Lens unit, optical instrument comprising lens unit, and imaging apparatus

Abstract

To provide a lens unit that, even when a use environment has a wide temperature range, can reduce the possibility that desired optical performance cannot be obtained.SOLUTION: A lens unit comprises a first lens and a second lens. The diameter D1 of the outer peripheral end of the first tapered part of the first lens is made larger than the diameter D2 of the outer peripheral end of the tapered part of the second lens. In an environment at a temperature of 25°C, the outer peripheral end of the first lens tapered part and the outer peripheral end of the second lens tapered part are separated by a predetermined distance. In an environment at a temperature higher or lower than 25°C, the distance between the outer peripheral end of the first lens tapered part and the outer peripheral end of the second lens tapered part is set to be smaller than the predetermined distance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a lens unit, an optical device including the lens unit, and an imaging device. [Background technology]

[0002] Conventionally, when a lens is used in an optical instrument or an imaging device, a lens unit is formed by holding the lens on a holding member, and the lens unit is attached to the optical instrument or imaging device for use. In such a lens unit, for example, a holding hole for mounting the lens is provided in the holding member, and the lens is placed in this holding hole to position it in the optical axis direction. Then, the lens is fixed to the holding frame by, for example, an adhesive. In order not to deteriorate the optical performance of the optical instrument or imaging device at that time, a method of positioning with high accuracy for this position fixing is disclosed in Patent Document 1.

[0003] Patent Document 1 discloses a configuration in which one more holding member is added to the outside of the lens compared to the conventional configuration. Specifically, the holding members are an outer holding member provided with a tapered hole portion having a certain taper angle, and an inner holding member having a cylindrical surface portion on the inner circumference side that holds the lens side surface of the lens. The inner holding member is disposed on the outer circumference side of the lens, and the tapered hole portion of the outer holding member is brought into contact with the tapered surface portion of the inner holding member provided with a taper angle equal to the taper angle of the hole portion, thereby improving the precision of lens positioning during lens assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-113986 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the range of environmental temperatures in which an optical device or an image capture device is used is wide, the lenses are deformed according to the temperature. In such a case, even if multiple lenses are positioned with high accuracy during lens assembly, the desired optical performance may not be obtained due to deformation of the lenses, such as expansion or contraction in a plane perpendicular to the optical axis, at or near the upper or lower limit of the environmental temperature.

[0006] The present disclosure has been made in consideration of the above background, and has as one of its objectives to provide a lens unit that can maintain desired optical performance even when the temperature range of the usage environment is wide. [Means for solving the problem]

[0007] In order to solve the above problems, a lens unit according to one aspect of the present disclosure comprises: a first lens having a first lens tapered portion provided on an outer periphery of a first lens optical surface, and a first lens flat portion provided perpendicular to an optical axis on the outer periphery of the first lens optical surface; a second lens having a second lens optical surface facing the first lens optical surface, a second lens taper portion provided on an outer periphery of the second lens optical surface, spaced apart from and facing the first lens taper portion, and a second lens flat portion provided on the outer periphery of the second lens optical surface, perpendicular to the optical axis, and in contact with the first lens flat portion; a diameter D1 of an outer circumferential end of the first lens taper portion is larger than a diameter D2 of an outer circumferential end of the second lens taper portion; In an environment at a temperature of 25° C., the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion are spaced apart by a predetermined distance; In an environment where the temperature is higher or lower than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to provide a lens unit that can maintain desired optical performance even when the temperature range of the usage environment is wide. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a plan view of a lens unit according to an embodiment of the present disclosure. [Diagram 2] 2 is a cross-sectional view taken along line AA of the lens unit shown in FIG. [Diagram 3] FIG. 3 is an exploded cross-sectional view of the lens unit shown in FIG. [Figure 4] 2 is an enlarged cross-sectional view of a contact portion between a first lens and a second lens shown in FIG. 1. [Diagram 5] 1 is a flowchart showing one embodiment of a manufacturing method of a lens unit. [Figure 6] FIG. 11 is a cross-sectional view showing a modified example of the lens unit. [Figure 7(a)] 1 is an external perspective view of an in-vehicle camera equipped with a lens unit according to the present disclosure. [Figure 7(b)] 1 is a diagram showing an outline of components of an in-vehicle camera equipped with a lens unit according to the present disclosure. [Figure 8] FIG. 11 is a cross-sectional view of a lens unit used in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Exemplary embodiments for carrying out the present disclosure will be described in detail with reference to the accompanying drawings. However, the dimensions, materials, and relative positions of components described in the following embodiments are arbitrary, and the configuration of the device to which the present disclosure is applied can be changed according to various conditions. In addition, the same reference numerals are used in the drawings to indicate elements that are the same or functionally similar.

[0011] It is anticipated that the lens unit according to the present disclosure will be used in, for example, surveillance cameras used outdoors, vehicle-mounted cameras, and the like, in a temperature range ranging from low temperatures of minus several tens of degrees to high temperatures of around 100 degrees. In the following description, for convenience, the direction along the optical axis of the lens unit is defined as the optical axis direction, and the direction along a plane perpendicular to the optical axis is defined as the horizontal direction.

[0012] First Embodiment A first embodiment of the present disclosure will be described below with reference to Figs. 1 to 5. Fig. 1 shows a plan view of a lens unit 1 according to the first embodiment of the present disclosure, and Fig. 2 shows a schematic configuration of a cross section taken along line AA of the lens unit 1 in Fig. 1. Fig. 3 is an exploded cross-sectional view of the lens unit in Fig. 2, and Fig. 4 is an enlarged cross-sectional view of a contact portion between a first lens 11 and a second lens 12.

[0013] The lens unit 1 according to this embodiment includes a first lens 11, a second lens 12, a pressing member 13, and a holding member 14. In this embodiment, the pressing member 13 has a ring shape. The holding member 14 has a cylindrical shape and has an abutment portion 141 protruding inward from one end side of the cylindrical shape. Both lenses are inserted into the cylindrical shape in the order of the second lens 12 and the first lens 11 until the second lens 12 abuts against the abutment portion 141. Then, the pressing member 13 is inserted into the cylindrical shape behind the first lens 11, and these lenses are sandwiched between the holding portion abutment portion 141 and the pressing member 13, thereby fixing these lenses in the holding member 14.

