Lens module, imaging device

Abstract

To provide an imaging apparatus that can prevent positional shift with a stable configuration even if a change in temperature occurs.SOLUTION: An imaging apparatus (1) has: a housing (2); an image pickup device (5a) that is held in the housing; a lens unit (30) that has a plurality of lenses (7) and a lens frame (3) holding the plurality of lenses; and a ring-shaped connection part (4). The housing has a first inner diameter part (2b). A first attachment part (4a) is provided on an inner diameter of the connection part, and a second attachment part (4b) is provided on an outer diameter of the connection part. The connection part holds the outer diameter of the lens frame with the first attachment part therebetween. The housing holds the outer diameter of the connection part with the second attachment part therebetween. The lens frame has a first fit and slide part (3f) that can be fitted to the first inner diameter part of the housing and slide in an optical axis direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an imaging device. [Background technology]

[0002] Imaging devices used in outdoor environments, such as in-vehicle cameras and surveillance cameras, are expected to be able to operate stably in a wide range of temperatures, from low to high. Temperature changes cause the components of the lens unit to expand and contract, which changes the distance from the rearmost part of the lens unit to the focal plane (back focus), resulting in a decrease in the resolution of the imaging device.

[0003] Patent Document 1 discloses a lens assembly in which an inner telescopic section and an outer telescopic section extend and retract to offset a shift in back focus of a lens unit. Patent Document 2 discloses a camera in which a ring-shaped variable member extends and retracts based on temperature changes to offset a shift in back focus of an optical system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6391122 [Patent Document 2] Patent No. 6912530 Summary of the Invention [Problem to be solved by the invention]

[0005] In the lens assembly disclosed in Patent Document 1, dimensional variations (processing variations) among the multiple components easily cause misalignment (optical axis misalignment) between the optical axis of the lens unit and the imaging center of the sensor. In the camera disclosed in Patent Document 2, the changeable member must be fixed with an adhesive to hold it in place without interfering with its expansion and contraction. In this case, in an environment with large temperature differences, the adhesive's adhesive strength deteriorates, and there is a possibility that each component may peel off or fall off.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an imaging device that has a stable configuration and is capable of suppressing positional deviation even when temperature changes occur. [Means for solving the problem]

[0007] A lens module according to one aspect of the present invention includes a housing, a lens unit having a plurality of lenses and a lens frame that holds the plurality of lenses, and a ring-shaped connecting portion, the housing having a first inner diameter portion, a first attachment portion provided on the inner diameter portion of the connecting portion, a second attachment portion provided on the outer diameter portion of the connecting portion, the connecting portion holding the outer diameter portion of the lens frame via the first attachment portion, the housing holding the outer diameter portion of the connecting portion via the second attachment portion, and the lens frame having a first fitting sliding portion that fits into the first inner diameter portion of the housing and is slidable in an optical axis direction. An elastic body is disposed between the outer diameter portion of the connecting portion and the inner diameter portion of the housing. do.

[0008] Other objects and features of the present invention are illustrated in the following examples. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an imaging device that has a stable configuration and is capable of suppressing positional deviation even when temperature changes occur. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an imaging device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view of the imaging device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] An imaging device 1 according to this embodiment will be described with reference to Fig. 1 and Figs. 2(A) and (B). Fig. 1 is a cross-sectional view of the imaging device 1. Fig. 2(A) is an exploded perspective view of the imaging device 1 as seen from the object side. Fig. 2(B) is an exploded perspective view of the imaging device 1 as seen from the image side.

[0013] The housing 2 has an opening and includes an inner diameter threaded portion 2a, an inner diameter fitting portion (first inner diameter portion) 2b, an inner diameter fitting portion (second inner diameter portion) 2e, and a sensor unit holding portion 2c. The sensor unit 5 includes an imaging element 5a such as a CMOS sensor, and a sensor plate 5b. The imaging element 5a is held to the sensor plate 5b with a UV adhesive or the like. The sensor unit 5 is attached to the sensor unit holding portion 2c of the housing 2 and fixed with screws 6.

