JP7224250B2 - Lens mount and barrel - Google Patents

Description

The present invention relates to a structure for holding lens elements.

Here, a lens unit in which a plurality of transmissive lenses are linearly arranged in a lens barrel, which is used for video cameras, microscopes, thermal imagers, etc., for example, will be described. In particular, the design and manufacture of tight tolerance lens units will be described. An optical system having a structure in which a plurality of refractive transmission lenses are combined and held and fixed in a lens barrel is called a lens unit.
In a low-cost lens unit, the outer periphery of a lens element is a cylindrical surface, and a lens mount having an inner cylindrical surface substantially coinciding with the cylindrical surface is built into the lens barrel, the lens element is fitted into the lens mount, and the screw is screwed. It is common to adopt a so-called drop-in type structure in which a cut presser ring or the like is used for fixing. A lens unit that employs a drop-in structure requires a certain amount of clearance between the lens element and the lens mount for the operation of inserting the lens element into the lens mount. For this reason, there is a limit to strictly setting the relative eccentricity tolerance between a plurality of lens elements constituting the lens unit, which is typically about 0.1 mm. On the other hand, lens units that require high imaging performance, such as objective lenses for microscopes and pickup lenses for optical disk drives, require decentration tolerances on the order of 1/100 mm or 1/1000 mm. In this case, a lens unit is disclosed that employs a method of holding a plurality of lens elements in individual partial barrels, adjusting the eccentric deviation between the lens elements between the partial barrels, and bringing it within tolerance (for example, patent Reference 1). Further, a lens unit is disclosed in which the outer circumference of the lens element is tapered and the lens mount is fitted with the tapered shape (for example, Patent Document 2). Although it is a similar idea, there has been disclosed a lens mounting method in which not only the fitting of the lens mount but also the fitting of the threads between the pressing ring and the lens barrel are used (for example, Patent Document 3).

According to the lens units of Patent Documents 2 and 3, since no gap is generated between the lens mount and the lens element, decentration deviation can be reduced.
In Japanese Patent Laid-Open No. 2002-200000, these eccentricity reduction techniques that do not depend on assembly adjustment work are collectively referred to as auto-centering. The same designation is used for the same reduction technique in this specification.

JP-A-11-203706 JP 2010-134378 A U.S. Pat. No. 9,244,245

In the conventional lens unit, it was necessary to perform assembly adjustment in order to reduce the eccentric deviation. For this reason, advanced assembling and manufacturing techniques are required and much time is required for manufacturing. In addition, additional mechanical parts and equipment for adjustment are required. On the other hand, if auto-centering technology is employed, the assembly adjustment can be dispensed with. However, in a lens unit that employs auto-centering, high-precision processing is required for the shape of the fitting portion between the lens mount and the lens element, and dedicated processing and inspection devices are required.
As described above, the conventional lens unit has the problem that advanced processing technology, special parts and equipment are required to maintain the concentricity accuracy.

The main object of the present invention is to solve such problems. More specifically, the main object of the present invention is to realize a lens mount that can maintain high concentric accuracy even with a simple assembly work and that does not require special parts or equipment for maintaining concentric accuracy. do.

A lens mount according to the present invention includes:
A circular lens element having a spherical surface and a flat surface at its periphery, said spherical surface sloping upward toward the center when said spherical surface is considered to be the upper part of said periphery and said plane is considered to be the lower part of said periphery. A lens mount internally holding a
a support portion that is in contact with the flat surface of the peripheral portion of the lens element and supports the lens element;
a groove provided in the support;
A spherical surface coinciding with the spherical surface of the peripheral portion of the lens element is provided as an opposing spherical surface, a part of the opposing spherical surface is in contact with the spherical surface of the peripheral portion of the lens element, and the part of the opposing spherical surface is in contact with the spherical surface of the peripheral portion of the lens element. a spacer that holds the lens element, the other part of the facing spherical surface is not in contact with the spherical surface of the peripheral part, and the end of the other part of the facing spherical surface is arranged in the groove;
the peripheral portion of the lens element is sandwiched between the supporting portion and the spacer;
The groove is provided at a position where the center of the lens element coincides with a reference center required as the center of the lens element when the end of the other portion of the opposing spherical surface of the spacer is placed in the groove. .

