Patent Description:
The present disclosure relates to an imaging device, a mobile object, and a method for manufacturing an imaging device.

PTL <NUM> discloses a method for performing focus adjustment based on a thickness of a spacer inserted between an attachment reference surface for an imaging element and the imaging element. PTL <NUM> discloses a camera module comprising: a solid state imaging device mounted to a substrate; the barrel which holds a lens for forming a subject image on the solid state imaging device; and the holder which holds the barrel on the substrate to fix the position of the lens with respect to the solid state imaging device. The barrel and the holder are fixed to each other via a thermosensitive double-side adhesive film. PTL <NUM> discloses an imaging device constituted of a lens, an imaging device receiving the incident light and converting the incident light to be an electrical signal, a cylindrical member accommodating the lens, a holder holding the imaging device, a groove formed of an outer periphery surface of the cylindrical member and an inner periphery surface of the holder, an adhesive provided in the groove with the outer periphery surface and the inner periphery surface being contacted with each other, and an anchor mechanism provided in the groove. PTL <NUM> discloses a camera device composed of an image pickup lens, an image pickup element, a lens holding member, a circuit board, and screws. A focal-distance holding member is provided between the image pickup element and the circuit board. Alternatively, a clearance may be provided between the image pickup element and the circuit board. The material of a lead frame of the image pickup element may be the same as that of the lens holding member. Preferably, a clearance X may be provided between the image pickup element and the circuit board. The material of the lead frame of the image pickup element is different from that of the lens holding member. If a linear expansion coefficient of the lens holding member is α1 and that of the lead frame is α2, X=L1×α1/α2 is established.

PTL <NUM>: <CIT>; PTL <NUM>: <CIT>; PTL <NUM>: <CIT>; PTL <NUM>: <CIT>.

Embodiments of the present invention are defined by an imaging device according to claim <NUM>, a mobile object according to claim <NUM>, and a method for manufacturing according to claim <NUM>.

A further embodiment is defined by an imaging device according to dependent claim <NUM>.

According to the method disclosed in PTL <NUM>, when a substrate on which the imaging element is mounted and the spacer are fastened with screws to the attachment reference surface, a focus position may vary depending on the screw fastening force. In addition, an optical axis may tilt unless screws are fastened with equal force. Therefore, assembly needs to be carefully performed. An embodiment of the present disclosure provides an imaging device, a mobile object, and a method for manufacturing the imaging device with which focus adjustment can be facilitated and the displacement of the optical axis can be reduced.

An embodiment of the present disclosure will now be described with reference to the drawings. In the drawings, the same reference signs denote the same or similar components. The drawings referred to in the following description are schematic. Dimensional ratios in the drawings, for example, do not necessarily coincide with actual dimensional ratios.

As illustrated in <FIG>, an imaging device <NUM> according to an embodiment of the present disclosure may be mounted in a mobile object <NUM>. When the imaging device <NUM> is mounted in the mobile object <NUM>, the imaging device <NUM> may capture an image of a subject in a space around the mobile object <NUM>. The image captured by the imaging device <NUM> may be used, for example, to detect an object (human, vehicle, etc.) in the space around the mobile object <NUM>.

Examples of the mobile object <NUM> may include a vehicle and an aircraft. Examples of the vehicle may include an automobile, an industrial vehicle, a railroad vehicle, a daily use vehicle, and a fixed-wing airplane that runs on a runway. Examples of the automobile may include a passenger vehicle, a truck, a bus, a two-wheel vehicle, and a trolley bus. Examples of the industrial vehicle may include an industrial vehicle for agriculture and an industrial vehicle for construction. Examples of the industrial vehicle may include a forklift and a golf cart. Examples of the industrial vehicle for agriculture may include a tractor, a cultivator, a transplanter, a binder, a combine, and a mower. Examples of the industrial vehicle for construction may include a bulldozer, a scraper, an excavator, a crane truck, a dump truck, and a road roller. The vehicle may be a vehicle driven by human force. The categories of the vehicle are not limited to those described above. For example, the automobile may be an industrial vehicle capable of running on a road. The same vehicle may belong to two or more categories. Examples of the aircraft may include a fixed-wing airplane and a rotary wing aircraft.