[0014] In order to mount the lens unit 1 on a surveillance camera or an in-vehicle camera, it is assumed that the lens unit 1 will be exposed to a low temperature environment of -40 degrees to a high temperature environment of 100 degrees. Here, the first lens 11 and the second lens 12 are often manufactured as glass lenses made of different materials, and in this case, the linear expansion coefficients of the lenses are also different. When the environmental temperature changes, for example, in the shape of the first lens and the second lens described in detail later, the lens surfaces or the ends of the tapered surfaces described later may come into contact with each other due to radial expansion or the like, and the radial positional relationship may change. Such a change in the positional relationship caused by the environmental temperature may cause the optical performance to be not obtained at an environmental temperature of -40 degrees or 100 degrees, even if a predetermined optical performance can be achieved during lens assembly in a room temperature environment of 25 degrees, for example.

[0015] The present disclosure has been made from such a viewpoint. The lens unit 1 of the present embodiment suppresses the change in the lens spacing and reduces the deterioration of optical performance even when the individual lenses undergo thermal expansion or thermal contraction due to an environmental temperature of -40 degrees or 100 degrees. Next, a specific method for suppressing the change in the lens spacing will be described.

[0016] FIG. 3 shows an exploded cross-sectional view of the lens unit 1 described above. As shown in FIG. 3, the first lens 11 has a first lens flat portion 111, a first lens tapered portion 113, a first lens optical surface 115, a first lens pressing surface 117, and a first lens side surface 119. The first lens optical surface 115 is a surface disposed at a position facing the second lens 12, and constitutes an optically effective portion of the first lens 11. The first lens flat portion 111 is a flat surface perpendicular to the optical axis provided on the outer periphery of the first lens optical surface 115 on the side where the second lens 12 is located. The first lens tapered portion 113 is a surface provided on the outer periphery of the first lens optical surface 115 and on the inner periphery of the first lens flat portion 111, and is configured to have a conical surface shape. In this embodiment, the first lens taper portion 113 is provided so as to be continuous from the first lens optical surface 115 at the outer periphery of the first lens optical surface 115 and to be continuous with the first lens flat surface portion 111 at the inner periphery of the first lens flat surface portion 111. However, a first rounded portion having a curvature different from that of the first lens optical surface 115 is provided between the outer periphery of the first lens optical surface 115 and the first lens taper portion 113, so that they are not continuous. Also, a second rounded portion having a curvature is provided between the first lens taper portion 113 and the first lens flat surface portion 111, so that they are not continuous. The first lens pressing surface 117 is provided on the outer periphery of the surface opposite to the second lens 12 and is a surface that abuts against the pressing member 13. The first lens side surface 119 is configured as a surface that is parallel to the optical axis and faces the inner periphery of the holding member 14.

[0017] The second lens 12 has a second lens flat portion 122, a second lens tapered portion 124, a second lens optical surface 126, a holding member contact surface 128, and a second lens side surface 130. The second lens optical surface 126 is a surface disposed so as to face the first lens optical surface 115, and constitutes an optically effective portion of the second lens 12. The second lens flat portion 122 is a flat surface perpendicular to the optical axis provided on the outer periphery of the second lens optical surface 126 on the side where the first lens 11 is located. The second lens tapered portion 124 is a surface provided on the outer periphery of the second lens optical surface 126 and on the inner periphery of the second lens flat portion 122, and is configured to have a conical surface shape. In this embodiment, the second lens tapered portion 124 is provided so as to be continuous with the second lens optical surface 126 on the outer periphery of the second lens optical surface 126. However, a third radiused portion having a curvature different from that of the second lens optical surface 126 may be provided between the outer periphery of the second lens optical surface 126 and the second lens taper portion 124, so that they are not continuous. Also, a fourth radiused portion having a curvature may be provided between the second lens taper portion 124 and the second lens flat portion 122, so that they are not continuous. The holding member contact surface 128 is a surface that comes into contact with the holding portion abutment portion 141. The second lens side surface 130 is configured as a surface that is parallel to the optical axis and faces the inner peripheral surface of the holding member 14.

[0018] At this time, the inner and outer diameters of the first lens flat portion 111 and the second lens flat portion 122 are determined so that at least a portion of each annular shape can abut against each other. The outer and inner diameters of the first lens taper portion 113 and the outer and inner diameters of the second lens taper portion 124 are determined according to the relationship between the outer and inner diameters of these taper portions, the linear expansion coefficients of the first lens 11 and the second lens 12, and the expected environmental temperature.

[0019] Specifically, the linear expansion coefficient of the first lens 11 having a large inner diameter of the tapered portion is α1, and the outer diameter of the outer circumferential end of the tapered portion is D1 [mm]. The linear expansion coefficient of the second lens 12 having a small inner diameter of the tapered portion is α2, and the outer diameter of the outer circumferential end of the tapered portion is D2 [mm]. The maximum environmental temperature is TH, the minimum environmental temperature is TL, and the radial gap between the tapered portion outer diameter D1 of the first lens tapered portion 113 and the tapered portion outer diameter D2 of the second lens tapered portion 124 in an environment of temperature 25 degrees with the first lens flat portion 111 and the second lens flat portion 122 approximately abutting is A [mm]. At this time, if the relationship of the linear expansion coefficient is α1<α2, the gap amount A becomes smaller when the environmental temperature becomes high. At that time, the minimum value of the gap amount A that changes due to temperature rise is determined by the following formula (1). In this case, if the maximum environmental temperature TH is in the range of 25 degrees to 80 degrees, and if the linear expansion coefficient relationship is α1<α2, the gap amount A is equal to or greater than the distance determined by 55×(α2-α1)×D2. Also, if the maximum environmental temperature TH is in the range of 25 degrees to 100 degrees, and if the linear expansion coefficient relationship is α1<α2, the gap amount A is equal to or greater than the distance determined by 75×(α2-α1)×D2. A=(TH-25)×(α2-α1)×D2 (Formula 1)