[0014] The lens unit 30 has a lens frame 3 and a lens (imaging optical system) 7, and is disposed inside the housing 2. In this embodiment, the lens 7 is composed of three lenses: a first lens 7a, a second lens 7b, and a third lens 7c, but this is not limiting. The lens frame 3 has an outer thread portion 3a, a first lens holder 3c, a second lens holder 3d, a third lens holder 3e, a first fitting sliding portion 3f, and a second fitting sliding portion 3g. The lenses 7 are held inside the lens frame 3. The first lens 7a is held in contact with the first lens holder 3c. The second lens 7b is held in contact with the second lens holder 3d. The third lens 7c is held in contact with the third lens holder 3e.

[0015] The connecting portion 4 has an annular shape and has an inner diameter threaded portion (first mounting portion) 4a provided on the inner diameter of the annulus and an outer diameter threaded portion (second mounting portion) 4b provided on the outer diameter of the annulus. The connecting portion 4 is disposed outside the lens unit 30 and inside the housing 2. The inner diameter threaded portion 2a of the housing 2 and the outer diameter threaded portion 4b of the connecting portion 4 are threadedly engaged, thereby holding the connecting portion 4 to the housing 2. At this time, the connecting portion 4 and the housing 2 are not in contact with each other at any position other than the threaded position. Furthermore, the lens unit 30 is held by the connecting portion 4 by threadingly engaging the inner diameter threaded portion 4a of the connecting portion 4 with the outer diameter threaded portion 3a of the lens frame 3.

[0016] The first fitting sliding portion 3f of the lens unit 30 is slidably fitted into the fitting portion 2b provided on the inner diameter of the housing 2. That is, the first fitting sliding portion 3f is fitted into the inner diameter fitting portion 2b of the housing 2 and is slidable in the optical axis direction. Also, the second fitting sliding portion 3g of the lens unit 30 is slidably fitted into the inner diameter fitting portion 2e provided on the inner diameter of the housing 2. That is, the second fitting sliding portion 3 g is fitted into the inner diameter fitting portion 2e of the housing 2 and is slidable in the optical axis direction.

[0017] Preferably, the positions of the respective fittings in the optical axis direction are substantially the same as the positions of the first lens 7a and the third lens 7c in the optical axis direction. That is, the first fitting sliding portion 3f is disposed closest to the lens 7c, which is disposed closest to the image among the multiple lenses 7, and the second fitting sliding portion 3g is disposed closest to the lens 7a, which is disposed closest to the object among the multiple lenses 7. More preferably, the position of the first fitting sliding portion 3f in the optical axis direction is the same as the position of the lens 7c in the optical axis direction, and the position of the second fitting sliding portion 3g in the optical axis direction is the same as the position of the lens 7a in the optical axis direction. This makes it possible to suppress the amount of tilt of the entire lens unit 30.

[0018] In this embodiment, the first fitting sliding portion 3f, the inner diameter fitting portion (first inner diameter portion) 2b of the housing 2, the second fitting sliding portion 3g, and the inner diameter fitting portion (second inner diameter portion) 2e of the housing 2 preferably satisfy the following conditional formula (1).

[0019] |L2×α2-L1×α1|*Δt <L1-L2 … (1) In conditional formula (1), L1 is the inner diameter of the housing 2, L2 is the outer diameter of the lens unit 30, α1 is the thermal expansion coefficient of the housing 2, α2 is the thermal expansion coefficient of the lens frame 3, and Δt is the temperature change. For example, the inner diameter L1 is the diameter (minimum diameter) at the inner diameter fitting portion 2b of the housing 2, and the outer diameter L2 is the diameter (maximum diameter) at the first fitting sliding portion 3f of the lens frame 3. Alternatively, the inner diameter L1 is the diameter (minimum diameter) at the inner diameter fitting portion 2e of the housing 2, and the outer diameter L2 is the diameter (maximum diameter) at the second fitting sliding portion 3g of the lens frame 3.

[0020] A groove 4c is provided in the connecting portion 4. An elastic body 8 is housed in the groove 4c, and the elastic body 8 is sandwiched between the groove 4c and the inner diameter of the housing 2. That is, in this embodiment, the elastic body 8 is disposed (sandwiched) between the outer diameter of the connecting portion 4 and the inner diameter of the housing 2. This helps to strengthen the holding force between the housing 2 and the connecting portion 4.

