Patent Publication Number: US-2023152553-A1

Title: Lens unit and in-vehicle camera

Description:
TECHNICAL FIELD 
     The present invention relates to a lens unit suitable for an in-vehicle camera to be mounted on a vehicle such as an automobile, and an in-vehicle camera. 
     BACKGROUND ART 
     In recent years, in-vehicle cameras have been mounted on automobiles to support parking and to prevent a collision by use of image recognition, and further applications for automated driving have been attempted. 
     An automobile is exposed to a cold or hot environment, and thus such an in-vehicle camera is similarly exposed to a severe temperature environment. Moreover, there is a possibility that an in-vehicle camera disposed on an outer side of the automobile is affected by cold wind or snow, or is brought into an overheated state by sunlight. 
     Hence, there is a demand for an in-vehicle camera to be usable stably from a low temperature to a high temperature while an automobile is being used, and various temperature countermeasures have been proposed (see, for example, Patent Literature 1). 
     In recent years, cameras have been incorporated into mobile telephones (smartphones) or the like, and thus there is a large demand for high-performance and low-cost cameras, and relatively inexpensive resin lenses are widely used. 
     Also for an in-vehicle camera, a member such as a lens made of resin or a lens barrel made of resin can be used. However, regarding an in-vehicle camera disposed outside the vehicle, there is a possibility that the temperature becomes low or high as described above, the in-vehicle camera is exposed to rain, snow, hail, or the like, or the in-vehicle camera is hit by a bounced stone, a falling object from an automobile, or the like. Therefore, in a case where durability is considered to be important, a glass lens and a lens barrel made of metal are adopted in many cases. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2008-298968 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In a case of a camera with a certain level of high performance, by the way, a lens group including, for example, four or more lenses is used as lenses, and a plurality of lenses of the lens group are held to form a line with their optical axis directions being in alignment with one another in the lens barrel. In addition, an intermediate ring is provided to adjust an interval between the lenses in the optical axis direction, in some cases. 
     Further, in the lens barrel, for example, an outer circumferential surface of the lens or the intermediate ring is brought into contact with an inner circumferential surface of the lens barrel to be positioned in the radial direction, and the positions of the lens group on an object (subject) side and an image sensor side are regulated. The lens group is appropriately held in the lens barrel with being positioned in the optical axis direction. Therefore, the lenses of the lens group are stacked in the optical axis direction, and the individual lenses are not fixed to the lens barrel. 
     In a case where the lens barrel holds the lens group including such a plurality of lenses and the intermediate ring in alignment with one another in the optical axis direction, the length of the lens barrel along the optical axis direction becomes long. In a case where the lens barrel and the intermediate ring are made of metal having a relatively large expansion rate, the change amount in the length along the optical axis direction caused by a temperature change increases. In contrast thereto, the linear expansion coefficient of the glass lens is generally smaller than that of metal. For example, the elongation amount in the optical axis direction caused by a temperature rise of the lens barrel is larger than the elongation amount in the optical axis direction of the entire lens group. This causes a gap between the lenses of the lens group, and rattling occurs. 
     In this situation, a change in the lens interval or a state in which the lens is tilted to be inclined slightly (tilt) occurs. As a result, the optical performance is degraded. 
     The present invention has been made in view of the above circumstances, and has an object to provide a lens unit and an in-vehicle camera, which are capable of preventing rattling between lenses caused by a temperature change and suppressing a degradation in the optical performance. 
     Solution to Problem 
     In order to address the above issue, a lens unit according to the present invention includes: a lens group in which a plurality of lenses are aligned along an optical axis of the lenses; a lens barrel that integrally supports the lens group; an intermediate ring to be disposed between the lenses in at least one position of the lens group; and an elastic member having an annular shape and provided between the lens and the intermediate ring, the lens being adjacent to the elastic member in the optical axis direction, in which 
     the lens adjacent to the elastic member in the optical axis direction includes a recess having an annular shape to be recessed in an outer circumferential portion in the optical axis direction, 
     the elastic member is provided in a compressed state in the optical axis direction in the recess, and 
     the elastic member presses the lens disposed on an object side of the elastic member against an end portion of the lens barrel on the object side, also presses the lens disposed on an image side of the elastic member against an end portion of the lens barrel on the image side via the intermediate ring, and absorbs rattling that occurs in association with a relative movement of the lens barrel and the lens group in the optical axis direction caused by a temperature change. 
