Patent Publication Number: US-2023152576-A1

Title: Image pickup apparatus

Description:
BACKGROUND 
     Technical Field 
     The disclosure relates to image pickup apparatuses such as in-vehicle cameras and surveillance cameras. 
     Description of the Related Art 
     Image pickup apparatuses to be used in outdoor environments, such as in-vehicle cameras and surveillance cameras, are required to have improved environmental performance such as waterproof performance. Japanese Patent No. 6054720 discloses an optical unit that secures waterproof performance by holding a sealing member between a lens having a first sealing area and a fixing portion having a second sealing area and fixing the lens in a lens barrel from a surface facing the object. 
     It is necessary for an image pickup apparatus having no focusing mechanism (fixed focus lens) to adjust a focus position of an optical system and an imaging plane with high accuracy in an assembly of the image pickup apparatus because the focus position of the optical system and the position of the imaging plane are not movable during use. Japanese Patent Laid-Open No. 2018-146772 discloses an image pickup apparatus in which a lens barrel is held by a barrel holding member movably in an optical axis direction relative to an image sensor, and the barrel holding member and the lens barrel are adhered to each other. 
     However, in the image pickup apparatus disclosed in Japanese Patent Laid-Open No. 2018-146772 in which the barrel holding member and the lens barrel are adhered together, a holding force between the barrel holding member and the lens barrel may be lowered due to softening of the adhesion portion under high temperature and high humidity. At this time, in an attempt to secure waterproof performance using the structure that always generates a force for pressing the lens toward the sensor side, as disclosed in Japanese Patent No. 6054720, the biasing force of the sealing member presses the lens barrel toward the sensor side and may cause the focus position to shift. 
     SUMMARY 
     The disclosure provides an image pickup apparatus that can restrain a focus position from shifting while securing waterproof performance. 
     An image pickup apparatus according to one aspect of this disclosure includes a sensor unit, a lens unit that includes a lens and a lens frame configured to hold the lens, a housing configured to hold the sensor unit and the lens unit, a cover portion configured to cover part of the lens, a first elastic body disposed between a groove portion provided in an outer diameter portion of the lens unit and an inner diameter portion of the housing, and a second elastic body disposed between the cover portion and the lens. In an optical axis direction, a first biasing force applied to the lens unit by the first elastic body acts in the same direction as a second biasing force applied to the lens unit by the second elastic body. 
     Further features of the disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a sectional view of a lens module according to this embodiment. 
         FIGS.  2 A and  2 B  are exploded perspective views of the lens module according to this embodiment. 
         FIG.  3    is a sectional view of an image pickup apparatus according to this embodiment. 
         FIG.  4    is an enlarged sectional view of the lens module according to this embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Referring now to the accompanying drawings, a detailed description will be given of an embodiment according to the disclosure. This embodiment is suitable for image pickup apparatuses, such as in-vehicle cameras and surveillance cameras, which are used in outdoor environments. In this embodiment, a housing structure, an electrical structure, etc. attached to a lens barrel are well-known technologies, and thus a detailed description thereof will be omitted in this embodiment. 
     Referring now to  FIG.  3   , a description will be given of a camera (image pickup apparatus)  100  according to this embodiment.  FIG.  3    is a sectional view of the camera  100 . A lens module  1  is partially exposed from an opening portion  2   a  provided in front (on the object side) of an exterior  2 , and is fixed to and held by the exterior  2  with unillustrated screws. An elastic body  3  is provided between the opening portion  2   a  in the exterior  2  and an outer circumferential portion (outer diameter portion) la of the lens module  1 . By sandwiching the elastic body  3  between the outer diameter portion  1   a  and the opening portion  2   a , a space between the lens module  1  and the exterior  2  is sealed and water can be prevented from entering the interior of the exterior  2  from the outside of the camera  100 . 
     Referring now to  FIGS.  1 ,  2 A, and  2 B , a detailed description will be given of the lens module  1  according to this embodiment.  FIG.  1    is a sectional view of the lens module  1 .  FIG.  2 A  is an exploded perspective view of the lens module  1  viewed from the object side, and  FIG.  2 B  is an exploded perspective view of the lens module  1  viewed from an image sensor side (image side). 
     A holding frame (housing)  4  of the lens module  1  has a circular opening portion  4   a , a rectangular opening portion  4   b , an inner diameter threaded portion  4   c , an outer diameter threaded portion  4   d , and a groove  4   e . The lens unit  50  includes a lens frame  5  and lenses  6   a ,  6   b , and  6   c , and is inserted into the circular opening portion  4   a . The outer diameter portion of the lens frame  5  includes an outer diameter threaded portion  5   a , and a groove (groove portion)  5   b . The groove  5   b  is tilted so that a diameter becomes smaller as a position approaches a cover portion. A first elastic body  7  is, for example, an O-ring having an annular shape and is housed in the groove  5   b . The lens frame  5  is held by the holding frame  4  as a result of that the outer diameter threaded portion  5   a  and the inner diameter threaded portion  4   c  of the holding frame  4  are screwed with each other while the first elastic body  7  is attached to the lens frame  5 . 
