JP2018185438A - Imaging device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device in which adjustment of the focus of a lens is not easily affected by tightening of screws.SOLUTION: An imaging device 1 comprises: a lens 2; an imaging element 3 that picks up a subject image formed by the lens 2; at least one plate-like member 4 that has optical transparency; and a holding member 5 that holds the lens 2, imaging element 3, and plate-like member 4. The holding member 5 has plate-like member holding parts 54 that allow insertion of at least one plate-like member 4 different in the entire thickness from a direction intersecting an optical path between the lens 2 and imaging element 3.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an imaging apparatus and a manufacturing method thereof.

  In an imaging apparatus, a configuration in which a unit including a lens is attached with a screw together with a lens focus adjustment member is known (see, for example, Patent Document 1).

JP 2009-194543 A

  The lens focus adjustment member can be appropriately selected in consideration of the positions of the lens and the image sensor after screwing so as to match the characteristics of the lens and the image sensor. The positions of the lens and the image sensor may deviate from assumptions due to screw tightening. That is, even when the adjustment member is appropriately selected, the focus of the lens may be shifted by tightening the screw.

  An object of the present disclosure is to provide an imaging apparatus in which adjustment of the focus of a lens is not easily affected by screw tightening and a manufacturing method thereof.

  An imaging apparatus according to an embodiment of the present disclosure includes a lens, an imaging element that captures a subject image formed by the lens, at least one plate-like member having optical transparency, the lens, and the imaging element. A holding member for holding the plate-like member. The holding member has a plate-like member holding portion in which the at least one plate-like member having a different overall thickness can be inserted from a direction intersecting an optical path between the lens and the imaging element.

  A manufacturing method of an imaging device according to an embodiment of the present disclosure includes a step of fastening a holding member that holds a lens and an imaging element that captures a subject image formed by the lens. The manufacturing method includes a step of measuring a resolution in a state where the imaging element is fastened. The manufacturing method includes a step of inserting into the holding member at least one plate-like member having optical transparency and having an overall thickness corresponding to the measurement result of the resolution.

  According to the imaging apparatus and the manufacturing method thereof according to an embodiment of the present disclosure, the adjustment of the lens focus is not easily affected by the screw tightening.

It is a top view showing an example of composition of an imaging device concerning one embodiment. It is AA sectional drawing of FIG. It is a top view which shows the example of a plate-shaped member holding part. 3 is a flowchart illustrating an example of a method for manufacturing an imaging device according to an embodiment. It is a graph which shows an example of a defocus characteristic. 3 is a flowchart illustrating an example of a method for manufacturing an imaging device according to an embodiment.

  As shown in FIGS. 1 and 2, the imaging device 1 according to an embodiment includes a lens 2, an imaging element 3, a plate-like member 4, and a holding member 5.

  The lens 2 forms a subject image incident on the imaging device 1 on the light receiving surface of the imaging element 3. The lens 2 includes a first lens 21 and a second lens 22. The number of lenses 2 is not limited to two, and may be one or three or more. The lens 2 is bonded to the holding member 5. The first lens 21 and the second lens 22 are joined to the first lens holding part 51 and the second lens holding part 52, respectively. The lens 2 may be bonded to the holding member 5 with a resin such as an adhesive. The lens 2 may be joined to the holding member 5 by a fitting structure. The lens 2 may be joined to the holding member 5 by fastening screws or the like.

  The image sensor 3 captures a subject image formed on the light receiving surface by the lens 2. The imaging device 3 may be configured by, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device). The image sensor 3 is mounted on the substrate 31. The substrate 31 is fastened to the image sensor holding portion 53 of the holding member 5 by the fastening member 32. The fastening member 32 may be a screw or a rivet. It can be said that the imaging element 3 is fastened to the holding member 5 via the substrate 31. The image sensor 3 may be fastened to the holding member 5 by the fastening member 32 without using the substrate 31.

  The plate-like member 4 is light transmissive and transmits light from the lens 2 toward the image sensor 3. The plate-like member 4 may be a cover for the lens 2 or the image sensor 3. The plate-like member 4 may be a band pass filter that transmits light having a predetermined wavelength. The plate-like member 4 may be an IR cut filter that cuts infrared rays (IR: Infra Red). The plate-like member 4 has a thickness in the Z-axis direction. The surfaces on the positive and negative directions of the Z-axis of the plate-like member 4 are assumed to have a rectangular shape. That is, the plate-like member 4 is assumed to be a rectangular plate having a thickness in the Z-axis direction. The plate-like member 4 is not limited to a rectangular plate. The plate-like member 4 may be a polygonal plate or a plate having a shape whose outer periphery is specified by a line segment or a curve.

