JP7662995B2 - marker - Google Patents

Description

The present invention relates to a marker.

Markers are attached to objects so that various automatic control devices can recognize them, thereby achieving high-precision automatic control. Such markers are used, for example, to control robots in production sites and in space missions.
Conventionally, markers printed on paper have been widely used because they are easy to make, but with such simple markers, the boundaries of the marks are unclear, and the size of the marks and the spacing between multiple marks change due to the expansion and contraction of the paper, making it difficult to ensure sufficient accuracy when high-precision control is required.

As a technique for realizing a highly accurate marker, Patent Document 1 discloses a technique for creating a marker by drilling holes in a metal plate by cutting and filling the metal plate with resin. However, with the technique disclosed in Patent Document 1, depending on the observation environment, sunlight or illumination light may be reflected off the surface of the metal plate or the surface of the resin, making it impossible to correctly recognize the marker.

Japanese Patent Application Publication No. 5-312521

The objective of the present invention is to provide a marker that is easy to recognize even in an environment where sunlight, lighting, etc., hits the marker.

The present invention solves the above problems by the following means. Note that, for ease of understanding, the following description will use symbols corresponding to the embodiments of the present invention, but the present invention is not limited to these.

The first invention is a marker (1) used to detect at least one of the distance to an observation position and the angle of inclination relative to the observation position, and the marker (1) is provided with a first anti-reflection layer (70) in which, from the observation side, at least a linear polarizer (73) and a quarter-wave plate (72) that imparts a phase difference of a quarter wavelength to transmitted light are laminated in this order.

The second invention is the marker (1) described in the first invention, characterized in that a second anti-reflection layer (80) is provided on the observation side of the first anti-reflection layer (70).

The third invention is a marker (1) according to the first or second invention, characterized in that the marks (2) that can be observed as independent shapes are arranged at intervals in at least three locations.

The fourth invention is the marker (1) described in the third invention, characterized in that the first anti-reflection layer (70) covers the mark (2) and is provided in an island shape over an area larger than the mark (2).

The fifth invention is the marker (1) described in the third invention, characterized in that the first anti-reflection layer (70) is provided across the boundary between the mark (2) and its peripheral portion.

The sixth invention is a marker (1) according to any one of the first to fifth inventions, characterized in that it comprises a transparent base layer (10), a first pattern (23) provided in at least a partial area on one surface of the base layer (10) and including a plurality of first display lines (21) arranged at equal intervals in a line-like pattern in a fixed arrangement direction, and a second pattern (43) provided at intervals from the first pattern (23) in the thickness direction of the base layer (10) and including a plurality of second display lines (41) arranged at equal intervals in a line-like pattern in the fixed arrangement direction, and has a moire display region (3, 4) that displays a moire pattern by a combination of the first pattern (23) and the second pattern (43).

The seventh invention is the marker (1) described in the sixth invention, characterized in that the linear polarizer (73) and the quarter-wave plate (72) cover the moire display area (3, 4) and are arranged in an island shape over an area larger than the moire display area (3, 4).

The eighth invention is the marker (1) described in the sixth invention, characterized in that the linear polarizer (73) and the quarter-wave plate (72) are provided across the boundary between the moire display area (3, 4) and its surrounding area.

The present invention provides a marker that is easy to recognize even in an environment where the marker is exposed to sunlight or lighting.

FIG. 1 illustrates an embodiment of a marker according to the present invention. 2 is a cross-sectional view of the marker taken along the line AA in FIG. 1. FIG. 3 is an enlarged view of range C in FIG. 2 . 4 is a graph showing the effects of the first antireflection layer 70 and the second antireflection layer 80. FIG. 2 is a diagram showing the marker 1 as viewed from an oblique direction. FIG. 13 shows a modified embodiment in which the colors of the first layer 20 and the second layer 30 are swapped.

