WO2021019362A1

WO2021019362A1 - Camera, method of positioning lens unit in camera, and stereo camera

Info

Publication number: WO2021019362A1
Application number: PCT/IB2020/056811
Authority: WO
Inventors: Shuji Takamatsu
Original assignee: Ricoh Company, Ltd.
Priority date: 2019-07-31
Filing date: 2020-07-21
Publication date: 2021-02-04

Abstract

A camera includes a sensor, a sensor holder holding the sensor, a lens unit including a lens configured to focus light on a photo-sensing surface of the sensor, and a nut contacting the sensor holder. In the camera, the lens unit includes external threads, and a fitting part formed on an outer region of a barrel unit containing the lens, the fitting part being coaxial with an optical axis of the lens. In the camera, the sensor holder includes a to-be-fitted part formed on an inner side of an installation hole for the lens unit, and internal threads threadably fitting to the external threads. In the camera, the to-be-fitted part is coaxial with the optical axis of the lens.

Description

[DESCRIPTION]

[Title of Invention]

CAMERA, METHOD OF POSITIONING LENS UNIT IN CAMERA, AND STEREO

CAMERA

[Technical Field]

[0001]

Embodiments of the present disclosure relate to a camera, a method of positioning a lens unit, and a stereo camera.

[Background Art]

[0002]

In the related art, technologies are known in the art to determine the relative positions of a pair of lens units in cameras such as stereo cameras with reference to a sensor holder such as the main body of the camera and to fix these lens units to the sensor holder.

[0003]

An apparatus is known in the art that is provided with a stationary barrel unit that has internal threads formed on its inner side, a movable barrel unit that has external threads formed on its peripheral surface to hold the lens and can be threadably fitted to the inner surface of the stationary barrel unit, and a nut that controls the relative rotation of the above elements (see, for example, PTL 1). In such a known apparatus, the relative positions of the movable barrel unit and the stationary barrel unit in the optical-axis direction of the lens are determined, and then the movable barrel unit and the stationary barrel unit are fixed by a nut.

[Citation List]

[Patent Literature]

[0004]

[PTL 1]

International Publication No. W02015-190812

[Summary of Invention]

[Technical Problem]

[0005]

However, in the known apparatuses (see, for example, PTL 1), there are some cases in which the relative positions of parts in the direction intersecting with the optical axes of the lenses cannot precisely be determined.

[0006]

The technologies according to the embodiments of the present disclosure aim at precisely determining the relative positions of a pair of lens units in the direction intersecting with the optical axis of the lens with reference to the sensor holder.

[Solution to Problem]

[0007]

[Advantageous Effects of Invention]

[0008]

With the technologies according to the embodiments of the present disclosure, the relative positions of a pair of lens units in the direction intersecting with the optical axis of the lens can precisely be determined with reference to the sensor holder.

[Brief Description of Drawings] [0009]

The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

[Fig. 1]

FIG. 1 is a block diagram illustrating an overall configuration of a pair of stereo cameras according to embodiments of the present disclosure.

[Fig. 2]

FIG. 2 is a block diagram illustrating a functional configuration of an image processing board according to embodiments of the present disclosure.

[Fig. 3]

FIG. 3 A, FIG. 3B, and FIG. 3C are diagrams each illustrating an image captured by a stereo camera according to embodiments of the present disclosure.

[Fig. 4]

FIG. 4 is an exploded perspective view of a stereo camera according to embodiments of the present disclosure.

[Fig. 5]

FIG. 5 is a sectional view of the components around a lens unit in a stereo camera, according to a first embodiment of the present disclosure.

[Fig. 6]

FIG. 6 is a flowchart of a positioning and fixation method for a lens unit, according to the first embodiment of the present disclosure.

[Fig. 7]

FIG. 7 is a sectional view of the components around a lens unit in a stereo camera, according to a second embodiment of the present disclosure.

[Fig. 8]

FIG. 8A and FIG. 8B are diagrams each illustrating how a nut elastically deforms, according to first and second modifications of the above embodiments of the present disclosure, where FIG. 8A illustrates a first modification of the embodiments of the present disclosure and FIG. 8B illustrates a second modification of the embodiments of the present disclosure.

[Description of Embodiments]

[0010]

Embodiments of the present disclosure are described below with reference to the accompanying drawings. In the drawings, like reference signs denote like elements, and overlapping description may be omitted.

[0011]

In the present embodiment, when a lens unit including a lens configured to focus light on a photo- sensing surface of a sensor is fitted to a sensor holder that holds the sensor, a fitting part that is coaxially formed with the optical axis of the lens included in the lens unit is fitted to a to-be-fitted part that is included in the sensor holder and is coaxially formed with the optical axis of the lens. Moreover, the lens unit is fitted to the sensor holder, using a nut contacting the sensor holder, the external threads included in the lens unit, and the internal threads included in the sensor holder. Due to such a configuration, the position of a lens unit in the direction intersecting with the optical axis of the lens can precisely be determined with reference to the sensor holder.