  The plate-like member 4 is composed of at least one member. When the plate-like member 4 is composed of one member, the entire thickness of the plate-like member 4 is the thickness of the member. When the plate-like member 4 is composed of two or more members, the thickness of the plate-like member 4 is a thickness obtained by adding the thicknesses of the respective members. The total thickness of the plate-like member 4 is represented by t. The total thickness of the plate-like member 4 can be varied depending on the number of inserted members or the thickness of each inserted member.

  The plate member 4 is held by the plate member holding portion 54 of the holding member 5. The plate-like member 4 may be joined to the plate-like member holding portion 54 with a resin such as an adhesive. The resin may have thermosetting property or UV (Ultra Violet) curable property.

The plate member 4 has a predetermined refractive index. The predetermined refractive index is assumed to be greater than the refractive index of air and is represented by n. The refractive index of air shall be considered to be unity. When the plate-like member 4 is positioned on the image forming side of the lens 2, the focal length of the lens 2 changes according to the optical path length of the light passing through the plate-like member 4. The difference between the focal length of the lens 2 without the plate-like member 4 and the focal length of the lens 2 with the plate-like member 4 is also referred to as a focal length change amount and is expressed by Δf. When the entire thickness of the plate-like member 4 is represented by t and the entire thickness of the plate-like member 4 is regarded as the optical path length, Δf is represented by the following formula (1).
Δf = t−t / n (1)

  According to equation (1), Δf is smaller than t. That is, an error in the overall thickness of the plate-like member 4 hardly affects the focal length change amount.

  The holding member 5 includes a first lens holding part 51 and a second lens holding part 52. The lens holding portion joins the lens 2 by various methods such as adhesion or fitting. The number of lens holding portions is not limited to two, and may be determined according to the number of lenses 2. The holding member 5 includes an image sensor holding unit 53. The image sensor holding portion 53 is configured to be screwable or engageable with the fastening member 32. The image sensor holding unit 53 holds the image sensor 3.

  The holding member 5 includes a plate-like member holding portion 54. The plate-like member holding unit 54 holds the plate-like member 4 between the lens 2 and the image sensor 3. The plate member holding portion 54 is configured such that the plate member 4 can be inserted from a predetermined direction. The predetermined direction may be a direction that intersects the optical path of light traveling from the lens 2 toward the image sensor 3. For example, in FIG. 2, when the optical path is along the Z-axis direction, the predetermined direction may be a direction intersecting the Z-axis direction. The predetermined direction may be the X-axis direction. The predetermined direction may be a direction in which the plate member 4 can be inserted in a space formed by the lens 2 and the image sensor 3 facing each other so as not to contact the lens 2 and the image sensor 3. The direction in which the plate member 4 is inserted is also referred to as the insertion direction of the plate member 4.

  The holding member 5 may be configured to include a material such as a resin. The holding member 5 is not limited to resin, and may include various materials.

  As shown in FIG. 3, the plate-like member holding portion 54 includes a stopper portion 541, a guide portion 542, and a support portion 543. 1 to 3, the plate-like member 4 is inserted from the negative direction of the X axis toward the positive direction. That is, the plate-like member holding portion 54 is configured so that the plate-like member 4 can be inserted from the negative direction of the X axis toward the positive direction. Since the plate-like member 4 can be inserted along the X-axis direction, the plate-like member 4 is inserted into the holding member 5 after the lens 2 and the image sensor 3 are joined or fastened to the holding member 5. Can be done. That is, after the plate-like member 4 is inserted into the holding member 5, a fastening operation such as a screw is not performed. Since the fastening operation is not performed after the plate-like member 4 is inserted, the focal length adjusted by the plate-like member 4 is easily maintained.

  In FIG. 3, it is assumed that the plate-like member 4 is inserted at a position indicated by a two-dot chain line. The position where the plate-like member 4 is inserted is also referred to as the insertion position of the plate-like member 4. The plate member holding portions 54 are provided at the four corners of the insertion position of the plate member 4. The plate-like member holding portion 54 may be provided as appropriate according to the shape of the plate-like member 4. The number of plate-like member holding portions 54 is not limited to four, and may be three or less, or may be five or more.