The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a diagram showing an embodiment of a marker according to the present invention.
Note that the figures shown below, including FIG. 1, are schematic views, and the size and shape of each part are exaggerated or omitted as appropriate for ease of understanding.
In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate.
In this specification, the terms plate, sheet, film, etc. are used, and in general usage, they are used in the order of thickness, plate, sheet, film, etc., and this specification follows that order. However, since such distinction in usage has no technical meaning, these terms can be used interchangeably as appropriate.
In the present invention, the term "transparent" refers to a material that transmits at least light of a wavelength to be used. For example, even if a material does not transmit visible light, if it transmits infrared light, it is treated as transparent when used for infrared applications.
It should be noted that the specific numerical values specified in this specification and claims should be treated as including a general error range. In other words, a difference of about ±10% means that there is no substantial difference, and values set within a range slightly exceeding the numerical range of this invention should be interpreted as being substantially within the scope of this invention.

As shown in FIG. 1, the marker 1 is configured as a plate having a substantially square shape when viewed from the normal direction of the surface on which the second anti-reflection layer 80 described later is provided, and includes the mark 2 and the moire display areas 3 and 4. In this embodiment, the shape viewed from the surface side is formed into a square shape of 60 mm x 60 mm. The marker 1 detects the relative positional relationship between the shooting position and the marker 1 (hereinafter also simply referred to as position detection) depending on how the mark 2 is observed, and further enables more accurate position detection depending on how the moire displayed in the moire display areas 3 and 4 is observed. Note that the surface of the marker 1 shown in FIG. 1 is the front side (front surface) on which the surface is observed, and the opposite side is the back side (rear surface), and in FIG. 2 described later, the side on which the second anti-reflection layer 80 is provided is the front side (front surface) on which the surface is observed. The external dimensions of the marker 1 are not limited to the above example, and can be changed as appropriate, for example, to 10 mm x 10 mm, 20 mm x 20 mm, 40 mm x 40 mm, 44 mm x 44 mm, 80 mm x 80 mm, etc.

The marks 2 are arranged at intervals in total, two near the two upper corners and one near the center of the lower left and right in Fig. 1. The marks 2 are configured so as to be observable as marks having independent shapes. Note that an independent mark refers to a form in which multiple marks are not connected and each can be recognized individually.
It is desirable that at least three marks 2 are arranged. This is because, for example, by calculating three center of gravity positions of the marks 2 from the observation results of the marks 2, the relative position, distance, and inclination between the observation position (camera, etc.) and the marker 1 can be accurately detected. Furthermore, if the number of marks 2 is more than three, for example, when some marks 2 are not clearly observed due to some obstacle, the positions can be detected from the observation results of the remaining marks 2. Furthermore, by using multiple marks 2, the accuracy of position detection can be improved.
Furthermore, in this embodiment, the mark 2 is configured to have a circular shape, but is not limited to a circular shape, and may be a polygonal shape such as a triangle or a rectangle, or may be another shape.

The moire display areas 3 and 4 display moire M. In FIG. 1, both moire display areas 3 and 4 show a state in which moire M is displayed in the center of the moire display areas 3 and 4. The position at which this moire M is displayed moves when the relative position (angle) between the marker 1 and the observation position changes. In this embodiment, the length of the longitudinal direction of both moire display areas 3 and 4 is 30 mm, and the position at which the moire M is displayed moves along this longitudinal direction. The moire display areas 3 and 4 are arranged so that their longitudinal directions are perpendicular to each other. The moire display areas 3 and 4 have the same configuration except for the arrangement direction, so the following explanation will focus on the moire display area 3.

FIG. 2 is a cross-sectional view of the marker taken along the line AA in FIG.
The marker 1 is configured in a thin plate shape and includes a base layer 10, a first layer 20, a second layer 30, a third layer 40, a reflective layer 50, an adhesive layer 61, a first anti-reflection layer 70, an adhesive layer 62, and a second anti-reflection layer 80. The order in which these layers are stacked from the back surface side is the reflective layer 50, the third layer 40, the base layer 10, the first layer 20, the second layer 30, the adhesive layer 61, the first anti-reflection layer 70, the adhesive layer 62, and the second anti-reflection layer 80.