The imaging device <NUM> illustrated in <FIG> includes a lens unit <NUM> and an imaging element <NUM>.

The lens unit <NUM> includes a plurality of optical members, such as lenses. The lenses included in the lens unit <NUM> may, for example, be lenses having a wide angle of view, such as fisheye lenses. The lens unit <NUM> focuses a subject image on a light-receiving surface of the imaging element <NUM>.

The imaging element <NUM> includes, for example, a charge coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor. A plurality of pixels (light receiving elements) are arranged on the light-receiving surface of the imaging element <NUM>. The imaging element <NUM> captures the subject image focused on the light-receiving surface and creates a captured image. The imaging device <NUM> may output the captured image to an external device mounted in the mobile object <NUM>. The external device may be, for example, an electronic control unit (ECU), a display, or a navigation device. The imaging device <NUM> may have a function of performing a predetermined image process, such as a white balance adjustment process, an exposure adjustment process, or a gamma correction process, on the captured image.

In the example illustrated in <FIG>, the imaging device <NUM> is a monocular camera including a single imaging system composed of the lens unit <NUM> and the imaging element <NUM>. However, the imaging device <NUM> is not limited to this. The imaging device <NUM> may instead be a stereo camera that includes a plurality of imaging systems that cooperate with each other to capture images of a target from different visual points. When the imaging device <NUM> is a stereo camera, two lens units <NUM>, for example, are disposed next to each other with an interval therebetween in a vehicle width direction of the mobile object <NUM> so that optical axes thereof are parallel to each other. Accordingly, the imaging systems capture images of substantially the same area from different visual points. The imaging device <NUM> may be fixed to, for example, a front bumper, a fender grille, a side fender, a light module, a hood, etc., of a vehicle.

The structure of the imaging device <NUM> will now be described with reference to <FIG>.

As illustrated in <FIG>, the imaging device <NUM> includes the lens unit <NUM>, the imaging element <NUM>, and an imaging substrate <NUM> on which a housing <NUM> and the imaging element <NUM> are mounted.

The lens unit <NUM> includes a plurality of lenses 101a to 101e and a lens barrel <NUM>, and possibly non-claimed spacing rings 120a to 120d and a non-claimed retainer <NUM>. In the following description, the lenses 101a to 101e will be referred to as lenses <NUM> when they are not distinguished from each other. Also, the spacing rings 120a to 120d will be referred to as spacing rings <NUM> when they are not distinguished from each other.

The lenses 101a to 101e are arranged in the direction of an optical axis OA. In other words, the lenses 101a to 101e are arranged such that optical axes thereof coincide with the optical axis OA. In the following direction, a direction orthogonal to the optical axis direction in a plan view viewed in the optical axis direction will be referred to as a radial direction, and a direction that circulates around the optical axis direction will be referred to as a circumferential direction.

The lenses <NUM> may be made of a glass or a resin, such as polycarbonate (PC), cyclo-olefin polymer (COP), cyclo-olefin copolymer (COC), or poly(methyl methacrylate) (PMMA).

The lens barrel <NUM> is a cylindrical member having an opening <NUM> larger than the lenses 101a to 101e. The lens barrel <NUM> has an internal space in which the lenses <NUM> are contained and held. More specifically, the lens barrel <NUM> contains the lenses 101a to 101e such that the lens 101e, the lens 101d, the lens 101c, the lens 101b, and the lens 101a are arranged in that order from the opening <NUM>. Thus, among the lenses <NUM>, the lens 101e is closest to the opening <NUM>. In addition, among the lenses <NUM>, the lens 101a is at a side farthest from the opening <NUM> (hereinafter referred to as "bottom"). The lens barrel <NUM> contains the lenses <NUM> such that the central axis of the lens barrel <NUM> coincides with the optical axis OA. The lens barrel <NUM> may be made of, for example, aluminum or stainless steel.