  The stopper portion 541 is located on the positive side of the X axis with respect to the insertion position of the plate-like member 4. The plate-like member 4 is inserted from the negative side of the X axis, and comes into contact with the stopper 541 at the end of the positive side of the X axis, whereby the position of the plate-like member 4 in the X-axis direction is determined. Is done. The state where the plate-like member 4 is inserted into the holding member 5 is also referred to as the inserted state of the plate-like member 4. That is, the end of the plate-like member 4 comes into contact with the stopper portion 541 when the plate-like member 4 is inserted.

  The guide portion 542 is located on each side of the positive direction and the negative direction of the Y axis with respect to the insertion position of the plate-like member 4. The guide part 542 extends along the insertion direction of the plate-like member 4. The guide part 542 is provided in each plate member holding part 54. The plate-like member 4 is brought into contact with the guide portion 542 at the ends on the positive and negative directions of the Y-axis, whereby the position of the plate-like member 4 in the Y-axis direction is determined.

  The support portion 543 is located on the negative side of the Z axis with respect to the insertion position of the plate-like member 4. The support part 543 is provided in each plate-like member holding part 54. The position of the plate member 4 in the Z-axis direction is determined by the plate member 4 coming into contact with the support portion 543 on the surface on the negative direction side of the Z-axis.

  The stopper portion 541 is provided in the plate-like member holding portion 54 that is located on the positive side of the X axis. It can be said that the plate-like member holding portion 54 located on the positive side of the X axis includes an L-shaped rib formed by the stopper portion 541 and the guide portion 542. On the other hand, the stopper part 541 is not provided in the plate-like member holding part 54 located on the negative direction side of the X axis. It can be said that the plate-like member holding portion 54 located on the negative side of the X axis does not include an L-shaped rib. When the stopper portion 541 is not provided on the negative direction side of the X axis, the plate-like member 4 is easily inserted from the negative direction side of the X axis as compared with the case where the stopper portion 541 is provided.

  The support portion 543 may have a recess such as a hole or a groove for holding the adhesive. The stopper part 541 or the guide part 542 may have a hole or a groove for injecting the adhesive into the plate-like member holding part 54.

  The imaging device 1 according to the present embodiment can be manufactured by, for example, a manufacturing method shown in the flowchart of FIG.

  According to the manufacturing method according to the present embodiment, the image sensor 3 is fastened to the holding member 5 that holds the lens 2 (step S1). When the image pickup device 3 is fastened to the holding member 5, the positional relationship between the lens 2 held by the holding member 5 and the image pickup device 3 is determined. That is, in the state where the image sensor 3 is fastened, the position of the light receiving surface of the image sensor 3 viewed from the lens 2 is determined. The light receiving surface of the image sensor 3 is located in the positive direction of the Z axis when viewed from the lens 2. The position of the light receiving surface is represented by a Z coordinate with the center of the lens 2 as the origin.

  According to the manufacturing method according to the present embodiment, the resolution of the imaging device 1 in a state where the imaging device 3 is fastened is measured (step S2). The resolution can be calculated based on the captured image of the resolution chart. The resolution chart may include a pattern in which lines and spaces are repeated, a pattern in which dots are repeated, or a pattern in which lines are arranged in a radial pattern. The resolution chart may include various patterns such as characters or graphics. The closer the captured image of the resolution chart is to the pattern of the original resolution chart, the higher the resolution.

  The resolution changes according to the Z coordinate of the light receiving surface with respect to the center of the lens 2. It is assumed that the Z coordinate of the light receiving surface coincides with the best focus position of the lens 2 when the resolution is maximized. The best focus position of the lens 2 corresponds to a position away from the center of the lens 2 by a focal length. When the Z coordinate of the light receiving surface coincides with the best focus position of the lens 2, it can be said that the distance between the lens 2 and the light receiving surface coincides with the focal length of the lens 2.

  The relationship between the resolution and the Z coordinate of the light receiving surface is also referred to as defocus characteristics. The defocus characteristic is expressed as a graph shown in FIG. 5, for example. The resolution in the defocus characteristic is maximized when the Z coordinate of the light receiving surface is the best focus position. The further the Z coordinate of the light receiving surface is from the best focus position, the lower the resolution can be. The defocus characteristic may be standardized from a result measured in advance. In the process of the flowchart of FIG. 4, the defocus characteristic is assumed to be a standardized characteristic from a result measured in advance. Based on the defocus characteristic, the Z coordinate of the light receiving surface in a state in which the image sensor 3 is fastened can be determined corresponding to the resolution calculated from the imaging result of the resolution chart. Based on the defocus characteristic, the difference between the Z coordinate of the light receiving surface and the best focus position of the lens 2 in a state where the image sensor 3 is fastened can be calculated. The difference between the Z coordinate of the light receiving surface and the best focus position of the lens 2 in a state where the image sensor 3 is fastened is also referred to as a focus shift amount.