The substrate layer 10 is made of a glass plate. By making the substrate layer 10 of a glass plate, it is possible to suppress the expansion and contraction of the marker 1 due to temperature changes and moisture absorption. The linear expansion coefficient of the glass plate is, for example, about 31.7×10 ⁻⁷ /° C., and dimensional change due to temperature changes is very small. The linear expansion coefficient of ceramics is, for example, about 28×10 ⁻⁷ /° C., and dimensional change due to temperature changes is very small, similar to glass. Therefore, ceramics may be used for the substrate layer. In order to suppress dimensional change due to temperature changes, it is desirable for the substrate layer 10 to have a linear expansion coefficient of 35×10 ⁻⁶ /° C. or less.
The thickness of the base layer 10 is preferably 0.3 mm or more and 2.3 mm or less. If the thickness of the base layer 10 is less than 0.3 mm, it will break during cutting and additional processing will not be possible, and if it is thicker than 2.3 mm, when it is made into a multi-sided substrate, it will be too heavy to transport. The thickness of the base layer 10 in this embodiment is 0.7 mm.

The first layer 20 is formed of a resist material colored black (first color). The resist material constituting the first layer 20 in this embodiment is a resist material in a state after losing its photosensitivity as a result of performing a development process on a photosensitive resist material used in a photolithography process. Examples of the resist material used for the first layer 20 (in the case of black color) include PMMA, ETA, HETA, HEMA, and mixtures with epoxy. Examples of materials that are colored black include carbon, blackened titanium, nickel oxide, and the like.
In this embodiment, since the first layer 20 is formed from a resist material, the surface of the first layer 20 can be formed very smoothly, which is desirable as a base for forming the second layer 30 described below. In addition, since the first layer 20 is formed from a resist material, the first pattern 23 described below can be produced accurately and easily.
The thickness of the first layer 20 (in the case of black) is desirably 1 μm or more and 5 μm or less. If the thickness of the first layer 20 is 1 μm or less, it cannot be formed uniformly, and if it is thicker than 5 μm, the curing reactivity of the resin with ultraviolet light is insufficient.

The first layer 20 constitutes the portion of the mark 2 that appears black. The first layer 20 also constitutes a first pattern 23 for displaying a moire in the moire display area 3. The first pattern 23 is disposed in a region that will become the moire display area 3 on one surface (front surface) of the base layer 10.
In the first pattern 23, the first display lines 21 are arranged at equal intervals in a line pattern in a fixed arrangement direction in the longitudinal direction of the moire display area 3. The areas between adjacent first display lines 21 where no first display lines 21 are provided are first non-display areas 22, and the first display lines 21 and the first non-display areas 22 are arranged alternately. The first pattern 23 is formed by photolithography processing.

The second layer 30 is formed of a resist material colored white (second color). The resist material constituting the second layer 30 in this embodiment is a resist material in a state after losing its photosensitivity as a result of performing a development process on a photosensitive resist material used in a photolithography process. Examples of the resist material used for the second layer 30 (in the case of white color) include, for example, PMMA, ETA, HETA, HEMA, or a mixture with epoxy. Examples of materials colored white include titanium oxide, zirconia, barium titanate, etc.
The second layer 30 is provided with three openings 31 that open positions that will become the marks 2 and make the first layer 20 visible, and also has two openings 32 that open positions that will become the moire display regions 3 and 4 and make the first layer 20 and the third layer 40 visible. These openings 31 and 32 are formed by photolithography.

It is desirable that the thickness of the second layer 30 is 3 μm or more and 100 μm or less. If the thickness of the second layer 30 is thinner than 3 μm, the first layer 20 underneath will be visible, reducing the contrast and decreasing the visibility of the mark 2 (ease of detection by automatic recognition). Also, if the thickness of the second layer 30 is thicker than 100 μm, when the mark 2 is observed from an oblique direction, the area where the first layer 20 is not visible due to being shaded by the second layer 30 will increase at the periphery of the opening 31, resulting in increased distortion of the shape of the observed mark 2.