[0012]

In the following description, a binocular stereo camera provided with a pair of cameras according to the present embodiment is described as an example. Firstly, an overall configuration or operation of the stereo camera 100 according to the present embodiment is described below with reference to FIG. 1 to FIG. 3. [0013]

FIG. 1 is a block diagram illustrating an overall configuration of the stereo camera 100 according to the present embodiment. As illustrated in FIG. 1, the stereo camera 100 includes a pair of lens units 20a and 20b, a pair of sensors 30a and 30b, a pair of sensor controllers 40a and 40b, and an image processing board 50. In the following description, the pair of lens units 20a and 20b, the pair of sensors 30a and 30b, and the pair of sensor controllers 40a and 40b may be referred to simply as a pair of lens units 20, a pair of sensors 30, and a pair of sensor controllers 40, respectively, when it is not necessary to distinguish these terms from each other. This is applicable to other elements or components with a subscript a or b.

[0014]

Among the above elements of the stereo camera 100, each one of the pair of lens units 20 includes a plurality of lenses, and is configured to form an image of an object on the corresponding one of the pair of sensors 30. The pair of sensors 30 capture an image of the object formed by the pair of lens units 20, and outputs the data of the captured image to the image processing board 50 through the pair of sensor controllers 40. In the present embodiment, the term“image data” refers to the data indicating the brightness values of a plurality of pixels that make up an image.

[0015]

In FIG. 1, the specification of the lens unit 20a may be equivalent to that of the lens unit 20b, and the specification of the sensor 30a may be equivalent to that of the sensor 30b. Moreover, the specification of the sensor controller 40a may be equivalent to that of the sensor controller 40b. A two-dimensional imaging device such as a charge coupled device (CCD) and a complementary metal oxide semiconductor (CMOS) may be used for the pair of sensors 30.

[0016]

The pair of lens units 20a and 20b are arranged in the direction intersecting with the optical axes of the lenses, and are attached and fixed to a main body 10 of the stereo camera 100. Moreover, the pair of lens units 20a and 20b are arranged such that the optical axis 211a of the lens included in the lens unit 20a becomes approximately parallel to the optical axis 211b of the lens included in the lens unit 20b. In the present embodiment, the distance in the X-direction (see FIG. 4) between the optical axis 211a of the lens included in the lens unit 20b and the optical axis 211b of the lens included in the lens unit 20b is referred to as the base-line length B.

[0017]

For example, the sensor controller 40 controls the exposure of the sensor 30, the reading of the image data, the communication with an external circuit, and the transmission of the image data. The sensor controller 40 is electrically connected to the image processing board 50 through a data bus 61 and a serial bus 62.

[0018]

The image processing board 50 is an electronic circuit board provided with a central processing unit (CPU) 51, a field-programmable gate array (FPGA) 52, a random access memory (RAM) 53, a read only memory (ROM) 54, a serial interface (I/F) 55, and a data interface (I/F) 56. These elements are electrically connected to each other through the data bus 61.

[0019]

Among these elements, the CPU 51 is configured by a processor or the like, and controls the operation of the image processing board 50 in a centralized manner. Moreover, the CPU 51 performs at least one of image processing and image recognition processes on the image data that is captured and obtained by the pair of sensors 30 and is output through the pair of sensor controllers 40.

[0020]

For example, the RAM 53 is configured by a volatile semiconductor memory, and is used as a work area in which the CPU 51 executes a program. The RAM 53 provides a storage area for temporarily storing data therein when various types of signal processing and image processing are applied.

[0021]

For example, the ROM 54 is configured by a nonvolatile semiconductor memory, and stores various kinds of programs and various kinds of parameters that operate on the stereo camera 100.

[0022]

The CPU 51 uses the RAM 53 as a work area, and executes a program stored, for example, in the ROM 54 to implement various kinds of functions as will be described later in detail. Some of or the entirety of the functions that the CPU 51 has may be implemented by hardware using wired logic connection.

[0023]

The image data that is output through the sensor controller 40 is transferred to the RAM 53 of the image processing board 50 through the data bus 61.

[0024]

The FPGA 52 executes processing that needs to be done in real time on the image data stored in the RAM 53. The processing that needs to be done in real time includes image processing such as gamma correction and distortion correction (i.e., the collimation processes of right-and- left images).

[0025]

The CPU 51 and the FPGA 52 can send, for example, instructions to change the value of exposure control by the sensor, instructions to change the image reading parameters, and instructions to exchange various kinds of setting data to the sensor controller 40 through the serial bus 62.

