Optical system and position detection method

Abstract

To detect a position by a simple configuration in an optical system for detecting a position of an object.SOLUTION: On a surface of an object OB, optical elements 1 for performing reflection operation, diffraction operation, or light emitting operation are disposed side by side in a first direction (track) and a second direction (position coordinates). A light radiation section 13 applies light to respective tracks T1 to T5 on the basis of light generated by a light source 11. A light-condensing section 21 receives light from the respective tracks T1 to T5, and position detection sections 23, 24 read the wavelength of light received by the light-condensing section 21, and detect position coordinates X1 to X13 to which light is applied from a combination of the read wavelengths. The optical elements 1 are provided such that the combination of wavelengths of light received by the light-condensing section 21 differs according to the position coordinates X1 to X13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical systems for use in aligning articles, for example in the electronics field. [Background technology]

[0002] In recent years, devices that align two objects have been used in a variety of fields. A typical example is the field of electronic components. For example, in high-density mounting of electronic boards and the like, it is essential to mount a large number of circuit components in predetermined positions on the board, and alignment is performed using marks (alignment marks, crosses, etc.) formed on the board and electronic components. For this reason, accurate reading of alignment marks is necessary for high-precision assembly (mounting).

[0003] Generally, this reading is done using a camera attached to the mounting machine. The camera here refers to a device equipped with an imaging lens group and an image sensor for imaging the alignment marks. For example, light from an alignment mark on a circuit board passes through an imaging lens group and forms an image on the imaging surface of the image sensor. The image sensor outputs this image, which is analyzed by downstream electronic circuits. The analysis results in the coordinates of the mark. Similarly, the coordinates can be obtained from the alignment marks on electronic components. Mounting is performed by moving the circuit board or electronic component so that the two coordinates match. For example, in XYZ space, they are moved so that the X and Y coordinates match, and then they are brought into close contact in the Z direction and glued. Furthermore, a single alignment mark cannot detect misalignment in the rotational direction. For this reason, two or more alignment marks are used. For this reason, multiple cameras are installed, one for each alignment mark.

[0004] As can be seen from recent trends in electronic devices, there is a trend toward miniaturization of circuit boards and electronic components. As a result, the spacing between alignment marks formed on circuit boards and electronic components is also becoming narrower. As a result, the spacing between multiple cameras must also be narrowed. However, because the camera contains an imaging lens system, image sensor, etc., the housing must be large to a certain extent. For this reason, there is a limit to how narrow the spacing between multiple cameras can be.

[0005] Therefore, Patent Document 1 describes a configuration that uses optical path spacing expansion to view closely spaced alignment marks. In this configuration, an optical system exists between two cameras and an object (a substrate with alignment marks on its surface). This optical system has a deflection mirror (first mirror) close to the object and a deflection mirror (second mirror) close to the camera. Each deflection mirror is inclined at approximately 45° with respect to the optical axis (the direction in which light travels). Light from the alignment marks is bent outward by the first mirror and upward by the second mirror. This makes it possible to view closely spaced alignment marks even when the cameras are spaced widely apart. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-190958 Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, mounting machines have mechanisms for adhesion, processing, etc. in addition to alignment, so it is desirable to design them to make the most efficient use of the space between the image sensor and the target. However, in a configuration such as that described in Patent Document 1, a complex optical system is inserted between the image sensor and the target, which makes the entire mechanism complex and reduces design freedom.

[0008] In view of the above, an object of the present disclosure is to provide an optical system for detecting the position of an object that enables position detection with a simple configuration. [Means for solving the problem]

[0009] The reason for the above problem is that the coordinate acquisition method involves imaging, capturing an image, and analyzing the image. Therefore, in the present disclosure, a different coordinate acquisition method is used to detect the position of the target object.