The third layer 40 is formed from a resist material colored black (first color). In this embodiment, the third layer 40 is made of the same material as the first layer 20, and the preferred film thickness is also the same as that of the first layer 20. Because the third layer 40 is formed from a resist material, the second pattern 43 described below can be produced accurately and easily.

The third layer 40 is provided with a second pattern 43 for displaying a moire in the moire display region 3. The second pattern 43 is disposed opposite the first pattern 23 in a region that will become the moire display region 3 on the rear surface of the base layer 10. In this embodiment, the first pattern 23 is provided on one surface of the base layer 10, and the second pattern 43 is provided on the other surface, but they may be provided on different base materials or the like and then bonded together to produce the structure.
In the second pattern 43, the second display lines 41 are arranged at equal intervals in a line pattern in a fixed arrangement direction in the longitudinal direction of the moire display area 3. The areas between adjacent second display lines 41 where no second display line 41 is provided are second non-display areas 42, and the second display lines 41 and the second non-display areas 42 are arranged alternately. The second pattern 43 is formed by photolithography processing.

The reflective layer 50 is a layer that reflects light that arrives from the front side (observation side) of the marker 1 through the opening 32 back to the front side. The reflective layer 50 can be made of, for example, PMMA, ETA, HETA, HEMA, or a mixture with epoxy, and is preferably white in order to enhance the contrast with the first display line 21 and the second display line 41. Examples of materials that can be colored white include titanium oxide, zirconia, and barium titanate.

The reflective layer 50 may be laminated in close contact with the marker 1 as in this embodiment, or may be a separate reflective material disposed on the back side of the marker 1. However, the configuration of this embodiment in which the reflective layer 50 is laminated in close contact with the marker 1 as in this embodiment is more desirable in that it makes the moire M significantly easier to see. The reason for this is explained below.

The moire M that is originally desired to be observed is a moire observed due to interference between the first display line 21 and the second display line 41. However, even if only the first display line 21 and only the second display line 41 are used, unnecessary moire (extraneous noise image) may occur depending on the conditions. When unnecessary moire of the second display line 41 occurs due to light scattered at the side portion of the second display line 41, i.e., the end face portion of the second display line 41 on the second non-display area 42 side and returning to the observer side, it is considered that the unwanted moire interferes with the moire M that is originally desired to be seen and interferes with the observation of the moire M. Therefore, by providing the reflective layer 50 so as to fill the second non-display area 42, the above phenomenon can be avoided and the moire M can be observed more clearly.
For the above reasons, it is sufficient that the reflective layer 50 is provided at least in the second non-display region 42, but it is preferable that the reflective layer 50 is provided so as to cover the back surface side of the second display line 41, as shown in Fig. 2. The reason for this is that the reflection of light from the edge portion on the back surface side of the second display line 41 is suppressed, and the main component of the periodic reflected light can be eliminated.

The adhesive layer 61 is a layer of adhesive for attaching the first antireflection layer 70 onto the first layer 20 and the second layer 30. The adhesive layer 61 can be made of, for example, PMMA, urethane, silicone, or the like.
The thickness of the adhesive layer 61 is preferably 0.5 μm or more and 50 μm or less. If the thickness of the adhesive layer 61 is less than 0.5 μm, it is difficult to process uniformly and the unevenness of the base cannot be absorbed. If the thickness of the adhesive layer 61 is thicker than 50 μm, it takes time to remove the solvent during thick coating processing and the cost is high.
Moreover, the adhesive layer 61 is provided only in the same area as the area in which the first antireflection layer 70 is provided.

