JP2010054866A - Lens unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens unit that always maintains optical performance by having a simple configuration and making it easy to assemble taking into account of mass production of a lens unit, and that reduces performance deterioration caused by coat crack resulting from focus change and no accommodation of expansion due to a difference in expantion rate between a lens barrel and a lens, even in an environment where it is difficult to maintain image performance due to exposure to high temperature. <P>SOLUTION: An imaging lens composed of a plurality of lenses is accommodated in the lens barrel. A stepped part is formed around a face of one lens and a stepped part is formed around a face of the other lens, the one lens and the other lens being adjacent to each other and the faces having optical actions. One of the stepped parts is a projection formed on one of the lenses and the other is a recess formed in the other, so that the stepped parts join each other. They are held in the lens barrel by being joined and integrated together. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens unit used in an imaging apparatus including a solid-state imaging device such as a monitoring camera or a vehicle-mounted camera, and in particular, obtains imaging characteristics by using a plurality of lenses, and at a high temperature. The present invention relates to a lens unit in which performance degradation is reduced even in an environment where it is difficult to maintain imaging performance such as exposure.

  A lens unit that holds multiple lenses in a cylindrical lens barrel to obtain imaging characteristics and is compact and lightweight is widely used in digital cameras, mobile phone cameras, surveillance cameras, in-vehicle cameras, etc. It has been. These lens units, for example, when left outdoors or installed, become hot due to solar heat, etc., and when they expand, the lens position changes and the focal point changes, or the difference in expansion coefficient between the lens barrel and lens As a result, there is no escape space for expansion, causing the occurrence of coat cracks and the like, and it is difficult to maintain optical performance.

  Therefore, for example, in Patent Document 1, a lens barrel that is made of a material having a small linear expansion coefficient and holds a plastic lens, and is arranged on the outer peripheral side of the lens barrel, is formed in a cylindrical shape, and has a large linear expansion coefficient. The elastic member is made of a material and an elastic member that presses the lens barrel toward the subject. The first pressure contact portion provided on the lens barrel is pressed against the second pressure contact portion provided on the expansion member by the pressure of the elastic member. At least one of the first pressure contact portion and the second pressure contact portion is formed in a tapered surface from the center position on the subject side to the outer peripheral direction on the imaging surface side, and the change in the focal position of the photographing lens due to the temperature change is mechanically An imaging device is shown that is offset and corrected.

  In Patent Document 2, the object side opening of the front case is sealed with a pressing member using an O-ring to improve environmental resistance, and the opening of the pressing member is formed with a first lens using a second O-ring. An imaging device configured to be sealed to obtain high hermeticity is disclosed.

  In such a lens unit, it is important to hold a plurality of lenses constituting the optical system at appropriate positions and states in order to maintain optical performance. Therefore, in order to hold the lens at an appropriate position, the lens thickness interval and the thickness of the light shielding material and spacer are accurately controlled to maintain the interval, and the lens outer diameter and lens barrel inner diameter are manufactured with high accuracy. This makes it less susceptible to eccentricity.

  As a prior art having a configuration that is not easily affected by eccentricity as described above, for example, Patent Document 3 discloses an optical system that prevents optical axis shift due to a temperature change of an optical system including a plurality of lenses and can improve support accuracy. In the imaging lens structure in which a small-diameter opening is formed concentrically on one side of the optical axis direction of the barrel containing the lens and a large-diameter opening is formed concentrically on the other side, and a presser ring is provided on the large-diameter opening side, the barrel of one lens A lens located on the barrel large-diameter opening side by providing a lens-side support portion having a tapered section on the peripheral flange portion on the small-diameter opening side and a barrel-side support portion having a tapered cross-section on the lens support surface facing the one lens of the barrel. An imaging lens structure, an optical module, and a portable device that can secure high optical performance by interposing an elastic member between the presser ring and positioning and supporting the lens side support portion on the barrel side support portion by the biasing force of the elastic member Terminal, average These built, manufacturing method is shown in.

JP 2003-262778 A JP 2005-17951 A JP 2007-178541 A

  However, as described above, the lens unit composed of a plurality of lenses has been recently developed in spite of the importance of holding a plurality of lenses configured to maintain a good image quality in an appropriate position and state. Along with the downsizing of the image sensor, downsizing of the lens unit is required, and as a result, the accuracy of holding the lens in the proper position and state is dramatically increased, and the accuracy of the parts can be driven to the required accuracy. It has become difficult.

  Further, in recent years, mobile phone cameras, surveillance cameras, and in-vehicle cameras have become increasingly widespread in use temperature and guaranteed temperature, and it has become difficult to maintain performance in this wide temperature range.

  Although the lens unit described in Patent Document 1 described above is configured in consideration of such a temperature change, the focal position change of the imaging lens due to the temperature change is corrected by the selection and structure of the lens barrel material, The structure is difficult to improve in terms of miniaturization and environmental resistance, such as by double lens barrels.

  In addition, the lens unit described in Patent Document 2 has a configuration in which the lens barrel is sealed with a lens closest to the object side in order to improve environmental performance. There is a problem in that it is difficult to maintain the optical performance because the eccentricity occurs due to the gap generated by the difference between the two.

  Furthermore, the lens unit described in Patent Document 3 is configured to prevent the optical axis from being displaced even if a temperature change occurs by providing a taper. However, there is no escape from expansion due to the temperature change, resulting in a coating crack or the like. There is a problem that it becomes difficult to maintain optical performance.

  Therefore, in the present invention, taking into account the mass productivity of the lens unit, it is easy to assemble with a simple configuration, and even in an environment where it is difficult to maintain imaging performance, such as exposure to high temperatures, focus changes, lens barrel and lens expansion It is an object to provide a lens unit capable of constantly maintaining optical performance by reducing performance degradation due to coat cracks, etc., which are caused by the fact that there is no escape space due to the difference in rate.

