Optical unit and distance image capturing device

Abstract

To provide an optical unit that can easily achieve both high-precision alignment and suppression of stray light, etc. [Solution] The optical unit 50 has an element substrate 55 on which an imaging element 56 is arranged, a sensor cover 61 attached to the element substrate so as to cover the imaging element, and a lens holder 53 on which a lens 52 is attached, and the lens holder and sensor cover are joined together.The optical unit 50 has a stray light suppression section at the joint between the lens holder and the sensor cover that suppresses the generation of stray light entering the optical unit.

Description

[Technical Field]

[0001] The present invention relates to an optical unit, and also to a range image capturing device using the optical unit. [Background technology]

[0002] In order to ensure and improve the performance of an imaging device, it is important to precisely align the imaging element with the lens system that guides light to the imaging element. In addition, it is also important to minimize stray light or disturbance light that enters the device from sources other than the lens system.

[0003] In this regard, Patent Document 1 discloses a technology in which a light-shielding member having a ring-shaped or notched ring-shaped light-shielding protrusion is disposed between a stay that holds a lens unit and a substrate on which an imaging element is mounted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6133988 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 lists a stereo camera having a pair of imaging modules as an application of the technology. Each imaging module acquires a visible light image, so it is assumed that visible light is also entering the interior.

[0006] On the other hand, distance image capturing devices differ from general imaging devices such as the stereo camera described above in several respects, such as the fact that they often use infrared light, which is not visible light, and that they emit light for distance measurement from their own light source. For this reason, as will be described in detail later, it is not easy to achieve both high-precision alignment and suppression of stray light and the like simply by applying the technology of Patent Document 1.

[0007] In view of the above circumstances, an object of the present invention is to provide an optical unit that can easily achieve both high-precision alignment and suppression of stray light and the like. [Means for solving the problem]

[0008] A first aspect of the present invention is a camera having an element substrate on which an image sensor is arranged, a sensor cover attached to the element substrate so as to cover the image sensor, and a lens holder attached to which a lens is attached, By adhesive It is a cemented optical unit. This optical unit includes a stray light suppression portion at the joint between the lens holder and the sensor cover, which suppresses the occurrence of stray light entering the optical unit. the stray light suppression unit is composed of an alignment groove provided in the lens holder and a convex portion provided in the sensor cover and inserted into the alignment groove; In a direction perpendicular to the optical axis of the lens, the width of the alignment groove is wider than the width of the convex portion of the sensor cover.

[0009] A second aspect of the present invention is a distance imaging device including the optical unit according to the first aspect. [Effects of the Invention]

[0010] According to the present invention, an optical unit can be provided that easily achieves both high-precision alignment and suppression of stray light and the like. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a camera according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the general configuration of the camera. [Figure 3] FIG. [Figure 4] FIG. 2 is an exploded view showing the imaging unit of the camera. [Figure 5] FIG. 2 is a cross-sectional view of an optical unit of the imaging unit. [Figure 6] 4 is a schematic cross-sectional view showing a joint portion between a lens holder and a sensor cover in the optical unit. FIG. [Figure 7] 10 is a schematic cross-sectional view showing a joint portion between a lens holder and a sensor cover in a modified example of the optical unit. FIG. [Figure 8] 10A and 10B are schematic diagrams showing a lens holder and a sensor cover according to a modified example. [Figure 9] 10A and 10B are schematic diagrams showing a lens holder and a sensor cover according to a modified example. [Figure 10] 10A and 10B are schematic diagrams showing a lens holder and a sensor cover according to a modified example. [Figure 11] FIG. 10 is a schematic cross-sectional view showing a joint portion between a sensor cover and an element substrate in an optical unit according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a schematic diagram showing an element substrate according to a modified example of the optical unit. [Figure 13] 10 is a schematic cross-sectional view showing a joint portion between a sensor cover and an element substrate according to a modified example of the optical unit. FIG. [Figure 14] FIG. 10 is a schematic cross-sectional view showing an optical unit according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A first embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view showing a camera 1, which is a distance imaging device according to this embodiment. The camera 1 has a rectangular parallelepiped shape defined by a metal housing 10. Housing 10 has, on its front side, a first opening 2 for imaging and a second opening 3 for a light source that irradiates reference light. Two second openings 3 are provided, one on either side of first opening 2.

[0013] 2 is a schematic diagram showing the overall configuration of the camera 1. Inside the housing 10, a power supply board 20, a main board 30, and an imaging unit 40 are arranged. The power supply board 20 is connected to a power source and generates voltages for driving the various components of the camera 1. The main board 30 includes integrated circuits and is connected to the power supply board 20 and the imaging unit 40. The main board controls the operation of the power supply board 20 and the imaging unit 40 and performs correction processing of data handled by the imaging unit 40. The main board is also connected to a hub 31 used for connecting to the power supply Es and the external computer 200. There are no particular restrictions on the integrated circuits provided on the main board 30, and an FPGA (Field-Programmable Gate Array), ASIC (Application Specific Integrated Circuit), CPU, etc. can be selected and used as appropriate.