According to the present invention, high concentricity accuracy can be maintained even with simple assembly work, and no special parts or equipment are required to maintain concentricity accuracy.

2 is a cross-sectional view showing a configuration example of a lens unit according to Embodiment 1; FIG. 3 is a cross-sectional view for explaining the detailed structure of the lens mount according to Embodiment 1; FIG. 4 is a cross-sectional view of a spacer of the lens unit according to Embodiment 1; FIG. 4 is a cross-sectional view of a lens element of the lens unit according to Embodiment 1; FIG. FIG. 5 is an explanatory diagram for showing an example of the influence of manufacturing tolerances of the lens unit according to Embodiment 1; FIG. 5 is an explanatory diagram for showing an example of the influence of manufacturing tolerances of the lens unit according to Embodiment 1; FIG. 4 is a cross-sectional view showing the configuration of a lens unit that employs a conventional auto-centering lens mount; FIG. 5 is a cross-sectional view showing the influence of temperature environment changes on a lens unit that employs a conventional auto-centering lens mount.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail using drawing.

Embodiment 1.
*** Configuration description ***
FIG. 1 is a cross-sectional view showing the configuration of a lens unit according to this embodiment.
In FIG. 1, 1a and 1b are lens elements, 2 is a lens barrel, 3a and 3b are spacers, and 4a and 4b are retaining rings.
In the following description, the lens element 1a and the lens element 1b are collectively referred to as the lens element 1 when there is no need to distinguish between them. Moreover, when there is no need to distinguish between the spacer 3a and the spacer 3b, both are collectively referred to as the spacer 3.

The lens element 1a and the lens element 1b are transmissive lenses made of glass, and the front and back surfaces are processed into spherical or aspherical surfaces.
The lens element 1a and the lens element 1b each have a spherical surface and a flat surface on the periphery. Then, as shown in FIG. 1, the spherical lens element is a circular lens element in which the spherical surface is inclined upward toward the center when the spherical surface is regarded as the upper portion of the peripheral portion and the flat surface is regarded as the lower portion of the peripheral portion.
The spherical shapes and intervals of the surfaces of the lens elements 1a and 1b are determined by optical design so as to exhibit predetermined imaging performance, and specific dimensions vary depending on the application. FIG. 1 shows a two-group, two-lens unit using lens elements 1a and 1b, but the number of lens elements 1 varies depending on the application, and only one example is shown here. do not have.
The lens element 1a and the lens element 1b are rotationally symmetrical, and the spacers 3a and 3b, the pressing ring 4a and the pressing ring 4b are ring-shaped rotationally symmetrical and arranged substantially coaxially.
The lens barrel 2, the lens element 1a and the lens element 1b, and the holding ring 4a and holding ring 4b are made of metal such as an aluminum alloy, and are manufactured by cutting or using a 3D printer or the like.
Reference numeral 5 in FIG. 1 indicates a lens mount. That is, the lens mount 5 has a structure for holding the lens element 1 inside.

FIG. 2 is an enlarged view for explaining the detailed structure of the lens mount 5. As shown in FIG.
In FIG. 2, the same reference numerals as in FIG. 1 denote the same parts, and the description thereof is omitted.
The lens mount 5 includes a support portion 20 , a groove 7 provided in the support portion 20 , a spacer 3 a, a retaining ring 4 a and a threaded portion 6 .
The support portion 20 is a part of the lens barrel 2 and supports the lens element 1a from below. The lower portion of the peripheral portion of the lens element 1a is processed into a substantially flat surface, and the upper portion of the support portion 20 is flat in order to support the flat surface of the lens element 1a. The supporting portion 20 contacts the plane of the peripheral portion of the lens element 1a and supports the lens element 1a.
The spacer 3a has an annular shape when viewed from above, and the cross section of the ring has a substantially triangular cross-sectional shape. The spacer 3a has, on the hypotenuse portion of the substantially triangular shape, a spherical surface that coincides with the upper spherical surface of the peripheral portion of the lens element 1a as an opposing spherical surface. Here, the expression that the opposing spherical surface matches the upper spherical surface of the peripheral portion of the lens element 1a means that the curvature of the upper spherical surface of the peripheral portion of the lens element 1a and the curvature of the opposing spherical surface are substantially the same. do. A part of the opposing spherical surface is in contact with the peripheral spherical surface of the lens element 1a, and the part of the opposing spherical surface presses the lens element 1a. The other part of the opposing spherical surface is not in contact with the peripheral spherical surface, and the end of the other part of the opposing spherical surface is located in the groove 7 . Below, the end of the other portion of the opposing spherical surface is referred to as the lower end. That is, the lower end of the opposing spherical surface of the spacer 3a is arranged in the groove 7. As shown in FIG.
As shown in FIG. 2, the lens element 1a is held at an appropriate position by sandwiching the peripheral portion of the lens element 1a between the upper flat surface of the support portion 20 and the opposing spherical surface of the spacer 3a.
The pressing ring 4a presses the spacer 3a from above.
The threaded portion 6 is a threaded portion of the retaining ring 4 a or the lens barrel 2 . The retainer ring 4a has a male thread on its outer periphery, and the lens barrel 2 has a female thread to mesh with it. The axial force generated by the screw portion 6 is applied to the lens element 1a via the spacer 3a, and the lens element 1a is pressed against the support portion 20 of the lens barrel 2 and fixedly held.