[0026]

The serial interface 55 is an interface that sequentially transmits the digital data on a 1-bit-by- 1-bit basis. Alternatively, the serial interface 55 may be a connection interface that adopts such sequential transmission mode as above. The data interface (I/F) 56 is an interface that couples the image processing board 50 to an external device such as a personal computer (PC).

[0027]

FIG. 2 is a block diagram illustrating the functional configuration of the image processing board 50 in the stereo camera 100 according to the present embodiment.

[0028]

As illustrated in FIG. 2, the image processing board 50 includes a disparity detection unit 57 and a distance-image generation unit 58.

[0029]

Among these elements, the disparity detection unit 57 detects the disparity d between a pair of images captured by the pair of sensors 30a and 30b, respectively, and outputs the detected disparity d to the distance-image generation unit 58. The distance-image generation unit 58 calculates the distance D to an object based on the detected disparity d and the base-line length B as described above, using a first equation given below, and generates a distance image based on the calculated distance D to the object. In the present embodiment, the term“distance image” is an image that is generated by two-dimensionally arranging the pixels in which the distance to the object is replaced with brightness.

[0030]

D = (B x f) / d

[0031]

The reference sign“f” in the first equation indicates the focal length of the lens included in the lens unit 20.

[0032]

The operation of the stereo camera 100 according to the present embodiment is described below.

[0033]

FIG. 3 A, FIG. 3B, and FIG. 3C are diagrams each illustrating an image captured by the pair of sensors 30a and 30b, according to the present embodiment.

[0034]

FIG. 3A is a diagram illustrating an object 200 in the actual environment, according to the present embodiment. FIG. 3B is a diagram illustrating an image 30ai_m captured by the sensor 30a, according to the present embodiment. FIG. 3C is a diagram illustrating an image 30bi_m captured by the sensor 30b, according to the present embodiment.

[0035]

In FIG. 3B, the image of the object 200 corresponds to an object image 200ai_m. In FIG. 3C, the image of the object 200 corresponds to an object image 200bi_m.

[0036]

The disparity that is calculated based on the distance D to the object and the base-line length B is present between the image 30ai_m and the 30bi_m. For this reason, as illustrated in FIG. 3B and FIG. 3C, the position of the object image 200ai_m on the image is displaced in the horizontal directions (i.e., the right and left directions in FIG. 3B and FIG. 3C) with reference to the object image 200bi_m.

[0037]

The disparity detection unit 57 as illustrated in FIG. 2 shifts minute blocks of, for example, 7 x 7 pixels and 15 x 15 pixels on the image 30ai_m in the horizontal direction, and calculates the value of difference in brightness with a minute block of the same size on the image 30bi_m. In the present embodiment, the term“value of difference in brightness” indicates the sum total or average of the values of difference in brightness of between a plurality of pixels of the minute block on the image 30ai_m and a plurality of pixels of the corresponding minute block on the image 30bi_m. The amount of shift when the value of difference in brightness is minimized is detected as the disparity d between the pair of minute blocks.

[0038]

The distance-image generation unit 58, as illustrated in FIG. 2, calculates the distance D to an object for each pair of minute blocks based on the disparity d that is detected by the disparity detection unit 57 for each pair of minute blocks, using the first equation. Then, a distance image that is generated by two-dimensionally arranging the pixels in which the calculated distance D to the object is replaced with brightness is output. The minute block as described above may be a block of 1 x 1 pixel.

[0039]

A hardware configuration of the stereo camera 100 according to the present embodiment is described below.

[0040]

FIG. 4 is an exploded perspective view of the hardware configuration of the stereo camera 100 according to the present embodiment.

[0041]

As illustrated in FIG. 4, the stereo camera 100 according to the present embodiment is provided with a main body 10, a pair of lens units 20a and 20b fitted to the main body 10, and a pair of nuts 25a and 25b used to fix the pair of lens units 20a and 20b, respectively, to the main body 10. FIG. 4 illustrates a state in which the pair of lens units 20a and 20b and the pair of nuts 25a and 25b are detached from the main body 10.

[0042]

Among these elements, the main body 10 that serves as a sensor holder accommodates the pair of sensors 30 and the pair of sensor controllers 40. The pair of sensors 30 are held inside the main body 10 in a state where the photo-sensing surface of each sensor intersects with the Z- direction as indicated by an arrow in FIG. 4.

[0043]

An installation hole 11a to which the lens unit 20a is attached is formed on a side of the sensor 30a held inside the main body 10 in the positive Z-direction. A to-be-fitted part 11 la is formed on the inner side of the installation hole 11a, around a central axis along the Z-axis. More specifically, the to-be-fitted part 111a is formed on the inner side of the installation hole 11a within a prescribed range in the Z-axis direction.