  According to the manufacturing method according to the present embodiment, the plate-like member 4 is inserted into the plate-like member holding portion 54 based on the defocus amount (step S3). The focus of the lens 2 is adjusted so that the best focus position of the lens 2 matches the Z coordinate of the light receiving surface of the image sensor 3. That is, the focus of the lens 2 may be adjusted by moving the best focus position of the lens 2. By inserting the plate-like member 4 between the lens 2 and the light receiving surface of the image sensor 3, the best focus position of the lens 2 can be moved. By moving the best focus position of the lens 2 in accordance with the insertion of the plate-like member 4, the imaging apparatus 1 can be configured such that the Z coordinate of the light receiving surface matches the best focus position of the lens 2.

  The focus of the lens 2 can be adjusted by moving the best focus position of the lens 2 by the amount of defocus. That is, as shown in FIG. 5, the focus shift amount can be associated with the focal distance movement amount (Δf). Based on the relationship of the above formula (1), the entire thickness of the inserted plate-like member 4 can be adjusted so that the best focus position of the lens 2 approaches the Z coordinate of the light receiving surface. The focus shift amount can be calculated from the resolution measurement result. That is, the entire thickness of the plate-like member 4 can be adjusted based on the resolution measurement result. The imaging device 1 is configured so that the best focus position of the lens 2 is close to the Z coordinate of the light receiving surface, so that a captured image focused on the subject can be acquired.

  Based on equation (1), the amount of movement of the best focus position of the lens 2 can be made smaller than the amount of change in the overall thickness of the plate-like member 4. The imaging apparatus 1 according to the present embodiment can move the best focus position of the lens 2 with high accuracy by changing the overall thickness of the plate-like member 4.

  On the other hand, the focus of the lens 2 may be adjusted by moving the Z coordinate of the light receiving surface of the image sensor 3. For example, the Z coordinate of the light receiving surface can be moved by inserting a member such as a spacer between the lens 2 and the image sensor 3. The amount of movement of the Z coordinate of the light receiving surface is the same as or substantially the same as the thickness of a member such as a spacer. That is, the accuracy of adjusting the Z coordinate of the light receiving surface is determined according to the accuracy of the thickness of a member such as a spacer.

  The focus of the lens 2 can be adjusted with higher accuracy when adjusted by the overall thickness of the plate-like member 4 than when adjusted by inserting a member such as a spacer.

  In step S <b> 3, an adhesive for joining the plate-like members 4 may be applied or injected into the plate-like member holding portion 54. The adhesive may be injected between the plate member 4 and the plate member holding portion 54 after the plate member 4 is inserted into the plate member holding portion 54. The adhesive may be applied to the stopper portion 541 or the support portion 543 before the plate-like member 4 is inserted. The adhesive can be cured by a process such as drying, heating, or UV light irradiation to join the plate-like member 4 to the plate-like member holding portion 54.

  In step S2 of FIG. 4, the characteristic standardized from the result measured in advance regarding the relationship between the resolution and the Z coordinate of the light receiving surface is regarded as the defocus characteristic. The defocus characteristic may vary depending on individual differences between the lens 2 and the image sensor 3. For example, as in the manufacturing method shown in the flowchart of FIG. 6, the defocus characteristic may be measured before the imaging element 3 is fastened to the holding member 5.

  According to the manufacturing method shown in the flowchart of FIG. 6, the defocus characteristic is measured for a combination in which one holding member 5 holding the lens 2 and one image sensor 3 are selected (step S <b> 11). The defocus characteristic can be measured by calculating the resolution at each Z coordinate while changing the Z coordinate of the light receiving surface. In the measurement of the defocus characteristic, the Z coordinate of the light receiving surface when the resolution is maximum is specified. The resolution may be calculated for the Z coordinate on the positive side of the Z axis from the best focus position of the lens 2. The resolution may be calculated with respect to a Z coordinate corresponding to a range in which the best focus position of the lens 2 can change according to the insertion of the plate-like member 4.

  The processing from step S12 to step S14 is similar to the processing from step S1 to step S3 in FIG. In step S14, the entire thickness of the plate-like member 4 is determined similarly to step S3 of FIG. In step S14, the entire thickness of the plate-like member 4 is determined based on the defocus characteristics of the lens 2 and the image sensor 3 that are actually combined. As a result, the accuracy of adjusting the best focus position of the lens 2 can be improved.