In order to solve the above problems, the lens unit according to the present invention is
In a lens unit comprising an imaging lens composed of a plurality of lenses and a lens barrel that holds the imaging lens,
The one lens is convex on the other lens side and the other lens is on the one lens side around the surface having the optical action in the adjacent one lens and the other lens among the plurality of lenses. It has a step part which can be mutually fitted in a concave shape, is integrated by fitting, and is held by the lens barrel.

  In this way, among the plurality of lenses constituting the imaging lens, the adjacent one lens and the other lens are fitted and accommodated in the lens barrel, so that the two lenses are integrated into the lens barrel. As a result, assembly is facilitated. Even if it is exposed to harsh environments such as being exposed to high temperatures and there is thermal expansion etc., it is integrated so that there is little deviation in the lens spacing, and even if there is a misalignment of the axis, one lens and another lens As a result, the center of the axis shifts and performance degradation can be suppressed to a small extent.

Similarly, in order to solve the above problems, the lens unit according to the present invention is
In a lens unit comprising an imaging lens composed of a plurality of lenses and a lens barrel that holds the imaging lens,
The plurality of lenses and the lens barrel are formed of materials having different linear expansion coefficients, and the one lens adjacent to the lens and the surface having an optical function in the other lens are arranged around the surface having the optical action. The lens has a convex shape on the other lens side, and the other lens has a concave stepped portion on one lens side that can be fitted to each other. When the lens diameter is d, D and d satisfy the following expression (1).
0.005 mm <D-d <0.1 mm (1)

  In addition to fitting one adjacent lens and another lens in this way, the lens and the lens barrel are formed of materials having different linear expansion coefficients, and the inner diameter D and the lens diameter of the lens barrel are set to d. By providing a gap (clearance) given by equation (1) between them, the problem of the escape from disappearing due to the difference in expansion coefficient between the lens barrel and the lens can be solved. As a result, the lens unit that can be easily assembled and can always maintain the optical performance can be provided.

  The one lens and the other lens are the lens having the strongest refractive power and the lens having the strongest refractive power adjacent to the lens, thereby integrating the lenses that most affect the optical performance. Since the one lens and the other lens have positive and negative refracting power, axial misalignment and the like are offset, so a lens unit that can maintain optical performance can be provided. can do.

  The plurality of lenses constituting the imaging lens are, in order from the object side, a first lens having a negative refractive power having a convex surface on the object side and a second lens having a negative refractive power having a concave surface on the image side. And a third lens having a positive refractive power convex toward the object side, an aperture stop, and a fourth lens having a positive refractive power convex toward the image side. By using the second lens and the third lens as the lenses, the lenses to be fitted are other than the object side and the image plane side, so the degree of freedom in selecting the lens material can be increased.

And when the first lens is glass and the total angle of view with respect to the screen is 2 W, it is formed so as to satisfy the following formula (2). For example, in the case of a lens unit of a surveillance camera used outdoors, Although there is a possibility that it will be exposed to rain or wind, a glass lens can withstand such a bad environment, and by setting a larger angle of view, it can be a suitable lens that can image a wide range for monitoring purposes.
2W <130 ° ………………………………………………………… (2)

  Furthermore, since the one lens and the other lens are formed of a resin material, a highly accurate lens can be manufactured even when an aspheric surface or the like is used.

  Further, by providing a gap where a light-shielding material can be placed on the outer periphery of the surface having the optical action between the one lens and the other lens, unnecessary light into the lens barrel is cut off. Therefore, it is possible to prevent light caused by unnecessary flare, ghost, etc. from reaching the imaging surface.

  As described above, according to the present invention, a small lens unit can be easily assembled with a simple configuration, and even in an environment where it is difficult to maintain imaging performance, such as exposure to high temperatures, the lens interval and axial misalignment can be reduced. It is resistant to factors that degrade lens performance, such as optical axis misalignment, and can also prevent performance degradation due to coat cracks that occur due to the absence of expansion escape due to the difference in expansion coefficient between the lens barrel and lens. A lens unit capable of maintaining the performance can be provided.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the shape of the component described in this embodiment is not intended to limit the scope of the present invention, but merely an illustrative example.

  FIG. 1 is a cross-sectional view illustrating a basic configuration of a lens unit according to a first embodiment of the present invention. FIG. 2 illustrates fitting of two lenses among the imaging lenses constituting the lens unit according to the first embodiment. It is sectional drawing which shows a state.

  In the cross-sectional views of the lens unit 10 of Example 1 shown in FIGS. 1 and 2, the left side in the figure is the subject side (object side), the right side is the image side (imaging plane side), and the imaging lens (G0) 12 is , A first lens (L1) 14, a second lens (L2) 16, a third lens (L3) 18, a fourth lens (L4) 20, and an aperture stop (SP) 22. These lenses are arranged at predetermined positions in the lens barrel (T1) 24, and the lens holder (T2) 26 is screwed or bonded to the subject side (object side) of the lens barrel (T1) 24, or is caulked. To fix the first lens (L1) 14 and hold the imaging lens (G0) 12 in the lens barrel (T1) 24.

  A fourth lens holding portion 242 for positioning in the optical axis direction of the fourth lens (L4) 20 is provided on the inner surface of the lens barrel (T1) 24. For the other lenses and the aperture stop (SP) 22, first, the aperture stop (SP) 22 is provided in the aperture stop holding portion 202 provided in the fourth lens (L4) 20, and the third lens (L3) 18 is provided in the aperture stop. The second lens (L2) 16 is connected to the third lens holding part 182 provided to the third lens (L3) 18 and the first lens (L1) 14 is connected to the third lens holding part 222 provided on the (SP) 22. Are in contact with the first lens holding portion 162 provided on the second lens (L2) 16 and positioned in the optical axis direction.