The lens barrel <NUM> has a thread groove <NUM> in the outer periphery thereof. The housing <NUM> has a threaded portion (thread crest) <NUM> configured to engage with the thread groove <NUM> in the outer periphery of the lens barrel <NUM>. The imaging device <NUM> includes an adhesive member <NUM> positioned between the thread groove <NUM> in the outer periphery of the lens barrel <NUM> and the threaded portion <NUM> of the housing <NUM>. More specifically, the lens barrel <NUM> is accommodated in the housing <NUM> and screw fastened to the housing <NUM>, possibly at a non-claimed first fixing section <NUM>. The threaded portion <NUM> is formed on an inner peripheral surface of an accommodation space of the housing <NUM> that accommodates the lens barrel <NUM> at a position corresponding to the first fixing section <NUM>. In addition, a thread groove <NUM> that engages with the threaded portion <NUM> is formed in an outer peripheral surface of the lens barrel <NUM> at a position corresponding to the first fixing section <NUM>. The adhesive member <NUM> is applied to at least one of the threaded portion <NUM> on the inner peripheral surface of the accommodation space of the housing <NUM> and the thread groove <NUM> in the outer peripheral surface of the lens barrel <NUM>. The adhesive member <NUM> is, for example, an adhesive having a small coefficient of linear expansion.

By inserting the lens barrel <NUM> into the accommodation space of the housing <NUM> while rotating the lens barrel <NUM> in the circumferential direction, the lens barrel <NUM> can be screwed into the accommodation space of the housing <NUM> such that the threaded portion <NUM> on the inner peripheral surface of the accommodation space of the housing <NUM> engages with the thread groove <NUM> in the outer peripheral surface of the lens barrel <NUM>. The lens barrel <NUM> and the housing <NUM> are fixed by adhesion while the position of the lens barrel <NUM> is adjusted such that the lenses <NUM> focus the subject image on the light-receiving surface of the imaging element <NUM>. When the adhesive member <NUM> is a thermosetting adhesive, the thermosetting adhesive is cured to fix the lens barrel <NUM> and the housing <NUM>.

According to a non-claimed example, a filter <NUM> is positioned between the lens unit <NUM> and the imaging element <NUM>. The filter <NUM> may be, for example, an ultraviolet (UV)/infrared (IR) cut filter, a color filter, or a low-pass filter. The filter <NUM> may instead be a glass plate having an antireflection (AR) coating. The filter <NUM> is supported by a support portion <NUM>. The support portion <NUM> supports the filter <NUM>. The support portion <NUM> has a sealing structure so that no foreign matter adheres to the light-receiving surface of the imaging element <NUM>.

A first projecting portion <NUM> that projects radially outward is formed on the outer peripheral surface of the lens barrel <NUM>. The first projecting portion <NUM> is in contact with the housing <NUM> with a wave washer <NUM> provided therebetween when the lens unit <NUM> is accommodated in the housing <NUM>. When the lens barrel <NUM> is inserted into the accommodation space of the housing <NUM>, the wave washer <NUM> is pressed and urged by the first projecting portion <NUM> of the lens barrel <NUM> in the direction in which the lens barrel <NUM> is inserted. When the lens barrel <NUM> is rotated for position adjustment, it may be difficult to perform fine adjustment due to backlash. The backlash can be reduced by placing the wave washer <NUM> that is pressed and urged between the first projecting portion <NUM> of the lens barrel <NUM> and the housing <NUM>.