[0014] 3 is an exploded view of the camera 1. The imaging section 40 includes a light source board 41 on which a light source is attached, and an optical unit 50 including a lens and an imaging element. The optical unit 50 is an optical unit according to the present invention. The housing 10 has a main body 11 with an internal space and a lid 12. The power supply board 20, main board 30, and imaging unit 40 are arranged inside the main body 11, and the lid 12 is screwed to the main body 11, sealing the inside of the housing 10. A rubber packing 13 is arranged between the main body 11 and the lid 12, and the inside of the housing 10 is kept waterproof when the lid 12 is attached. A light-shielding cover 4 is attached to the first opening 2 and the second opening 3, and is configured to prevent natural light and the like that is not used to acquire a distance image (described later) from entering the housing 10.

[0015] 4 shows an exploded view of the imaging unit 40. The imaging unit 40 of this embodiment uses two vertical cavity surface emitting lasers (VCSELs) as light sources, and two VCSELs 42 are attached to a light source substrate 41. The VCSELs 42 are just an example, and it is of course possible to use other light sources. The optical unit 50 includes a lens barrel 51 to which a lens 52 is attached, a lens holder 53 to which the lens barrel 51 is fixed, and an element substrate 55 to which an imaging element 56 is mounted. The imaging element 56 may be, for example, a CMOS image sensor, and is attached to the surface of the element substrate 55 facing the first opening 2. Furthermore, the imaging element 56 is covered by a sensor cover 61 to which a bandpass filter 62 is attached, and light that passes through the lens 52 and enters the imaging element 56 is configured to reach the imaging element 56 after passing through the bandpass filter 62.

[0016] A metal support block 60 is disposed around the lens 52 and lens holder 53 between the light source substrate 41 and the element substrate 55. The support block 60 is in contact with the light source substrate 41 and the element substrate 55, and is configured so that heat generated by the VCSEL 42 and the image sensor 56 when they are driven is dissipated to the outside of the housing 10 via the support block 60.

[0017] On the surface of the sensor cover 61 opposite to the surface facing the imaging element 56, a convex portion 63 for alignment is formed around the band-pass filter 62. The convex portion 63 according to this embodiment has a square frame shape when viewed from the front, and is positioned approximately concentrically with the band-pass filter 62.

[0018] 5 is a cross-sectional view of optical unit 50. An alignment groove 53a having a generally square shape in front view is formed on the lower side of lens holder 53, facing sensor cover 61. The width of alignment groove 53a is wider than the width of convex portion 63 of sensor cover 61, and the dimensions are such that the entire convex portion 63 can enter alignment groove 53a and, when inserted, lens holder 53 and sensor cover 61 can move relative to each other within a certain range.

[0019] When manufacturing the optical unit 50, the lens holder 53 side and the element substrate 55 side are each produced, and the lens holder 53 and the sensor cover 61 are joined together in a state in which the lens 52 and the image sensor 56 are aligned. This alignment involves both adjusting the optical axis position of the lens 52 relative to the image sensor 56 in a planar direction along the light receiving surface of the image sensor 56, and adjusting the distance between the lens 52 and the image sensor 56 in a direction perpendicular to the planar direction (the up and down direction in FIG. 4 ).

[0020] Alignment is performed by inserting the convex portion 63 of the sensor cover 61 into the alignment groove 53a of the lens holder 53, lightly and temporarily fixing them together with an adhesive, while checking the image captured by the image sensor 56. Once alignment is complete, the adhesive is allowed to harden completely, fixing the positional relationship between the lens holder 53 and the sensor cover 61 and completing the optical unit 50. For the alignment work described above, a light-curing adhesive such as an ultraviolet-curing adhesive is suitable. Since there are individual differences between the lens holder 53 side and the element substrate 55 side, the relative positional relationship between the lens holder 53 and the sensor cover 61 in the completed optical unit 50 basically differs from one to another.

[0021] The camera 1 acquires a distance image based on the reflected light from the target object, which is the reference light emitted from the VCSEL 42, which is the light source, using the image sensor 56, and measures the distance to the object using the time-of-flight (TOF) method. In camera 1, the presence of the above-described light-shielding cover 4 almost completely prevents visible light with a wavelength significantly different from that of the reference light from entering housing 10. However, it is not possible to completely prevent natural light with the same or similar wavelength as the reference light from entering housing 10. Furthermore, a small portion of the reference light emitted from VCSEL 42 is reflected by light-shielding cover 4 and remains within housing 10. If this light enters optical unit 50 and reaches image sensor 56, it becomes stray light that generates noise and adversely affects the ranging performance of camera 1.