  Further, on the inner surface of the lens barrel (T1) 24, the portion facing the outer peripheral surface of each lens (L1, L2, L3, L4) constituting the imaging lens (G0) 12 and the outer peripheral surface of the aperture stop (SP) 22 are arranged. Lens facing portions 248, 250, 252, and 254 are provided at the facing portions through predetermined clearances described later corresponding to the diameters of the respective lenses. Furthermore, when the O-ring 28 is disposed in the O-ring holding portion indicated by 246 of the lens barrel (T1) 24 and the first lens (L1) 14 is fixed by the lens pressing (T2) 26, the first lens (L1 ) 14 presses the O-ring 28 from the subject side (object side) to the image side (imaging plane side). Therefore, the O-ring 28 is crushed between the O-ring holding portion 246 and the image plane side of the first lens (L1) 14 so that the liquid cannot penetrate into the lens barrel (T1) 24 with a sealing effect. It has become.

  Further, the first lens (L1) 14 comes into contact with the first lens holding portion 162 provided on the second lens (L2) 16, so that the second lens (L2) 16 to the fourth lens (L4) 20 are moved to the object. Since the lens is pressed toward the image side (imaging plane side) from the side, even if there is an impact or the like, the optical axis shift of each lens (L1, L2, L3, L4) can be prevented.

  In addition, 30 arranged on the image plane side of the imaging lens (G0) 12 is a glass block (G) provided by design corresponding to a crystal low-pass filter, an infrared cut filter, a protective glass for protecting the imaging element, and the like. is there. Reference numeral 32 denotes an image plane (IP) of the imaging lens (G0) 12, on which a photosensitive surface of a solid-state imaging device constituted by a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is arranged. Further, a gap is provided between the second lens (L2) 16 and the third lens (L3) 18, and a light-shielding material (T3) 34 is placed on the outer peripheral side of the surface having an optical action, so that the lens barrel (T1). Unnecessary light that enters 24 is cut so that light caused by unnecessary flare, ghost, etc. does not reach the image plane (IP) 32.

  The imaging lens (G0) 12 of Example 1 is configured as an optical system in which the focus from an infinite object to a short-distance object is a pan focus, and the lens unit 10 is not extended, but the lens unit 10 May be extended to the object side, or a part of the plurality of lenses constituting the imaging lens (G0) 12 may be extended so that focusing can be performed.

  As shown in the drawing, the first lens (L1) 14 in the imaging lens (G0) 12 has a convex surface on the object side (object side) and a convex surface on the image side. The absolute value of the refractive power of the object side surface is smaller than that of the surface, and the lens is made of a meniscus glass lens having negative refractive power (optical power = reciprocal of focal length). By making the object side convex in this way, for example, even if water droplets are ejected from the object side, the water droplets can escape to the periphery, which is combined with the use of the O-ring 28 as described above. Therefore, environmental performance can be satisfied. Furthermore, by using the first lens (L1) 14 as a glass lens that is superior in environmental performance such as hardness compared to a plastic lens, the lens unit 10 that can withstand harsh environments can be obtained.

Further, in the lens unit 10 of the present invention, the angle of view of the first lens (L1) 14 is set to 2 W with respect to the screen so as not to generate a lot of blind spots particularly as a surveillance camera or a vehicle-mounted camera. When forming, the following equation (2) is satisfied.
2W <130 ° ………………………………………………………… (2)

  The second lens (L2) 16 is a plastic lens that has a negative refractive power with a concave surface facing the image side and is formed by molding a resin material. The third lens (L3) 18 is a biconvex positive lens. It is a plastic lens formed by molding a resin material having refractive power. A lens made of a resin material is superior to a lens made of glass in terms of molding stability, weight, and cost. In addition, the lens made of the resin material of the present embodiment taking advantage of the molding uses a rotationally symmetric aspherical surfaces on both sides (object side and image side). Thus, by expanding the degree of freedom from the spherical surface, good imaging performance is obtained with a small number of components.

  The second lens (L2) 16 has a curvature on the image surface side that is weak in refractive power from the center toward the periphery, and the object side and image surface side surfaces are surfaces having no inflection points. When an inflection point is generated, it is difficult to obtain good imaging performance over the entire screen due to the influence of curvature of field due to molding variations in a part of the screen, as in this embodiment. By adopting the shape, good imaging performance can be ensured over the entire screen even with a compact number of lenses.

  The fourth lens (L4) 20 is a lens having a positive refractive power with a substantially convex shape on the subject side (object side) and a strong convex surface on the image side (imaging surface side), and molding a resin material. There is a plastic lens formed by. By adopting such a shape, the amount of MTF performance deterioration at a position close to the aperture stop (SP) 22 such as a thickness shift, a gap in the optical axis direction with respect to the aperture stop (SP) 22, and a shift in the optical axis direction is reduced. The lens is easy to manufacture.

  The aperture stop (SP) 22 includes a fourth lens (L4) 20 at the aperture stop holder 202 in the fourth lens (L4) 20 and a third lens (L3) at the third lens holder 222 in the aperture stop (SP) 22. ) 18 is arranged in contact with. If the aperture stop (SP) 22 is arranged closer to the image side than the fourth lens (L4) 20, it is not preferable because the lens system is enlarged, and the second lens (L2) 16 and the third lens (L3) 18 are not connected. If it is arranged in the middle, it is disadvantageous for increasing the back focus. Therefore, by disposing the lens between the third lens (L3) 18 and the fourth lens (L4) 20, it is possible to correct various aberrations and make the lens system compact.

  Although the imaging lens (G0) 12 shown in FIGS. 1 and 2 is configured with four lenses (L1, L2, L3, L4), the present invention is not limited to this. The imaging lens (G0) 12 is not limited to the configuration shown in the figure as long as it has a plurality of lenses.

  Of the imaging lens (G0) 12 constituting the lens unit 10 of the present invention thus configured, the second lens (L2) 16 and the third lens (L3) 18 are shown in a fitted state in FIG. As described above, the second lens (L2) 16 includes a stepped portion 164 that is concave on the third lens (L3) 18 side, and the third lens (L3) 18 around the surfaces having optical effects. Has a convex step portion 184 on the second lens (L2) 16 side, and the respective step portions are configured to be fitted to each other, and are integrated by press-fitting each other.

