   6. The projection according to any one of claims 3 to 5, wherein an inner peripheral surface of the lens barrel is formed with a projecting portion serving as a reference position with which a peripheral edge of one surface of the lens contacts when the lens is assembled from both ends of the lens barrel. The lens unit described.

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