JP7679028B2 - Marker - Google Patents

Description

The present invention relates to a marker.

Markers such as those described in Patent Document 1 are known in the past. These markers are attached to objects in order to recognize the object's position, orientation, and the like. By photographing the marker with a camera, the relative positional relationship between the camera and the marker can be recognized based on the appearance of the marker in the image, etc.

JP 2020-85771 A

The markers described above are configured to obtain predetermined visual information from the observation position in order to indicate the relative positional relationship between the camera and the marker. The positional relationship between the camera and the marker is then calculated based on the positional relationship of the pattern of visual information in the image, etc., but there is a possibility that a deviation in accuracy may occur when grasping the positional relationship. In this case, there is a possibility that the accuracy of recognizing the position of the marker may decrease.

The object of the present invention is to provide a marker whose position can be recognized with high accuracy.

A marker according to one aspect of the present invention has a position recognition unit in which the visual information observed at the observation position changes depending on the observation direction, and the position recognition unit changes the light intensity of the visual information observable at the observation position depending on the observation angle from the observation position to the position recognition unit.

The marker position recognition unit changes the light intensity of the visual information observable at the observation position according to the observation angle from the observation position to the position recognition unit. Such changes in light intensity can be used as a parameter indicating minute changes in the observation angle by previously grasping the correspondence with the observation angle. Furthermore, a method of calculating the observation angle by grasping the changes in light intensity can reduce the number of processes that cause accuracy deviations compared to a method of calculating the observation angle by grasping the positional relationship of patterns in the visual information. As a result, it is possible to recognize the position of the marker with high accuracy.

The position recognition unit may have a plurality of arranged lens sections and a recognition unit formed on the rear side of the lens sections to generate visual information. In this case, this can be a suitable configuration for the position recognition unit.

The recognition units may be formed in multiple locations spaced apart from one another for each lens unit. Such a position recognition unit can increase the amount of information obtained from visual information compared to a position recognition unit in which one recognition unit is formed for each lens unit.

The recognition unit may have a shape that changes the intensity of light observable at the observation position depending on the observation angle. In this case, it is possible to easily change the intensity of light simply by adjusting the shape of the recognition unit.

The position recognition unit may have a lens unit and a retroreflective material provided on the back side of the recognition unit. In this case, the part of the visual information that corresponds to the recognition unit can be made to shine brightly by retroreflection. Therefore, it is possible to grasp the change in light intensity while reducing the influence of disturbance factors such as sunlight and dark places.

The position recognition unit can display a plurality of visual areas spaced apart from one another as visual information, and may vary the number of visual areas and change the light intensity of any of the visual areas depending on the observation angle from the observation position to the position recognition unit. It is easier to grasp the number of visual areas than to grasp the change in the light intensity of the visual areas. It is therefore possible to grasp the approximate observation angle based on the number of visual areas, and to grasp minute observation angles based on the change in the light intensity of the visual areas.

A marker according to one aspect of the present invention is a marker having a position recognition unit in which the visual information observed at an observation position changes depending on the observation direction, and the position recognition unit is capable of displaying a visual area shown in a predetermined display mode as visual information, and may change at least one of the shape and number of visual areas observable at the observation position depending on the observation angle from the observation position to the position recognition unit.

The marker position recognition unit changes at least one of the shape and number of visual areas observable at the observation position, depending on the observation angle from the observation position to the position recognition unit. Such changes in the shape and number of visual areas can be used as an index showing changes in the observation angle by grasping the corresponding relationship with the observation angle in advance. Furthermore, a method of calculating the observation angle by grasping the changes in the shape and number of visual areas can reduce the number of steps that cause accuracy deviations, compared to a method of calculating the observation angle by grasping the positional relationship of patterns in visual information. As a result, it is possible to recognize the position of the marker with high accuracy.

The present invention provides a marker whose position can be recognized with high accuracy.

1A to 1C are diagrams showing how the marker according to the present embodiment is used; FIG. 2 is a perspective view showing a marker according to the present embodiment. FIG. 3A is a plan view of the position recognition unit, and FIG. 3B is a diagram showing a cross-sectional structure of the position recognition unit. FIG. 4 illustrates an example of a recognition unit. FIG. 13 is a diagram showing the relationship between the observation angle and visual information. FIG. 13 is a diagram showing the relationship between the observation angle and visual information. FIG. 13 is a diagram illustrating a position recognition unit according to a comparative example. FIG. 13 is a perspective view showing a marker according to a comparative example. FIG. 13 is a diagram showing a marker position recognition unit according to a modified example. FIG. 13 is a diagram showing a marker position recognition unit according to a modified example.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, identical or equivalent elements are given the same reference numerals, and duplicate descriptions will be omitted.