FIG. 3 is an enlarged view of the area C in FIG.
The first antireflection layer 70 covers the mark 2 and the moire display areas 3 and 4, and is provided in an island shape in an area slightly larger than these. Specifically, the first antireflection layer 70 is provided in an island shape in an area 2 to 3 mm larger on one side (radius) than the mark 2. Similarly, the first antireflection layer 70 is provided in an island shape in an area 2 to 3 mm larger on one side (expansion width on one side) than the moire display areas 3 and 4.
By providing the first antireflection layer 70 in an island shape and not providing the first antireflection layer 70 in other portions, it is possible to easily provide the first antireflection layer 70 later as necessary. Furthermore, when strong light such as sunlight is incident on only one island-shaped first antireflection layer 70, if the first antireflection layer 70 (including the first antireflection layer base material 71) is connected, the first antireflection layer base material 71 acts as a light guide plate and propagates to other island-shaped first antireflection layers 70, thereby preventing the light from affecting the other islands.

The first antireflection layer 70 is constructed by sequentially laminating a quarter-wave plate 72 and a linear polarizer 73 that impart a phase difference of a quarter wavelength to transmitted light on a first antireflection layer substrate 71, which is a transparent film material. The first antireflection layer 70 is disposed on the first layer 20 and the second layer 30 by an adhesive layer 61 provided on the first antireflection layer substrate 71. This first antireflection layer 70 polarizes external light into linearly polarized light by the linear polarizer 73, and then converts it into circularly polarized light by the subsequent quarter-wave plate. The external light converted into circularly polarized light has a rotation direction reversed by reflection in the first layer 20 and the second layer 30, and is further converted into linearly polarized light by the quarter-wave plate 72. Here, since the rotation direction of the circularly polarized light of the reflected light is opposite to that at the time of incidence, the direction of the linearly polarized light converted into linearly polarized light by the quarter-wave plate 72 is perpendicular to the direction when the light was converted into linearly polarized light at the time of incidence. Therefore, the linearly polarized light converted from the reflected light is blocked by the linear polarizer 73, and the reflected light can be efficiently reduced.

The first anti-reflection layer substrate 71 is made of a transparent resin so that the first layer 20 and the second layer 30 can be observed.

The quarter-wave plate 72 can be made of a liquid crystal material, a film material, etc. Examples of film materials that can be used include stretched cycloolefin polymer films and stretched acrylic films. When using a liquid crystal material, an orientation film for orienting the liquid crystal material is first prepared, and then a coating liquid is applied, which is then dried and hardened to produce the plate.

The adhesive layer 62 is a layer of adhesive for attaching the second anti-reflection layer 80 onto the first anti-reflection layer 70, and can be made of the same material as the adhesive layer 61 described above.

The second anti-reflection layer 80 is provided on the first anti-reflection layer 70 with the same size as the first anti-reflection layer 70, i.e., in an island shape, via the adhesive layer 62, and exerts a so-called AR (anti-reflection) effect. For example, the anti-reflection film described in Japanese Patent No. 3332482, Japanese Patent No. 4712236, etc. can be applied to the second anti-reflection layer 80, and one of the forms thereof is used in this embodiment. By providing the second anti-reflection layer 80 in an island shape, it is possible to obtain an effect similar to that obtained by providing the above-mentioned first anti-reflection layer 70 in an island shape.
The second antireflection layer 80 includes a second antireflection layer substrate 81 , a high refractive index layer 82 , and a low refractive index layer 83 .

The second anti-reflection layer substrate 81 has an adhesive layer 62 laminated on one side and a high refractive index layer 82 laminated on the other side. The second anti-reflection layer substrate 81 is made of a transparent resin so that the first layer 20 and the second layer 30 can be observed.