[0022] In the optical unit 50, one of the main paths through which stray light is expected to enter is the gap between the lens holder 53 and the sensor cover 61. Furthermore, due to the alignment described above, adhesive may be placed between the underside of the lens holder 53 and the sensor cover 61, which may result in the two being fixed without contacting each other, increasing the possibility of stray light entering. In the optical unit 50 according to this embodiment, the convex portion 63 of the sensor cover 61 is inserted into the alignment groove 53a of the lens holder 53 and the two are fixed together, and the alignment groove 53a and the convex portion 63 form the stray light suppression unit 100. For this reason, as shown in FIG. 6 , one of the inner surfaces of the alignment groove 53a is always located inside the convex portion 63. This causes much of the light that enters through the gap to be reflected by this inner surface, significantly reducing the amount of light that reaches the bandpass filter 62. As a result, this can contribute to suppressing both the generation of stray light and the amount of light, if any, that occurs.

[0023] The configuration of the stray light suppression unit for reducing stray light generated by the gap between the lens holder 53 and the sensor cover 61 according to this embodiment is not limited to the above-described embodiment. In the modified example shown in Fig. 7, the lens holder 53 does not have the alignment groove 53a, and only the peripheral wall 54 for defining the range of relative movement protrudes downward. Furthermore, after the lens holder 53 and the sensor cover 61 are fixed together, a light-blocking paste 72 functioning as a stray light suppressor is disposed around the entire periphery of the lens holder 53 so as to cover the adhesive 71 located in the gap between the lens holder 53 and the sensor cover 61. Even with this configuration, it is possible to reduce stray light generated by the gap between the lens holder 53 and the sensor cover 61. Naturally, this configuration may be combined with the alignment groove 53a.

[0024] 8, the cross-sectional shape of the convex portion 63A has a slope, and the inner surface of the alignment groove 53a is also sloped. In this way, when the height of the convex portion and the depth of the alignment groove are the same, the contact area of ​​the adhesive is increased compared to the aspect shown in the embodiment, and the lens holder 53 and the sensor cover 61 can be more firmly bonded. The slope may be provided on only one of the convex portion and the alignment groove, or the slope angle may be different between the convex portion and the alignment groove.

[0025] 9, the lower end of the lens holder 53 protrudes like a brim, so that the lens holder 53 has a shade 73 that functions as a stray light suppressor. Such a shade is highly effective in preventing light that is emitted from the VCSEL 42 and then reflected by the light-shielding cover 4 from entering the gap between the lens holder 53 and the sensor cover 61. The effect of the shade 73 is enhanced by extending it outward beyond the sensor cover 61 as shown in the figure, but this is not essential and the shade 73 may be sized to remain within the range of the sensor cover 61 in a front view. Instead of or in addition to the shade 73, it is also possible to provide a shade that protrudes inward.

[0026] 10, a second convex portion 65 that functions as a stray light suppression portion is further provided in the sensor cover 61 within the area surrounded by the convex portion 63. In this way, a portion of the light that passes through the gap between the lens holder 53 and the sensor cover 61 and enters the lens holder 53 is reflected, further reducing the amount of light that reaches the bandpass filter 62. The position and height of the second convex portion 65 can be set appropriately within a range that does not interfere with the lens holder 53 during the alignment process and does not interfere with the lens holder 53 and lens 52 when bonded, and the higher the position, the greater the effect that can be obtained.

[0027] A second embodiment of the present invention will be described with reference to the drawings, starting with Fig. 11. In the following description, components common to those already described will be assigned the same reference numerals and redundant description will be omitted. Another route through which stray light can enter the optical unit 50 is the joint between the sensor cover 61 and the element substrate 55. The sensor cover 61 does not require highly accurate alignment and is usually attached without alignment, so a large gap is unlikely to form between the sensor cover 61 and the element substrate 55. However, since light that does enter can easily reach the imaging element 56, it is preferable to take measures to prevent this. In this embodiment, a configuration for suppressing such stray light will be described.

[0028] 11 has a downwardly protruding light-shielding wall 81 located inside a peripheral wall 80 that protrudes downward and is joined to the element substrate 55. This allows most of the light that enters through the gap between the peripheral wall 80 and the element substrate 55 to be reflected by the light-shielding wall 81, which functions as a stray light suppression section, and to be prevented from reaching the image sensor 56. The light-shielding wall 81 is preferably formed so as to surround the imaging element 56 in the normal direction relative to the light-receiving surface of the imaging element 56. There is no superiority or inferiority in the shape as long as it surrounds the imaging element, and any desired shape, such as a circular frame or a polygonal frame, can be set taking into consideration interference with other components on the element substrate 55, etc. The protruding length of the light-shielding wall 81 is preferably as long as possible within a range that does not cause interference with the element substrate 55 when the sensor cover 61 is attached.