     According to such a configuration, in a case where a gap along the optical axis direction occurs between the lenses of the lens group due to a difference in linear expansion coefficient between the lens barrel and the lens caused by a temperature rise, and rattling occurs, the elastic member presses the lens disposed on the object side of the elastic member against the end portion on the object side of the lens barrel, also presses the lens disposed on the image side of the elastic member against the end portion on the image side of the lens barrel via the intermediate ring, and thus absorbs the rattling. 
     Therefore, the rattling between the lenses caused by a temperature change can be prevented, and degradation in optical performance can be suppressed. 
     Note that the elastic member may be formed of rubber or a plate spring. 
     In addition, in the above configuration, another lens is provided between the lenses that sandwich the elastic member in the optical axis direction, and 
     an outer circumferential portion of the another lens is bonded and fixed with the intermediate ring. 
     According to such a configuration, the outer circumferential portion of another lens is bonded and fixed with the intermediate ring. Thus, the intermediate ring enables such another lens to move to the image side of the lens barrel, and rattling does not occur at such another lens. 
     In addition, a lens unit according to the present invention includes: a lens group in which a plurality of lenses are aligned along an optical axis direction of the lenses; a lens barrel that integrally supports the lens group; and an elastic member having an annular shape and disposed between the lenses in at least one position of the lens group, in which 
     the lenses that sandwich the elastic member in the optical axis direction have respective abutment surfaces in abutment with each other in parts of outer circumferential surfaces facing each other, 
     one of the lenses that sandwich the elastic member in the optical axis direction includes a recess having an annular shape to be recessed in the optical axis direction on an outer circumferential surface on an outer circumferential side of the abutment surface, 
     the elastic member is provided in a compressed state in the optical axis direction in the recess, and 
     the elastic member presses the lens disposed on an object side of the elastic member against an end portion of the lens barrel on the object side, also presses the lens disposed on an image side of the elastic member against an end portion of the lens barrel on the image side, and absorbs rattling that occurs in association with a relative movement of the lens barrel and the lens group in the optical axis direction caused by a temperature change. 
     According to such a configuration, in a case where a gap along the optical axis direction occurs between the lenses of the lens group due to a difference in linear expansion coefficient between the lens barrel and the lens caused by a temperature rise, and rattling occurs, the elastic member presses the lens disposed on the object side of the elastic member against the end portion on the object side of the lens barrel, also presses the lens disposed on the image side of the elastic member against the end portion on the image side of the lens barrel, and thus absorbs the rattling. 
     Therefore, the rattling between the lenses caused by a temperature change can be prevented, and degradation in optical performance can be suppressed. 
     In addition, the lenses that sandwich the elastic member in the optical axis direction have the abutment surfaces that abut each other in parts of their outer circumferential surfaces facing each other. Therefore, the abutment surfaces are in abutment with each other, and thus rattling does not occur at the lenses at room temperature. 
     In addition, in the above configuration, the elastic member may be disposed at a position where sensitivity between surfaces is lowest among the plurality of lenses constituting the lens group, the sensitivity between the surfaces being sensitivity in image formation relative to a distance between lens surfaces. 
     According to such a configuration, the elastic member presses the lens disposed on the object side of the elastic member against the end portion on the object side of the lens barrel, and also presses the lens disposed on the image side of the elastic member against the end portion on the image side of the lens barrel. Therefore, even though a predetermined gap occurs between the lenses, the elastic member is disposed at a position where the sensitivity between the surfaces is the lowest, and thus degradation in optical performance can be suppressed. 
     An in-vehicle camera according to the present invention includes: the lens unit; 
     a substrate including an image sensor; and 
     a support member that supports the lens unit in a state where the lens unit is positioned with respect to the substrate. 
     Advantageous Effects of Invention 
     According to the present invention, rattling between lenses caused by a temperature change can be prevented, and degradation in optical performance can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a cross-sectional view illustrating a lens unit of an in-vehicle camera according to a first embodiment of the present invention. 
         FIG.  2    is a cross-sectional view illustrating a lens unit of an in-vehicle camera according to a twentieth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     A lens unit in the present embodiment is used for an in-vehicle camera, and is, for example, fixed and installed on an outer surface side of an automobile, and its wiring is drawn into the automobile to be connected with a display or other apparatuses. 