Figure 1 is a diagram showing how the marker 1 according to this embodiment is used. Figure 1 shows a state in which a forklift 100 approaches a loading object 101 in order to load the loading object 101. A marker 1 is attached to the loading object 101. The forklift 100 is equipped with a camera 102 and a computing device 103. The camera 102 captures an image of the loading object 101. The camera 102 has a light that can irradiate an observation range. The computing device 103 calculates the positional relationship between the forklift 100 and the marker 1 based on the image of the marker 1 among the images captured by the camera 102. As a result, the computing device 103 calculates the positional relationship between the forklift 100 and the loading object 101.

Note that marker 1 may be used for purposes other than aligning the forklift 100. For example, in FIG. 1, a collaborative robot arm may be used instead of the forklift 100. In this case, FIG. 1 shows the state when the collaborative robot arm approaches the alignment reference marker (corresponding to "101") in order to align the reference marker with the reference marker. Marker 1 is attached to the reference marker. The collaborative robot arm is equipped with a camera 102 and a computing device 103 similar to those of the forklift 100. In this case, the computing device 103 calculates the positional relationship between the collaborative robot arm and marker 1 based on the image of marker 1 among the images captured by the camera 102. As a result, the computing device 103 calculates the positional relationship between the collaborative robot arm and the reference marker. As a result, the reference coordinate point for operation changes depending on the stopping position of the robot arm installed on an Automatic Guided Vehicle (AGV)-type automated transport vehicle, but by offsetting the displacement of the position information of the reference marker and the robot arm, the positional relationship can be determined, enabling complex control system operations to be realized.

2(a) is a perspective view showing the marker 1 according to this embodiment. FIG. 2(b) is an exploded perspective view showing the marker 1 according to this embodiment. As shown in FIG. 2, the marker 1 is a plate-like member having a substantially rectangular shape. The marker 1 has a mark section 2 and a position recognition section 3 on its surface. Note that the arrangement and shape of the mark section 2 and the position recognition section 3 are merely examples and can be changed as appropriate. The marker 1 is constructed by laminating a main body section 10 and a retroreflective member 11. Note that in the following description, the terms "left-right direction D1," "up-down direction D2," and "thickness direction D3" are used to describe the state when the marker 1 is attached to the loading object 101 as a reference. However, there is no particular limitation on how the marker 1 is attached to the loading object 101.

The main body 10 is a plate-shaped molded part formed by injection molding or the like. The resin material of the main body 10 may be a thermoplastic resin or a thermosetting resin. The main body 10 has a position recognition part 3 and a rectangular plate-shaped base part 12. The position recognition part 3 and the base part 12 are integrally formed by a single molding process. Therefore, the position recognition part 3 and the base part 12 are configured as a single molded part. The base part 12 has an upper area 12A where the position recognition part 3 is arranged, and a lower area 12B where the mark part 2 is arranged. The retroreflective member 11 is a plate-shaped part laminated on the back surface of the base part 12 of the main body 10, and the surface is configured as a retroreflective surface. The retroreflective member 11 is a reflective member that uses the principle that when light is incident on the retroreflective surface, the light is reflected toward the position from which the light was incident.

The mark section 2 is formed in the lower region 12B of the base section 12 of the main body section 10. The mark section 2 is a section that displays a predetermined pattern or the like. These patterns function as identification information by being linked to the ID number or the like of the loading object 101. For example, when the camera 102 detects a predetermined pattern on the mark section 2, the computing device 103 can search for the ID number linked to the pattern to identify the loading object 101 (see FIG. 1). The mark section 2 is formed, for example, by attaching a sheet on which a pattern is printed to the main body section 10. The pattern on the mark section 2 may be shown in a predetermined color or may be shown with a retroreflective material.

The position recognition unit 3 is a part in which the visual information observed changes depending on the observation direction. That is, the visual information that can be obtained from the position recognition unit 3 in the image captured by the camera 102 changes depending on the positional relationship between the marker 1 and the camera 102. The details of the recognition information obtained by the position recognition unit 3 will be described later. The position recognition unit 3 is formed in the upper region 12A of the base part 12 of the main body part 10. Here, the marker 1 according to this embodiment has position recognition units 3A and 3B. The position recognition unit 3A is arranged in the lower region of the upper region 12A, and the position recognition unit 3B is arranged in the upper region of the upper region 12A. The lower position recognition unit 3A can show visual information that can obtain the relative angle between the marker 1 and the camera 102 in the left-right direction D1. In addition, the other position recognition unit 3B can show visual information that can obtain the relative angle between the marker 1 and the camera 102 in the up-down direction D2. As a result, when the camera 102 detects an image of each position recognition unit 3A, 3B, the calculation device 103 calculates the relative angle between the camera 102 and the marker 1 in the left-right direction D1 and the up-down direction D2 based on the visual information obtained from each position recognition unit 3, and recognizes the positional relationship between the marker 1 and the forklift 100. In addition, jet black lines 15 are transferred to the upper region 12A of the base unit 12 around the position recognition units 3A, 3B to recognize the distance between the observation position and the marker 1.