[0044]

Internal threads 112a are coaxially formed with the central axis of the to-be-fitted part 111a, on a side of the to-be-fitted part 111a in the positive Z-direction. When something is coaxially formed with some sort of axis of a different object in the present embodiment, the axis of the former object approximately matches the axis of the latter object. Note also that such matching does not indicate a complete match with no error and may have a difference that is small enough to be considered to be an error. This applies to the cases described below where term“match” is used.

[0045]

The internal threads 112a are formed on the inner side of the installation hole 11a within a prescribed range in the Z-axis direction, on a side of the to-be-fitted part 111a in the positive Z- axis direction. Further, an abutment plane 113 that includes a plane intersecting with the Z- axis direction is formed on a side of the internal threads 112a in the positive Z-direction.

[0046]

The lens unit 20a is described below. The lens unit 20a includes a lens 21a and a barrel unit 22a. Among these elements, the lens 21a includes a plurality of lenses that are arranged in the Z-axis direction. The lens 21a focuses the light on the photo-sensing surface of the sensor 30a to form an image of the object on the photo-sensing surface. The central axes of the multiple lenses of the lens 21a match one another. Such central axes are equivalent to the optical axis of the lens 21a.

[0047]

The lens unit 20a and the installation hole 11a of the main body 10 are formed such that the optical axis of the lens 21a intersects with the photo-sensing surface of the sensor 30a that is held inside the main body 10 when the lens unit 20a is attached to the main body 10.

[0048]

The barrel unit 22a is a tubular- shaped member that contains the lens 21a. A fitting part 221a that is to be fitted to the to-be-fitted part 11 la as described above is formed on the outer regions of the barrel unit 22a. The fitting part 221a is formed around a central axis along the Z-axis, and is formed on the outer regions of the barrel unit 22a within a prescribed range in the Z-axis direction. The central axis of the fitting part 221a is coaxially formed with the optical axis of the lens 21a contained in the barrel unit 22a.

[0049]

External threads 222a are formed on the outer regions of the barrel unit 22a on a side of the fitting part 221a in the positive Z-direction, and the external threads are coaxial with the central axis of the fitting part 221a. In other words, there are three central axes including the central axis of the fitting part 221a, the optical axis of the lens 21a, and the central axis of the external threads 222a, and these central axes match one another. The external threads 222a are formed on the outer regions of the barrel unit 22a within a prescribed range in the Z-axis direction, on a side of the fitting part 221a in the positive Z-axis direction.

[0050]

The external threads 222a are formed on the outer regions of the barrel unit 22a, and a pin face 223a that serves as a to-be-engaged part in which a tool is to be engaged is formed on a side of the external threads 222a in the positive Z-direction. The pin face 223a is a rectangular concave portion of predetermined size, and is formed on the outer circumferential surface of the barrel unit 22a. Alternatively, a plurality of pin faces 223a may be formed at various positions on the outer regions of the barrel unit 22a in the circumferential direction.

[0051]

The to-be-engaged part is not limited to the pin face 223a as long as a tool can be made engaged to that to-be-engaged part. More specifically, if the shape of the tool is concave, the to-be- engaged part may be formed in a convex shape. If the shape of the tool is made of a combination of a concave portion and convex portion, the to-be-engaged part may be made of a combination of a convex portion and concave portion. When the tool is a hexagonal wrench, the to-be-engaged part may be formed in a hexagonal concave shape. When the tool is a spanner wrench or lug wrench, the outer regions of the barrel unit are not necessarily circular shaped but may be formed in a polygonal shape.

[0052]

A tool is engaged in the pin face 223 and an assembler or assembling equipment moves the tool in the circumferential direction of the barrel unit 22a, the barrel unit 22a rotates around the central axis of the external threads 222a.

[0053]

The nut 25a is described below in detail. As illustrated in FIG. 4, the nut 25a is a ring-shaped member that has internal threads 251a formed on its inner side. Moreover, a pin face 252a that serves as a to-be-engaged part in which a tool is to be engaged is arranged on the outer regions of the nut 25a. The pin face 252a is used to rotate the nut 25a around the central axis of the internal threads 251a. The configurations and functions of the pin face 252a are similar to the pin face 223 a of the lens unit 20a as described above, and thus redundant descriptions are omitted where appropriate.

[0054]

On the other hand, in the main body 10, an installation hole lib is formed on the other side of the installation hole 11a in the positive X-direction. The installation hole lib is a hole in which the lens unit 20b is installed. The lens unit 20b is installed in the installation hole lib, and is fixed by the nut 25a. The lens unit 20b is fixed to the installation hole 1 lb such that the optical axis of the lens 21b included in the lens unit 20b will be parallel to the Z-axis direction. Due to such configurations as described above, the optical axis of the lens 21a in the lens unit 20a becomes approximately parallel to the optical axis of the lens 21b in the lens unit 20b. The distance between the optical axis of the lens 21a and the optical axis of the lens 21b in the X-direction is equivalent to the base-line length B as described above.