FIG. 3 is a cross-sectional view of the spacer 3a.
A surface 8 (facing spherical surface) of the spacer 3a in contact with the lens element 1a has a shape obtained by cutting a part of the spherical surface 9. As shown in FIG. The lower end of the surface 8 intersects the side surface of the spacer 3a, which is a substantially cylindrical surface, at an acute angle.

FIG. 4 is a cross-sectional view of the lens element 1a.
A surface 10 of the lens element 1a in contact with the spacer 3a has a shape obtained by cutting a part of the spherical surface 11. As shown in FIG. Furthermore, the spherical surface 11 has substantially the same curvature as the spherical surface 9 . Therefore, the surfaces 8 and 10 are in contact with each other without any gap. It is desirable that the gap between surfaces 8 and 10 be at most 10 micrometers. That is, it is necessary to match the curvatures of the spherical surfaces 11 and 9 so that the gap between the surfaces 8 and 10 is 10 micrometers or less.

Again, refer to FIG.
The acute angle portion (lower end of the inclined surface) on the lower side of the spacer 3a is sized so that it protrudes downward from the planar portion on the lower side of the lens element 1a when assembled.
The lower acute-angled portion of the spacer 3 a (the lower end of the facing spherical surface) is arranged so as to fit into the groove 7 of the support portion 20 . The inner diameter side of the groove 7 is tapered so that the surface 8 (opposed spherical surface) of the spacer 3a meshes with the inner diameter side of the groove 7 with a slight gap. In other words, when the acute-angled portion of the spacer 3a is arranged in the groove 7, a spherical surface that coincides with the surface 8 (opposing spherical surface) is provided at a position in the groove 7 facing the surface 8 (opposing spherical surface) of the spacer 3a. there is Here, the fact that the surface 8 (opposing spherical surface) and the spherical surface in the groove 7 match means that the curvature of the surface 8 (opposing spherical surface) and the curvature of the spherical surface in the groove 7 are substantially the same. The surface 8 (opposing spherical surface) of the spacer 3 a faces the spherical surface in the groove 7 without touching it, and the lower acute angle portion (lower end of the opposing spherical surface) of the spacer 3 a is arranged in the groove 7 .
The groove 7 is provided at a position where the center of the lens element 1a coincides with the reference center required as the center of the lens element 1a when the acute-angled portion (lower end of the opposing spherical surface) of the spacer 3a is placed in the groove 7. It is A reference center is a logical center required in common for all lens elements 1 included in the lens barrel 2 . A groove corresponding to the groove 7 is also provided in the lens mount of the lens element 1b, and the center of the lens element 1b also coincides with the reference center by arranging the acute-angled portion of the spacer 3b in the groove. As a result, the lens element 1a and the lens element 1b become concentric, ensuring high concentric accuracy.
The depth of the groove 7 is small, preferably less than 2 millimeters. For example, it is conceivable that the groove 7 has a depth of 1 mm. Also, the gap between the spherical surface of the groove 7 and the surface 8 of the spacer 3a functions to allow manufacturing tolerances.