In this embodiment, it is assumed that the marker 1 is used under visible light, and the adhesive layer 61, the adhesive layer 62, and the second antireflection layer substrate 81 are configured to be transparent to white light. Specifically, the adhesive layer 61, the adhesive layer 62, and the second antireflection layer substrate 81 each desirably have a total light transmittance of 90% or more in the region where the wavelength of light is 400 nm to 700 nm. Since the first antireflection layer 70 includes a linear polarizing plate, it is desirably a total light transmittance of 40% or more. More desirably, when the adhesive layer 61, the first antireflection layer 70, the adhesive layer 62, and the second antireflection layer substrate 81 are measured together, it is desirably a total light transmittance of 30% or more in the region where the wavelength of light is 400 nm to 700 nm.

The thickness of the second antireflection layer substrate 81 is preferably 7 μm or more and 250 μm or less. If the thickness of the second antireflection layer substrate 81 is less than 7 μm, lamination processing is difficult. If the thickness of the second antireflection layer substrate 81 is thicker than 250 μm, the substrate becomes too bulky and heavy, and the cost becomes high.
The refractive index of the second antireflection layer substrate 81 is preferably 1.45 or more and 1.55 or less.
In addition, the second antireflection layer substrate 81 needs to be relatively thicker than the high refractive index layer 82 and the low refractive index layer 83 formed thereon. The reason is that if the second antireflection layer substrate 81 is thin, it needs to be treated as a term related to the equation of optical interference, but if the second antireflection layer substrate 81 is thick, this term can be ignored.

The high refractive index layer 82 is a layer having a refractive index relatively higher than that of the low refractive index layer 83 , and is provided on the second antireflection layer substrate 81 .
The low refractive index layer 83 has a refractive index relatively lower than that of the high refractive index layer 82 , and is provided on the high refractive index layer 82 .
In this embodiment, a configuration in which two layers, a high refractive index layer 82 and a low refractive index layer 83, are stacked has been exemplified, but various configurations described in Japanese Patent No. 3,332,482, Japanese Patent No. 4,712,236, etc. can also be applied.

In addition, it is desirable that the combined characteristics of the adhesive layer 61, the first antireflection layer 70, the adhesive layer 62, and the second antireflection layer substrate 81 have a total light transmittance of 10% or more. If the total light transmittance is less than 10%, a sufficient amount of light cannot be secured.

FIG. 4 is a graph showing the effects of the first antireflection layer 70 and the second antireflection layer 80. As shown in FIG.
In order to confirm the effect of providing the first anti-reflection layer 70 and the second anti-reflection layer 80, two types of markers were actually prepared, one with the first anti-reflection layer 70 and the other with the second anti-reflection layer 80. Furthermore, for comparison, a marker was prepared in which a so-called matte film having a fine uneven shape formed on the surface was attached instead of the first anti-reflection layer 70 and the second anti-reflection layer 80. Then, the three types of markers were photographed by applying light so that the reflected light was strong at the position of the mark 2 and returned to the camera, and the change in light intensity depending on the position near the part where the black and white of the mark 2 are inverted was quantified and shown in FIG. 4. L1 in the figure is the result of a marker in which the first anti-reflection layer 70 and the second anti-reflection layer 80 are not provided, that is, nothing is provided on the surface of the mark 2. L2 is the result of a marker with a matte film attached. L3 is the result of the marker of this embodiment, that is, the marker in which the first anti-reflection layer 70 and the second anti-reflection layer 80 are provided.