  Therefore, the second lens (L2) 16 and the third lens (L3) 18 have the same air gap and the same optical axis deviation. Further, the relative displacement between the second lens (L2) 16 and the third lens (L3) 18 is reduced, and the number of parts can be reduced by fitting them before being assembled into the lens barrel (T1) 24. And easy to incorporate. The concave step 164 and the convex step 184 for press-fitting the second lens (L2) 16 and the third lens (L3) 18 may be either convex or concave. It goes without saying that, when press-fitting, each lens can be fitted with a force that does not cause distortion.

Further, the second lens (L2) 16 and the third lens (L3) 18 have a linear expansion coefficient, for example, the second lens (L2) 16 is 6 (10 ⁻⁵ / ° C.), and the third lens (L3) 18 is 7 (10 ⁻⁵ / ° C.), when the material is relatively close, the expansion / contraction due to the temperature change is substantially the same, and the structure can withstand the temperature change. In addition, it is possible to reduce environmental factors such as optical axis misalignment and contribute to improving environmental performance.

  As described above, the second lens (L2) 16 has a concave step 164, and the third lens (L3) 18 has a convex step 184, so that the third lens (L3) 18 has a convex step 184. The convex step 184 serves to reduce warpage during molding and protect the surface that performs the optical action. The concave step 164 of the second lens (L2) 16 has a thickness near the edge. Plays a role in reducing weight and contributes to weight reduction and performance improvement.

  Further, as described above, a light shielding material (T3) 34 is provided between the second lens (L2) 16 and the third lens (L3) 18, and the image plane ( IP) 32 blocks light caused by unnecessary flare, ghost, and the like. In addition, this light shielding material (T3) 34 performs sanitization around the surface having the optical action on the third lens (L3) 18 side of the second lens (L2) 16 to shield unnecessary light. It is good also as such a structure.

  The focal lengths of these lenses (L1, L2, L3, L4) are, for example, -5.79002 mm for the first lens (L1) 14, -2.5505 mm for the second lens (L2) 16, and the third lens (L3). ) 18 is 3.0339075 mm, the fourth lens (L4) 20 is 3.530383 mm, the second lens (L2) 16 has the strongest refractive power, the third lens (L3) 18 is next, and each lens is refracted. The second lens (L2) 16 has a negative force, and the third lens (L3) 18 has a positive force.

  That is, the second lens (L2) 16 and the third lens (L3) 18 have a positive refractive power and a negative refractive power, and a lens having the strongest refractive power and a lens having a strong refractive power adjacent thereto. In this way, the lens that most affects the optical performance is integrated, and the fitting portions of the second lens (L2) 16 and the third lens (L3) 18 are integrated. Since it is possible to suppress the influence of axial misalignment by integrating (fitting) it after making it into a circular shape and making it rotate relatively to achieve the optimum position where the axial misalignment is minimized, A lens unit capable of maintaining optical performance can be provided.

  In the lens unit 10 according to the present invention, as shown in FIG. 2, D is the first lens (L1) 14, the second lens (L2) 16, and the third lens (L3) 18 in the lens barrel (T1) 24. When the inner diameter d of each of the fourth lenses (L4) 20 and d are the outer diameters of the respective lenses, a relationship of D> d is established between D and d, and each of the imaging lenses (G0) 12 is provided. (Dd) gap (clearance) is provided between the lens and the lens barrel (T1) 24. Therefore, each lens of the imaging lens (G0) 12 and the lens barrel (T1) 24 are formed of materials having different linear expansion coefficients, so that the amount of expansion differs in a place where the temperature changes rapidly, and the lens is pressed. Coat cracks and performance degradation are prevented.

  In a normal lens unit, each lens is tightly fitted in the lens barrel so as not to be loose. In this way, a gap is provided between the imaging lens (G0) 12 and the lens barrel (T1) 24. As a result, an optical axis shift occurs, resulting in deterioration of optical performance. However, in the lens unit 10 according to the first embodiment of the present invention, as described with reference to FIG. 2, the second lens (L2) 16 and the third lens (L3) 18 are integrated, so that L2 and L3. The air interval is always constant, and the optical axis shift amount is the same. In addition, when the second lens (L2) 16 and the third lens (L3) 18 are made of a material whose relative deviation amount is reduced and the linear expansion coefficient is relatively close, the expansion / contraction due to the temperature change becomes substantially the same, and the temperature With a configuration that can withstand changes, it is possible to contribute to the improvement of environmental performance by reducing factors such as air gap deviation and optical axis deviation, which cause deterioration of optical performance.

However, if the clearance between the imaging lens (G0) 12 and the lens barrel (T1) 24 is too wide, the amount of MTF performance deterioration increases, and if it is too narrow, the lens is pressed to cause coat cracks and performance deterioration. Therefore, in order to improve environmental performance while maintaining high optical characteristics, it is important to set D and d so as to satisfy the following expression (1).
0.005 mm <D-d <0.1 mm (1)

For example, in the configuration shown in FIGS. 1 and 2, the linear expansion coefficient of the lens barrel (T1) 24 is 1.5 (10 ⁻⁵ / ° C.), and the first lens (L1) 14 that is a glass lens is 0.59. (10 ⁻⁵ / ° C.), as described above, the second lens (L2) 16 is 6 (10 ⁻⁵ / ° C.), the third lens (L3) 18 is 7 (10 ⁻⁵ / ° C.), and a plastic lens. The fourth lens (L4) 20 is 6 (10 ⁻⁵ / ° C.), the diameter D corresponding to the first lens (L1) 14 of the lens barrel (T1) 24 is 13.71 mm, and the first lens (L1) 14 has a diameter d of 13.7 (tolerance −0.01) mm, a diameter D corresponding to the second lens (L2) 16 and the third lens (L3) 18 of the lens barrel (T1) 24 is 9.605 mm, The diameter d of the second lens (L2) 16 and the third lens (L3) 18 is 9.6 (tolerance−0.005) m. m, the diameter D of the lens barrel (T1) 24 corresponding to the fourth lens (L4) 20 is 7.005 mm, and the diameter d of the fourth lens (L4) 20 is 7.0 (tolerance−0.005) mm. And

  In this case, when the temperature rises by 80 ° C., the diameter D corresponding to the first lens (L1) 14 of the lens barrel (T1) 24 is 0.016452 mm, and the diameter d of the first lens (L1) 14 is 0.0064664 mm. The lens barrel (T1) 24 has an increment of 0.0099856 mm larger, the diameter D corresponding to the second lens (L2) 16 and the third lens (L3) 18 is 0.011526 mm, and a third lens having a large expansion coefficient. The diameter d of (L3) 18 is increased by 0.05376 mm, the increment of the third lens (L3) 18 is 0.042234 mm larger, the diameter D corresponding to the fourth lens (L4) 20 is 0.008406 mm, and the fourth lens ( The diameter d of L4) 20 is increased by 0.0336 mm, and the increment of the fourth lens (L4) 20 is increased by 0.025194 mm. Accordingly, in this case, both are within the range of the formula (1).