The degree of eccentric deviation of the lens element 1a depends on the engagement accuracy between the groove 7 and the acute-angled portion of the spacer 3a, that is, the size of the gap, and determines the eccentric position accuracy of the lens element 1a. Therefore, when the required eccentricity tolerance is large, it is possible to increase the gap and relax the machining tolerance of the groove 7 . On the other hand, when the eccentricity tolerance requirement is small, the working tolerance of the groove 7 is tightened, but in some cases, the working dimensions of the groove 7 are determined by matching the actual product after the lens element 1a and the spacer 3a are manufactured. The machining of the grooves 7 can be performed by using a precision lathe.

There is a gap between the spacer 3 a and the inner wall (vertical surface) of the lens barrel 2 . Unlike a general drop-in type lens mount, the machining accuracy of the inner wall of the lens barrel 2 does not affect the eccentric deviation of the lens element 1a. The gap may be large compared to drop-in lens mounts, for example 0.5 millimeters.

FIG. 5 is an explanatory diagram showing the influence of manufacturing tolerances of the lens unit according to Embodiment 1. FIG. In FIG. 5, the same reference numerals as in FIGS. 1 to 4 denote the same parts, and the description thereof is omitted.
Reference numeral 12 is the center of the spherical surface 9 . FIG. 5 shows a state in which the spacer 3a is tilted with respect to the lens element 1a.

The spacer 3a presses the lens element 1a by the axial force of the screw of the pressing ring 4a. At this time, the spacer 3a is inclined with respect to the lens element 1a depending on the processing accuracy of the screw of the pressing ring 4a and the flatness of the contact surface with the spacer 3a, so this phenomenon must be allowed as a tolerance. . The spacer 3a has a rotational degree of freedom with respect to the spherical surface 9, and even if it rotates around the center 12, no gap is generated between the spacer 3a and the lens element 1a.

FIG. 6 is an explanatory diagram showing the influence of manufacturing tolerances of the lens unit according to Embodiment 1. FIG. In FIG. 6, the same reference numerals as in FIGS. 1 to 5 denote the same parts, and the description thereof is omitted.
FIG. 6 shows a state in which the spherical surface 8 of the spacer 3a is processed eccentrically with respect to the outer diameter. Due to the eccentricity error, the thickness of the spacer 3a is a on the left side and b on the right side, and a<b, so that the spacer 3a has a wedge shape as a whole. Due to the contact between the spacer 3a and the lens element 1a, the spherical surface 8 is coaxial with the lens element 1a and the outer diameter is decentered with respect to the lens element 1a.

Even if the lens element 1a is fixed to the lens barrel 2 with the two types of manufacturing errors shown in FIGS. . This is because the eccentric deviation of the lens element 1a with respect to the barrel 2 is determined depending on the positional relationship between the spherical surface 8 of the spacer 3a and the tapered portion of the groove 7, and the above two types of manufacturing errors are different from the accuracy of the spherical surface 8. irrelevant. Naturally, if the two types of tolerances are relaxed too much, and if the acute-angled portion of the spherical surface 8 collides with the bottom of the groove 7 or does not mesh with the groove 7, eccentric deviation will occur. 5 and 6 emphasize manufacturing errors for the sake of clarity of explanation, and eccentric deviation will not occur if manufactured with general tolerances.

Here, the operation of a conventional lens unit employing auto-centering will be described.
FIG. 7 is a cross-sectional view showing a cross-section around an arbitrary lens in a conventional lens unit employing auto-centering. In FIG. 7, 200 is a lens element, 210 is a barrel, and 220 is a spacer.
The lens element 200 is machined into a tapered shape with a conical surface cut off at the end, and is fitted with a lens mount integrated with the lens barrel 2 having a shape in which the unevenness of the tapered shape is reversed, and is held down by a spacer 220. there is Auto-centering is realized by the tapered fitting. The lens element 200 is made of glass, and the lens barrel 210 is made of an aluminum alloy.