Figure 3(a) is a plan view of the position recognition unit 3A for acquiring the relative angle in the left-right direction D1 between the marker 1 and the camera 102. Figure 3(b) shows the cross-sectional structure of the position recognition unit 3A for acquiring the relative angle in the left-right direction D1 between the marker 1 and the camera 102. Note that the position recognition unit 3B for acquiring the relative angle in the up-down direction D2 between the marker 1 and the camera 102 has a similar configuration to the position recognition unit 3A, except for the orientation.

3B, the position recognition unit 3A includes a lens layer 20 and a pattern transfer layer 21. The lens layer 20 and the pattern transfer layer 21 are integrally formed as molded parts of the main body 10. A retroreflective member 11 is provided on the back surface of the pattern transfer layer 21. The lens layer 20 is a layer in which a plurality of lens portions 22 are arranged. The pattern transfer layer 21 is a layer to which a pattern of a recognition portion 30 for forming visual information is transferred. With this configuration, the position recognition unit 3A has a plurality of arranged lens portions 22 and a recognition portion 30 formed on the back surface side of the lens portions 22 to form visual information. In the following description, the angle in the left-right direction D1 between the optical axis of the camera 102 and the thickness direction D3 of the marker 1 is defined as the observation angle θ with respect to the position recognition unit 3A from the observation position. In addition, the state in which the optical axis of the camera 102 is perpendicular to the surface of the marker 1 is defined as "observation angle θ = 0°".

Here, the patterns in the areas other than the recognition section 30 (general section 31) are arranged at intervals equal to or greater than the wavelength of the target light source, and a concave-convex structure with a depth of an aspect ratio of 1 or greater is formed. Specifically, in the case of a visible range of wavelengths of 400 nm to 700 nm, a concave-convex structure is formed with intervals of 700 nm or greater, and a structure with a depth of 700 nm or greater and an aspect ratio of 1 or greater is formed. In the best case, the structures are spaced 10 μm to 100 μm apart, and the structure has a depth of 10 μm to 100 μm and an aspect ratio of 1 or greater. In this way, when structures 10 times larger than the wavelength are used, the scattering effect of light can be effectively utilized, making it possible to improve the pattern contrast of the recognition section 30.

The uneven structure formed on the pattern transfer layer 21 can also function as a periodic uneven structure or a random uneven structure, and can be made to function using a rectangular structure. Furthermore, by making the uneven structure have a bullet-like shape with a tapered tip when viewed from the surface of the pattern transfer layer 21, it is possible to reduce surface reflection, obtain a better light scattering effect, and obtain a pattern of the recognition portion 30 with higher contrast.

Each lens portion 22 has a curved surface on the front side when viewed from the vertical direction D2, and is configured to extend in the vertical direction D2 with the same cross-sectional shape. A plurality of such lens portions 22 are arranged in the horizontal direction D1 to form the lens layer 20. In the position recognition unit 3B, a plurality of lens portions 22 extending in the horizontal direction D1 are arranged in the vertical direction D2. The lens portions 22 are configured with lenses called lenticular lenses. When the position recognition unit 3A is viewed from a certain observation position with the line of sight AX, light is focused at the focusing position CP of the pattern transfer layer 21 due to the influence of the curved surface of the lens portion 22. Therefore, at the observation position, the image of the focusing position CP of the pattern transfer layer 21 is visible throughout the entire horizontal direction D1 of each lens portion 22. The focusing position CP moves in the horizontal direction D1 as the observation angle θ changes.

The shape of the lens portion 22 is not particularly limited. For example, the curvature of the curved surface of the lens may be changed as appropriate. The number of lens portions 22 (one or more is sufficient) and the span are also not particularly limited. The lens portion 22 may be formed by resin molding, or may be formed by processing. The lens portion 22 may be configured separately from the main body portion 10.

Although the shape of the lens portion 22 is not particularly limited, the focal position of the lens portion 22 is located on the surface of the pattern transfer layer 21 in order to resolve the pattern of the recognition portion 30 with high resolution.

As shown in FIG. 3(a), the pattern transfer layer 21 has a number of recognition sections 30 that form visual information. In FIG. 3 and other figures, the grayscaled parts correspond to the recognition sections 30. Note that FIG. 3(a) shows the appearance of the pattern transfer layer 21 in a state different from how it actually appears as visual information from the observation position. FIG. 3(a) shows the appearance of the pattern transfer layer 21 as it appears when it is assumed that light is transmitted directly without being focused by the lens sections 22 (when it is assumed that the curved lens surfaces of all lens sections 22 are flat).