According to a non-claimed example, a second projecting portion <NUM> that projects radially inward is provided on an inner peripheral surface of the lens barrel <NUM> at the bottom of the lens barrel <NUM>. The second projecting portion <NUM> of the lens barrel <NUM> has an inner diameter less than the outer diameter of the lens 101a closest to the bottom. Accordingly, the second projecting portion <NUM> serves as a holder that holds the lens 101a.

The spacing rings <NUM> are annular members having an outer diameter substantially equal to the inner diameter of the lens barrel <NUM> and an inner diameter substantially equal to the outer diameter of a lens portion of each lens <NUM> described below. The spacing rings <NUM> serve as holders that hold the lenses <NUM> in the lens barrel <NUM>. The spacing rings <NUM> also serve as spacers that adjust the distances between the lenses <NUM> in the optical axis direction.

The spacing ring 120a is positioned between an object-side surface (surface adjacent to the opening <NUM>) of the lens 101a and an image-side surface (surface adjacent to the bottom) of the lens 101b. The spacing ring 120b is positioned between an object-side surface of the lens 101b and an image-side surface of the lens 101c. The spacing ring 120c is positioned on an object-side surface of the lens 101c. The spacing ring 120d is positioned between the spacing ring 120c and an image-side surface of the lens 101d. The lens 101e is positioned in contact with an object-side surface of the lens 101d. The intervals between the lenses <NUM> contained in the lens barrel <NUM> in the optical axis direction are adjusted by the spacing rings 120a to 120d.

As described above, the lens barrel <NUM> has the opening <NUM> larger than the outer diameters of the lenses <NUM>. In addition, the second projecting portion <NUM>, which projects radially inward and which is capable of holding the lens 101a closest to the bottom, is provided on the inner peripheral surface of the lens barrel <NUM> at the bottom of the lens barrel <NUM>. Accordingly, the lens 101a, the spacing ring 120a, the lens 101b, the spacing ring 120b, the lens 101c, the spacing ring 120c, the spacing ring 120d, the lens 101d, and the lens 101e are inserted into the lens barrel <NUM> through the opening <NUM> in that order.

The retainer <NUM>, which serves as a holding member, is in contact with the lens 101e, which is one of the lenses <NUM> that is closest to the opening <NUM>, and thereby holds the lenses <NUM> from the side adjacent to the opening <NUM>. The retainer <NUM> includes an outer peripheral portion <NUM> and a contact portion <NUM>.

The outer peripheral portion <NUM> is fixed to the outer peripheral surface of the lens barrel <NUM>. For example, as illustrated in <FIG>, the outer peripheral portion <NUM> is fixed to the outer peripheral surface of the lens barrel <NUM> at a second fixing section <NUM>, which is closer to the opening <NUM> than the first projecting portion <NUM>. The outer peripheral portion <NUM> is, for example, fixed by being screwed onto the lens barrel <NUM>. In this case, for example, a thread crest is formed on the outer peripheral surface of the lens barrel <NUM> at a position corresponding to the second fixing section <NUM>. In addition, a thread groove that engages with the thread crest formed on the outer peripheral surface of the lens barrel <NUM> is formed in an inner peripheral surface of the outer peripheral portion <NUM> at a position corresponding to the second fixing section <NUM>. The retainer <NUM> is fixed to the outer peripheral surface of the lens barrel <NUM> by pushing the retainer <NUM> into the housing <NUM> in the optical axis direction while rotating the retainer <NUM> in the circumferential direction.

The contact portion <NUM> extends radially inward from an end portion of the outer peripheral portion <NUM> adjacent to the opening <NUM>. When the retainer <NUM> is fixed to the outer peripheral surface of the lens barrel <NUM>, the contact portion <NUM> is in contact with the lens 101e closest to the opening <NUM> and holds the lenses <NUM> in the optical axis direction.

The imaging element <NUM> captures the subject image incident thereon through the lens <NUM>. The housing <NUM> holds the imaging element <NUM>.