FIG. 8 is a cross-sectional view for explaining the influence of temperature changes on a conventional lens unit that employs conventional auto-centering. In FIG. 8, the same reference numerals as in FIG. 7 denote the same parts, and the description thereof is omitted.
FIG. 7 shows the state at the manufacturing temperature. In an environment without air conditioning, for example, in a vehicle-mounted optical sensor lens unit or the like, the ambient temperature changes greatly. When the ambient temperature becomes higher than the temperature at the time of manufacture, the temperature of the lens unit itself also rises due to the influence thereof, and the lens unit expands as shown in FIG. 8, changing its shape and dimensions.
In a tapered lens mount, linear expansion in the lateral direction of the paper acts in the direction of separating the lens mount and lens element 200 . Although this phenomenon is emphasized in FIG. 8 to illustrate this phenomenon, in reality there is no significant change in the separation, and the force received from the spacer 220 presses the lens element 200 against the lens mount and moves downward on the plane of the paper. Even if this displacement is slight, performance deterioration cannot be ignored in the case of a lens unit that requires high imaging performance.
Also, the lens element 200 may be tilted and fixed with respect to the lens barrel 210 (the optical axis of the lens element 200 is tilted). In this case, the formed image is degraded.

In this embodiment, the optical axes of the lens elements 1a are not tilted when the temperature rises because they are received by their flat portions.
Further, even if a gap is formed on the peripheral edge of the lens element 1a when the temperature rises, the tip of the spacer 3a having a spherical portion with inverted unevenness that engages with the spherical portion on the peripheral edge of the lens element 1a is inserted into the groove 7. shape, the lens element 1a is pressed and held by an axial force. Therefore, it is possible to obtain the effect that high concentricity accuracy can be maintained even when the temperature changes.
That is, since the upper flat surface of the support portion 20 and the opposing spherical surface of the spacer 3a sandwich the peripheral portion of the lens element 1a, the lens element 1a can be kept in an appropriate position even if the temperature rises. Further, even if the lens barrel 2 expands due to temperature rise and the support portion 20 is displaced leftward in FIG. can be held in place.

The structure and function of the lens mount of the lens element 1a have been described above. The lens mount of the lens element 1b has the same function as the lens mount of the lens element 1a, except that the lens mount has a different diameter. As described above, a groove corresponding to the groove 7 is also provided in the lens mount of the lens element 1b, and the center of the lens element 1b is aligned with the reference center by arranging the sharp-angled portion of the spacer 3b in the groove. do. As a result, the lens element 1a and the lens element 1b become concentric, ensuring high concentric accuracy.

Moreover, the materials for all the parts in the lens unit are described above as an example, and other materials may be used. For example, in the case of an infrared lens unit, germanium, silicon, zinc selenide, or the like may be used instead of glass as the material of the lens element 1 .
In the above description, as shown in FIG. 1, the lens unit in which the convex portion of the lens element 1 faces upward has been described. configuration). Further, a lens unit in which the convex portion of the lens element 1 faces sideways (a configuration in which FIG. 1 is rotated 90 degrees to the right or left) may be used. Furthermore, in FIG. 1, the convex portions of the lens unit 1b and the convex portions of the lens unit 1a are oriented in the same direction. It is good (the convex portion of the lens unit 1b faces the convex portion of the lens unit 1a).

***Description of the effect of the embodiment***
According to the present embodiment, it is possible to minimize the eccentric deviation of the lens, so that the lens unit can be manufactured in a short period of time compared to a lens unit that requires assembly and adjustment.
For example, in the lens unit disclosed in Patent Literature 1, it was necessary to perform assembly adjustment in order to reduce the eccentric deviation. For this reason, there is a problem that a lot of time is required for manufacturing, and additional mechanical parts or equipment for adjustment are required, resulting in an increase in manufacturing cost.
According to this embodiment, the acute-angled portion of the spacer 3a is arranged in the groove 7, the surface 8 of the spacer 3a and the surface 10 of the lens element 1a are brought into contact, and the peripheral edge of the lens element 1a is held by the spacer 3a and the support portion 20. By sandwiching, the center of the lens element 1a can be aligned with the reference center. By aligning the center of the lens element 1b with the reference center in the same procedure, the lens element 1a and the lens element 1b can be made concentric, and high concentric accuracy can be maintained with a simple processing operation. Also, the lens barrel 2 can be manufactured in a short time. Also, no special parts or equipment are required.