[0020] Furthermore, when the linear expansion coefficient relationship is α1>α2, the void volume A decreases when the ambient temperature drops. In this case, the value of the void volume A that changes with temperature drop is determined by the following formula (2). If the minimum ambient temperature TL is in the range of 25 degrees to -20 degrees, and the linear expansion coefficient relationship is α1>α2, the void volume A is greater than or equal to the distance determined by 45×(α1-α2)×D1. If the minimum ambient temperature TL is in the range of 25 degrees to -40 degrees, and the linear expansion coefficient relationship is α1>α2, the void volume A is greater than or equal to the distance determined by 65×(α1-α2)×D1. A=(25-TL)×(α1-α2)×D1 (Formula 2)

[0021] Note that the temperature during the manufacture of the lens unit 1 (25 degrees) can be defined as the reference temperature Ts, and the assumed operating temperatures (TH, TL) can be defined as Td. At this time, for the parts (TH - 25)×(α2 - α1) and (25 - TL)×(α1 - α2) in the above two equations, they can be summarized as a coefficient of (Td - Ts)×(α2 - α1). When Td ≥ Ts, the clearance A is determined based on this coefficient and the outer diameter D2 of the tapered portion of the second lens 12. When Td < Ts, the clearance A is determined based on this coefficient and the outer diameter D1 of the tapered portion of the first lens 11. And the outer diameter D1 of the tapered portion 113 of the first lens taper is set such that D2 + A ≤ D1 ≤ D2 + 2A. A more preferable outer diameter D1 of the tapered portion 113 of the first lens is D2 + A.

[0022] At the reference temperature Ts, the difference between the outer diameter D1 of the tapered portion and the outer diameter D2 of the tapered portion is set to a value larger than the clearance A calculated as above. By setting the difference between these outer diameters at the reference temperature Ts to such a value, it is possible to avoid the tapered portions of the respective lenses coming into contact due to thermal deformation over the entire environmental temperature range from -40 degrees to 100 degrees. Furthermore, it is possible to suppress the occurrence of the tapered portion riding up. As a result, even if thermal expansion or thermal contraction occurs in each lens, the possibility of the desired optical performance not being obtained in the lens unit 1 can be reduced.

[0023] Next, a suitable taper angle θ on the tapered surface of each lens will be described with reference to FIG. 4. FIG. 4 is an enlarged cross-sectional view of the contact portion between the first lens 11 and the second lens 12. In the following description, the taper angle θ is the angle formed by the optical axis and the tapered surface in cross-section A - A.

[0024] Here, in order to obtain a stable inter-lens distance in the optical axis direction between the first lens 11 and the second lens 12 during assembly of the lens unit 1, it is preferable that the taper angle θ is equal to or greater than 45 degrees and less than 90 degrees. By setting the taper angle θ to such a value, the second lens 12 and the first lens 11 can be easily inserted into the holding member 14 until their contact surfaces come into contact with each other. Also, in order to bring the first and second lens flat portions 111 and 122 of both lenses into contact with each other, it is necessary to have a gap between the first and second lens taper portions 113 and 124, so it is preferable that the taper angles θ of both taper portions are the same.

[0025] Moreover, when assembling the lens unit 1, the first lens 11 is pushed into the inside of the holding member 14 while the first lens taper portion 113 is partially in contact with the second lens taper portion 124. By continuing the insertion of the first lens 11 into the holding member 14 in this state, the first lens 11 is aligned with the second lens 12, and finally, the first lens flat portion 111 abuts against the second lens flat portion 122, and this insertion operation is completed. Here, when the static friction coefficient between the second lens flat portion 122 and the first lens flat portion 111 is 0.5 or less, if the taper angle θ is less than 67 degrees, particularly suitable alignment is performed even if the load during pushing is small. Furthermore, by applying vibration in the horizontal direction (in a plane perpendicular to the pushing direction) while satisfying the condition of this taper angle θ, it is possible to perform alignment more smoothly.

[0026] From the above, it is preferable that the taper angle θ of the first lens taper portion 113 is equal to the taper angle θ of the second lens taper portion 124, and is in the range of 45 degrees or more and less than 90 degrees with respect to the optical axis of the lens from the viewpoint of lens workability and ease of assembly. From the viewpoint of centering of both lenses, it is more preferable that the taper angle θ is an angle of 45 degrees or more and less than 67 degrees. When the taper angle θ satisfies this condition, it is possible to easily manufacture the lens unit 1 with reduced possibility that the desired optical performance will not be obtained even if thermal expansion or thermal contraction occurs in each lens.

[0027] Next, the assembly of the lens unit 1 according to one embodiment of the present disclosure will be described with reference to the flowchart in Fig. 5. Assembling of the lens unit 1 is performed at a normal temperature of 25°C. Also, the lens unit 1 is assembled so that the maximum environmental temperature TH is 100°C and the gap amount A at a temperature of 25°C is 5 μm (0.005 mm).

[0028] First, in step S501, the material of the first lens 11, the material of the second lens 12, and the shape of each optical surface are determined based on the optical conditions required for the lens unit 1. Next, in step S502, the linear expansion coefficient α1 of the first lens 11, the linear expansion coefficient α2 of the second lens 12, the environmental temperature (reference temperature Ts) during the manufacture of the lens unit, and the expected use temperature (Td) are referenced. Then, based on these and the magnitude relationship between Ts and Td, it is determined which one to use. The amount of gap A is determined based on either the outer diameter D1 or D2 of the tapered portion of the first and second lenses 11 and 12. As a result, the dimensions of the first lens 11 and the second lens 12 are determined, and these lenses are manufactured.

[0029] 5, in step S503, the second lens 12 is inserted into the holding member 14. This operation is ended in step S504 when the holding member contact surface 128 of the second lens is brought into contact with the abutment portion 141 of the holding member 14. At this time, it does not matter whether the second lens side surface 130 of the second lens is in contact with the holding member 14 or not.

[0030] Next, in step S505, the first lens 11 is inserted into the holding member 14. At this time, if the taper angle θ of the first and second lens taper portions 113, 124 with respect to the optical axis is equal to or greater than 67 degrees and less than 90 degrees, the insertion is performed while applying vibration to the holding member 14 and the first lens 11 in a direction within a plane perpendicular to the insertion direction (horizontal direction). This operation ends in step S506 when the first lens flat portion 111 is brought into contact with the second lens flat portion 122.