[0055]

All of the main body 10, the lens unit 20, and the nut 25 are made of aluminum (Al). As these elements are made of the same material, the difference in linear expansion among these elements is small. Accordingly, when the air temperature around these elements changes to high temperature or low temperature, the lens unit 20 can be prevented from getting loosened or changed in position with reference to the installation hole 11. As a matter of course, as long as the above elements are made of a material of the same type, a material other than aluminum may be used. As long as the difference in linear expansion among the above elements is small, different types of materials may be used.

[0056]

The configurations and functions of the installation hole lib are similar to those of the installation hole 11a as described above, and the configurations and functions of the lens unit 20b are similar to those of the lens unit 20a as described above. Further, the configurations and functions of the nut 25b are equivalent to those of the nut 25a as described above. In view of these circumstances, overlapping descriptions of the above elements are omitted where appropriate.

[0057]

The components around each one of the lens units 20 according to the first embodiment of the present disclosure are described below with reference to FIG. 5.

[0058]

FIG. 5 is a sectional view of the components around one of the pair of lens units 20 in the stereo camera 100, according to the first embodiment of the present disclosure.

[0059]

Moreover, FIG. 5 is a sectional view of a state in which the lens unit 20 is attached to the installation hole 11 of the main body 10 and is fixed by the nut 25. [0060]

In FIG. 5, the sensor 30 is fixed onto a sensor board 301, and the sensor board 301 is fixed inside the main body 10. As a result, the sensor 30 is held inside the main body 10. The photo-sensing surface of the sensor 30 is orthogonal to the optical axis 211 of the lens 21, which is indicated by a dot-and-dash line in FIG. 5. Note also that the lens 21 may include a plurality of lenses and such lenses are included in the obliquely-hatched area inside the barrel unit 22.

[0061]

As illustrated in FIG. 5, a to-be-fitted part 111 and internal threads 112 are formed on the inner side of the installation hole 11 of the main body 10 in a coaxial manner to the optical axis 211. Moreover, a fitting part 221 and external threads 222 are formed on the outer regions of the barrel unit 22 of the lens unit 20 in a coaxial manner to the optical axis 211. Further, the internal threads 251 are formed on the inner side of the nut 25 in a coaxial manner to the optical axis 211. By contrast, the face of the nut 25 on the side in the negative Z-direction abuts the abutment plane 113 of the installation hole 11.

[0062]

The fitting part 221 and the to-be-fitted part 111 are described below in detail. The fitting part 221 is coaxially formed with a high degree of precision compared with the other parts of the barrel unit 22. In a similar manner, the to-be-fitted part 111 is also coaxially formed with a high degree of precision compared with the other parts of the installation hole 11. The to-be- fitted part 111a and the to-be-fitted part 111b are formed such that the precision of the relative positions of the to-be-fitted part 111 and the to-be-fitted part 111b in the X-direction will be higher than the other parts.

[0063]

Due to such a configuration, once the fitting part 221 is fitted to the to-be-fitted part 111, the central axis of the fitting part 221 matches the central axis of the to-be-fitted part 111 with a high degree of precision. Moreover, the relative positions of the central axis of the fitting part 221 and the central axis of the to-be-fitted part 111 in the X-direction are determined with a high degree of precision. In other words, the fitting part 221 may serve as a knock pin to effect precise positioning, and the to-be-fitted part 111 may serve as a hole that achieves sliding fit for a knock pin.

[0064]

In addition to coaxial formation with a high degree of precision, at least one of the surface roughness and the cylindricity of the fitting part 221 and the to-be-fitted part 111 may be formed with a high degree of precision. Due to such a configuration, the central axes can be matched with a further improved degree of precision, and the relative positions can be determined with a further improved degree of precision. Moreover, the attaching operation goes smoothly as the outer surface of the fitting part 221 can slide smoothly on the inner surface of the to-be- fitted part 111.

[0065]

A method of positioning the lens unit 20 and fixing the lens unit 20 to the main body 10 of the stereo camera 100 is described below with reference to FIG. 6.

[0066]

FIG. 6 is a flowchart of a positioning and fixation method for the lens unit 20, according to the present embodiment.

[0067]

Firstly, in a step S61, the assembler threadably fits the internal threads 251 of the nut 25 to the external threads 222 of the lens unit 20 in order to attach the nut 25 to the outer regions of the barrel unit 22. However, such attachment is done on a temporary basis at this stage. The nut 25 is attached as it is moved forward in the positive Z-axis direction within the range of the external threads 222 in the Z-axis direction. As a result, some of the external threads 222 are exposed to the air on the side of the nut 25 in the negative Z-direction.