     A sensor unit  8  includes a sensor (image sensor)  8   a  such as a CMOS sensor. The sensor unit  8  is inserted into the rectangular opening portion  4   b  in the holding frame  4 , attached to an unillustrated receiving portion provided inside the rectangular opening portion  4   b , and fixed with unillustrated screws. A cover  12  is fixed to the holding frame  4  with unillustrated screws so as to cover the back surface of the sensor unit  8 . Due to this structure, the lens unit  50  and the sensor unit  8  are held by the holding frame  4 . Since the lens unit  50  is held in the holding frame  4  by screwing (screw engagement), the position of the sensor unit  8  can be adjustable along the optical axis OA (optical axis direction). 
     Next follows a description of focusing as an optical adjustment. A focus position of the lens unit  50  and a position of an imaging plane of the sensor unit  8  are different for each component due to manufacturing variations in a component and assembly. In a case where the manufacturing variation is large relative to a depth of focus, a relationship between the focus position of the lens unit  50  and the position of the imaging plane of the sensor unit  8  may not coincide with each other within a range of the depth of focus even if the assembly is made without care. In such a case, it is necessary to adjust the relationship between the focus position of the lens unit  50  and the position of the imaging plane of the sensor unit  8  during assembly so that they coincide with each other within the range of the depth of focus. Therefore, an optical position adjustment (focusing) is made while the focus performance is confirmed by using a captured image or an evaluation value in the image. More specifically, in the optical position adjustment, an evaluation chart is set in front (on the object side) of the lens unit  50 , and the resolution and contrast value are checked from a captured chart image, the lens unit  50  is moved relative to the imaging plane in the optical axis direction to a position that satisfies the required image quality. 
     A description will now be given of a pressing ring  9 . The pressing ring  9  is a cover portion that partially covers the lens (front lens)  6   a  of the lens unit  50 , and has an inner diameter threaded portion  9   a , a contact surface  9   b , and an inner circumferential portion (inner diameter portion)  9   c . The lens  6   a  is the frontmost lens among the plurality of lenses  6   a ,  6   b , and  6   c  in the lens unit  50  and is disposed closest to the object. A third elastic body  11  having an annular shape is housed in the groove  4   e  in the holding frame  4 . A second elastic body  10  is disposed (sandwiched) between the contact surface  9   b  of the pressing ring  9  and the lens  6   a . The second elastic body  10  is, for example, an O-ring having an annular shape. While the third elastic body  11  is sandwiched between the inner diameter portion  9   c  and the groove  4 E in the holding frame  4 , the inner diameter threaded portion  9   a  of the pressing ring  9  and the outer diameter threaded portion  4   d  of the holding frame  4  are screwed with each other, and thereby the pressing ring  9  is held by the holding frame  4 . When the second elastic body  10  and the third elastic body  11  are sandwiched due to this structure, hermetical sealing is made and water can be prevented from entering the lens unit  50  and the sensor unit  8  housed inside the holding frame  4 . In this embodiment, the pressing ring  9  is a separate member from the holding frame  4 , but the holding frame  4  and the pressing ring  9  may be integrated with each other. 
     Referring now to  FIG.  4   , a description will be given of a relationship of biasing forces in this structure.  FIG.  4    is an enlarged sectional view of the lens module  1 . A biasing force F 1  is generated by disposing (sandwiching) the first elastic body  7  between the groove  5   b  in the lens frame  5  and the inner diameter portion of the holding frame  4 . The groove  5   b  has a tilted surface that is tilted so that a diameter decreases as a position approaches the cover portion  9  (the bottom surface of the groove  5   b  is tilted so that the distance from the optical axis OA becomes smaller as the position approaches the cover portion (the object)). Thus, the biasing force F 1  is generated in a direction orthogonal to the tilted groove  5   b . The biasing force F 1  can be divided into a component force (first biasing force) F 1 S in the optical axis direction and a component force (third biasing force) F 1 R in a direction orthogonal to the optical axis. Due to the component force F 1 S, the biasing force acts to press the lens unit  50  against the holding frame  4  in a direction toward the sensor unit  8 . A frictional force is generated by the component force F 1 R and acts as resistance in the circumferential direction, thereby displacement in the optical axis direction can be suppressed even under disturbances such as vibration and impact. 