In this embodiment, the recognition portion 30 of the pattern transfer layer 21 is in a state where it can be reflected by the retroreflective member 11, and the portion other than the recognition portion 30 (hereinafter referred to as the general portion 31) is in a state where reflection by the retroreflective member 11 is prevented. For example, when molding the main body portion 10, the recognition portion 30 is molded as a smooth flat surface, and the general portion 31 is molded as a rough surface. The molding surface of the mold for the portion corresponding to the recognition portion 30 may be a smooth surface, and the molding surface of the mold for the portion corresponding to the general portion 31 may be a rough surface. Therefore, in terms of visual information, the portion corresponding to the recognition portion 30 appears shiny due to reflection by the retroreflective member 11. In terms of visual information, the portion corresponding to the general portion 31 appears dark because it is not reflected by the retroreflective member 11.

The shape and arrangement of the multiple recognition sections 30 will be described. In the pattern transfer layer 21, recognition regions ER1, ER2, ER3, ER4... in which the recognition sections 30 are arranged in a straight line and blank regions in which no recognition sections 30 are provided are formed alternately in the vertical direction D2. Note that in FIG. 3(a), recognition region ER1 is formed at the bottom, and recognition regions ER2, ER3, ER4... are formed in order from the bottom. In recognition region ER1, one recognition section 30 is formed that extends in a straight line in the horizontal direction D1 with a constant thickness.

In the recognition regions ER2, ER3, ER4, etc., the multiple recognition units 30 have a symmetrical shape and are arranged symmetrically with respect to the center position CL1 of the position recognition unit 3A. Specifically, in the region to the right of the center position CL1, the recognition units 30 in the recognition regions ER2, ER3, ER4, etc. extend from the center position CL2 of each lens unit 22 to the left. The length in the left-right direction D1 of each recognition unit 30 gradually decreases in the order of the recognition regions ER2, ER3, ER4, etc. The left end of the recognition unit 30 in the recognition region ER2, which has the longest length, extends to a position that reaches the center position CL2 of the other adjacent lens unit 22 on the left side. The left end of the recognition unit 30 in the recognition region ER3 extends to a position slightly spaced to the right from the center position CL2 of the other adjacent lens unit 22 on the left side. As a result, a gap is formed between the left end of one recognition unit 30 and the right end of the other recognition unit 30 adjacent to it on the left side (the center position CL2 of the lens unit 22). The size of this gap gradually increases in the order of recognition regions ER2, ER3, ER4, etc. In the region to the left of the center position CL1, the recognition units 30 in the recognition regions ER2, ER3, ER4, etc. have a configuration that is symmetrical to the recognition units 30 in the recognition regions ER2, ER3, ER4, etc. in the region to the right.

Here, the number of recognition parts for each lens part will be explained. For example, in the position recognition part 150 of the marker according to the comparative example shown in FIG. 7, one recognition part 130 extending linearly in the vertical direction D2 is formed for one lens part 122 (see FIG. 7(a)). In this case, for the lens part 122 whose light collection position coincides with the recognition part 130 due to the observation angle, the image of the recognition part 130 is displayed on the entire lens part 122 in the visual information (see FIG. 7(b)). In this comparative example, one recognition part 130 is formed for each lens part 122. In contrast, in the marker 1 according to this embodiment, the recognition parts 30 are formed at the positions of the recognition areas ER1, ER2, ER3, ER4, etc. with a gap between them in the vertical direction D2 for each lens part 22. Therefore, a plurality of recognition parts 30 spaced apart from each other are formed for each lens part 22.

