Lens unit and camera module

Abstract

To suitably seal an internal space.SOLUTION: A lens unit 1 includes: a plurality of lenses 20 including a first lens 21 closest on the side of an object and a fourth lens 24 on the side of an image from the first lens; a frame member 29 for holding the fourth lens 24; a body tube 3 for storing the plurality of lenses 20 and the frame members 29; a first sealing material 61 for sealing between the first lens 21 and the body tubes 3; a second sealing material 62 for sealing between the body tube 3 and the frame members 29 ; and a third sealing material 63 for sealing between the frame member 29 and the fourth lens 24.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lens unit and a camera module.

Background Art

[0002] In recent years, cameras have been used in various applications, and those used outdoors, such as surveillance cameras and in-vehicle cameras, have been increasing. In this type of camera, when the temperature difference between the inside of the lens unit and the outside air becomes large, dew may form on the lens surface. The temperature difference occurs when the temperature inside the lens unit rises due to the lens portion that is in contact with the outside air and electronic components such as the imaging element. In particular, since the surface of the first lens is directly in contact with the outside air, it is most susceptible to the influence, and dew is likely to form on the back surface (image side surface) of the first lens when the temperature difference is large, such as in winter. Dew formed on the lens surface affects the quality of the acquired image and, consequently, various controls by image processing, so it is desirable to appropriately prevent it.

[0003] In the technique described in Patent Document 1, an intermediate spacer is disposed between the first lens and the second lens, and an adhesive medium (adhesive) is filled between the first lens and the intermediate spacer and between the second lens and the intermediate spacer. Thereby, the space surrounded by the first lens, the intermediate spacer, and the second lens is sealed. However, in this case, since an adhesive is applied between the first lens and the intermediate spacer, the interval between the first lens and the second lens varies depending on the application amount, which has an adverse effect on the performance.

[0004] In the technique described in Patent Document 2, a notch is provided on the upper end surface of the second lens, and an elastic sealing member is sandwiched between the end surface of the first lens and the second lens. Thereby, the space between the first lens and the second lens is sealed. However, when an elastic material is directly sandwiched between the lenses, a large pressure is applied to the lenses, and there is a risk that the optical surface may be deformed. In particular, in the case of a plastic lens that is more likely to be deformed than a glass lens, the performance may be significantly deteriorated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to suitably seal an internal space.

Means for Solving the Problems

[0007] To achieve the above object, the present invention is a lens unit, a plurality of lenses including a first lens on the object side and an Nth lens on the image side of the first lens, a frame member that holds the Nth lens, a lens barrel that houses the plurality of lenses and the frame member, a first sealing material that seals between the first lens and the lens barrel, a second sealing material that seals between the lens barrel and the frame member, a third sealing material that seals between the frame member and the Nth lens, and is provided with.

Effects of the Invention

[0008] According to the present invention, the internal space can be suitably sealed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] [Overall Configuration of Camera Module] FIG. 1 is a cross-sectional view of a camera module 100 according to the present embodiment. As shown in FIG. 1, the camera module 100 includes a lens unit 1, a camera case 102, and an imaging element 104. The camera case 102 houses the lens unit 1 with the first lens 21 of the lens unit 1 exposed forward.

[0012] The imaging element 104 is a solid-state imaging element that detects a subject image formed by the imaging optical system 2 of the lens unit 1 and performs photoelectric conversion. For example, the imaging element 104 is an image sensor such as a CMOS type or a CCD type. The imaging element 104 is fixed to a sensor holder 106 in a state of being mounted on an imaging element substrate 105. The sensor holder 106 is fixed to the lens barrel 3 of the lens unit 1 with the imaging element 104 positioned with respect to the imaging optical system 2 of the lens unit 1.

[0013] [Overall Configuration of Lens Unit] The lens unit 1 includes an imaging optical system 2 and a lens barrel 3. Hereinafter, the direction along the optical axis Ax of the lens unit 1 (imaging optical system 2) is referred to as the "axial direction", the direction perpendicular to the axial direction is referred to as the "radial direction", and the rotational direction centered on the optical axis Ax is referred to as the "circumferential direction".

[0014] The imaging optical system 2 is a single-focus optical system that forms a subject image on the imaging surface (projection surface) of the imaging element 104, and has a plurality of lenses 20 and a diaphragm 28 (see FIG. 2). In the drawings, illustration of a part of the optical surface of each lens 20 is omitted. The plurality of lenses 20 includes the first lens 21 to the seventh lens 27 in order from the object side (the left side in FIG. 1). However, the imaging optical system 2 may include at least two lenses 20, namely, the first lens 21 and the fourth lens (the Nth lens) 24.