  In the clearance below the lower limit value of the equation (1), when the expansion of the plastic lens occurs due to temperature fluctuation, the difference in the linear expansion coefficient between each lens (L1, L2, L3, L4) and the lens barrel (T1) 24 The gap (D−d) between the lens barrel (T1) 24 and each lens becomes narrow due to the difference in expansion amount due to the above. In addition, as described above, since each lens is pressed in the image plane direction for the purpose of sealing liquid or the like in the optical axis direction, there is no place to release the expansion of the material, and each lens surface that performs an optical action is removed. A change in shape occurs, and a change accompanying the change causes a crack in the coat for improving the transmittance, making it difficult to satisfy environmental performance. On the other hand, if the clearance exceeds the upper limit of equation (1), it is possible to withstand changes due to expansion due to environmental changes such as temperature changes, but the amount of optical axis misalignment increases and good optical performance is achieved over the entire temperature range. It becomes difficult to maintain.

In addition, from the viewpoint of maintaining the above optical performance, the numerical range in the above formula (1) is further set as the following formula (1a), so that it is possible to improve environmental performance while maintaining good optical performance. It becomes.
0.005 mm <D-d <0.01 mm (1a)

  As described above, in the lens unit 10 of the first embodiment, an appropriate power arrangement, an aspherical arrangement, and a portion that is caused by the largest optical performance deterioration factor are fitted and integrated, and the imaging lens (G0) is integrated. 12 and the lens barrel (T1) 24 are provided with an appropriate gap, and while achieving good optical performance and environmental performance improvement as a lens unit for an image sensor, it is possible to achieve compactness and cost reduction. Yes.

  The parameters of the imaging lens (G0) 12 and the aperture stop (SP) 22 constituting the lens unit 10 of Example 1 described above are shown below. This imaging lens (G0) 12 has a focal length of 1.38 mm, an F number of 2.59, a diagonal field angle of 166.67 °, an image height of 2.3 mm, and a total lens length of 11.47 mm.

In the following parameters, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the i-th surface, di is the distance between the i-th surface and the (i + 1) -th surface, and ni and νi are the refractions with respect to the d-line, respectively. Indicates the rate and Abbe number. Further, two surfaces (10, 11) closest to the image side are glass blocks (G) 30 provided by design, such as a quartz low-pass filter and protective glass. Further, in the aspherical shape, the displacement in the optical axis direction at the position of the height H from the optical axis is set to x with respect to the surface vertex, and R is the paraxial radius of curvature, and A, B, C, D, E are non- When the spherical coefficient K is a conic constant, it is expressed by the following equation (3).

The unit of the following parameters is mm, and * indicates an aspherical surface.
i r d n ν
1 18.980 0.700 1.729 54.7
2 3.400 3.045
3 * -8.030 0.700 1.530 56.2
4 * 1.676 0.556
5 * 2.443 2.474 1.585 39.9
6 * -4.00 1.412
7 (aperture) ∞ 0.443
8 * 78.850 2.142 1.530 56.2
9 *-1.900 0.100
10 ∞ 1.200 1.516 64.1
11 ∞ 2.220
Image plane ∞

The following are aspheric coefficients.
Surface number K A B C D
3: 0.360000 -7.86000E-04 -1.28500E-04 1.95000E-05 0.00000E + 00
4: -1.050000 -2.80000E-02 2.68660E-05 1.41700E-04 0.00000E + 00
5: -1.260000 -4.91700E-03 -5.13000E-04 -8.33000E-07 0.00000E + 00
6: -1.550000 1.31200E-02 -1.87200E-03 6.01300E-05 0.00000E + 00
8: 14.220000 -2.04000E-02 2.82400E-02 -8.41800E-03 -7.13000E-04
9: 0.323350 2.42600E-02 1.27000E-02 -5.61600E-03 2.83600E-03

  FIG. 3 is a cross-sectional view showing a basic configuration of a lens unit according to a second embodiment of the present invention. FIG. 4 shows fitting of two lenses among the imaging lenses constituting the lens unit of the second embodiment. It is sectional drawing which shows a state.

  The sectional view of the lens unit 50 according to the second embodiment shown in FIGS. 3 and 4 is the same as that of the first embodiment shown in FIGS. 1 and 2. The object side (object side) and the right side are the image side (imaging plane side), and the imaging lens (G0) 52 includes a first lens (L1) 54, a second lens (L2) 56, and a third lens (L3). 58, a fourth lens (L4) 60, and an aperture stop (SP) 62. These lenses are arranged at predetermined positions in the lens barrel (T1) 64, and the lens holder (T2) 66 is screwed or glued to the subject side (object side) of the lens barrel (T1) 54, or is caulked. The first lens (L1) 54 is fixed and the imaging lens (G0) 52 is held by the lens barrel (T1) 64.

  A fourth lens holding portion 644 for positioning in the optical axis direction of the fourth lens (L4) 20 is provided on the inner surface of the lens barrel (T1) 64. The other lenses and the aperture stop (SP) 62 are configured such that the aperture stop (SP) 62 is first provided in the aperture stop holder 602 provided in the fourth lens (L4) 60, and the third lens (L3) 58 is provided as the aperture stop. The second lens (L2) 56 is connected to the third lens holding part 582 provided on the third lens (L3) 58 and the first lens (L1) 14 is connected to the third lens holding part 622 provided on the (SP) 62. Are in contact with the first lens holding portions 562 provided on the second lens (L2) 16 and positioned in the optical axis direction.