A rotational displacement caused by thermal expansion or contraction of the adhesive member <NUM> due to temperature variation will now be described with reference to <FIG> and <FIG>. The adhesive member <NUM> expands or contracts in response to temperature variation. An amount of rotational displacement (lens rotation angle) θ of the lens unit <NUM> due to temperature variation may be determined by using an amount of thermal expansion or contraction Δg of the adhesive member <NUM> and a nominal screw diameter M as in Expression (<NUM>) given below. <NUM>]<MAT>.

According to a non-claimed example, the nominal diameter (outer diameter of the lens barrel <NUM>) M is assumed to be <NUM>, and the amount of thermal expansion or contraction Δg is assumed to be <NUM>. In this case, according to Expression (<NUM>), the lens rotation angle θ is <NUM> degrees. Accordingly, when the adhesive member <NUM> thermally expands or contracts, the lens unit <NUM> may tilt by <NUM> degrees at a maximum. <FIG> is an enlarged view of the first fixing section <NUM>. Assuming the worst case, a screw clearance in a state of screw abutment illustrated in <FIG> is used in the calculation. However, such a case is unlikely because suppression of the rotation occurs in practice.

Referring to <FIG>, in the present example, a distance f from a sensor surface of the imaging element <NUM> to an image-side principal point P is <NUM> in terms of an air conversion distance. A screw fastening position of the first fixing section <NUM> (position at which the lens barrel <NUM> and the housing <NUM> are fixed by adhesion) may be regarded as a rotation center Q of the lens unit <NUM>. The rotation center is ideally at the image-side principal point P. This is because the focus position does not change when the image-side principal point P is the rotation center. Assuming the worst case where the screw fastening position of the first fixing section <NUM> is at an end of a screw engagement portion, a distance d between the image-side principal point P and the rotation center Q is <NUM>. Assume that the lens rotation angle θ due to temperature variation is <NUM> degrees.

<FIG> shows the displacement of the optical axis caused when the lens rotation angle θ due to temperature variation of the adhesive member <NUM> is <NUM> degrees. The horizontal axis represents the distance from the sensor surface of the imaging element <NUM> to the rotation center Q. The vertical axis represents the displacement of the optical axis. As is clear from <FIG>, the displacement of the optical axis is small when the screw fastening position of the first fixing section <NUM> (that is, the rotation center Q) is close to the image-side principal point P. Therefore, as illustrated in <FIG> and <FIG>, the thread groove <NUM> formed in the outer periphery of the lens barrel <NUM> at the first fixing section <NUM> is provided in a range including a position at which a principal plane of the optical system including the lenses <NUM> (plane extending through the image-side principal point P and perpendicular to the optical axis OA) crosses the outer periphery of the lens barrel <NUM>.

For example, the image-side surface of the lens 101a, which is one of the lenses <NUM> that is closest to the imaging element <NUM>, may be positioned in a range along the optical axis OA of the lenses <NUM> corresponding to a range in which the thread groove <NUM> in the outer periphery of the lens barrel <NUM> and the threaded portion <NUM> of the housing <NUM> engage with each other. In such a case, the rotation center Q may be positioned close to the image-side principal point P, and the displacement of the optical axis can be reduced. Referring to the graph of <FIG>, even when, for example, the distance d between the image-side principal point P and the rotation center Q is <NUM> as described above, the displacement of the optical axis is as small as <NUM> pixels. When binocular lenses are used, the displacement of the optical axis is calculated as <NUM> pixels based on the mean square of two displacements of <NUM> pixels.

A method for manufacturing the imaging device <NUM> will now be described with reference to <FIG>.

In step S101, the lens barrel <NUM> in which the lenses <NUM> are held and that has the thread groove <NUM> in the cylindrical outer periphery thereof is prepared. In addition, the housing <NUM> having the threaded portion <NUM> configured to engage with the thread groove <NUM> is prepared. The thread groove <NUM> is provided at a position at which the principal plane of the optical system including the lenses <NUM> crosses the outer periphery of the lens barrel <NUM>.