[0015] Among the plurality of lenses 20, the first lens 21 located closest to the object side exposes the object-side surface 21a to the outside. Among the first lens 21, the surface on the image side (the right side in FIG. 1) excluding the optical surface is painted black for light shielding.

[0016] The fourth lens 24 is an example of the Nth lens according to the present invention and is held (for example, caulked and fixed) by the frame member 29. The frame member 29 is formed in a substantially annular plate shape and holds the fourth lens 24 in the inner diameter portion while positioning it in the radial direction and the axial direction. The material of the frame member 29 is not particularly limited and may be metal or resin. However, when the frame member 29 is made of metal, the fixing of the fourth lens 24 may be other than caulking (for example, an adhesive, etc.). An IR cut coat is applied to the optical surface (for example, the object-side surface) of the fourth lens 24. The IR cut coat suppresses the incidence of light having a wavelength outside the visible light region onto the imaging element 104.

[0017] The aperture 28 is disposed at the axial position between the third lens 23 and the fourth lens 24 (frame member 29) (see FIG. 2). However, the position of the aperture 28 may be in the vicinity of the fourth lens 24 and may be between the fourth lens 24 and the fifth lens 25. Note that a light shielding plate that shields the outside diameter side more than the optical surface of each lens 20 may be disposed between each lens 20 and the frame member 29 except for the position of the aperture 28 (between the third lens 23 and the fourth lens 24).

[0018] Each lens 20 except the fourth lens 24, the aperture 28, and the frame member 29 are axially positioned with both axially outer side surfaces in contact with adjacent ones. The seventh lens 27 closest to the image side is in contact with the bottom surface of the lens barrel 3. The first lens 21 is caulked and fixed (thermally caulked) to the object-side end of the lens barrel 3. Thereby, the imaging optical system 2 including the plurality of lenses 20 is integrated with the lens barrel 3 in a positioned state.

[0019] The material of each lens 20 is not particularly limited, but in this embodiment, the first lens 21 and the fourth lens 24 are glass, and the remaining lenses 20 are plastic. The first lens 21 exposed to the outside is made of a glass lens because it is required to have scratch resistance, abrasion resistance, chemical resistance, etc. The fourth lens 24 disposed near the aperture 28 is made of a glass lens that is less likely to change its surface shape when the temperature changes, for the purpose of suppressing focus shift and performance change when the temperature changes. Also, the IR cut coat applied to the fourth lens 24 is easier to apply in terms of manufacturing on a glass lens than on a plastic lens. The lenses 20 other than the first lens 21 and the fourth lens 24 are made of plastic lenses solely for cost reduction.

[0020] The lens barrel 3 is formed in a substantially cylindrical shape and houses the imaging optical system 2 inside. The lens barrel 3 is composed of, for example, resin, metal, a material in which glass fiber is mixed with resin, etc.

[0021] [Sealing Structure of Lens Unit] The lens unit 1 has a sealing structure for preventing fogging of the first lens 21. Specifically, among the inside of the lens barrel 3, the internal space S including the image-side surface 21b of the first lens 21 is sealed (sealed) from the outside by the first sealing material 61 to the fourth sealing material 64.

[0022] The first sealing member 61 is an O-ring and seals between the first lens 21 and the lens barrel 3. The first lens 21 has a notch 21c as an O-ring groove on the image side of the outer peripheral portion. The first sealing member 61 is disposed in the notch 21c and is radially compressed between the outer peripheral surface in the notch 21c and the inner peripheral surface of the lens barrel 3. Note that the first sealing member 61 is not limited to an O-ring.

[0023] The second sealing member 62 is an O-ring and seals between the lens barrel 3 and the frame member 29. The lens barrel 3 has a stepped portion 34 that is located on the outer diameter side step by step toward the object side on the outer diameter side of the fifth lens 25. The second sealing member 62 is disposed in the stepped portion 34 and is axially compressed between the object side surface of the stepped portion 34 and the image side surface 29a on the outer peripheral side of the frame member 29. Note that the second sealing member 62 is not limited to an O-ring.

[0024] Figure 2 is an enlarged view of part A in Figure 1. As shown in Figure 2, the third sealing member 63 is an adhesive and seals between the frame member 29 and the fourth lens 24. The frame member 29 has a convex portion 29b for caulking and fixing the fourth lens 24 at the inner diameter portion on the object side. The fourth lens 24 has a stepped portion 29c on the outer peripheral portion on the object side that is recessed toward the image side toward the outer diameter side. The stepped portion 29c is located on the outer diameter side of the effective diameter required for image acquisition. The stepped portion 29c is provided so that the third sealing member 63 (adhesive) does not flow into the optical surface within the optical effective diameter. The third sealing member 63 is filled in a recess 29d defined by the convex portion 29b of the frame member 29 and the stepped portion 29c of the fourth lens 24 to seal between the frame member 29 and the fourth lens 24. Note that the position of the third sealing member 63 only needs not to reach the optical surface of the fourth lens 24 and may be on the image side.