  Further, on the inner surface of the lens barrel (T1) 64, the portion facing the outer peripheral surface of each lens (L1, L2, L3, L4) constituting the imaging lens (G0) 52 and the outer peripheral surface of the aperture stop (SP) 62 are arranged. Lens peripheries holding portions 648, 650, 652, and 654 are provided at the facing portions through predetermined clearances corresponding to the expressions (1) and (1a) corresponding to the diameters of the respective lenses. Further, an O-ring 68 is arranged in the O-ring holding portion indicated by 646 of the lens barrel (T1) 64, and when the first lens (L1) 54 is fixed by the lens pressing (T2) 66, the first lens (L1 ) 54 presses the O-ring 68 from the subject side (object side) to the image side (imaging plane side). Therefore, the O-ring 68 is crushed between the O-ring holding portion 646 and the image plane side of the first lens (L1) 54 so that the liquid cannot penetrate into the lens barrel (T1) 64 with a sealing effect. It has become.

  Further, when the first lens (L1) 54 comes into contact with the first lens holding portion 562 provided on the second lens (L2) 56, the second lens (L2) 56 to the fourth lens (L4) 60 are moved to the object. Since the lens is pressed toward the image side (imaging plane side) from the side, even if there is an impact or the like, the optical axis shift of each lens (L1, L2, L3, L4) can be prevented. Glasses 30 and 32 arranged on the image plane side of the imaging lens (G0) 52 are provided by design corresponding to a crystal low-pass filter, an infrared cut filter, a protective glass for protecting the imaging device, and the like as described above. The photosensitive surface of the solid-state imaging device composed of CCD or CMOS is arranged on the image plane (IP) of the block (G) and the imaging lens (G0) 52 as in the first embodiment. Reference numeral 74 denotes a light shielding material (T3) 34.

  The imaging lens (G0) 52 of the second embodiment is also configured as an optical system in which the focus from an infinite object to a short-distance object is a pan focus, and the lens unit 50 is not extended, but the lens unit 50 May be configured so that focusing can be extended to the object side, or a part of the plurality of lenses constituting the imaging lens (G0) 52 can be extended.

  The first lens (L1) 54 in the imaging lens (G0) 52 has a convex surface on the object side (object side) and a convex surface on the object side, as in the first embodiment. The absolute value of the refractive power of the object-side surface is smaller than that of the lens surface, and it is a meniscus glass lens having negative refractive power (optical power = reciprocal of focal length). Therefore, the lens unit 50 that can withstand harsh environments can be obtained by using a glass lens that satisfies the environmental performance by using the O-ring 68 and has excellent environmental performance such as hardness compared to a plastic lens. it can.

In addition, in the lens unit 50 of the second embodiment, the angle of view of the first lens (L1) 54 is set to 2 W with respect to the screen so that there are not many blind spots as a surveillance camera or a vehicle-mounted camera. Then, it is formed so as to satisfy the following formula (2).
2W <130 ° ………………………………………………………… (2)

  The second lens (L2) 56 is a plastic lens formed by molding a resin material having a negative refractive power with a concave surface facing the image side, and the third lens (L3) 58 is a biconvex positive lens. It is a plastic lens formed by molding a resin material having refractive power. Since it is made of a resin material, it is superior to a glass lens in terms of molding stability, weight, and cost. In addition, the lens made of the resin material of the present embodiment taking advantage of the molding uses a rotationally symmetric aspherical surfaces on both sides (object side and image side). Thus, by expanding the degree of freedom from the spherical surface, good imaging performance is obtained with a small number of components.

  The second lens (L2) 56 has a curvature on the image plane side that is weak in refractive power from the center toward the periphery, and the object side and image plane side surfaces are surfaces having no inflection points. When an inflection point is generated, it is difficult to obtain good imaging performance over the entire screen due to the influence of curvature of field due to molding variations in a part of the screen, as in this embodiment. By adopting the shape, good imaging performance can be ensured over the entire screen even with a compact number of lenses.

  The fourth lens (L4) 60 is a lens having a positive refractive power with the image side (image forming surface side) as a strong convex surface, and is a plastic lens formed by molding a resin material. By adopting such a shape, the amount of MTF performance deterioration at a location close to the aperture stop (SP) 62 such as a thickness shift, a gap in the optical axis direction with respect to the aperture stop (SP) 62, and a shift in the optical axis direction is reduced. The lens is easy to manufacture.

  The aperture stop (SP) 62 includes a fourth lens (L4) 60 at the aperture stop holding unit 602 in the fourth lens (L4) 60 and a third lens (L3) at the third lens holding unit 622 in the aperture stop (SP) 62. ) 18 and are arranged in contact with each other. If the aperture stop (SP) 62 is arranged closer to the image side than the fourth lens (L4) 60, it is not preferable because the lens system is enlarged, and the second lens (L2) 56 and the third lens (L3) 58 If it is arranged in the middle, it is disadvantageous for increasing the back focus. Therefore, by disposing the lens between the third lens (L3) 58 and the fourth lens (L4) 60, various aberrations can be corrected and the lens system can be made compact.

  The imaging lens (G0) 52 shown in FIGS. 3 and 4 shows a case where the imaging lens (G0) 52 is composed of four lenses (L1, L2, L3, L4), but is the same as in the case of the first embodiment. The present invention is not limited to this, and it is obvious that the imaging lens (G0) 52 is not limited to the illustrated configuration as long as it has a plurality of lenses.

  Of the imaging lens (G0) 52 constituting the lens unit 50 of the present invention configured as described above, the second lens (L2) 56 and the third lens (L3) 58 are shown in a fitted state in FIG. As described above, the second lens (L2) 56 has a concave step 564 on the side of the third lens (L3) 58 and the third lens (L3) 58 around the surfaces having the respective optical functions. Has a convex step portion 584 on the second lens (L2) 56 side, and the respective step portions are configured to be fitted to each other, and are integrated by press-fitting each other.