     First Embodiment 
     As illustrated in  FIG.  1   , a lens unit  20  of an in-vehicle camera in the present embodiment includes: a lens barrel  10  having a cylindrical shape; a plurality of (six) lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  disposed in the lens barrel  10 ; an optical filter  9  disposed at an end portion on a (image-forming) side (a side on which an image sensor  8  is disposed) where the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  of the lens barrel  10  form an image; a press member  18 , which presses the lens  1  in the lens barrel  10  at an end portion on an object side to be imaged; and three intermediate rings  11 ,  12 , and  13 , each of which functions as a spacer. Note that In  FIG.  1    and  FIG.  2    to be described later, an end portion on the object side is an upper end portion, and an end portion on the image side is a lower end portion. 
     The in-vehicle camera in the present embodiment includes: the above-described lens unit  20 ; a substrate  16 , which includes the image sensor  8 ; a support member (mount)  17 , which supports the lens barrel  10  in a state where the lens barrel  10  is positioned with respect to the substrate  16  including the image sensor  8 ; and an installation member, not illustrated, for installing the substrate  16  in an automobile. 
     Note that in  FIG.  1    illustrating the present embodiment and  FIG.  2    illustrating a second embodiment to be described later, hatching of lenses  1 ,  2 ,  3 ,  4 ,  5 , and  5  constituting the lens unit  20  is omitted. 
     The plurality of lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6 , which are fixed with and supported by the lens barrel  10 , are disposed with their optical axes being in alignment with one another, and the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  are disposed along one optical axis to constitute one group that is a lens group  19  used for imaging. Therefore, in the following, in simply describing an optical axis, the optical axis of each of the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  will be indicated, and the optical axis of the lens group  19  will also be indicated. 
     The first intermediate ring  11  from the object side among the intermediate rings  11 ,  12 , and  13  is disposed between the first lens  1  and the second lens  2 , the lens  1  is in contact with an upper end portion of the intermediate ring  11 , and the lens  2  is in contact with a lower end portion of the intermediate ring  11 . The second intermediate ring  12  is disposed between the second lens  2  and the third lens  3 , the lens  2  is in contact with an upper end portion of the intermediate ring  12 , and the lens  3  is in contact with a lower end portion of the intermediate ring  12 . 
     In addition, the third intermediate ring  13  is disposed between the fourth lens  4  and the sixth lens  6 . 
     Furthermore, an elastic member  15  is disposed between the fourth lens  4  and the third intermediate ring  13 . Therefore, the elastic member  15  is in contact with an upper end portion of the intermediate ring  13 , and the lens  6  is in contact with a lower end portion of the intermediate ring  13 . 
     The lens  4 , which is adjacent to the elastic member  15  in the optical axis direction, includes a recess  4   a , which has an annular shape, and which is recessed in an outer circumferential portion in the optical axis direction. The elastic member  15  is provided in a compressed state in the optical axis direction in the recess  4   a.    
     In addition, the position where sensitivity between surfaces, which is the sensitivity in image formation relative to a distance between lens surfaces of the plurality of lenses constituting the lens group  19 , is the lowest between the lenses  4  and  5 , and the elastic member  15  is provided between them. However, the lens  5  is smaller in diameter than the lens  4 , and its outer circumferential portion is separated from the inner circumferential surface of the lens barrel  10 . As described above, the recess  4   a  is provided in the outer circumferential portion of the lens  4 , and the elastic member  15  is provided in the recess  4   a.    
     In the present embodiment, the elastic member  15  includes an annular wave spring (wave washer) made of metal. The wave spring, for example, has a disk shape, has an annular shape with a hole in the central portion, and has a wavy shape along the circumferential direction, as the position along the axial direction orthogonal to the disk changes depending on the position in the circumferential direction. 
     Such an elastic member  15  elastically presses the lenses  1 ,  2 ,  3 , and  4  disposed on the object side of the elastic member  15  against the press member  18  provided at an end portion on the object side of the lens barrel  10 , and also presses the lens  6  disposed on the image side of the elastic member  15  against an inner flange portion  21  provided at an end portion on the image side of the lens barrel  10  via the intermediate ring  13 , and thus absorbs rattling that occurs in association with a relative movement in the optical axis direction of the lens barrel  10  and the lens group  19  caused by a temperature change (for example, a temperature change from a normal temperature to a high temperature). 