[0031] The first lens 11 and the second lens 12 are made of a glass material, and the taper angle θ is set to 67 degrees or more and less than 90 degrees. Furthermore, as described above, the first lens 11 is vibrated in a horizontal plane when inserted, thereby aligning the optical axes of these lenses. Therefore, if either the first lens side surface 119 of the first lens 11 or the second lens side surface 130 of the second lens 12 is fixed to the inner circumference of the holding member 14, the other lens is also disposed at a desired position relative to the holding member 14. In addition, by determining which of the first lens side surface 119 and the second lens side surface 130 is to abut against the holding member 14 according to the relationship between the expected temperature Td during use and the reference temperature Ts, it is possible to eliminate the constraint from the abutting surface against the thermal deformation of the lens that is not abutting. As described above, by making only one of these lenses abut against the inside of the holding member 14, it is easy to align the optical axes of each lens. However, in cases where the restriction on the outer diameter of the lenses by the holding member 14 is not a significant problem, for example, because the expected temperature Td is not significantly different from the reference temperature Ts, or because the holding member 14 is relatively easy to deform, both lenses may abut against the inside of the holding member 14.

[0032] Finally, in step S507, pressing member 13 is inserted into holding member 14. Then, in step S508, pressing member 13 is brought into contact with first lens pressing surface 117, and the pressing member 13 is fixed to holding member 14. For example, by going through the above steps, a lens unit according to the present disclosure can be manufactured.

[0033] In the above embodiment, the pressing member 13 is shown as a cylindrical part such as a crimping ring, but the form is not limited to the shape of the embodiment. For example, parts such as a plurality of pawls or screws can be used as the pressing member 13. Also, the above-mentioned manufacturing method is one example, and the steps other than the method of determining the gap amount A in step S502 can be replaced by various known and available methods.

[0034] Furthermore, in order to obtain the effects of the present disclosure, it is preferable that both lenses expand or contract individually in response to the environmental temperature, and therefore it is preferable that first lens optical surface 125 of first lens 11 and second lens optical surface 126 of second lens 12 are separated from each other. However, the present disclosure is not limited to such an embodiment, and as long as a certain degree of deformation of both lenses is tolerable, an optical resin or the like may be filled between both optical surfaces.

[0035] <Modification of the first embodiment> In the first embodiment, as shown in FIG. 3, the positional relationship between the first lens flat portion 111 and the first lens tapered portion 113 in the first lens 11 is such that the flat portion is on the outer periphery side. In addition, the positional relationship between the second lens flat portion 122 and the second lens tapered portion 124 in the second lens 12 is such that the flat portion is on the outer periphery side. However, the positional relationship between the flat portion and the tapered portion in these lenses may be reversed. Such a configuration will be described below with reference to FIG. 6. FIG. 6 shows a lens unit 61 according to this modified example in the same format as FIG. 2 or FIG. 3.

[0036] In this modification, the first lens 611 has a first lens flat portion 6111, a first lens tapered portion 6113, a first lens optical surface 6115, and a first lens side surface 6119. In this modification, there is no surface corresponding to the first lens pressing surface 117, and the pressing member 13 presses the upper curved surface of the first lens 611 toward the second lens 612 in the optical axis direction. The first lens optical surface 6115 is a surface disposed at a position facing the second lens 612, and constitutes the optical surface of the first lens 611. The first lens flat portion 6111 is a flat surface perpendicular to the optical axis provided on the outer periphery of the first lens optical surface 6115 on the side where the second lens 612 is located. The first lens flat portion 6111 is a surface that is continuous from the first lens optical surface 6115 at the outer periphery of the first lens optical surface 6115 and is continuous with the first lens flat portion 6111 at the inner periphery of the first lens taper portion 6113. The first lens taper portion 6113 is configured to have a conical surface shape. The first lens side surface 6119 is configured as a surface that is parallel to the optical axis and faces the inner periphery surface of the holding member 14.

[0037] The second lens 612 has a second lens flat portion 6122, a second lens tapered portion 6124, a second lens optical surface 6126, a holding member contact surface 6128, and a second lens side surface 6130. The second lens optical surface 6126 is a surface disposed so as to face the first lens optical surface 6115, and constitutes the optical surface of the second lens 612. The second lens flat portion 6122 is a flat surface perpendicular to the optical axis provided on the outer periphery of the second lens optical surface 6126 on the side where the first lens 611 is located. The second lens tapered portion 6124 is a surface provided so as to be continuous with the second lens flat portion 6122 on the outer periphery of the second lens flat portion 6122, and is configured to have a conical surface shape. The holding member contact surface 6128 is a surface that comes into contact with the holding portion abutting portion 141. Second lens side surface 6130 is configured as a surface that is parallel to the optical axis and faces the inner circumferential surface of holding member 14.

[0038] In the lens unit 61 having such a configuration, the gap amount A between the inner circumferential ends of both tapered portions 6113, 6124 when the first lens flat portion 6111 and the second lens flat portion 6122 are in contact with each other can be obtained by the same formula as in the first embodiment. Therefore, even in the lens unit 61 having such a configuration, it is possible to reduce the possibility that the desired optical performance will not be obtained even if thermal expansion or thermal contraction occurs in each lens.

[0039] <Application example of the first embodiment> Next, an imaging device equipped with the lens unit 1 according to the first embodiment described above, an example of which is an on-vehicle camera, will be described with reference to the drawings. Fig. 7 shows a schematic configuration of the on-vehicle camera according to the present disclosure, with Fig. 7(a) showing an external perspective view and Fig. 7(b) showing an outline of the components.

[0040] The vehicle-mounted camera 100 according to the present disclosure includes an internal optical system 102 having a plurality of lenses, an imaging element 103 that receives light that has passed through the optical system, and a housing 101 that includes these components and to which the lens unit 1 described as the first embodiment is applied. The vehicle-mounted camera 100 is assumed to be mounted in an automobile that is exposed to direct sunlight outdoors in summer, for example, and placed in a temperature environment of several tens of degrees. By using the lens unit 1 according to the first embodiment, it is possible to reduce the possibility that the lens unit 1 will not be able to achieve the desired optical performance even in such an environment. The imaging element 103 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. The image sensor has a function of converting light incident via the optical system 102 into an electrical signal.