4, in the result (L1) of the marker having nothing on the surface of the mark 2, the reflection of the illumination light appears as a waveform (near pixel positions 0.10 to 0.30), and no waveform corresponding to the shape of the mark 2 was observed. Note that the light intensity in the absence of the second anti-reflection layer 80 was too strong, exceeding the measurement limit (2.50E+02).
In the results for the marker with the matte film (L2), data was obtained that allowed the light intensity of the white part (near pixel positions 0-0.25) and the black part (near pixel positions 0.25-0.35) to be recognized separately according to the position of the mark 2. However, due to the light diffusion effect of the matte film, it is clear that the black part is floating (near pixel positions 0.25-0.35), in other words, the light intensity of the black part is high. The reason that the black part is floating is thought to be that the light of the white part penetrates into the black part due to the diffusion effect of the matte film. When the light intensity of the black part increases, the contrast decreases, so there is a concern that the detection accuracy will decrease when the position of the mark 2 is detected by photographing it.
In contrast to these, in the results (L3) for the marker provided with the first anti-reflection layer 70 and the second anti-reflection layer 80, data was obtained that allowed recognition of the light intensity of the white portion (near pixel position 0 to 0.25) and the light intensity of the black portion (near pixel position 0.25 to 0.35) by appropriately separating them according to the position of the mark 2.
In addition, in the result (L3) of the marker provided with the first anti-reflection layer 70 and the second anti-reflection layer 80, the light intensity is generally reduced, but this reduces the light intensity of the black color in particular (around pixel positions 0.25 to 0.35). Therefore, the contrast of the obtained image is very good, and position detection can be performed with higher accuracy.
As can be seen from FIG. 4, if the first antireflection layer 70 and the second antireflection layer 80 are disposed so as to straddle the mark 2 and its periphery, the shape (contour) of the mark can be clearly captured by the camera.
Furthermore, if the first anti-reflection layer 70 and the second anti-reflection layer 80 are arranged only on the mark 2 with the same shape and size as the mark 2, the transparent base material layer portion and the ¼ wavelength plate will act as a light guide plate, causing light to be emitted from the transparent base material layer portion and the end of the ¼ wavelength plate, resulting in the problem of the shape (contour) of the mark becoming unclear.

Next, an example of a method of using the marker 1 of this embodiment will be described.
Fig. 5 is a diagram showing the marker 1 as viewed from an oblique direction. Fig. 5 shows an example of the marker 1 being observed from the oblique direction indicated by the arrow B in Fig. 2, but without being tilted in the up-down direction in Fig. 1.
When the marker 1 is observed from an oblique direction inclined from its normal direction, for example, as shown in Fig. 5, the moire M in the moire display area 3 is observed moving in the longitudinal direction of the moire display area 3. When the marker 1 is observed from an oblique direction inclined from its normal direction to the longitudinal direction of the moire display area 4, the moire M in the moire display area 4 is observed moving in the longitudinal direction of the moire display area 4. Therefore, by observing both the moire M in the moire display area 3 and the moire M in the moire display area 4, the relative position (angle of inclination) between the marker 1 and the observation position can be accurately detected. That is, the marker 1 can be used in combination with an imaging unit and a calculation unit to form part of an angle sensor.

Here, when the observation position of the moire M is moved to a position significantly deviated from the normal direction of the marker 1, a different moire pattern is observed, and the moire patterns are observed one after another. Therefore, when the observation position is at a position significantly deviated from the normal direction of the marker 1, the correct position detection may not be possible.
However, the marker 1 of this embodiment includes the mark 2. The position detection using the mark 2 allows position detection even when the observation position is significantly deviated from the normal direction of the marker 1. On the other hand, the position detection using the moire display areas 3 and 4 allows position detection with higher accuracy than that using the mark 2. Therefore, by using the position detection using the mark 2 in combination with the position detection using the moire display areas 3 and 4, the range of application can be expanded compared to the case where only the moire display areas 3 and 4 are used. In other words, even if the observation position is significantly deviated from the normal direction of the marker 1, the position detection can be performed using the mark 2, and the observation position can be automatically moved according to the detection result, and the position detection using the moire display areas 3 and 4 can be performed at the stage where final highly accurate position control is required.

As described above, the relative positions of the observation position and the marker 1 are expected to have various positional relationships. Therefore, there may be a positional relationship in which illumination light, sunlight, etc. are reflected specularly toward the observation position. Even in such a case, the marker 1 of this embodiment has a first anti-reflection layer 70 and a second anti-reflection layer 80, so that the reflected light can be appropriately diffused, and the number of situations in which the marker's mark 2 and the moire display areas 3 and 4 can be observed can be increased.