In step S102, the adhesive member <NUM> is applied to at least one of the thread groove <NUM> and the threaded portion <NUM>.

In step S103, the thread groove <NUM> and the threaded portion <NUM> are engaged with each other and the focus position is adjusted. The image-side surface of the lens 101a closest to the imaging element <NUM> is positioned in the range along the optical axis OA of the lenses <NUM> corresponding to the range in which the thread groove <NUM> in the outer periphery of the lens barrel <NUM> and the threaded portion <NUM> of the housing <NUM> engage with each other.

In step S104, the adhesive member <NUM> is cured to fix the positions of the lens barrel <NUM> and the housing <NUM>.

As described above, according to the present embodiment, the imaging device <NUM> includes the lens barrel <NUM> in which the lenses <NUM> are held and that has the thread groove <NUM> in the cylindrical outer periphery thereof. The imaging device <NUM> also includes the housing <NUM> that holds the imaging element <NUM> and that has the threaded portion <NUM> configured to engage with the thread groove <NUM> in the outer periphery of the lens barrel <NUM>. Accordingly, the lens barrel <NUM> can be inserted into the accommodation space in the housing <NUM> such that the threaded portion <NUM> and the thread groove <NUM> engage with each other. Therefore, focus adjustment can be facilitated.

In addition, in the present embodiment, the thread groove <NUM> in the outer periphery of the lens barrel <NUM> may be provided in a range including the position at which the principal plane of the optical system including the lenses <NUM> crosses the outer periphery of the lens barrel <NUM>. In addition, the image-side surface of the lens 101a that is closest to the imaging element <NUM> may be positioned in the range along the optical axis OA of the lenses <NUM> corresponding to the range in which the thread groove <NUM> and the threaded portion <NUM> engage with each other. According to the above-described structure, the rotation center Q may be positioned close to the image-side principal point P, so that the displacement of the optical axis can be reduced.

Although typical examples have been described in the embodiment, it is obvious to those skilled in the art that various alterations and replacements are possible within the scope of the present claims. Therefore, the present invention is not to be regarded as being limited to the above-described embodiment, and various modifications and alterations are possible without departing from the scope of the claims.

Claim 1:
An imaging device (<NUM>) comprising:
a lens barrel (<NUM>) in which a plurality of lenses (<NUM>, 101a, 101b, 101c, 101d, 101e) are held and that has a thread groove (<NUM>) in a cylindrical outer periphery of the lens barrel (<NUM>), wherein a projecting portion (<NUM>) that projects radially outward is formed on an outer peripheral surface of the lens barrel (<NUM>);
an imaging element (<NUM>) that captures a subject image incident on the imaging element (<NUM>) through the plurality of lenses (<NUM>, 101a, 101b, 101c, 101d, 101e);
a housing (<NUM>) that holds the imaging element (<NUM>) and that includes a threaded portion (<NUM>) configured to engage with the thread groove (<NUM>) in the cylindrical outer periphery of the lens barrel (<NUM>); and
an adhesive member (<NUM>) positioned between the thread groove (<NUM>) in the cylindrical outer periphery of the lens barrel (<NUM>) and the threaded portion (<NUM>) of the housing (<NUM>),
wherein the thread groove (<NUM>) is provided in a range that includes a position at which a principal plane of an optical system including the plurality of lenses crosses the cylindrical outer periphery of the lens barrel (<NUM>), the optical system comprising the plurality of lenses (<NUM>, 101a, 101b, 101c, 101d, 101e),
wherein the projecting portion (<NUM>) is in contact with the housing (<NUM>) with a wave washer (<NUM>) provided therebetween, and
wherein the wave washer (<NUM>) is configured to be pressed and urged by the projecting portion (<NUM>) of the lens barrel (<NUM>) in the direction in which the lens barrel (<NUM>) is inserted, when the lens barrel (<NUM>) is inserted into the housing (<NUM>).