[0068] Subsequently, in a step S62, the assembler fits the fitting part 221 of the lens unit 20 to the to- be- fitted part 111 of the installation hole 11, and threadably fits the external threads 222, which are exposed to a negative-Z-direction side of the nut 25, to the internal threads 112. As a result, the lens unit 20 is attached to the installation hole 11. However, such attachment is done on a temporary basis in a similar manner to the above. When the external threads 222 are threadably fitted to the internal threads 112, the fitting part 221 is fitted to the to-be-fitted part 111 in such a manner that the outer circumferential surface of the fitting part 221 slides on the inner surface of the to-be-fitted part 111.

[0069]

Subsequently, in a step S63, the assembler adjusts the external threads 222 that are threadably fitted to the internal threads 112 in the lens unit 20 so as to move the lens unit 20 back and forth in the Z-axis direction. By so doing, the focusing of the lens 21 is adjusted.

[0070]

A pair of images that are captured by the pair of sensors 30 are displayed on an external monitor or the like, and an assembler can adjust the focusing as desired while viewing the displayed images. In so doing, the assembler uses the tool that is engaged in the pin face 223 to rotate each one of the pair of lens units 20 around the optical axis of the lens 21. By so doing, the external threads 222 that are threadably fitted to the internal threads 112 can be adjusted.

[0071]

After the focusing has been adjusted, in a step S64, the assembler threadably fits the internal threads 251 of the nut 25 to the external threads 222 of the lens unit 20, and moves the nut 25 forward in the negative Z-axis direction. As a result, the face of the nut 25 on the side in the negative Z-direction abuts the abutment plane 113 of the installation hole 11. After the abutment, the internal threads 251 are threadably fitted to the external threads 222 such that the nut 25 moves forward in the negative Z-axis direction. As a result, the nut 25 generates an axial force in the positive Z-axis direction. The nut 25 and the lens unit 20 are fixed to the installation hole 11 by the generated axial force. In the step S64, the assembler uses the tool that is engaged in the pin face 252 to rotate the nut 25 around the optical axis of the lens 21. By so doing, the internal threads 251 that are threadably fitted to the external threads 222 can be adjusted.

[0072]

Due to the steps as described above, the relative positions of the pair of lens units 20 can be determined, and the pair of lens units 20 can be fixed to the main body 10. In FIG. 6, example cases in which the assembler controls the positioning and the fixation of the lens unit 20 are depicted. However, no limitation is indicated thereby, and automatic regulation or automatic control may be implemented using, for example, assembling equipment.

[0073]

As described above, the stereo camera 100 according to the present embodiment calculates the distance to an object based on the disparity between a pair of images captured by the pair of sensors 30, using the first equation. The base-line length B that is used in the first equation is a value that is determined in advance, for example, when the specification of the stereo camera 100 is determined or when the stereo camera 100 is designed. For this reason, if an error in the base-line length B is caused when the pair of lens units 20a and 20b are fitted to the main body 10, an error in measurement of the distance by the stereo camera 100 may increase. In particular, when the detected disparity becomes small due to, for example, the fact that the object is at a position far away from the stereo camera 100, the influence of the base-line length B on the distance measurement stands out.

[0074]

When the pair of lens units 20 are fitted to the main body 10, the external threads 222 that are formed on the lens unit 20 are threadably fitted to the internal threads 112 of the installation hole 11. However, this may be insufficient to achieve precise positioning of the lens unit 20 due to an error present at the external threads 222 or the internal threads 112. If the external threads 222 and the internal threads 112 are to be processed with a high degree of precision in order to reduce the error in positioning, threads that have a complicated shape need to be processed with a high degree of precision, and the manufacturing cost of the stereo camera may increase.

[0075]

A fitting part such as a knock pin that is formed at an area other than the outer regions of the barrel unit 22 may be fitted to a hole that achieves sliding fit, which is formed at an area of the main body 10 other than the inner side of the installation hole 11. However, in such a configuration, parts such as a knock pin need to be added to a stereo camera, and a hole that achieves sliding fit needs to be additionally formed. As a result, the manufacturing cost of the stereo camera may increase.

[0076]

In the present embodiment, when the pair of lens units 20 are fitted to the main body 10, the fitting part 221 that is coaxially formed with the optical axis of the lens 21 in the lens unit 20 is fitted to the to-be-fitted part 111 that is formed on the main body 10 in a coaxial manner to the optical axis of the lens 21.