As described above, the marker 1 of this embodiment can improve the situation in which it becomes difficult to recognize the indicators and other elements indicated by the marker 1 due to illumination light or sunlight, and can provide a marker that is easy to recognize even in an environment where sunlight, illumination light, etc., hits the marker.

(Modifications)
The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present invention.

(1) In the embodiment, the first anti-reflection layer 70 and the second anti-reflection layer 80 are described by citing an example in which sheet-like members are attached. However, this is not limiting, and for example, the layers forming the first anti-reflection layer 70 and the second anti-reflection layer 80 may be directly laminated together.

(2) In the embodiment, an example has been described in which two types of antireflection layers, a first antireflection layer 70 and a second antireflection layer 80, are provided. This is not limiting, and for example, the second antireflection layer 80 may be omitted.

(3) The second anti-reflection layer 80 has been described as having a layer that exhibits a so-called AR (anti-reflection) effect. However, the present invention is not limited to this, and for example, a matte film with fine irregularities may be provided as the second anti-reflection layer.

(4) In the embodiment, the first anti-reflection layer 70 and the second anti-reflection layer 80 are partially provided in an island shape. However, the present invention is not limited to this. For example, the first anti-reflection layer 70 and the second anti-reflection layer 80 may be provided on the entire surface of the marker.

(5) In the embodiment, an example in which the first layer 20 is black and the second layer 30 is white has been described. This is not limited to the above, and for example, as shown in FIG. 6, the first layer 20 may be white and the second layer 30 may be black. The combination is not limited to black and white, and may be a combination of other colors such as blue and yellow. Furthermore, a configuration in which more layers are stacked and observed in three or more colors may be used, for example by adding a third layer observed in a third color. In addition, the color difference in the present invention is not limited to the difference in color expressed by the combination of RGB, but may also include differences due to the multi-tone expression of a single color.

1 Marker 2 Mark 3 Moire display area 4 Moire display area 10 Base layer 20 First layer 21 First display line 22 First non-display area 23 First pattern 30 Second layer 31 Opening 32 Opening 40 Third layer 41 Second display line 42 Second non-display area 43 Second pattern 50 Reflective layer 61 Adhesive layer 62 Adhesive layer 70 First anti-reflection layer 71 First anti-reflection layer base material 72 1/4 wavelength plate 73 Linear polarizer 80 Second anti-reflection layer 81 Second anti-reflection layer base material 82 High refractive index layer 83 Low refractive index layer

Claims (6)

A marker used to detect at least one of a distance to an observation position and a relative inclination angle to the observation position,
At least three marks that are observable as independent shapes are arranged at intervals;
a first antireflection layer including at least a linear polarizer and a quarter-wave plate that imparts a phase difference of a quarter wavelength to transmitted light, laminated in this order from the observation side ;
The first antireflection layer covers the mark and is provided in an island shape over an area larger than the mark . 2. The marker of claim 1 ,
a second antireflection layer is provided on the observation side of the first antireflection layer;
A marker characterized by: The marker according to claim 1 or 2 ,
the first antireflection layer is provided across the boundary between the mark and its peripheral portion;
A marker characterized by: The marker according to any one of claims 1 to 3 ,
A transparent base layer;
a first pattern provided in at least a portion of a region on one surface of the base material layer, in which a plurality of first display lines are arranged at equal intervals in a line pattern in a certain arrangement direction;
a second pattern in which a plurality of second display lines are arranged at equal intervals in the certain arrangement direction, the second pattern being spaced apart from the first pattern in a thickness direction of the base layer;
Equipped with
a moire display area that displays a moire pattern by a combination of the first pattern and the second pattern;
A marker characterized by: The marker according to claim 4 ,
the linear polarizer and the quarter-wave plate are provided in an island shape covering the moire display area and in an area larger than the moire display area;
A marker characterized by: 6. The marker of claim 5 ,
the linear polarizer and the quarter-wave plate are provided across the boundary between the moire display area and its peripheral area;
A marker characterized by:

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