In addition, in the present embodiment, the spacer and the lens element are in contact with each other on the spherical surface and have a rotational degree of freedom on the spherical surface. For this reason, compared with a conventional lens mount that employs auto-centering, which has no degree of freedom of rotation, assembly is easier, and tolerance for processing accuracy of the presser ring can be relaxed.
In conventional lens units that employ auto-centering, high-precision processing is required for the shape of the fitting portion between the lens mount and the lens element. was there.

Moreover, according to the present embodiment, it is easy to manufacture parts. The reason for this is that although the shape of the spherical portion of the spacer requires dimensional accuracy, the positional relationship between the spherical portion and the external shape only needs to meet general tolerances. Concentric accuracy with the lens barrel is not required. Concerning grooves in the lens barrel, machining precision of the tapered portion and concentricity with the lens barrel are required, but the machining area can be reduced compared to conventional lens mounts that employ auto-centering.

Further, according to the present embodiment, it is possible to reduce the amount of displacement of the lens elements due to environmental temperature changes. Therefore, it is possible to reduce the deterioration of imaging performance due to environmental temperature changes.
As described above, in the configuration employing the conventional auto-centering function, the change in lens position due to temperature change tends to increase due to the difference in coefficient of linear expansion between the lens element and the lens mount. According to this embodiment, even if a gap is formed at the periphery of the lens element when the temperature rises, the lens element is held by pressing it with an axial force, so high concentricity accuracy can be maintained even when the temperature changes.
In addition, in a conventional configuration employing an auto-centering function, it is conceivable to use a material having a coefficient of linear expansion close to that of the lens element for the barrel including the lens mount as a countermeasure against displacement due to temperature rise. However, in general, lens element materials, such as glass and silicon, have a low coefficient of linear expansion. Structural materials with a low coefficient of linear expansion, such as titanium alloys and invar, have higher material costs and processing costs than aluminum and the like. According to this embodiment, there is no need to use such expensive materials for the lens mount.

Embodiment 2.
*** Configuration description ***
The configuration of the lens unit according to this embodiment is the same as that shown in FIGS. In this embodiment, it is assumed that the coefficient of linear expansion of the spacer 3 and the coefficient of linear expansion of the lens element 1 are substantially the same. In this embodiment, the spacer 3 is assumed to be made of, for example, kovar, pure titanium, titanium alloy, or invar.

Kovar is an alloy of iron, nickel and cobalt with a coefficient of linear expansion of 5.2×10 ⁻⁶ K ⁻¹ . The coefficient of linear expansion of pure titanium and titanium alloys is 8.8×10 ⁻⁶ K ⁻¹ . Invar is an alloy composed mainly of iron and nickel, and has a coefficient of linear expansion of 1.2×10 ⁻⁶ . On the other hand, there are various kinds of glass that is the material of the lens element 1. For example, quartz glass has a glass density of 4.7×10 ⁻⁶ . When the lens element 1 is an infrared lens, the linear expansion coefficient of the material is 2.6×10 ⁻⁶ for silicon, 5.7×10 ⁻⁶ for germanium, and 7.1×10 for zinc selenide. ^-6 . The material of the lens element 1 varies depending on the application, and the material of the spacer 3 is selected on the condition that the coefficient of linear expansion is close to the coefficient of linear expansion.

In the conventional configuration illustrated in FIGS. 7 and 8, the lens element 200 is made of glass and the lens barrel 210 is made of aluminum alloy, as described above. Therefore, the coefficient of linear expansion of the lens element 200 is about three to one quarter of the coefficient of linear expansion of the barrel 210 .

The displacement of the lens element 200 depending on the environmental temperature can be improved by selecting the material of the lens barrel 210 so that the coefficient of linear expansion is close to that of the lens element 200 . However, such materials, such as Kovar, pure titanium, titanium alloys, and Invar, are generally regarded as difficult-to-work materials, and the manufacturing cost increases compared to the case where aluminum alloys are selected.