[0025] Also, the second sealing member 62 and the third sealing member 63 suppress, for example, warm moisture from the imaging element 104 from flowing into the internal space S from the image side direction through the gap between the outer peripheral surface of each lens 20 except the fourth lens 24 and the inner peripheral surface of the lens barrel 3. Here, the "gap" between the lens 20 and the lens barrel 3 described above is formed solely due to the configuration in the actual device. Specifically, when the lens 20 is a plastic lens, a gate cut portion (protrusion) is formed during molding, and the above-mentioned gap is generated by the gate cut portion. When the lens 20 is a glass lens and the lens barrel 3 is made of resin, three or more D-cuts are formed on the inner peripheral surface of the lens barrel 3 to align the optical axes Ax of the plurality of lenses 20. Therefore, the lens 20 and the lens barrel 3 do not contact each other except at the D-cut portions, and the above-mentioned gap is generated. When the lens 20 is a glass lens and the lens barrel 3 is made of metal, the above-mentioned gap is generated in order to set the fitting dimensions of each other to a tolerance (for example, clearance fit or transition fit) that can avoid press-fitting.

[0026] As shown in FIG. 1, the fourth sealing material 64 seals the air hole 35 of the lens barrel 3. The air hole 35 communicates with the outside between the first lens 21 and the second lens 22 in the lens barrel 3 and opens on the outer surface of the lens barrel 3. The air hole 35 is a vent for leak inspection to confirm the sealing performance of the internal space S. The leak inspection is performed by pressurizing or depressurizing the inside of the lens barrel 3 after assembling the lens unit 1. By opening the air hole 35 during the leak inspection, the soundness of the first sealing material 61 to the third sealing material 63 can be preferably confirmed. The leak inspection may be a pressurization type or a depressurization type, but if depressurized from the image side, the third sealing material 63 on the object side can be prevented from dropping off to the object side. In addition, the air hole 35 also functions as a vent when the imaging optical system 2 is incorporated into the lens barrel 3. At the time of assembly, since it is assembled into the lens barrel 3 with the first sealing material 61 attached to the first lens 21, the air inside the lens barrel 3 cannot be released unless the air hole 35 is opened. The air hole 35 is closed by, for example, a resin-made fourth sealing material 64 after the leak inspection is performed. Note that the position of the air hole 35 is not particularly limited as long as it is in the axial direction between the first lens 21 and the frame member 29, that is, at a position where the internal space S of the lens barrel 3 communicates with the outside.

[0027] [Technical Effects of the Present Embodiment] As described above, according to the present embodiment, between the first lens 21 and the lens barrel 3 is the first sealing material 61, between the frame member 29 that holds the fourth lens (the Nth lens) 24 and the lens barrel 3 is the second sealing material 62, and between the frame member 29 and the fourth lens 24 is the third sealing material 63, and each is sealed. Thereby, without disposing an adhesive or an elastic material between adjacent lenses 20, the internal space S including the image side surface 21b of the first lens 21 is sealed. Therefore, the gap between the lenses does not vary depending on the application amount of the adhesive, and the optical surface is not deformed by the elastic material compressed between the lenses. Therefore, the internal space S can be suitably sealed.

[0028] Further, according to the present embodiment, an IR cut coat is provided on the optical surface of the fourth lens 24. Thereby, it is possible to suppress light having a wavelength outside the visible light region from entering the imaging device 104.

[0029] Further, according to the present embodiment, the lens barrel 3 has an air hole 35 that communicates the inside and the outside at an axial position between the first lens 21 and the frame member 29. Thereby, in a state where the air hole 35 is opened, a leak inspection for confirming the sealing property of the internal space S can be suitably performed. The air hole 35 may be sealed with a fourth sealing material 64 after the leak inspection.

[0030] Further, according to the present embodiment, the third sealing material 63 is an adhesive and is filled in a recess 29d defined by the fourth lens 24 (a stepped portion 29c provided outside the optical effective diameter thereof) and the frame member 29. Therefore, unlike the case where an adhesive is filled between two lenses 20 or between a lens 20 and the lens barrel 3, no compressive force is applied to the third sealing material 63 after curing. For example, when the first lens 21 is thermally caulked to the lens barrel 3, a force that compresses each lens 20 in the axial direction acts. At this time, for example, if an adhesive is filled between two lenses 20, the adhesive layer is crushed by the compressive force of the thermal caulking, and the interval between the lenses 20 changes or variations occur. Alternatively, a part of the adhesive layer may be fractured by the compressive force, and there is a possibility that it may not be sealed properly. Further, if an adhesive is filled between the lens 20 and the lens barrel 3, peeling occurs at the interface between the lens 20 or the lens barrel 3 and the adhesive. In particular, thermoplastic engineering plastics such as PA materials and PPS materials used for lens barrels of in-vehicle cameras are difficult-to-adhere materials, and interface peeling easily occurs due to the force during thermal caulking. In the present embodiment, as described above, since no compressive force is applied to the third sealing material 63 after curing, the occurrence of interface peeling is suppressed, and thus the internal space S can be preferably sealed.

