JP7749178B2 - Camera Support Structure - Google Patents

Description

The present invention relates to a camera support structure that can effectively prevent camera position changes caused by thermal expansion.

Patent Document 1 shows a support structure for a stereo camera that uses a pair of cameras on the left and right to enable three-dimensional measurement. In this case, one of the pair of cameras (more precisely, the camera stand) is fixed to a base plate, while the other is installed on a rail, and the two are connected by a connecting member made of a material with a low thermal expansion coefficient, so that the relative position between the cameras, which is important for three-dimensional measurement, does not change even if the base plate expands and deforms (first conventional example).

Patent document 2 also shows a shape measurement device in which a stand on which a pair of cameras is mounted is cooled with a refrigerant to prevent camera positional changes due to thermal expansion (second prior art example).

Patent Publication No. 2020-056898 Patent Publication No. 2015-200529

However, the first conventional example had the problem that while it could effectively absorb thermal expansion and deformation in the direction connecting the two cameras, it was unable to accommodate deformation in any other direction. Furthermore, the second conventional example had the problem of requiring a refrigerant circulation path within the mount and the installation of a cooling device, which made the structure more complicated and increased costs.

The present invention aims to solve these problems by providing a camera support structure that can easily and inexpensively suppress camera position changes due to thermal expansion.

In order to achieve the above object, in the camera support structure of the first invention, the camera (1) is fixed to one surface of a receiving member (5) made of the same material as the housing (11) of the camera (1), and a protrusion (51) made of the same material protrudes from the center of the other surface of the receiving member (5). The protrusion (51) is inserted into a recess (41) provided in the base (2) , and at least a portion of the inner surface of the recess (41) abuts against the outer surface of the protrusion (51), thereby holding the protrusion (51) within the recess (41).

In this first invention, the receiving member and the protruding portion integral with it expand as the temperature rises, but because the diameter of the protruding portion can be made small, the increase in diameter due to thermal expansion can be kept small, and the increase in diameter is approximately uniform around the entire circumference. In this state, the protruding portion is held within the recess by having at least a portion of the inner surface of the recess abut against the outer surface of the protruding portion, so that even if the receiving member expands due to heat, the positional change of the receiving member supported by the protruding portion and the camera fixed to it is kept small.

In the second aspect of the present invention, three or more equally spaced locations on the inner peripheral surface of the recess (41) are brought into local contact with the outer peripheral surface of the protrusion (51).

According to the second invention, the inner peripheral surface of the recess is locally abutted against the outer peripheral surface of the protrusion, further minimizing positional changes of the protrusion and receiving member due to thermal expansion.

In this third invention, the receiving member (5) serves as an upper base, and the rod-shaped protrusion (51) is integrally formed with the upper base (5). The base (2) is provided with a lower base (4) molded from the same material, and the recess (41) is formed in the lower base (4).

In the stereo lamella of the fourth invention, the cameras are mounted on both ends of the base (2) using the camera support structure described in any one of the first to third inventions.

The symbols in parentheses above indicate, for reference purposes, the correspondence with the specific means described in the embodiments below.

As described above, the camera support structure of the present invention makes it possible to easily and inexpensively suppress changes in camera position due to thermal expansion.

1 is a plan view of a camera supported on a base by the support structure of the present invention; 1 is an enlarged plan view of a camera supported on a base by the support structure of the present invention; 3 is a partial cross-sectional front view of the support structure of the present invention for supporting a camera, the cross-section being taken along line III-III in FIG. 2; FIG. 1 is a front view of a calibration board. FIG. 2 is a rear view of a camera supported on a base by the support structure of the present invention. 1 is a partial cross-sectional front view of a support structure of the present invention supporting a camera, showing thermal expansion. FIG. 10A and 10B are diagrams illustrating the amount of change in the position of the camera in the X and Y directions due to a change in temperature. 1 is a side view of a stereo camera supported on a base by the support structure of the present invention. FIG.

Please note that the embodiment described below is merely an example, and various design improvements made by those skilled in the art that do not deviate from the gist of the present invention are also included within the scope of the present invention.

(First embodiment)
In Fig. 1, camera 1 is supported on the tip end of a long plate-shaped base 2 by a structure described in detail below, and the base end of base 2 is fixed to an optical surface plate 3. Base 2 is made of a material, such as invar, whose thermal expansion coefficient is sufficiently small within the operating temperature range of camera 1. A rectangular lower base 4 is fixedly attached to base 2. An upper base 5, which is a rectangular receiving member with a slightly smaller diameter, is positioned on lower base 4 (Fig. 2), and a rectangular parallelepiped housing 11 of camera 1 is connected and fixed to upper base 5 as shown in Fig. 3.

The thick lower base 4 is made of the same Invar material as the base 2, and has a recess in its center with a through-hole 41 extending vertically. Furthermore, the lower base 4 has threaded holes 42 extending horizontally from each of its four sides to the through-hole 41, and a set screw 43 is threaded into each of the threaded holes 42.