[0077]

Due to such a configuration, the central axis of the fitting part 221 can be matched to the central axis of the to-be-fitted part 111 with a high degree of precision, and the relative positions of the optical axis 211a of the lens unit 20a and the optical axis 211b of the lens unit 20b in the X- direction can be determined with a high degree of precision. Moreover, the error in the base line length B can be reduced in the manufacturing process of the stereo camera 100, and the precision of the measurement of the distance to an object by the stereo camera 100 can be secured.

[0078]

Due to this configuration, the manufacturing cost can be reduced compared with the cases in which the processing precision of threads that have a complicated shape such as the external threads 222 and the internal threads 112 is improved to improve the processing precision of cylindrical components such as the fitting part 221 and the to-be-fitted part 111.

[0079]

Further, additional parts such as a knock pin are not necessary, and additional formation of, for example, a hole that achieves sliding fit is not necessarily. Accordingly, an increase in cost due to such additional parts or additional formation as above can be reduced.

[0080]

Moreover, in the present embodiment, the pin face 223 in which a tool is to be engaged is formed on the outer regions of the barrel unit 22. As a tool is engaged in the pin face 223, the barrel unit 22 can easily be rotated around the optical axis 211, and the lens unit 20 can easily be attached to the main body 10.

[0081]

Moreover, in the present embodiment, the pin face 252 in which a tool is to be engaged is formed on the outer regions of the nut 25. As a tool is engaged in the pin face 252, the nut 25 can easily be rotated around the optical axis 211, and the lens unit 20 can easily be fixed to the main body 10 using the nut 25.

[0082]

Second Embodiment

[0083]

A stereo camera 100A according to a second embodiment of the present disclosure is described below. In view of the first embodiment of the present disclosure, like reference signs denote like elements, and overlapping description may be omitted.

[0084]

In the present embodiment, a nut 25A that is included in the stereo camera 100A abuts the abutment plane 113 of the installation hole 11 such that the nut 25 A has a cavity 26 on the inward side. Due to such a configuration, even when the linear expansion differs among the main body 10, the lens unit 20, and the nut 25A, the loose fit of the lens unit 20 for the installation hole 11 or the changes in position of the lens unit 20 with reference to the installation hole 11 can be reduced.

[0085]

FIG. 7 is a sectional view of the components around one of the pair of lens units 20 in the stereo camera 100A, according to the second embodiment of the present disclosure.

[0086]

As illustrated in FIG. 7, the nut 25 A abuts the abutment plane 113, having a cavity 26 therebetween.

[0087]

The cavity 26 is a cavity that is formed on the inward side of the nut 25A as the nut 25A, where a circular- shaped concave portion is formed on the inward side of the face of the nut 25A that abuts the abutment plane 113, abuts the abutment plane 113, and the cavity 26 is shaped like a bracelet.

[0088]

As the cavity 26 is formed, the nut 25A can have a tolerance for elastic deformation when one of the pair of lens units 20 is fixed to the main body 10 by tightening the nut 25A. Due to such a configuration, when the air temperature around the stereo camera 100A changes and the linear expansion differs from one another among the main body 10, the lens unit 20, and the nut 25, the elastically-deformed portion of the nut 25A can absorb the loose fit of the lens unit 20 for the main body 10 or the changes in position of the lens unit 20 with reference to the main body 10.

[0089]

FIG. 8A and FIG. 8B are diagrams each illustrating how the nut 25A elastically deforms, according to the second embodiment of the present disclosure.

[0090]

More specifically, FIG. 8A and FIG. 8B are magnified views of an area C indicated by a broken line in FIG. 7. FIG. 8 A and FIG. 8B illustrate first and second modifications of the embodiments of the present disclosure, respectively.

[0091]

In FIG. 8A, the nut 25A has an abutment part 25x that abuts the main body 10, and the abutment part 25x is elastically deformed such that the contact portion of the abutment part 25x shifts in the positive Y-direction. By contrast, in FIG. 8B, the abutment part 25x is elastically deformed such that the contact portion of the abutment part 25x shifts in the negative Y-direction. As the changes in position are absorbed by the nut 25A that is elastically deformed as above, the loose fit of the lens unit 20 for the main body 10 or the changes in position of the lens unit 20 with reference to the main body 10 can be reduced. Moreover, in the present embodiment, the loose fit of the lens unit 20 for the main body 10 or an error in the base-line length B due to the changes in position can be reduced. As a result, the precision of the measurement of the distance to an object by the stereo camera 100A can be secured. In FIG. 8A and FIG. 8B, merely the nut 25A is illustrated. However, no limitation is indicated thereby, and the nut 25B on the other side may also be elastically deformed in a similar manner to the nut 25A so as to achieve similar advantageous effects.

[0092]

The other aspects of the present embodiment are similar to those of the first embodiment of the present disclosure as described above.

[0093]

Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present disclosure may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.