Next, referring to FIG. 4(a), the shape of each recognition unit 30 will be described. Note that FIG. 4 shows the recognition unit 30 on the right side of the center position CL1 (see FIG. 3), but the recognition unit 30 on the left side has a similar shape except that it is symmetrical. As shown in FIG. 4(a), the recognition unit 30 has a main body portion 32 and an adjustment portion 33. The main body portion 32 is a portion that extends in the left-right direction D1 with a constant width. The adjustment portion 33 is provided at the end of the left side (the center position CL1 side) of the main body portion 32, and is a portion whose width narrows as it extends to the left. In this embodiment, the adjustment portion 33 is formed in a triangular shape so that it tapers toward the left side. When the light collection position CP is the general portion 31 on the left side of the recognition unit 30 (light collection position CP1), visual information is displayed such that the lines are not visible, as shown in the area to the right of the recognition areas ER3 and ER4 in FIG. 6(a). When the light collecting position CP is the main body 32 of the recognition unit 30 (light collecting position CP3), visual information is displayed such that a line of a width (referred to as a reference width) corresponding to the main body 32 is visible, as shown in the right-hand region of the recognition regions ER1, ER2, and ER3 in FIG. 6(d). When the light collecting position CP is the adjustment unit 33 of the recognition unit 30 (light collecting position CP2), visual information is displayed such that a line thinner than the reference width is visible, as shown in the right-hand region of the recognition region ER2 in FIG. 6(a) and the right-hand region of the recognition region ER3 in FIG. 6(d). In FIG. 6(a) and (d), for convenience, the line formed by the image of the recognition unit 30 is shown as a black line, but in reality, it is a line formed by the retroreflected light. Therefore, in the visual information, the part shown by the thick line of the reference width is shown with strong light, and the part shown by the thin line is shown with weak light. The more the focusing position CP overlaps with the adjustment unit 33 on the left side, the thinner the line in the visual information becomes, and the lower the light intensity becomes. The more the focusing position CP overlaps with the adjustment unit 33 on the right side, the thicker the line in the visual information becomes, and the higher the light intensity becomes. Note that the area in the visual information that is visually recognized as a specific shape (here, a line) due to the overlap between the focusing position CP and the recognition unit 30 is sometimes referred to as the visual area 40.

In this way, when the observation angle θ causes the focusing position CP to become the adjustment unit 33, the corresponding location is visually indicated by weak light. The recognition unit 30 has the adjustment unit 33 as a shape that changes the intensity of the light observable at the observation position according to the observation angle θ.

To change the intensity of light observable at the observation position using the adjustment unit 33, the light passes through the lens unit 22 and is focused at the pattern transfer layer 21, and the adjustment unit 33 uses a pattern structure in which the size of the adjustment unit 33 is smaller than the size of the focus, thereby changing the intensity of the light. In addition, since the intensity distribution of the focused light when the light is focused has a Gaussian distribution or a normal distribution depending on the lens shape, the shape of the adjustment unit 33 can be changed to a curved shape or other pattern shape depending on the intensity distribution of the focused light, thereby allowing the intensity to change linearly depending on the measurement position.

The shape of the adjustment section 33 is not limited to that shown in FIG. 4(a). For example, an adjustment section 33 having a curved shape as shown in FIG. 4(b) may be used. Also, an adjustment section 33 having a trapezoidal shape as shown in FIG. 4(c) may be used.

Next, the relationship between the observation angle θ and visual information will be described with reference to Figures 5 and 6. Note that Figures 5 and 6 are enlarged views of the area indicated by "A1" in Figure 3(a). Figure 5(b) shows a state in which the line of sight AX is perpendicular to the position recognition unit 3A (observation angle θ = 0°). At this time, as shown in Figure 5(c), the focusing position CP at each position overlaps with the recognition unit 30 only in recognition area ER1, and does not overlap in the other recognition areas ER2, ER3, ER4, etc. In this case, as shown in Figure 5(a), in the visual information, a line of the reference width is displayed only in the area corresponding to recognition area ER1.

Figure 5 (e) shows a state in which the line of sight AX is inclined to the right with respect to the position recognition unit 3A (the observation angle θ is positive to the right). At this time, as shown in Figure 5 (f), the focusing position CP in the right-hand region overlaps with the main body parts 32 of all recognition units 30 in recognition areas ER1, ER2, ER3, ER4, etc. In this case, as shown in Figure 5 (d), the visual information displays a line of the reference width at locations corresponding to all recognition areas ER1, ER2, ER3, ER4, etc. As shown in Figure 5 (f), the focusing position CP in the left-hand region overlaps with the main body part 32 of the recognition unit 30 in recognition area ER1 and with the adjustment part 33 of the recognition unit 30 in recognition area ER2, but does not overlap with the other recognition areas ER3, ER4, etc. In this case, as shown in FIG. 5(d), in the visual information, a line of the standard width is displayed in a location corresponding to the recognition area ER1, a thin line is displayed in a location corresponding to the recognition area ER2, and no line is displayed in the other recognition areas ER3, ER4, etc. Furthermore, FIG. 5(h) shows a state in which the line of sight AX is tilted further to the right with respect to the position recognition unit 3A (the observation angle θ is positive to the right). At this time, as shown in FIG. 5(i), the focusing position CP in the left side area overlaps with the main body 32 of the recognition unit 30 in the recognition areas ER1 and ER2, and with the adjustment unit 33 of the recognition unit 30 in the recognition area ER3, but does not overlap with the other recognition areas ER4, etc. In this case, as shown in FIG. 5(g), in the visual information, a line of the standard width is displayed in a location corresponding to the recognition areas ER1 and ER2, a thin line is displayed in a location corresponding to the recognition area ER3, and no line is displayed in the other recognition areas ER4, etc.