  According to the imaging device 1 according to the present embodiment, after the lens 2 and the imaging device 3 are fastened with screws or the like, the best of the lens 2 is set so that the Z coordinate of the light receiving surface matches the best focus position of the lens 2. The positional relationship between the focus position and the image sensor 3 can be adjusted. When the positional relationship between the best focus position of the lens 2 and the image pickup device 3 is adjusted before fastening of each member, the adjustment may be necessary again due to the positional deviation between the members that may be caused by fastening. That is, by adjusting the positional relationship between the best focus position of the lens 2 and the image pickup element 3 after the fastening of each member, the adjustment of the focus of the lens 2 is less affected by the fastening of a screw or the like. As a result, the Z coordinate of the light receiving surface is easily adjusted to the best focus position of the lens 2.

  According to the imaging device 1 according to the present embodiment, the focus of the lens 2 can be adjusted by changing the overall thickness of the plate-like member 4. The focus adjustment accuracy of the lens 2 is less affected by the dimensional error of the member when adjusted by the overall thickness of the plate-like member 4 than when adjusted by a member such as a spacer. That is, in the present embodiment, the focus of the lens 2 can be adjusted with higher accuracy.

  According to the imaging apparatus 1 according to the present embodiment, the best focus position of the lens 2 can be adjusted by changing the overall thickness of the plate-like member 4. When the plate-like member 4 is an existing member that functions as a cover, a filter, or the like, the best focus position of the lens 2 can be adjusted by adjusting the existing component without adding a new component. As a result, the number of parts can be reduced.

  Although the embodiments according to the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. Accordingly, it should be noted that these variations or modifications are included in the scope of the present disclosure. For example, functions included in each component or step can be rearranged so as not to be logically contradictory, and a plurality of components or steps can be combined into one or divided. It is. Although the embodiment according to the present disclosure has been described centering on an apparatus, the embodiment according to the present disclosure can also be realized as a method including steps executed by each component of the apparatus. The embodiment according to the present disclosure can also be realized as a method, a program, or a storage medium storing a program executed by a processor included in the apparatus. It should be understood that these are included within the scope of the present disclosure.

  In the present disclosure, descriptions such as “first” and “second” are identifiers for distinguishing the configuration. The configurations distinguished by the description of “first” and “second” in the present disclosure can exchange numbers in the configurations. For example, the first lens can exchange the identifiers “first” and “second” with the second lens. The identifier exchange is performed at the same time. The configuration is distinguished even after the identifier is exchanged. The identifier may be deleted. The configuration from which the identifier is deleted is distinguished by a code. Based on only the description of identifiers such as “first” and “second” in the present disclosure, it should not be used as an interpretation of the order of the configuration, or as a basis for the existence of identifiers with smaller numbers.

  In the present disclosure, the X axis, the Y axis, and the Z axis are provided for convenience of description and may be interchanged. The configuration according to the present disclosure has been described using an orthogonal coordinate system configured by the X axis, the Y axis, and the Z axis. The positional relationship between the components according to the present disclosure is not limited to the orthogonal relationship.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Lens 21 1st lens 22 2nd lens 3 Image pick-up element 31 Board | substrate 32 Fastening member 4 Plate-shaped member 5 Holding member 51 1st lens holding part 52 2nd lens holding part 53 Imaging element holding part 54 Plate-shaped member holding | maintenance Part 541 stopper part 542 guide part 543 support part

Claims (6)

A lens,
An image sensor that images a subject image formed by the lens;
At least one plate-like member having optical transparency;
A holding member that holds the lens, the imaging element, and the plate member;
The image pickup apparatus having a plate-like member holding portion in which the holding member can insert the at least one plate-like member having a different overall thickness from a direction intersecting an optical path between the lens and the image pickup element.   The imaging apparatus according to claim 1, wherein the plate-like member is a bandpass filter. The plate-like member holding part is
A guide portion extending along the insertion direction of the plate-like member;
The imaging apparatus according to claim 1, further comprising a stopper portion with which an end portion of the plate-shaped member comes into contact with the plate-shaped member inserted.   The imaging device according to any one of claims 1 to 3, wherein the plate-like member is an IR cut filter. Fastening a holding member that holds a lens and an image pickup device that picks up a subject image formed by the lens;
Measuring the resolution in a state in which the image sensor is fastened;
And a step of inserting at least one plate-like member having light transmittance and having an overall thickness corresponding to the measurement result of the resolution into the holding member.   The method of manufacturing an imaging apparatus according to claim 5, further comprising a step of measuring a defocus characteristic between the lens and the imaging element before the imaging element is fastened to the holding member.

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