  Therefore, the second lens (L2) 56 and the third lens (L3) 58 have the same air gap and the same optical axis deviation. In addition, the relative displacement between the second lens (L2) 56 and the third lens (L3) 58 is reduced, and the number of parts is reduced by fitting them before being assembled into the lens barrel (T1) 64. And easy to incorporate. The concave step 564 and the convex step 584 for press-fitting the second lens (L2) 56 and the third lens (L3) 58 may be either convex or concave. It goes without saying that, when press-fitting, each lens can be fitted with a force that does not cause distortion.

The second lens (L2) 56 and the third lens (L3) 58 have a linear expansion coefficient, for example, the second lens (L2) 56 is 6 (10 ⁻⁵ / ° C.), and the third lens (L3) 58 is When a material relatively close to 7.2 (10 ⁻⁵ / ° C.) is used, the expansion / contraction due to temperature change is substantially the same, and the structure can withstand temperature change, and the air gap that causes deterioration of optical performance It is possible to contribute to the improvement of environmental performance by reducing factors such as deviation and optical axis deviation.

  As described above, the second lens (L2) 56 is provided with a concave step 564, and the third lens (L3) 58 is provided with a convex step 584. The convex step portion 584 serves to reduce warpage during molding and protect the optically acting surface. The concave step portion 564 of the second lens (L2) 56 has a thickness near the edge. Plays a role in reducing weight and contributes to weight reduction and performance improvement.

  Further, as described above, a light shielding material (T3) 74 is provided between the second lens (L2) 56 and the third lens (L3) 58 so as to cut the unnecessary light, thereby reducing the image plane ( IP) 32 blocks light caused by unnecessary flare, ghost, and the like. The light shielding material (T3) 74 shields unnecessary light by sanitizing the surface of the second lens (L2) 56 that has an optical function on the third lens (L3) 58 side. It is good also as such a structure.

  The focal lengths of these lenses (L1, L2, L3, L4) are, for example, -6.473172 mm for the first lens (L1) 54, -2.197712 mm for the second lens (L2) 56, and the third lens (L3). ) 58 is 2.596598 mm, the fourth lens (L4) 60 is 2.474036 mm, the second lens (L2) 56 has the strongest refractive power, and the third lens (L3) 58 is more than the fourth lens (L4) 60. Although weak, the refractive power is strong and the refractive power of each lens is negative for the second lens (L2) 56 and positive for the third lens (L3) 58.

  That is, the second lens (L2) 56 and the third lens (L3) 58 have a positive and negative relationship with respect to each other and a lens having the strongest refractive power and a lens having a strong refractive power adjacent thereto. In this way, the lens that most affects the optical performance is integrated, and the fitting portion of the second lens (L2) 56 and the third lens (L3) 58 is integrated. Since it is possible to suppress the influence of axial misalignment by integrating (fitting) it after making it into a circular shape and making it rotate relatively to achieve the optimum position where the axial misalignment is minimized, A lens unit capable of maintaining optical performance can be provided.

  In the lens unit 50 of the second embodiment of the present invention, as in the first embodiment, D is the first lens (L1) 54, the second lens (L2) 56, and the third lens in the lens barrel (T1) 64. (L3) 58 and the fourth lens (L4) 60 where the inner diameter at each position and d is the outer diameter of each lens, a relationship of D> d is established between D and d, and the imaging lens (G0 ) 52 and the lens barrel (T1) 64 are provided with a gap (clearance) of (Dd). Therefore, each lens of the imaging lens (G0) 52 and the lens barrel (T1) 64 are formed of materials having different linear expansion coefficients, so that the amount of expansion differs in a place where the temperature changes rapidly, and the lens is pressed. Coat cracks and performance degradation are prevented.

It is important that the clearance between the imaging lens (G0) 52 and the lens barrel (T1) 64 is set so as to satisfy the following formula (1), more preferably the following (1a) as described above. is there.
0.005 mm <D-d <0.1 mm (1)
0.005 mm <D-d <0.01 mm (1a)

3 and FIG. 4, for example, the linear expansion coefficient of the lens barrel (T1) 24 is 1.5 (10 ⁻⁵ / ° C.), and the first lens (L1) 14 that is a glass lens is 0. .59 (10 ⁻⁵ / ° C.), as described above, the second lens (L2) 16 is 6 (10 ⁻⁵ / ° C.), the third lens (L3) 18 is 7.2 (10 ⁻⁵ / ° C.), The fourth lens (L4) 20 which is a plastic lens is 6 (10 ⁻⁵ / ° C.), the diameter D corresponding to the first lens (L1) 14 of the lens barrel (T1) 24 is 13.4005 mm, the first The diameter d of the lens (L1) 14 is 13.4 (tolerance −0.01) mm, and the diameter D corresponding to the second lens (L2) 16 and the third lens (L3) 18 of the lens barrel (T1) 24 is 9 .605 mm, the diameter d of the second lens (L2) 16 and the third lens (L3) 18 is 9.6 (tolerance− 0.005) mm, the diameter D corresponding to the fourth lens (L4) 20 of the lens barrel (T1) 24 is 7.2005 mm, and the diameter d of the fourth lens (L4) 20 is 7.2 (tolerance−0.005). ) Mm.

  In this case, when the temperature rises by 80 ° C., the diameter D corresponding to the first lens (L1) 14 of the lens barrel (T1) 24 is 0.0160806 mm, and the diameter d of the first lens (L1) 14 is 0.0063248 mm. The lens barrel (T1) 24 has a larger increment of 0.0097558 mm, the diameter D corresponding to the second lens (L2) 16 and the third lens (L3) 18 is 0.011526 mm, and a third lens having a large expansion coefficient. The diameter d of (L3) 18 increases by 0.05376 mm, the increment of the third lens (L3) 18 increases by 0.042234 mm, the diameter D corresponding to the fourth lens (L4) 20 is 0.0086406 mm, and the fourth lens ( The diameter d of L4) 20 is increased by 0.03456 mm, and the increment of the fourth lens (L4) 20 is 0.0259194 mm larger. Therefore, in this case, it is within the range of the expression (1).