Figure 6 (b) shows a state in which the line of sight AX is inclined to the left with respect to the position recognition unit 3A (the observation angle θ is positive to the left). At this time, as shown in Figure 6 (c), the focusing position CP in the left area overlaps with the main body parts 32 of all recognition units 30 in recognition areas ER1, ER2, ER3, ER4, etc. In this case, as shown in Figure 6 (a), the visual information displays a line of the reference width at locations corresponding to all recognition areas ER1, ER2, ER3, ER4, etc. As shown in Figure 6 (c), the focusing position CP in the right area overlaps with the main body part 32 of the recognition unit 30 in recognition area ER1 and with the adjustment part 33 of the recognition unit 30 in recognition area ER2, but does not overlap with the other recognition areas ER3, ER4, etc. In this case, as shown in FIG. 6(a), in the visual information, a line of the standard width is displayed at a location corresponding to the recognition area ER1, a thin line is displayed at a location corresponding to the recognition area ER2, and no lines are displayed in the other recognition areas ER3, ER4, etc. Furthermore, FIG. 6(e) shows a state in which the line of sight AX is further tilted to the left with respect to the position recognition unit 3A (the observation angle θ is positive to the left). At this time, as shown in FIG. 6(f), the focusing position CP in the right-side area overlaps with the main body 32 of the recognition unit 30 in the recognition areas ER1, ER2, and ER3, and with the adjustment unit 33 of the recognition unit 30 in the recognition area ER4, and does not overlap with the other recognition areas above that. In this case, as shown in FIG. 6(d), in the visual information, a line of the standard width is displayed at a location corresponding to the recognition areas ER1, ER2, and ER3, a thin line is displayed at a location corresponding to the recognition area ER4, and no lines are displayed in the other recognition areas above that.

As described above, the position recognition unit 3A can indicate which side the line of sight AX is tilted to depending on whether all the lines are displayed in the left or right area. The position recognition unit 3A can also change the number of lines in the visual area 40 according to the observation angle θ from the observation position to the position recognition unit 3A. Therefore, by counting the number of lines of the reference width in the visual information, it is possible to grasp the approximate value of the observation angle θ. The position recognition unit 3A also changes the light intensity of the visual information observable at the observation position according to the observation angle θ from the observation position to the position recognition unit 3A. That is, it is possible to grasp the detailed value of the observation angle θ based on the light intensity of lines thinner than the reference width. The relationship between the number of lines and the observation angle θ, and the relationship between the light intensity of thin lines and the observation angle θ can be measured in advance and stored in a database in the computing device 103.

Next, we will explain the function and effect of the marker 1 according to an embodiment of the present invention.

Marker 1 has a position recognition unit in which the visual information observed at the observation position changes depending on the observation direction, and position recognition unit 3 changes the light intensity of the visual information observable at the observation position depending on the observation angle θ from the observation position to position recognition unit 3.

The position recognition unit 3 of the marker 1 changes the light intensity of the visual information observable at the observation position according to the observation angle θ relative to the position recognition unit 3 from the observation position. Such changes in light intensity can be used as a parameter indicating minute changes in the observation angle θ by grasping the correspondence with the observation angle θ in advance. Furthermore, a method of calculating the observation angle θ by grasping the change in light intensity can reduce the number of processes that cause accuracy deviations compared to a method of calculating the observation angle by grasping the positional relationship of patterns in the visual information (for example, the method of Figure 8 described below). As a result, it is possible to recognize the position of the marker 1 with high accuracy.

First, for comparison with the marker 1 of the present embodiment, a marker 111 according to a comparative example as shown in FIG. 8 will be described. The marker 111 according to the comparative example has reference points 104 at the four corners of the main body 110, a position recognition unit 113 between the reference points 104 (see also FIG. 7), and a mark unit 112 in the center of the main body 110. A method for calculating the observation angle θ using such a marker 111 will be described. First, the calculation device grasps the position of the reference point from the image. In this process, a precision deviation (e.g., 0.25 mm) occurs in order to grasp the position of the reference point. Next, the calculation device grasps the position of the visual area 140 of the position recognition unit 113 from the image. In this process, a precision deviation (e.g., 0.25 mm) occurs in order to grasp the position of the visual area 140. Next, the calculation device measures the distance between the reference point 104 and the visual area 140. In this process, a precision deviation (e.g., 0.25 mm) occurs in order to measure the distance L1 between the two. Next, the calculation device calculates the observation angle θ by replacing the measured distance information with the observation angle θ. In this way, when the marker 111 according to the comparative example is used, deviations in accuracy occur in the three steps.