The thin upper base 5 is made of the same material as the housing 11 of the camera 1, which in this embodiment is made of aluminum. A protrusion 51, which in this embodiment is rod-shaped, is formed downward at the center of the underside of the upper base 5. This protrusion 51 is inserted into the through-hole 41, and the tips of the set screws 43 provided on the lower base 4 abut on all four sides against its outer periphery, holding the upper base 5 in place.

Recesses 54 are formed in the four corners of the underside of the upper base 5, and fixing screws 52 are inserted into each recess 54. The camera 1 is mounted and fixed on the upper base 5 by screwing each fixing screw 52 into the underside of the housing 11.

A calibration board 6 such as that shown in Figure 4 is placed at a predetermined distance (e.g., 3 m) opposite the lens unit 12 of the camera 1, which is installed on the base 2 using this support structure. The calibration board 6 has multiple (49 in this embodiment) black dots 61 of known size arranged at equal intervals in the X-Y direction on a flat surface, and is photographed by the camera 1. During photography, the entire base 2 is heated from below to 30°C to 55°C using a heat gun 7, as shown in Figure 5, and the average amount of shift in the images of each black dot 61 at that time is calculated. This average amount of shift corresponds to the positional change of the camera 1 due to thermal expansion. A thermometer 53 for measuring temperature is attached to the lower base 5.

The principle behind minimizing positional changes of the camera 1 due to thermal expansion is that, as shown in Figure 6, the camera housing 11 and the upper base 5 are made of the same material (aluminum in this embodiment), so there is no difference in the thermal expansion coefficient between them. This prevents deformation of the lower edge of the camera housing 11, which is mounted and fixed to the upper base 5, and the resulting misalignment of the camera 1. The rod-shaped protrusion 51 expands as the temperature rises, but because the diameter of the protrusion 51 can be made small (for example, about 8 mm), the increase in diameter due to thermal expansion is kept small and the increase in diameter is approximately uniform around the entire circumference. Furthermore, because the outer periphery of the protrusion 51 is locally held on all four sides by the tips of the fixing screws 43, displacement of the upper base 5 due to thermal expansion is kept small, and ultimately, positional changes of the camera 1 in the X-Y plane and the Y-Z plane are also kept small.

Figure 7 shows the amount of positional change of camera 1 in the X and Y directions calculated from the shift in the image of black spot 61 on calibration board 6, converted to a value assuming a distance to calibration board 6 of 1 m. As shown in Figure 7, in both the X and Y directions, the amount of positional change of camera 1 is kept to 0.2 mm or less over a temperature change range of 30°C to 55°C. Because the resolution of the camera 1 used is 0.5 mm, the positional change of camera 1 due to thermal expansion is kept to 1 pixel or less.

Second Embodiment
Fig. 8 shows a stereo camera configured by a pair of cameras 1 supported by the support structure described in the first embodiment. In Fig. 8, a long plate-shaped base 2 made of invar is swingably supported on a stand (not shown) by a shaft 21 at the center of the plate surface, and the base 2 is held in a substantially horizontal position with its lower edge abutting against circular rubber stoppers 22 at symmetrical positions on the left and right. A camera 1 is provided on each end of the plate surface of the base 2, facing downward, and the support structure on the base 2 for each camera 1 is the same as that described in the first embodiment.

This structure minimizes positional changes due to thermal expansion on the left and right cameras 1, allowing them to accurately measure the three-dimensional shape of an object located below, such as a hot-formed product.

(Other embodiments)
In the above embodiments, the protrusion is locally supported at four locations in the circumferential direction, but it is sufficient if the protrusion is locally supported at three or more locations. However, local support is not necessarily required.
The protrusion does not necessarily have to be rod-shaped. The protrusion may be manufactured separately from the upper base, and the lower base may be manufactured integrally with the base.
The lens portion of the camera does not necessarily have to be located at the position shown in each of the above embodiments relative to the protrusion.

1...camera, 11...housing, 2...base, 4...lower base, 41...recess, 43...set screw, 5...receiving member (upper base), 51...protrusion, 6...calibration board.

Claims (4)

A camera support structure in which a camera is fixed to one surface of a receiving member made of the same material as the camera housing, a protrusion made of the same material is made to protrude from the center of the other surface of the receiving member, and the protrusion is inserted into a recess provided in a base , with at least a portion of the inner surface of the recess abutting against the outer surface of the protrusion, thereby holding the protrusion within the recess. 2. The camera support structure according to claim 1, wherein the inner peripheral surface of the recess is locally abutted against the outer peripheral surface of the protrusion at three or more equally spaced locations in the circumferential direction . A camera support structure as described in claim 1 or 2, in which the receiving member is an upper base, the rod-shaped protrusion is integrally formed with the upper base, a lower base molded from the same material is provided on the base, and the recess is formed in the lower base. A stereo camera in which the cameras are mounted on both ends of the base using the camera support structure described in any one of claims 1 to 3.