     In addition, an inner flange portion  13   a  is provided at an end portion on the object side of the intermediate ring  13 , and an outer circumferential portion of the lens (another lens)  5  is bonded and fixed with the inner flange portion  13   a . Therefore, the lens  5  is supported by the intermediate ring  13 , and moves to the image side together with the intermediate ring  13 , when the elastic member  15  presses and moves the intermediate ring  13  to the image side. 
     In the lens barrel  10 , a male screw portion is formed on the outer circumference of an end portion on the object side, a female screw portion formed on the inner circumference of the press member  18  having an annular shape is screwed to such a male screw portion, and the press member  18  is fixed to an end portion on the object side of the lens barrel  10 . The six lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6 , the three intermediate rings  11 ,  12 , and  13 , and the elastic member  15  are disposed with being sandwiched between the press member  18  and the inner flange portion  21 , which is provided at an end portion on the image side of the lens barrel  10 . Note that a predetermined number of diaphragm members each having a disk shape may be provided at predetermined positions between the press member  18  and the inner flange portion  21 . 
     In addition, the lens barrel  10  is joined with an inner circumferential surface of the support member  17 , and is supported by the support member  17 . Further, the support member  17  is formed in a substantially cylindrical shape, the lens barrel  10  is disposed in its inside, and the outer circumferential side of the lens barrel  10  and the inner circumferential side of the support member  17  are joined with each other. Further, an end portion on the image sensor  8  side of the support member  17  is fixed with the substrate  16 , on which the image sensor  8  is mounted. Accordingly, the support member  17  supports the lens unit  20  including the lens barrel  10  with the lens unit  20  being positioned with respect to the image sensor  8 . 
     In addition, in the present embodiment, the lenses  1  to  6  are made of glass, for example, so-called optical glass, and the lens barrel  10  and the intermediate rings  11  to  13  are each made of metal, for example, an aluminum alloy. 
     In the lens unit  20  and the in-vehicle camera, as described above, the six lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6 , the three intermediate rings  11 ,  12 , and  13 , and the elastic member  15  are disposed with being sandwiched between the press member  18  and the inner flange portion  21  at the end portion on the image side of the lens barrel  10 . 
     In such an in-vehicle camera, a usable temperature range is preferably wide. For example, it can be preferably used in a range of −40° C. to 105° C. In this case, for example, in a case where a design is based on 25° C. that is within a range of normal temperature, when the temperature rises, even though it is within a range up to 105° C., a difference occurs between a change amount due to thermal expansion of the total lengths along the optical axis direction of the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  and the three intermediate rings  11 ,  12 , and  13  disposed in a stacked manner and a change amount due to thermal expansion of the length along the optical axis direction of the lens barrel  10  (the length from the press member  18  to the inner flange portion  21 ), and a gap occurs between the lenses  1  to  6 . 
     In this case, a gap is generated among the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  of the lens group  19 , a gap is generated among the respective lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  along the optical axis direction, and rattling occurs in some cases. In this case, the elastic member  15  presses the lenses  1 ,  2 ,  3 , and  4  disposed on the object side of the elastic member  15  against the press member  18  at an end portion on the object side of the lens barrel  10 , also presses the lens  6  disposed on the image side of the elastic member  15  against the inner flange portion  21  disposed at an end portion on the image side of the lens barrel  10  via the intermediate ring  13 , and thus absorbs the rattling. 
     Therefore, the rattling between the lenses caused by a temperature change can be prevented, and degradation in optical performance can be suppressed. 
     In addition, the outer circumferential portion of the lens  5  is bonded and fixed with the inner flange portion  13   a  of the intermediate ring  13 . Thus, the intermediate ring  13  enables the lens  5  to move to the image side of the lens barrel, and rattling does not occur at the lens  5 . 
     Note that, in the present embodiment and a second embodiment to be described later, the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  are made of glass, and the lens barrel  10  is made of metal. However, even though these are made of resin, the present invention is applicable, in a case where a difference in thermal expansion coefficient due to a difference in material or the like generates a difference between a displacement amount due to the thermal expansion of the lens group  19  and a displacement amount due to the thermal expansion of the lens barrel  10  as described above. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described with reference to  FIG.  2   . 
     The lens unit  20  in the second embodiment is different from that in the first embodiment in that the fifth lens  5  is larger in diameter than the lens  5  in the first embodiment. Therefore, in the following, this point and its peripheral part will be described, and the same components as those in the first embodiment are denoted by the same reference numerals, and the descriptions will be omitted. 