[0041] As described above, the lens unit 1 according to the present disclosure includes at least a first lens 11 and a second lens 12. The first lens 11 has, for example, a first lens optical surface 115, a first lens taper portion 113 provided on the outer periphery of the first lens optical surface 115, and a first lens flat portion 111 provided perpendicular to the optical axis on the outer periphery of the first lens optical surface 115. The second lens 12 has, for example, a second lens optical surface 126 facing the first lens optical surface 115, and a second lens taper portion 124 provided on the outer periphery of the second lens optical surface 126 facing the first lens taper portion 113. The second lens 12 further has a second lens flat portion 122 provided perpendicular to the optical axis on the outer periphery of the second lens optical surface 126 and arranged to abut against the first lens flat portion 111. When the taper portion outer diameter D1 of the outer peripheral end of the first lens taper portion 113 is larger than the taper portion outer diameter D2 of the outer peripheral end of the second lens taper portion 124, the linear expansion coefficient α1 of the first lens 11 and the linear expansion coefficient α2 of the second lens 12 are selected. This selection is made such that the distance between these outer peripheral ends decreases as the difference between the reference temperature Ts during manufacturing and the assumed temperature Td during use increases. Further, when D1 is larger than D2, the predetermined distance (gap amount A) at the reference temperature Ts between the outer peripheral end of the first lens taper portion and the outer peripheral end of the second lens taper portion in a state where the first lens flat portion 111 and the second lens flat portion 122 are in contact is determined as follows. That is, when Td ≧ Ts, it is determined based on D2 as shown in Equation (1), and when Td < Ts, it is determined based on D1 as shown in Equation (2). Specifically, the outer diameter D1 of the outer peripheral end of the first lens taper portion 113 is preferably set larger than the outer diameter D2 of the outer peripheral end of the second lens taper portion 124. Also, at this time, in an environment at a temperature of 25°C, the distance between the outer peripheral end of the first lens taper portion 113 and the outer peripheral end of the second lens taper portion 124 is set to be separated by a predetermined distance. Then, in an environment at a temperature higher or lower than 25°C, the distance between the outer peripheral end of the first lens taper portion 113 and the outer peripheral end of the second lens taper portion 124 is set to be smaller than the predetermined distance.

[0042] More specifically, when Td ≥ Ts, the void fraction A is determined by the difference between Td and Ts, the difference between α1 and α2, and D2 (Equation (1)). When Td < Ts, the void fraction A is determined by the difference between Td and Ts, the difference between α1 and α2, and D1 (Equation (2)). In the above-described embodiment, as the reference temperature Ts, for example, 25 degrees, which is the temperature during manufacturing because it is easy to determine the diameter at the time of design, is adopted. However, the reference temperature Ts is not limited to this. For example, when considering mounting the lens unit on an in-vehicle camera, the average temperature of the usage environment of the in-vehicle camera may be used as the reference temperature Ts. Also, as the assumed temperature Td, 100 degrees is adopted in the embodiment, but the upper limit of the assumed temperature is not limited to 100 degrees. For example, it may be set by multiplying a safety factor by the maximum value of the temperature of the in-vehicle camera actually measured outdoors. Note that, as in the embodiment, when Ts is 25 degrees and Td is 100 degrees, the void fraction A can be set to be equal to or greater than the distance determined by 75×(α2 - α1)×D2 obtained from Equation (1).

[0043] Also, in the above-described embodiment, the case where Td is -40 degrees as the lower limit of the assumed temperature is adopted. However, for example, it may be set by multiplying a safety factor by the minimum value of the temperature of the in-vehicle camera actually measured outdoors. Note that, as in the embodiment, when Ts is 25 degrees and Td is -40 degrees, the void fraction A is preferably set to be equal to or greater than the distance determined by 65×(α1 - α2)×D1 obtained from Equation (2).

[0044] The angles formed by the first lens taper portion 113 of the first lens 11 and the second lens taper portion 124 of the second lens 12 with the optical axis are preferably 45 degrees or more and less than 90 degrees from the viewpoint of manufacturing the lens unit 1. The formed angles are more preferably 45 degrees or more and less than 67 degrees.

[0045] As described above, the lens unit 1 according to the present disclosure also includes a holding member 14 that houses the first lens 11 and the second lens 12 and has an abutment portion 141 that abuts against a holding member contact surface 128 provided on the surface opposite to the second lens flat portion 122. The abutment portion 141 can be provided so as to protrude inward from the inner peripheral surface of the holding member 14 having a cylindrical shape. The lens unit 1 also includes a pressing member 13 that abuts against the surface (117) opposite to the first lens flat portion 111 and clamps the first lens 11 and the second lens 12 together with the abutment portion 141. At least one of the outer peripheral surface (side surface 119) of the first lens 11 and the outer peripheral surface (side surface 130) of the second lens 12, or both, can be abutted against the inner peripheral surface of the holding member 14. In the illustrated embodiment, the first lens optical surface 115 and the second lens optical surface 126 are spaced apart from each other. However, the present disclosure is not limited to the embodiment, and the space between these optical surfaces may be filled with, for example, an optical resin.

[0046] In addition, the present disclosure can also be configured as a method for manufacturing the above-described lens unit. The method includes inserting the second lens 12 into the holding member 14, inserting the first lens 11 into the holding member 14, and continuing this until the first lens flat surface portion 111 abuts against the second lens flat surface portion 122. The method further includes inserting the pressing member 13 into the holding member 14 to fix these lenses to the holding member 14. Also, when fixing the lens, the pressing member 13 presses and fixes the first lens 11 in the insertion direction of the first lens 11 from the surface opposite to the surface where the first lens flat surface portion 111 of the first lens 11 is provided. Here, let the diameter of the outer peripheral end of the first lens tapered portion 113 be the tapered portion outer diameter D1, and the diameter of the outer peripheral end of the second lens tapered portion 124 be the tapered portion outer diameter D2. Let the linear expansion coefficient of the first lens 11 be α1, and the linear expansion coefficient of the second lens 12 be α2. And let the reference temperature during the manufacture of the lens unit 1 be Ts, and the assumed temperature during the use of the lens unit 1 be Td. Further, in the lens unit 1, assume that D1 is larger than D2. At this time, in the state where the first lens flat surface portion 111 and the second lens flat surface portion 122 are in contact, when Td ≧ Ts, the void amount A at Ts determined based on D2 is obtained, and when Td < Ts, the void amount A at Ts determined based on D1 is obtained. Then, the D1 set as D1 = D2 + 2A in the first lens 11 is used as the outer diameter of the first tapered portion.