     In this embodiment, the radial size (diameter of the ring) of the second elastic body  10  having the annular shape is smaller than the radial size of the first elastic body  7  having the annular shape. Thereby, in a case where the biasing forces applied to the lens unit  50  are equal to each other, the resistance in the circumferential direction generated by the first elastic body  7  during assembly of the pressing ring  9  is larger than the resistance in the circumferential direction generated by the second elastic body  10 . Thus, during assembly of the pressing ring  9 , the lens unit  50  is restrained from moving in the circumferential direction and is less likely to shift in the optical axis direction. In addition to the frictional force by the biasing force F 1 R in the direction orthogonal to the optical axis generated by the first elastic body  7 , the holding frame  4  and the lens unit  50  may be adhered to each other before the pressing ring  9  is assembled. For example, the fixation can be enhanced by adhesion around the inner diameter threaded portion  4   c  of the holding frame  4  and the outer diameter threaded portion  5   a  of the lens unit  50  after focusing. 
     The second elastic body  10  is sandwiched between the lens  6   a  and the contact surface  9   b  of the pressing ring  9 , thereby generating a biasing force (second biasing force) F 2 . The biasing force F 2  generates a biasing force that presses the lens unit  50  toward the sensor unit  8  relative to the holding frame  4 . 
     Due to the above structure, the component force F 1 S and the component force F 1 R are generated in a case where the holding frame  4  and the lens unit  50  are held together by screw engagement and the first elastic body  7  held in the tilted groove  5   b  so that the diameter becomes smaller as the position approaches the cover portion (the object) is sandwiched between the holding frame  4  and the groove  5   b . Since a single elastic body can generate a biasing force in the optical axis direction and a biasing force in the direction orthogonal to the optical axis without preparing a biasing member for each direction, this structure contributes to the miniaturization of the lens module  1 . 
     The component force F 1 R in the direction orthogonal to the optical axis generated by the first elastic body  7  generates resistance in the circumferential direction. This structure can prevent the holding force from being lowered by temperature changes in an external environment, etc., more effectively than the holding structure using only adhesion, and can suppress displacement of the lens unit  50  in the optical axis direction. 
     In addition to the biasing force F 1 R, the lens unit  50  and the holding frame  4  may be adhered to each other before the pressing ring  9  is attached after focusing. Thereby, the holding force can be further enhanced. 
     Focusing is available while backlash (screw play) in the optical axis direction between the outer diameter threaded portion  5   a  of the lens frame  5  and the inner diameter threaded portion  4   c  of the holding frame  4  is always biased toward the sensor unit  8  by the component force F 1 S in the optical axis direction generated by the first elastic body  7 . Thereafter, waterproof performance is secured by assembling the second elastic body  10  between the pressing ring  9  and the frontmost lens  6   a  of the lens unit  50 . At this time, even if the lens unit  50  is pressed toward the sensor unit  8  relative to the holding frame  4  by the biasing force F 2  generated by the second elastic body  10 , both the biasing force F 1 S and the biasing force F 2  act in a single direction as the optical axis direction (same direction). That is, in the optical axis direction, the first biasing force (biasing force F 1 S) applied to the lens unit  50  by the first elastic body  7  acts in the same direction as the second biasing force (biasing force F 2 ) applied to the lens unit  50  by the second elastic body  10 . Therefore, the lens unit  50  will not be out of focus due to the biasing force F 2 . This structure can restrain the focus position of the lens unit  50  from shifting under various environments while waterproof performance is secured. 
     the first elastic body  7  may have a diameter larger than that of the second elastic body  10 . Thereby, the torque generated by the biasing force F 1 S of the first elastic body  7  becomes stronger than the torque generated by the second elastic body  10 . Therefore, when the pressing ring  9  and the second elastic body  10  are assembled, the lens unit  50  is less likely to displace during assembly. 
     This embodiment suppresses displacement in the optical axis direction under high temperature and humidity by holding the housing and the lens unit by screw (or thread) engagement. In addition, this embodiment can suppress displacement caused by the biasing force of the elasticity body for securing waterproof performance by setting, to the same direction, the components in the optical axis direction of the biasing force generated by the elastic body for eliminating the backlash (screw play) and the biasing force generated by the elastic body for securing the waterproof performance. Therefore, this embodiment can provide an image pickup apparatus that can restrain the focus position from shifting while securing the waterproof performance. 
     While the disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. For example, this embodiment uses screwing as an example of a mechanical engagement, but can use another mechanical engagement, such as fitting (or mating). 
     This application claims the benefit of Japanese Patent Application No. 2021-187607, filed on Nov. 18, 2021, which is hereby incorporated by reference herein in its entirety.