In the lens unit according to the present embodiment, as described above, the spacer 3 uses a material whose coefficient of linear expansion is close to that of the lens element 1. Therefore, it is as if the lens element 1 and the spacer 3 expand with temperature as if they were made of the same material.
As shown in FIG. 2, the composite shape of the lens element 1a and the spacer 3a around the lens mount 5 can be regarded as parallel planes. Therefore, the separation effect between the lens element and the lens mount caused by the lateral linear expansion that occurs in the conventional lens unit shown in FIGS. 7 and 8 does not occur in the lens unit according to the second embodiment. However, the separating action between the lens element 1a and the lens mount 5 due to the influence of linear expansion in the vertical direction remains. However, the amount of deformation due to linear expansion is related to increase in proportion to the size of the object. is less than or equal to Therefore, compared with a lens unit employing a conventional auto-centering lens mount, it is possible to reduce the amount of displacement of the lens elements due to environmental temperature changes.

***Description of the effect of the embodiment***
In this embodiment, the spacer can be the only component that uses a difficult-to-process material. Therefore, it is possible to reduce the volume of materials used and the amount of processing compared to a lens unit that employs a conventional auto-centering lens mount and a lens barrel made of difficult-to-process materials. In addition, it is possible to relax the processing precision tolerance, and it is possible to reduce the material cost and the manufacturing cost.

Although the embodiments of the present invention have been described above, these two embodiments may be combined for implementation.
Alternatively, one of these two embodiments may be partially implemented.
Alternatively, these two embodiments may be partially combined and implemented.
It should be noted that the present invention is not limited to these embodiments, and various modifications can be made as necessary.

1 lens element, 1a lens element, 1b lens element, 2 barrel, 3 spacer, 3a spacer, 3b spacer, 4a holding ring, 4b holding ring, 5 lens mount, 6 screw portion, 7 groove, 8 spherical surface, 9 spherical surface, 10 spherical surface, 11 spherical surface, 12 center of spherical surface, 20 support, 200 lens element, 210 barrel, 220 spacer.

Claims (9)

A circular lens element having a spherical surface and a flat surface at its periphery, said spherical surface sloping upward toward the center when said spherical surface is considered to be the upper part of said periphery and said plane is considered to be the lower part of said periphery. A lens mount internally holding a
a support portion that is in contact with the flat surface of the peripheral portion of the lens element and supports the lens element;
a groove provided in the support;
A spherical surface coinciding with the spherical surface of the peripheral portion of the lens element is provided as an opposing spherical surface, a part of the opposing spherical surface is in contact with the spherical surface of the peripheral portion of the lens element, and the part of the opposing spherical surface is in contact with the spherical surface of the peripheral portion of the lens element. a spacer that holds the lens element, the other part of the facing spherical surface is not in contact with the spherical surface of the peripheral part, and the end of the other part of the facing spherical surface is arranged in the groove ;
a pressing ring that presses the spacer from above ;
the peripheral portion of the lens element is sandwiched between the supporting portion and the spacer;
The groove is provided at a position where the center of the lens element coincides with a reference center required as the center of the lens element when the end of the other portion of the opposing spherical surface of the spacer is placed in the groove. lens mount. a spherical surface coinciding with the facing spherical surface is provided at a position in the groove facing the facing spherical surface of the spacer when the end of the other part of the facing spherical surface of the spacer is arranged in the groove;
2. A lens mount according to claim 1, wherein said opposing spherical surface of said spacer opposes the spherical surface in said groove without being in contact therewith, and an end of said other portion of said opposing spherical surface is disposed within said groove. 2. The lens mount according to claim 1, wherein the spacer has a substantially triangular cross-sectional shape, and the facing spherical surface is provided on the oblique side of the substantially triangular cross-sectional shape. 2. A lens mount according to claim 1, wherein the end of said other portion of said opposing spherical surface of said spacer is disposed within said groove even if said supporting portion and said groove are displaced due to thermal expansion. 2. The lens mount of claim 1, wherein said groove has a depth of 2 millimeters or less. 2. A lens mount according to claim 1, wherein the linear expansion coefficient of said spacer is substantially the same as the linear expansion coefficient of said lens element. 7. A lens mount according to claim 6, wherein said spacer is made of Kovar, pure titanium, titanium alloy or Invar. A lens barrel comprising a plurality of lens mounts according to claim 1 . The groove of each lens mount is provided at a position where the lens elements held by each lens mount are concentric when the end of the other portion of the opposing spherical surface of the spacer of each lens mount is placed in the groove of each lens mount. The lens barrel according to claim 8.

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