[0047] By using the lens unit 1 as described above or the lens unit 1 obtained by the manufacturing method, in the lens unit 1, it is possible to reduce the possibility that the desired optical performance cannot be obtained even in the use environment of, for example, an in-vehicle camera. Although the present disclosure shows an example in which the lens unit 1 is applied to an in-vehicle camera, the lens unit 1 is also applicable to a compact digital camera, a single-lens reflex digital camera, a mirrorless digital camera, mobile devices such as smartphones and tablets, which are imaging devices other than in-vehicle cameras. Also, as an optical device, it is also applicable to binoculars, microscopes, telescopes, etc.

[0048] <Example> The effects of the present disclosure will be described below with reference to examples that embody the present disclosure and comparative examples for the examples. Note that the following examples are examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0049] The positional fluctuation of each lens in the optical axis direction was measured by placing CL-P015 and CL-P070, multi-color laser coaxial displacement meters of the CL-3000 series manufactured by KEYENCE, above and below the lens unit 1.

[0050] [Example 1] The lens unit 1 according to this embodiment has a cross-sectional shape shown in Fig. 2. In this embodiment, the first lens 11 is made of M-TAFD305 (manufactured by HOYA: linear expansion coefficient α1 = 60 × 10 -7 / °C). The lens shape was a convex meniscus lens with an outer diameter of Φ32.4 mm, a total height of 10.0 mm, a center thickness of 5.0 mm, and an edge thickness of 1.7 mm. The second lens 12 was made of M-BACD12 (manufactured by HOYA: linear expansion coefficient α2 = 69 × 10 -7 / ℃) was used. The lens shape was a concave meniscus lens with an outer diameter of Φ32.4 mm, total height of 7.6 mm, center thickness of 1.9 mm, edge thickness of 3.6 mm, and tapered outer diameter D2 of Φ28.0 mm. The lens unit was designed with the maximum environmental temperature TH set to 100 degrees.

[0051] In this embodiment, the relationship between the linear expansion coefficient α1 of the first lens 11 having the large taper portion outer diameter D1 and the linear expansion coefficient α2 of the second lens 12 having the small taper portion outer diameter D2 is α1≦α2. If the ambient temperature during manufacturing, 25 degrees, is taken as the reference temperature Ts, the amount of gap A between the outer circumferential end of the first lens taper portion 113 and the outer circumferential end of the second lens taper portion 124 can be calculated using the following formula (1). A=(TH-25)×(α2-α1)×D2 (Formula 1) Since A≈0.002 [mm], the outer diameter D1 of the tapered portion of the first lens 11 is obtained by adding A to D2, which is Φ28.002. In addition, the angle between the optical axis and the first lens tapered portion 113 and the second lens tapered portion 124 is set to 60 degrees, and a flat portion is disposed on the outside of the tapered portion.

[0052] Next, in a location where the room temperature was 25°C, the second lens 12 and the first lens 11 were inserted in this order into the holding member 14. At this time, by applying a force from the optical axis direction, the tapered portions 113, 124 of the first and second lenses acted as guides and these lenses were inserted into the holding member 14. After the first lens 11 was inserted, when the first lens flat portion 111 and the second lens flat portion 122 were observed from above the first lens 11, it was confirmed that interference fringes were present.

[0053] Finally, the first lens 11 was held down from above using a crimping ring (holding member 13) to assemble the lens unit 1. After that, KEYENCE CL-3000 series CL-P015 multi-color laser coaxial displacement meter was placed above and below the lens unit to measure the positional relationship of the lenses. At this time, in order to bring the horizontal position closer to the center of the lenses, the first lens 11 was aligned with the apex and the second lens 12 was aligned with the bottom, and the total height of the center of the lens unit 1 was measured to be 7.740 mm.

[0054] Next, the entire lens unit 1 was heated to a temperature of 100°C using a heater and measured again using the same method, finding that the total height of the center of the lens unit 1 was 7.744 mm. The variation in the total height of the center of the lens unit 1 calculated from the shape and linear expansion coefficient of the lens unit 1 was 3.4 μm, confirming that the variation in the distance between the first lens 11 and the second lens 12 was favorable at 1 μm or less.

[0055] [Comparative Example 1] Next, as a comparative example, a lens unit 1 was produced under the following conditions, and measurements were carried out in the same manner as in Example 1. The details are described below.

[0056] In this comparative example, the first lens 11 is made of M-TAFD305 (manufactured by HOYA; linear expansion coefficient 60×10 -7 / °C), an outer diameter Φ32.4 mm, a total height 10.0 mm, a center thickness 5.0 mm, an edge thickness 1.7 mm, and a tapered outer diameter Φ28.0 mm. -7 A concave meniscus lens with a temperature of 30°C (100°F), outer diameter Φ32.4 mm, total height 7.6 mm, center thickness 1.9 mm, edge thickness 3.6 mm, and tapered outer diameter Φ28.0 mm was used. The maximum environmental temperature TH was set to 100°C. The angle between the first lens tapered portion and the second lens tapered portion and the optical axis was set to 30°, and a flat portion was placed on the outside of the tapered portion.

[0057] Next, in a location with an indoor temperature of 25°C, the second lens 12 and the first lens 11 were inserted in this order into the holding member 14. At this time, by applying force from the optical axis direction, the tapered portions of the first and second lenses acted as guides, and these lenses were inserted into the holding member 14. After the first lens 11 was inserted, when the flat portion and tapered portion of the first lens 11 and the second lens 12 were observed from above the first lens 11, it was confirmed that interference fringes were formed on both.