In contrast, a method for detecting the observation angle θ using the marker 1 of this embodiment will be described. First, the arithmetic device 103 acquires an image of the visual information of the position recognition unit 3A from the camera 102. Here, it is assumed that the visual information shown in FIG. 5(g) is obtained. First, the arithmetic device 103 determines that the observation angle θ is positive to the right because all the lines on the right side are visible. Also, since there are two lines of the reference width on the left side, the arithmetic device 103 determines that the observation angle θ is at least 2° or more by checking against the database. In this process, the arithmetic device 103 only performs a calculation to count the number of lines, so no deviation in accuracy occurs. Next, the arithmetic device 103 calculates the difference in light intensity between the top of the visible line (the line in the recognition area ER3) and the line one below (or the line of the reference width). In this process, there is room for a slight deviation in accuracy (for example, 10 ⁻⁹ mm) in the assumption that the light intensity is grasped. The arithmetic device 103 converts the obtained light intensity difference into information on the observation angle θ by checking against the database. In this process, the calculation device 103 only performs a calculation to convert the light intensity difference into angle information, so no accuracy deviation occurs. If the angle obtained from the light intensity difference is 1.75°, the calculation device 103 calculates the observation angle θ by adding it to the observation angle θ obtained from the number of lines, and calculates "2° + 1.75° = 3.75°". In this way, when the marker 1 is used, the number of times accuracy deviation occurs during the process is smaller than in the comparative example of FIG. 8, and the accuracy deviation that occurs is also small. Therefore, by using the marker 1 of this embodiment, the position of the marker 1 can be recognized with high accuracy.

The position recognition unit 3 may have a plurality of arranged lens sections 22 and a recognition unit 30 formed on the rear side of the lens sections 22 to form visual information. In this case, this can be a suitable configuration for the position recognition unit 3.

The recognition unit 30 may be formed with multiple recognition units 30 spaced apart from each other for each lens unit 22. Such a position recognition unit 3 can increase the amount of information obtained from visual information compared to a position recognition unit 3 in which one recognition unit 30 is formed for each lens unit 22.

The recognition unit 30 may have a shape that changes the intensity of light observable at the observation position according to the observation angle θ. In this case, it is possible to easily change the intensity of light simply by adjusting the shape of the recognition unit 30.

The position recognition unit 3 may have a lens unit 22 and a retroreflective member 11 provided on the back side of the recognition unit 30. In this case, the part of the visual information that corresponds to the recognition unit 30 can be made to shine brightly by retroreflection. Therefore, it is possible to grasp the change in light intensity while reducing the influence of external disturbance factors such as sunlight and dark places.

The position recognition unit 3 can display a plurality of visual areas spaced apart from each other as visual information, and may vary the number of visual areas 40 and change the light intensity of any of the visual areas 40 according to the observation angle from the observation position to the position recognition unit 3. It is easier to grasp the number of visual areas 40 than to grasp the change in the light intensity of the visual areas 40. Therefore, it is possible to grasp an approximate observation angle θ based on the number of visual areas 40, and to grasp a minute observation angle θ based on the change in the light intensity of the visual areas 40.

The marker 1 has a position recognition unit 3 in which the visual information observed at the observation position changes depending on the observation direction, and the position recognition unit 3 is capable of displaying a visual area 40 shown in a predetermined display mode as visual information, and may change at least one of the shape and number of the visual areas 40 observable at the observation position depending on the observation angle θ from the observation position to the position recognition unit 3.

The position recognition unit 3 of the marker 1 changes the number of visual areas 40 (number of lines) observable at the observation position according to the observation angle θ from the observation position to the position recognition unit 3. Such a change in the number of visual areas 40 can be used as an index showing a change in the observation angle θ by grasping the corresponding relationship with the observation angle θ in advance. Furthermore, a method of grasping the change in the number of visual areas 40 and calculating the observation angle θ can reduce the number of steps that cause accuracy deviations compared to a method of grasping the positional relationship of patterns in visual information and calculating the observation angle (e.g., the method of FIG. 8). As a result, it is possible to recognize the position of the marker with high accuracy.

In addition, in the marker 1 according to this embodiment, the main body 10 is integrally molded including the position recognition unit 3. The recognition unit 30 can also be integrally formed by molding. Therefore, since the molded part can be given a position recognition function as it is, alignment and the like are not required, the number of parts can be reduced, and precise alignment and the like are not required.

The present invention is not limited to the above-described embodiments.