     As illustrated in  FIG.  2   , in the present embodiment, the lens  5  is larger in diameter than the lens  5  in the first embodiment, its outer circumferential surface is in contact with an inner circumferential surface of the lens barrel  10 , and the curvatures of the upper surface and the lower surface of the lens  5  are larger than the curvatures of the upper surface and the lower surface of the lens  5  in the first embodiment. 
     In addition, the lenses  4  and  5 , which sandwich the elastic member  15  in the optical axis direction, have respective abutment surfaces  4   b  and  5   b  in abutment with each other in parts of their outer circumferential surfaces facing each other, and these abutment surfaces  4   b  and  5   b  are in abutment with each other. 
     The abutment surface  4   b  is provided on an inner side in the radial direction with respect to the recess  4   a , and is a flat surface orthogonal to the optical axis direction. The abutment surface  5   b  is a flat surface orthogonal to the optical axis direction, faces the abutment surface  4   b , extends to the inner circumferential surface of the lens barrel  10 , and is in abutment with the elastic member  15 . 
     The elastic member  15  is provided in a compressed state in the optical axis direction in the recess  4   a . The position where sensitivity between surfaces, which is the sensitivity in image formation relative to a distance between lens surfaces of the plurality of lenses constituting the lens group  19 , is the lowest between the lenses  4  and  5 , and the elastic member  15  is provided between them. 
     In addition, the outer circumferential surface of the lens  5  is in contact with the inner circumferential surface of the lens barrel  10 . Therefore, the intermediate ring  13  does not have an inner flange portion unlike the intermediate ring  13  in the first embodiment, and the lens  5  is in abutment with an upper end portion of the intermediate ring  13 . 
     In the lens unit  20  and the in-vehicle camera, as described above, the six lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6 , the three intermediate rings  11 ,  12 , and  13 , and the elastic member  15  are disposed with being sandwiched between the press member  18  and the inner flange portion  21  at the end portion on the image side of the lens barrel  10 . 
     In such an in-vehicle camera, a usable temperature range is preferably wide as in the first embodiment. For example, it can be preferably used in a range of −40° C. to 105° C. In this case, for example, in a case where a design is based on 25° C. that is within a range of normal temperature, when the temperature rises, even though it is within a range up to 105° C., a difference occurs between a change amount due to thermal expansion of the total lengths along the optical axis direction of the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  and the three intermediate rings  11 ,  12 , and  13  disposed in a stacked manner and a change amount due to thermal expansion of the length along the optical axis direction of the lens barrel  10  (the length from the press member  18  to the inner flange portion  21 ), and a gap occurs between the lenses  1  to  6 . 
     In this case, a gap is generated among the lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  of the lens group  19 , a gap is generated among the respective lenses  1 ,  2 ,  3 ,  4 ,  5 , and  6  along the optical axis direction, and rattling occurs in some cases. In this case, the elastic member  15  presses the lenses  1 ,  2 ,  3 , and  4  disposed on the object side of the elastic member  15  against the press member  18  at an end portion on the object side of the lens barrel  10 , also presses the lenses  5  and  6  disposed on the image side of the elastic member  15  against the inner flange portion  21  disposed at an end portion on the image side of the lens barrel  10 , and thus absorbs the rattling. 
     Therefore, the rattling between the lenses caused by a temperature change can be prevented, and degradation in optical performance can be suppressed. 
     In addition, the lenses  4  and  5 , which sandwich the elastic member  15  in the optical axis direction, have the respective abutment surfaces  4   b  and  5   b  in abutment with each other in parts of their outer circumferential surfaces facing each other. Therefore, the abutment surfaces  4   b  and  5   b  are in abutment with each other, and thus rattling does not occur at the lenses  4 ,  4  at room temperature. 
     Note that from the viewpoint of ensuring reliability, in the present embodiment described above, an annular wave spring (wave washer) made of metal is used as the elastic member  15 . However, an O-ring made of resin may be used, in a case where the degree of requirement for the reliability is low. This is because the O-ring made of resin also has defects such as a change in expansion due to temperature and degradation over time in elastic force. 
     REFERENCE SIGNS LIST 
     
         
           10  Lens barrel 
           1 ,  2 ,  3 ,  4 ,  5 ,  6  Lens 
           4   a  Recess 
           4   b ,  5   b  Abutment surface 
           8  Image sensor 
           11 ,  12 ,  13  Intermediate ring 
           15  Elastic member 
           16  Substrate 
           17  Support member 
           19  Lens group 
           20  Lens unit