  As described above, the lens unit 50 according to the second embodiment also has a configuration in which an appropriate power arrangement, an aspheric arrangement, and a portion that is caused most by the optical performance deterioration factor are fitted and integrated, and the imaging lens (G0). By providing a gap between the lens barrel (T1) 64 and the lens barrel (T1) 64, it is possible to achieve compactness and cost reduction while realizing good optical performance and environmental performance improvement as a lens unit for an image sensor.

  The parameters of the imaging lens (G0) 52 and the aperture stop (SP) 62 constituting the lens unit 50 of the second embodiment described above are shown below. This imaging lens (G0) 52 has a focal length of 1.222 mm, an F number of 2.80, a diagonal angle of view of 132.1 °, an image height of 2.3 mm, and a total lens length of 12.655 mm.

In the following parameters, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the i-th surface, di is the distance between the i-th surface and the (i + 1) -th surface, and ni and νi are the refractions with respect to the d-line, respectively. Indicates the rate and Abbe number. Further, two surfaces (10, 11) on the most image side are glass blocks (G) 30 provided by design, such as a crystal low-pass filter and protective glass, the unit is mm, and * indicates an aspherical surface. The same as the case of 1.
i r d n ν
1 13.210 0.730 1.713 53.9
2 3.406 2.217
3 * -11.536 0.700 1.530 56.2
4 * 1.039 0.538
5 * 1.790 2.600 1.632 23.0
6 * -9.687 0.775
7 (Aperture) ∞ 0.360
8 * -9.888 1.750 1.530 56.2
9 * -1.233 1.025
10 ∞ 0.800 1.516 64.1
11 ∞ 1.160
Image plane ∞

The following are aspheric coefficients.
Surface number K A B C D
3: -11.000000 -9.00000E-03 9.52400E-04 -2.20200E-05 0.00000E + 00
4: -1.672000 -1.25900E-02 2.74900E-04 2.49700E-05 0.00000E + 00
5: -0.781000 -1.85650E-02 5.27300E-03 -8.07850E-04 0.00000E + 00
6: 0.000000 4.29830E-02 -1.40000E-02 1.00000E-03 0.00000E + 00
8: 0.000000 -7.47400E-02 6.46300E-02 -7.50000E-02 3.00000E-02
9: -0.777000 9.05150E-03 9.88160E-04 -8.25500E-03 3.45400E-03

  According to the present invention, it is suitable for a lens unit using a solid-state image sensor, particularly a surveillance camera or an in-vehicle camera, and a lens unit that is required to have good optical performance and is satisfactory in environmental performance can be realized.

It is sectional drawing which shows the basic composition of Example 1 of the lens unit which becomes this invention. It is sectional drawing which shows the fitting state of two lenses among the imaging lenses which comprise the lens unit of Example 1. FIG. It is sectional drawing which shows the basic composition of Example 2 of the lens unit which becomes this invention. It is sectional drawing which shows the fitting state of two lenses among the imaging lenses which comprise the lens unit of Example 2. FIG.

Explanation of symbols

10 Lens unit 12 Imaging lens (G0)
14 First lens (L1)
16 Second lens (L2)
162 First lens holding portion 164 Concave step portion of second lens 18 Third lens (L3)
182 Second lens holding portion 184 Convex step portion of the third lens 20 Fourth lens (L4)
202 Aperture stop holder 22 Aperture stop (SP)
222 Third lens holder 24 Lens barrel (T1)
242 Fourth lens holding portion 246 O-ring holding portion 248, 250, 252, 254 Lens periphery holding portion 26 Lens holding (T2)
28 O-ring 30 Glass block (G)
32 Image plane (IP)
34 Shading material (T3)

Claims (8)

In a lens unit comprising an imaging lens composed of a plurality of lenses and a lens barrel that holds the imaging lens,
The one lens is convex on the other lens side and the other lens is on the one lens side around the surface having the optical action in the adjacent one lens and the other lens among the plurality of lenses. The lens unit has a concave stepped portion that can be fitted to each other, is integrated by fitting, and is held by the lens barrel. In a lens unit comprising an imaging lens composed of a plurality of lenses and a lens barrel that holds the imaging lens,
The plurality of lenses and the lens barrel are formed of materials having different linear expansion coefficients, and the one lens adjacent to the lens and the surface having an optical function in the other lens are arranged around the surface having the optical action. The lens has a convex shape on the other lens side, and the other lens has a concave stepped portion on one lens side that can be fitted to each other. The lens unit is characterized in that when the lens diameter is d, D and d satisfy the following expression (1).
0.005 mm <D-d <0.1 mm (1)   The lens unit according to claim 1 or 2, wherein the one lens and the other lens include a lens having the strongest refractive power and a lens having a strong refractive power adjacent to the lens.   The lens unit according to claim 3, wherein the one lens and the other lens have positive and negative refractive powers.   The plurality of lenses constituting the imaging lens are, in order from the object side, a first lens having a negative refractive power having a convex surface on the object side, a second lens having a negative refractive power having a concave surface on the image side, The third lens having a positive refractive power convex toward the object side, the aperture stop, and the fourth lens having a positive refractive power convex toward the image side. The lens unit according to any one of claims 1 to 4, wherein the lens unit is the second lens and the third lens. The lens according to any one of claims 1 to 5, wherein the first lens is made of glass, and is formed so as to satisfy the following expression (2) when the total angle of view with respect to the screen is 2 W. unit.
2W <130 ° ………………………………………………………… (2)   The lens unit according to claim 1, wherein the one lens and the other lens are formed of a resin material.   8. The gap according to claim 1, wherein a gap in which a light shielding material can be disposed is provided on an outer periphery of the surface having the optical action between the one lens and another lens. Lens unit.

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