[0021] Next, we will explain focus correction due to temperature changes in the imaging device 1. The position where the inner diameter threaded portion 4a of the connecting portion 4 of the imaging device 1 is threaded with the outer diameter threaded portion 3a of the lens frame 3 is located closer to the image side than the position where the inner diameter threaded portion 2a of the housing 2 is threaded with the outer diameter threaded portion 4b of the connecting portion 4 and the first lens holding portion 3c of the lens frame 3. The thermal expansion coefficient of the connecting portion 4 is greater than the thermal expansion coefficients of the housing 2 and the lens frame 3.

[0022] Here, an example will be described in which the ambient temperature rises. When the temperature of the lens 7 rises in conjunction with an increase in the ambient temperature, changes in the refractive index of the lens 7 and changes in its characteristics, such as thermal deformation, occur, causing the image-forming position of the lens 7 to shift away from the image sensor 5a toward the object side. As the temperature rises further, the housing 2 thermally expands in a direction extending toward the object side based on the sensor unit holding portion 2C. Similarly, the lens frame 3 thermally expands in a direction extending toward the object side based on the screw engagement position of the connecting portion 4 and the lens frame 3. As a result, the image-forming position of the lens 7 shifts away from the image sensor 5a toward the object side. Meanwhile, as the temperature rises, the connecting portion 4 thermally expands in a direction extending toward the image side based on the screw engagement position of the connecting portion 4 and the housing 2.

[0023] The operation of the connecting portion 4 changes the characteristics of the lens 7 and the imaging element 5 due to thermal expansion of the housing 2 and the lens frame 3. a This allows compensation for the displacement of the image forming position that tends to move away from the image sensor 5 toward the object side. a The positions of the two can be matched within the range of the depth of focus, making it possible to maintain good image quality without blurring.

[0024] Next, we will explain the behavior of the fitting portion between the lens frame 3 and the housing 2. For example, consider a case where the housing 2 and the lens frame 3 are made of the materials and have the dimensions shown in Table 1 below. In this case, the gap between the fitting portion between the lens frame 3 and the housing 2 at room temperature is 21.5 - 21.493 = 0.007 mm, meaning that there is a minimum gap of 7 μm. For example, when the temperature change Δt is +80°C, the temperature change causes |21.5 × 210 × 10 -7 -21.493×250x10 -7 It expands by |×80=0.0068 mm, or 6.8 μm. Because the gap set for the amount of expansion is large, the gap does not disappear due to expansion. Therefore, the extension due to expansion of the connecting portion 4 is not hindered, and the connecting portion 4 slides while fitting together. As a result, the only part interposed between the lens unit 30 and the sensor unit 5 is the housing 2, which reduces the factors that cause dimensional variation in the parts and makes it possible to reduce positional deviation between the optical axis of the lens unit 30 and the imaging center of the sensor unit 5, i.e., optical axis deviation.

[0025] [Table 1]

[0026] With the above configuration, the inner diameter threaded portion 4a of the connecting portion 4 is threadedly engaged with the outer diameter threaded portion 3a of the lens unit 30, and the outer diameter threaded portion 4b of the connecting portion 4 is threadedly engaged with the inner diameter threaded portion 2a of the housing 2, so that the lens unit 30 is threadably held in the housing 2 via the connecting portion 4. The connecting portion 4 also has a groove 4c, in which an elastic body 8 is housed, and the elastic body 8 is sandwiched between the groove 4c and the inner diameter of the housing 2. This assisted the holding force of the connecting portion 4 and the housing 2, making it possible to maintain stable holding even when temperature changes, such as high or low temperatures, occur.

[0027] In addition, the characteristics of the lens 7 change due to the expansion and contraction of the connecting portion 4 in response to changes in the environmental temperature, and the imaging element 5 changes due to the expansion and contraction of the housing 2 and the lens frame 3. aThis allows compensation for the displacement of the imaging position that tends to move away from the image sensor 5 even when a temperature change occurs. a Since the positions of the two images coincide within the range of the depth of focus, it is possible to maintain good image quality without blurring.