[0031] Further, according to the present embodiment, the first sealing material 61 is an O-ring and is compressed in the radial direction between the first lens 21 and the lens barrel 3. Thereby, unlike the case where the O-ring is compressed in the axial direction at the end face on the image side of the first lens 21, the inclination of the first lens 21 can be suppressed and the first lens 21 can be preferably arranged. That is, when the O-ring (elastic material) is compressed in the axial direction at the end face on the image side of the first lens 21, the first lens 21 receives the repulsive force of the O-ring in the axial direction when being incorporated into the lens barrel 3. Therefore, until the lens barrel 3 is caulked and fixed, the first lens 21 is in a floating state on the object side, and there is a possibility of tilting during fixing. In the present embodiment, since the first sealing material 61 of the O-ring is compressed in the radial direction between the first lens 21 and the lens barrel 3, such a situation can be suppressed.

[0032] [Others] As described above, an embodiment of the present invention has been described. However, the embodiments to which the present invention is applicable are not limited to the above-described embodiments and their modifications, and can be appropriately changed without departing from the spirit of the present invention.

[0033] For example, in the above embodiment, the second sealing member 62, which is an O-ring, is axially compressed between the lens barrel 3 and the frame member 29. However, for example, as shown in FIG. 3, the second sealing member 62 may be radially compressed between the lens barrel 3 and the frame member 29. Specifically, in this case, a notch 29d as an O-ring groove is formed on the image side of the outer peripheral portion of the frame member 29. Then, the second sealing member 62 is disposed in the notch 29d, and it may be radially compressed between the outer peripheral surface in the notch 29d and the inner peripheral surface of the lens barrel 3. Thereby, the inclination of each lens 20 during assembly can be suppressed. That is, when the second sealing member 62, which is an O-ring, is axially compressed, each lens 20 on the object side of the frame member 29 receives an axial repulsive force of the O-ring when incorporated into the lens barrel 3. Therefore, each of the lenses 20 and the frame member 29 is in a floating state on the object side until the first lens 21 is caulked and fixed to the lens barrel 3, and there is a possibility of tilting during fixing. In this modified example, since the second sealing member 62 of the O-ring is radially compressed between the frame member 29 and the lens barrel 3, such a situation can be suppressed. In this case, it is more effective to perform a lubrication treatment on the surface of the O-ring (second sealing member 62).

Explanation of Signs

[0034] 1 Lens unit 2 Imaging optical system 20 Lens 21 First lens 21a Object side surface 21b Image side surface 24 Fourth lens (nth lens) 29 Frame member 29a Image side surface 29b Convex portion 29c Concave portion 3 Lens barrel 34 Step portion 35 Air hole 61 First sealing member 62 Second sealing member 63 Third sealing member 64 Fourth sealing member 100 Camera module 104 Image sensor Axial optical axis

Claims

1. A plurality of lenses including a first lens closest to the object side and an Nth lens closer to the image side than the first lens; A frame member for holding the Nth lens; a lens barrel that houses the plurality of lenses and the frame member; a first sealant that seals a gap between the first lens and the lens barrel; a second sealant that seals between the lens barrel and the frame member; a third sealant that seals between the frame member and the Nth lens; A lens unit comprising:

2. The second seal is an O-ring. The lens unit according to claim 1 .

3. The Nth lens is a glass lens. The lens unit according to claim 1 .

4. An IR cut coat is applied to the optical surface of the Nth lens. The lens unit according to claim 3 .

5. the lens barrel has an air hole communicating between the inside and the outside, the air hole being located between the first lens and the frame member in the axial direction, The air hole is sealed with a fourth sealing material. The lens unit according to claim 1 .

6. A diaphragm is disposed in the vicinity of the Nth lens. The lens unit according to claim 1 .

7. the third sealing material is an adhesive; A recess defined by the frame member and the Nth lens is filled. The lens unit according to claim 1 .

8. the first sealing material is an O-ring and is compressed in a radial direction between the first lens and the lens barrel; The lens unit according to claim 1 .

9. the second sealing material is compressed in a radial direction or an axial direction between the lens barrel and the frame member; The lens unit according to claim 2 .

10. A lens unit according to any one of claims 1 to 9, an image sensor that photoelectrically converts an object image formed by the plurality of lenses; A camera module comprising:

Images