For example, the position recognition unit 3 of the marker 1 may change the shape of the visual area 40 observable at the observation position depending on the observation angle θ relative to the position recognition unit 3 from the observation position. For example, a position recognition unit 3A as shown in FIG. 9 may be adopted. FIG. 9(a) shows the pattern of the recognition unit 30, and FIG. 9(b) shows the shape pattern of the visual area 40 at "observation angle θ = 0°". In this way, by making the arrangement of the recognition unit 30 more complex, the shape pattern of the visual area 40 changes depending on the observation angle θ.

As shown in FIG. 10, the shape of the visual area 40 may be configured to show numbers according to the observation angle θ. In this way, when the visual area 40 is made to have a shape that shows a specific meaning, such as a number, the human eye can easily grasp the observation angle θ. Note that "A, B, C" in FIG. 10(a), (d), and (g) and "A, B" in FIG. 10(c), (f), and (i) show the positional relationship between the recognition unit 30 and the visual area 40. FIG. 10(c), (f), and (i) show the shape pattern of the part indicated by "A1" in FIG. 10(a), (d), and (g).

As described above, the change in shape of the visual area 40 can be used as an index showing the change in the observation angle θ by grasping the corresponding relationship with the observation angle θ in advance. Furthermore, the method of grasping the change in shape of the visual area 40 and calculating the observation angle θ can reduce the number of steps that cause accuracy deviations compared to a method of grasping the positional relationship of patterns in visual information and calculating the observation angle (e.g., the method of FIG. 8). As a result, it is possible to recognize the position of the marker with high accuracy.

In the above embodiment, a sheet of retroreflective material 11 is used, but the retroreflective structure may be formed on the back surface of the main body 10.

In addition, the same effect can be expected if the retroreflective member 11 is a reflective material.

The retroreflective material 11 on the back side of the position recognition unit 3A may be omitted. In this case, a rough surface may be formed on the recognition unit 30 during molding, and a flat surface may be formed on the general unit 31. Alternatively, the recognition unit 30 may be formed by painting or the like. In this case, a line corresponding to the color of the recognition unit 30 is displayed as the visual area 40 in the visual information. When the light collection position CP overlaps with the adjustment unit 33 of the recognition unit 30, a line of the thickness at that position is displayed. For example, when the recognition unit 30 is black and the general unit 31 is white, a thin line can be regarded as a place where the light intensity in the image is higher than a line of the reference width. In this way, the position recognition unit 3A can change the light intensity according to the observation angle.

1: marker, 3, 3A, 3B: position recognition section, 11: retroreflective member, 22: lens section, 30: recognition section, 40: visual area.

Claims (5)

A marker having a position recognition unit in which visual information observed at an observation position changes depending on an observation direction,
the position recognition unit changes a light intensity of the visual information observable at the observation position in accordance with an observation angle from the observation position to the position recognition unit;
The position recognition unit has a recognition unit that forms the visual information,
The recognition unit is
A body portion extending with a constant width;
an adjustment unit that changes the intensity of light observable at the observation position in accordance with the observation angle;
The adjustment portion is provided at one end of the main body portion, and has a width that narrows toward the one side,
The position recognition unit is
A plurality of lens portions arranged;
A marker having a recognition portion formed on a rear side of the lens portion and forming the visual information . The marker according to claim 1 , wherein a plurality of the recognition portions are formed spaced apart from each other for each of the lens portions. The marker according to claim 1 or 2 , wherein the position recognition unit has a retroreflective member provided on a rear side of the lens unit and the recognition unit. A marker having a position recognition unit in which visual information observed at an observation position changes depending on an observation direction,
the position recognition unit changes a light intensity of the visual information observable at the observation position in accordance with an observation angle from the observation position to the position recognition unit;
The position recognition unit has a recognition unit that forms the visual information,
The recognition unit is
A body portion extending with a constant width;
an adjustment unit that changes the intensity of light observable at the observation position in accordance with the observation angle;
The adjustment portion is provided at one end of the main body portion, and has a width that narrows toward the one side,
The position recognition unit is capable of displaying a plurality of visual areas spaced apart from each other as the visual information,
A marker that changes the number of visual areas and changes the light intensity of any of the visual areas according to an observation angle from the observation position to the position recognition unit. A marker having a position recognition unit in which visual information observed at an observation position changes depending on an observation direction,
The position recognition unit is
As the visual information, a visual area shown in a predetermined display mode can be displayed,
changing at least one of a shape and a number of the visual areas observable at the observation position according to an observation angle from the observation position to the position recognition unit;
The position recognition unit has a recognition unit that forms the visual information,
The recognition unit is
A body portion extending with a constant width;
an adjustment unit that changes the intensity of light observable at the observation position in accordance with the observation angle;
The adjustment portion is provided at one end of the main body portion, and has a width that narrows toward the one side,
The position recognition unit is
A plurality of lens portions arranged;
A marker having a recognition portion formed on a rear side of the lens portion and forming the visual information .

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