[0058] Finally, the first lens 11 was held down from above using a crimping ring to assemble the lens unit 1. After that, KEYENCE CL-3000 series CL-P015 multi-color laser coaxial displacement meter was placed above and below the lens unit 1 to measure the positional relationship of the lenses. At this time, in order to bring the horizontal position closer to the center of the lenses, the first lens 11 was aligned with the apex and the second lens 12 was aligned with the bottom, and the total height of the center of the lens unit 1 was measured to be 7.740 mm.

[0059] Next, the entire lens unit 1 was heated to a temperature of 100° C. using a heater and measured again using the same method, and the total height of the center of the lens unit was 7.747 mm. The variation in the total height of the center of the lens unit 1 calculated from the shape of the lens unit and the linear expansion coefficient was 3.4 μm, so the variation in the distance between the first lens 11 and the second lens 12 was 3 μm or more.

[0060] [Example 2] In this embodiment, a lens unit 81 having a structure shown in Fig. 8 is used. Fig. 8 shows the lens unit 81 used in this embodiment in the same format as Fig. 2 or Fig. 3. Lens unit 81 used in this embodiment differs from lens unit 1 described in Fig. 2 or Fig. 3 in that second lens 812 is a double-convex lens.

[0061] In this embodiment, the first lens 811 is made of M-BACD12 (manufactured by HOYA; linear expansion coefficient 69×10 -7 / °C), an outer diameter of Φ25.5 mm, a total height of 8.0 mm, a center thickness of 1.8 mm, an edge thickness of 2.7 mm, and a tapered outer diameter D1 of Φ22.5 mm were used. -7 / °C), an outer diameter of Φ27.0 mm, a center thickness of 7.0 mm, and an edge thickness of 1.5 mm were used. The lens unit 81 was designed with the minimum environmental temperature TL set to -40 degrees.

[0062] In this embodiment, the relationship between the linear expansion coefficient α1 of first lens 811 having a large taper portion outer diameter D1 and the linear expansion coefficient α2 of second lens 812 having a small taper portion outer diameter D2 is α1>α2. If the ambient temperature during manufacturing, 25 degrees, is taken as the reference temperature Ts, the amount of gap A between the outer circumferential end of first lens taper portion 8113 and the outer circumferential end of second lens taper portion 8124 can be calculated using the following formula (2). A=(25-TL)×(α1-α2)×D1 (Formula 2) Since A≈0.0015 [mm], the outer diameter D1 of the tapered portion of the first lens 811 is obtained by subtracting A from D2 to obtain Φ22.4985. In addition, the angle between the optical axis and the first lens tapered portion 8113 and the second lens tapered portion 8124 is set to 70 degrees, and a flat portion is disposed on the outer side of the tapered surface.

[0063] Next, in a location where the room temperature was 25°C, the second lens 812 and the first lens 811 were inserted in this order into the holding member 14. At this time, by applying a force from the optical axis direction, the first and second lens tapered portions 8113, 8124 acted as guides and these lenses were inserted into the holding member 14. After the first lens 811 was inserted, when the first lens flat portion 8111 and the second lens flat portion 8122 were observed from above the first lens 811, it was confirmed that interference fringes were produced.

[0064] Finally, the first lens 811 was pressed from above using a crimping ring (pressing member 13) to assemble the lens unit 81. After that, KEYENCE CL-3000 series CL-P015 multi-color laser coaxial displacement meter was placed above and below the lens unit to measure the positional relationship of the lenses. At this time, the horizontal position was aligned with the vertices of the first lens 811 and second lens 812 to get close to the center of the lenses, and the measurement revealed that the total height of the center of the lens unit 81 was 12.2 mm.

[0065] Next, the entire lens unit 81 was cooled to a temperature of -40°C and measured again using the same method, and the total height of the center of lens unit 81 was 12.195 mm. The variation in the total height of the center of lens unit 81 calculated from the shape and linear expansion coefficient of lens unit 81 was 5.2 μm, confirming that the variation in the distance between first lens 811 and second lens 812 was favorable at 1 μm or less.

[0066] As described above, according to the lens unit of this embodiment, the lens positioning accuracy can be improved, and this high accuracy can be maintained within the environmental temperature range of -40 degrees to 100 degrees.

[0067] The above disclosure includes the following configurations. (Configuration 1) a first lens having a first lens tapered portion provided on an outer periphery of a first lens optical surface, and a first lens flat portion provided on the outer periphery of the first lens optical surface perpendicular to an optical axis; a second lens having a second lens optical surface facing the first lens optical surface, a second lens taper portion provided on an outer periphery of the second lens optical surface, spaced apart from and facing the first lens taper portion, and a second lens flat portion provided on the outer periphery of the second lens optical surface, perpendicular to the optical axis, and in contact with the first lens flat portion; a diameter D1 of an outer circumferential end of the first lens taper portion is larger than a diameter D2 of an outer circumferential end of the second lens taper portion; In an environment at a temperature of 25° C., the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion are spaced apart by a predetermined distance; A lens unit, wherein in an environment where the temperature is higher or lower than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion is smaller than the predetermined distance. (Configuration 2) In an environment where the temperature is higher than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance, When the linear expansion coefficient of the first lens is α1 and the linear expansion coefficient of the second lens is α2 which is larger than α1, 2. The lens unit according to configuration 1, wherein the predetermined distance is equal to or greater than a distance determined by 75×(α2−α1)×D2. (Configuration 3) In an environment where the temperature is lower than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance, When the linear expansion coefficient of the first lens is α1 and the linear expansion coefficient of the second lens is α2 which is smaller than α1, 2. The lens unit according to configuration 1, wherein the predetermined distance is equal to or greater than a distance determined by 65×(α1−α2)×D1. (Configuration 4) 4. The lens unit according to any one of configurations 1 to 3, wherein an angle formed between the first lens taper portion and the optical axis and between the second lens taper portion and the optical axis is equal to or greater than 45 degrees and less than 90 degrees. (Configuration 5) 4. The lens unit according to any one of configurations 1 to 3, wherein an angle formed between the first lens taper portion and the optical axis and between the second lens taper portion and the optical axis is equal to or greater than 45 degrees and less than 67 degrees. (Configuration 6) 6. The lens unit according to any one of configurations 1 to 5, wherein a static friction coefficient between the first lens flat portion and the second lens flat portion is 0.5 or less. (Configuration 7) the first lens flat portion is provided on an outer periphery of the first lens tapered portion, The lens unit according to any one of configurations 1 to 6, wherein the second lens flat portion is provided on an outer periphery of the second lens tapered portion. (Configuration 8) the first lens flat portion and the first lens tapered portion are provided continuously, The lens unit according to any one of configurations 1 to 7, wherein the second lens flat portion and the second lens tapered portion are provided continuously. (Configuration 9) The lens unit according to any one of configurations 1 to 8, wherein the first lens and the second lens are glass lenses. (Claim 10) a holding member that houses the first lens and the second lens and has an abutting portion that abuts against a flat portion provided on a surface opposite to the second lens flat portion; The lens unit according to any one of configurations 1 to 9, further comprising a pressing member that contacts a surface opposite the first lens flat portion and, together with the abutment portion, holds the first lens and the second lens. (Configuration 11) a cylindrical holding member that houses the first lens and the second lens, 11. The lens unit according to any one of configurations 1 to 10, wherein at least one of an outer circumferential surface of the first lens and an outer circumferential surface of the second lens abuts against an inner circumferential surface of the holding member. (Configuration 12) a cylindrical holding member that houses the first lens and the second lens, 12. The lens unit according to any one of configurations 1 to 11, wherein an outer circumferential surface of the first lens and an outer circumferential surface of the second lens abut against an inner circumferential surface of the holding member. (Configuration 13) An optical system including the lens unit according to any one of configurations 1 to 12; A housing that houses the optical system; An optical instrument comprising: (Configuration 14) An optical system including the lens unit according to any one of configurations 1 to 12; an image sensor that receives light that has passed through the optical system; a housing containing the optical system and the imaging element; An imaging device comprising:

[0068] The present disclosure has been described above with reference to the embodiments, modifications, and examples, but the present disclosure is not limited to these embodiments. Inventions modified within the scope of the present disclosure and inventions equivalent to the present disclosure are also included in the present disclosure. In addition, the above-mentioned embodiments, modifications, and examples can be appropriately combined within the scope of the present invention. [Explanation of symbols]

[0069] 1, 61, 81... Lens unit 11, 611, 811... First lens 12, 612, 812...Second lens 13.... Retaining member 14... Holding member 111, 6111, 8111...First lens plane 113, 6113, 8113... First lens taper 115...First lens optical surface 122, 6122, 8122...Second lens flat section 124, 6124, 8124...Second lens taper part 126...Second lens optical surface 117: First lens pressing surface

Claims

1. a first lens having a first lens tapered portion provided on an outer periphery of a first lens optical surface, and a first lens flat portion provided on the outer periphery of the first lens optical surface perpendicular to an optical axis; a second lens having a second lens optical surface facing the first lens optical surface, a second lens taper portion provided on an outer periphery of the second lens optical surface, spaced apart from and facing the first lens taper portion, and a second lens flat portion provided on the outer periphery of the second lens optical surface, perpendicular to the optical axis, and in contact with the first lens flat portion; a diameter D1 of an outer circumferential end of the first lens taper portion is larger than a diameter D2 of an outer circumferential end of the second lens taper portion; In an environment at a temperature of 25° C., a distance between an outer circumferential end of the first lens taper portion and an outer circumferential end of the second lens taper portion is a predetermined distance, A lens unit, wherein in an environment where the temperature is higher or lower than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance.

2. In an environment where the temperature is higher than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance, When the linear expansion coefficient of the first lens is α1 and the linear expansion coefficient of the second lens is α2 which is larger than α1, 2. The lens unit according to claim 1, wherein the predetermined distance is equal to or greater than a distance determined by 75×(α2−α1)×D2.

3. In an environment where the temperature is lower than 25° C., the distance between the outer circumferential end of the first lens taper portion and the outer circumferential end of the second lens taper portion becomes smaller than the predetermined distance, When the linear expansion coefficient of the first lens is α1 and the linear expansion coefficient of the second lens is α2 which is smaller than α1, 2. The lens unit according to claim 1, wherein the predetermined distance is equal to or greater than a distance determined by 65×(α1−α2)×D1.

4. The lens unit according to claim 1 , wherein an angle formed between the first lens taper portion and the optical axis and between the second lens taper portion and the optical axis is equal to or greater than 45 degrees and less than 90 degrees.

5. The lens unit according to claim 1 , wherein an angle formed between the first lens taper portion and the optical axis and between the second lens taper portion and the optical axis is equal to or greater than 45 degrees and less than 67 degrees.

6. 2. The lens unit according to claim 1, wherein a static friction coefficient between the first lens plane portion and the second lens plane portion is 0.5 or less.

7. the first lens flat portion is provided on an outer periphery of the first lens tapered portion, The lens unit according to claim 1 , wherein the second lens flat portion is provided on an outer periphery of the second lens tapered portion.

8. the first lens flat portion and the first lens tapered portion are provided continuously, The lens unit according to claim 1 , wherein the second lens flat portion and the second lens tapered portion are provided contiguously.

9. The lens unit according to claim 1 , wherein the first lens and the second lens are glass lenses.

10. a holding member that houses the first lens and the second lens and has an abutting portion that abuts against a flat portion provided on a surface opposite to the second lens flat portion; The lens unit according to claim 1 , further comprising a pressing member that abuts against a surface opposite to the first lens flat portion and that, together with the abutting portion, holds the first lens and the second lens therebetween.

11. a cylindrical holding member that houses the first lens and the second lens, The lens unit according to claim 1 , wherein at least one of an outer circumferential surface of the first lens and an outer circumferential surface of the second lens abuts against an inner circumferential surface of the holding member.

12. a cylindrical holding member that houses the first lens and the second lens, The lens unit according to claim 1 , wherein an outer circumferential surface of the first lens and an outer circumferential surface of the second lens abut against an inner circumferential surface of the holding member.

13. An optical system including a lens unit according to any one of claims 1 to 12; A housing that houses the optical system; An optical instrument comprising:

14. An optical system including a lens unit according to any one of claims 1 to 12; an image sensor that receives light that has passed through the optical system; a housing containing the optical system and the imaging element; An imaging device comprising:

Images