[0028] Furthermore, by providing a fitting portion between the lens unit 30 and the housing 2, the only part interposed between the lens unit 30 and the sensor unit 5 is the housing 2. This reduces the factors that cause variations in the dimensions of the parts, making it possible to reduce the positional deviation between the optical axis of the lens unit 30 and the imaging center of the sensor unit 5, i.e., the optical axis deviation.

[0029] In this embodiment, the position in the optical axis direction of the first fitting sliding portion 3f of the lens unit 30 and the corresponding inner diameter fitting portion 2b of the housing 2 is approximately the same as that of the third lens 7c. Furthermore, the position in the optical axis direction of the second fitting sliding portion 3g of the lens unit 30 and the corresponding inner diameter fitting portion 2e of the housing 2 is approximately the same as that of the first lens 7a. This prevents the lens unit 30 from tilting relative to the sensor unit 5, making it possible to further reduce optical axis misalignment.

[0030] As described above, according to this embodiment, it is possible to provide an imaging device that has a stable configuration and can suppress positional deviation even when temperature changes occur. The imaging device of this embodiment is suitable for use in an in-vehicle camera, a surveillance camera, a network camera, or the like, but can also be applied to other imaging devices.

[0031] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0032] 1. Imaging device 2. Case 2b Inner diameter fitting portion (first inner diameter portion) 3 Lens frame 3f First fitting sliding part 4 Connecting part 4a Inner diameter thread portion (first mounting portion) 4b Outer diameter thread portion (second mounting portion) 5a Image sensor 7. Multiple lenses (imaging optical system) 30 Lens unit

Claims

1. The housing and a lens unit having a plurality of lenses and a lens frame for holding the plurality of lenses; a ring-shaped connecting portion; the housing has a first inner diameter portion; a first attachment portion is provided on an inner diameter portion of the connecting portion, and a second attachment portion is provided on an outer diameter portion of the connecting portion; the connecting portion holds an outer diameter portion of the lens frame via the first attachment portion, the housing holds an outer diameter portion of the connecting portion via the second mounting portion, the lens frame has a first fitting sliding portion that is fitted with the first inner diameter portion of the housing and is slidable in the optical axis direction, A lens module, characterized in that an elastic body is disposed between the outer diameter portion of the connecting portion and the inner diameter portion of the housing.

2. The lens module according to claim 1 , wherein the first mounting portion and the second mounting portion are each a screw.

3. the housing has a second inner diameter portion; 3. The lens module according to claim 1, wherein the lens frame has a second fitting sliding portion that fits into the second inner diameter portion of the housing and is slidable in the optical axis direction.

4. the first fitting sliding portion is disposed closest to a lens disposed closest to an image side among the plurality of lenses, 4. The lens module according to claim 3, wherein the second fitting sliding portion is disposed closest to the lens disposed closest to the object side among the plurality of lenses.

5. a position of the first fitting sliding portion in the optical axis direction is the same as a position of the lens disposed closest to the image side in the optical axis direction, 5. The lens module according to claim 4, wherein a position of the second fitting sliding portion in the optical axis direction is the same as a position of the lens disposed closest to the object side in the optical axis direction.

6. When the inner diameter of the first inner diameter portion of the housing is L1, the outer diameter of the first fitting sliding portion of the lens frame is L2, the thermal expansion coefficient of the housing is α1, the thermal expansion coefficient of the lens frame is α2, and the temperature change is Δt, |L2×α2−L1×α1|×Δt<L1−L2 6. The lens module according to claim 1, wherein the following condition is satisfied:

7. When the inner diameter of the second inner diameter portion of the housing is L1, the outer diameter of the second fitting sliding portion of the lens frame is L2, the thermal expansion coefficient of the housing is α1, the thermal expansion coefficient of the lens frame is α2, and the temperature change is Δt, |L2×α2−L1×α1|×Δt<L1−L2 6. The lens module according to claim 3, wherein the following condition is satisfied:

8. A lens module according to any one of claims 1 to 7; an imaging element held in the housing.

Images