[0094]

A stereo camera that is provided with a pair of lens units was described in the above embodiments of the present disclosure. However, no limitation is intended thereby.

[0095]

In a monocular camera that is provided with a single lens unit, the lens unit may be displaced in the direction intersecting with the optical axis of the contained lens. As a result, there are some cases in which the object image that is formed by the lens is displaced from the center of the sensor plane and the image quality deteriorates. If the embodiments of the present disclosure are applied to a monocular camera, the relative positions of a pair of lens units can precisely be determined with reference to the sensor holder. Accordingly, the displacement of the object image with reference to the center of the sensor plane can be reduced, and the quality of captured images can be secured.

[0096]

If the embodiments of the present disclosure are applied to a camera that is provided with three or more lens units, the displacement of the object image with reference to the center of the sensor plane can be reduced, and the quality of images that are captured by each lens unit can be secured.

[0097]

Further, in a similar manner to the embodiments of the present disclosure described as above, the embodiments of the present disclosure may be applied to a stereo camera that is provided with three or more lens units such that an error in the base-line length among the optical axes of the lenses of such multiple lens units will be reduced. As a result, the precision of the measurement of the distance to an object can be secured.

[0098]

The embodiments of the present disclosure include a method of determining the position of a lens unit. For example, such a method of determining the position of a lens unit may be applied to a camera that is provided with a sensor, a sensor holder holding the sensor, a lens unit including a lens configured to focus light on a photo-sensing surface of the sensor, and a nut contacting the sensor holder. The lens unit of the camera includes external threads and a fitting part that is formed on an outer region of the barrel unit that contains the lens . The fitting part is coaxial with an optical axis of the lens. The sensor holder of the camera includes a to- be-fitted part formed on an inner side of an installation hole for the lens unit, and internal threads that are threadably fitted to the external threads. The to-be-fitted part is coaxially formed with the optical axis of the lens. The method of determining the position of a lens unit includes a step of fitting the fitting part to the to-be-fitted part. Such a method can achieve advantageous effects similar to those achieved by the stereo camera according to the embodiments of the present disclosure as described above.

[0099]

This patent application is based on and claims priority to Japanese Patent Application Nos. 2019-141608 and 2020-101167, filed on July 31, 2019, and June 10, 2020, respectively, in the Japan Patent Office, the entire disclosures of which are hereby incorporated by reference herein. [Reference Sings List]

[0100]

10 Main body

11 Installation hole

111 To-be-fitted part

112 Internal threads

113 Abutment plane

20 Lens unit

200 Object 21 Lens

211 Optical axis

22 Barrel unit

221 Fitting part

222 External threads

223 Pin face

25 Nut

25x Abutment part

251 Internal threads

252 Pin face

26 Cavity

30 Sensor

301 Sensor board

40 Sensor controller

50 Image processing board

51 CPU

52 FPGA

53 RAM

54 ROM

55 Serial interface

56 Data interface

57 Disparity detection unit

58 Distance-image generation unit

61 Data bus

62 Serial bus

B Base-line length

D Distance to object

d Disparity

f Focal length

Claims

[CLAIMS]

[Claim 1]

A camera comprising:

a sensor;

a sensor holder holding the sensor;

a lens unit including a lens configured to focus light on a photo-sensing surface of the sensor; and

a nut contacting the sensor holder,

wherein the lens unit includes

a fitting part formed on an outer region of a barrel unit containing the lens, the fitting part being coaxial with an optical axis of the lens, and

external threads, and

wherein the sensor holder includes

a to-be-fitted part formed on an inner side of an installation hole for the lens unit, the to-be- fitted part being coaxial with the optical axis of the lens, and

internal threads threadably fitting to the external threads.

[Claim 2]

The camera according to claim 1,

wherein the nut has a cavity on an inward side of the nut.

[Claim 3]

The camera according to claim 1 or 2,

wherein a to-be-engaged part in which a tool is to be engaged is formed on an outer region of the barrel unit.

[Claim 4]

The camera according to claim 2,

wherein a to-be-engaged part in which a tool is to be engaged is formed on an outer region of the nut.

[Claim 5]

A method of positioning a lens unit in a camera,

the camera including a sensor, a sensor holder holding the sensor, a lens unit including a lens configured to focus light on a photo-sensing surface of the sensor, and a nut contacting the sensor holder,

the lens unit including external threads, and a fitting part formed on an outer region of a barrel unit containing the lens, the fitting part being coaxial with an optical axis of the lens, the sensor holder including a to-be-fitted part formed on an inner side of an installation hole for the lens unit, and internal threads threadably fitting to the external threads, the fitting part being coaxial with the optical axis of the lens,

the method comprising fitting the fitting part to the to-be-fitted part.

[Claim 6]

A stereo camera comprising

the camera according to any one of claims 1 to 4.