[0029] The configuration of the stray light suppression section that suppresses stray light entering from between the sensor cover 61 and the element substrate 55 is not limited to the one described above. 12 has a light absorbing section 82 that functions as a stray light suppression section around the imaging element 56. This allows most of the light that approaches the imaging element 56 while reflecting off the sensor cover 61 to be captured by the light absorbing section and prevented from reaching the imaging element 56. The light absorbing portion 82 can be, for example, a black or dark-colored member, and can be formed by attaching a sheet-like member, applying a paste and hardening it, etc. If the surface of the light absorbing portion 82 is excessively smooth, some light is likely to be reflected without being absorbed, so it is preferable that the surface of the light absorbing portion 82 has an appropriate degree of roughness. Depending on the material of the light absorbing portion 82, it is possible to expect an effect of suppressing a rise in temperature of the imaging element 56 during operation of the camera 1 by absorbing heat generated by the imaging element 56. Examples of materials that can be expected to be effective include graphite and silicone.

[0030] The embodiment shown in FIGS. 11 and 12 is an example in which the configuration functioning as a stray light suppression section is located in a space surrounded by the sensor cover 61 and the element substrate 55. As another example, as shown in Figure 13, even if a groove 83 is formed in the element substrate 55 and the sensor cover 61 and element substrate 55 are joined with the peripheral wall 80 inserted into the groove 83, the peripheral wall 80 and the groove 83 function as a stray light suppression section located at the joint between the sensor cover 61 and the element substrate 55, thereby suppressing stray light from entering between the sensor cover 61 and the element substrate 55.

[0031] Two or more of the configurations according to the aspects described in this embodiment can be combined. In addition, since the location where the configuration is provided is different from that of the first embodiment, by combining the configuration with each aspect of the first embodiment including the modified examples, it is possible to further reduce the generation of stray light.

[0032] Each embodiment of the present invention has been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and configuration changes and combinations within the scope that do not deviate from the gist of the present invention are also included.

[0033] For example, a stray light suppression unit may be provided in a location not mentioned in the above-described embodiment. In addition to the above-described paths, the gap between the lens barrel 51 and the lens 52 may also be a path for stray light to enter. However, by providing a shade 91 that protrudes from the outer periphery, as in the modified lens barrel 51A shown in FIG. 14, the shade 91 reduces the entry of light through the gap between the lens barrel 51 and the lens 52, and functions as a stray light suppression unit. This configuration is particularly effective for light that is emitted from the VCSEL 42 and then reflected by the light-shielding cover 4. The stray light suppression section corresponding to the gap between the lens barrel 51 and the lens 52 is not limited to the aspect shown in Fig. 14. Furthermore, such a stray light suppression section can be combined with either or both of the first and second embodiments. [Explanation of symbols]

[0034] 1. Camera (distance imaging device) 2 First opening 3 Second opening 4 Light-shielding cover 10. Cabinet 11 Main unit 12 Lid 13 Rubber packing 20 Power supply board 30 Main board 40 Imaging unit 41 Light source board 42 VCSEL 50 Optical Unit 51 Telescope tube 52 Lens 53 Lens holder 53a Alignment groove 55 Element substrate 56 image sensor 61 Sensor cover 63, 63A convex part 65 Second convex part 71 Adhesive 72 Light-blocking paste 73 Shades 81 Blackout wall 82 Light absorbing part 100 Stray light suppression section

Claims

1. An optical unit including: an element substrate on which an image sensor is disposed; a sensor cover attached to the element substrate so as to cover the image sensor; and a lens holder attached to which a lens is attached, the lens holder and the sensor cover being bonded together with an adhesive; a stray light suppression portion that suppresses the generation of stray light that enters the optical unit, at a joint portion between the lens holder and the sensor cover; the stray light suppression unit is configured with an alignment groove provided in the lens holder and a convex portion provided in the sensor cover and extending into the alignment groove, a width of the alignment groove in a direction perpendicular to the optical axis of the lens is greater than a width of the protrusion of the sensor cover; Optical unit.

2. The stray light suppression unit has a shade that protrudes in a brim-like shape from the lower end of the lens holder. The optical unit according to claim 1 .

3. The stray light suppression unit has a light-shielding paste provided around the entire periphery of the lens holder so as to cover the adhesive. The optical unit according to claim 1 .

4. The optical unit according to claim 1 , further comprising the stray light suppression unit in a space surrounded by the sensor cover and the element substrate.

5. An optical unit according to any one of claims 1 to 4, Range imaging device.

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