[0010] According to one aspect of the present disclosure, an optical system for detecting the position of an object includes optical elements that have a reflective, diffractive, or luminescent effect and are arranged on the surface of the object in a first direction and a second direction perpendicular to the first direction, the rows arranged in the first direction being tracks, and the rows arranged in the second direction corresponding to position coordinates, the optical system including a light source, a light emitting unit that irradiates light onto each track based on light emitted by the light source, a focusing unit that receives light from each track, and a position detection unit that reads the wavelengths of the light received by the focusing unit and detects the position coordinates at which the light is irradiated from the combination of wavelengths read, and the optical elements are arranged so that the combination of wavelengths of light received by the focusing unit differs depending on the position coordinates. [Effects of the Invention]

[0011] The present disclosure makes it possible to detect the position of an object with a simple configuration, thereby increasing the degree of freedom in designing the mechanism of a mounting machine, for example. [Brief explanation of the drawings]

[0012] [Figure 1] Configuration of the first embodiment [Figure 2] Reflective effect of reflective elements [Figure 3] FIG. 1 is a diagram for explaining the operation of the first embodiment. [Figure 4] (a) and (b) are examples of digital value assignment for position coordinates. [Figure 5] Configuration of the second embodiment [Figure 6] Wavelength-selective action of diffractive elements [Figure 7] 10A and 10B are diagrams for explaining the operation of the second embodiment. [Figure 8] Configuration of the third embodiment [Figure 9] Luminous action of phosphor elements [Figure 10] Configuration of the fourth embodiment [Figure 11] (a) to (c) are examples of light-emitting elements [Figure 12] Image of overlapping diffractive elements [Figure 13] Configuration of a modified example of the second embodiment [Figure 14] Image of mixed phosphor elements [Figure 15] Configuration of a modified example of the third embodiment [Figure 16] Mounting machine configuration [Figure 17] Plan view showing the configuration of the mounting machine DETAILED DESCRIPTION OF THE INVENTION

[0013] (overview) According to an aspect of the present disclosure, an optical system for detecting the position of an object includes optical elements that have a reflective, diffractive, or luminescent effect and are arranged on the surface of the object in a first direction and a second direction perpendicular to the first direction, the rows arranged in the first direction being tracks, and the rows arranged in the second direction corresponding to position coordinates, the optical system including a light source, a light emitting unit that irradiates light onto multiple tracks based on light emitted by the light source, a focusing unit that receives light from the multiple tracks, and a position detection unit that reads the wavelengths of the light received by the focusing unit and detects the position coordinates at which the light is irradiated from the combination of wavelengths read, and the optical elements are arranged so that the combination of wavelengths of light received by the focusing unit differs depending on the position coordinates.

[0014] According to this configuration, optical elements that exhibit reflective, diffractive, or luminescent properties are arranged in a row direction (tracks) and a column direction (position coordinates) on the surface of an object. A light emitting unit irradiates a plurality of tracks with light based on light generated by a light source, a light collecting unit receives light from the plurality of tracks, and a position detecting unit reads the wavelengths of the light received by the light collecting unit and detects the position coordinates where the light is irradiated from the combination of read wavelengths. The optical elements are arranged so that the combination of wavelengths of light received by the light collecting unit differs depending on the position coordinates. This eliminates the need for the processes of imaging → photography → image analysis, and allows the position coordinates where the light is irradiated to be detected from the combination of read wavelengths, making it possible to detect the position of an object with a simple configuration.

[0015] In the optical system according to the above aspect, the optical elements are reflective elements that reflect light, and the pattern of the presence or absence of reflective elements in each track is set according to position coordinates, the light source generates light having multiple wavelengths, and the light emitting unit irradiates multiple tracks with light having different wavelengths based on the light generated by the light source.

[0016] This allows the position of an object to be detected by utilizing the reflection effect. It also makes it easier to arrange the reflective elements. Furthermore, since the position of the object is detected based on the presence or absence of reflected light at each wavelength, the accuracy of position detection does not depend on the shape of the reflected light. This increases the degree of freedom in device design.

[0017] Furthermore, the reflective elements may be arranged such that the presence or absence of a reflective element differs by only one track at adjacent position coordinates.

[0018] This makes it easier to determine reading errors and correct abnormal values, improving the accuracy of position detection.

[0019] In the optical system according to the above aspect, the optical element may be a diffractive element that diffracts light, and the pattern of the diffraction grating period of the diffractive element in each track may be set according to position coordinates, the light source may generate light having multiple wavelengths, and the light emitting unit may irradiate the light generated by the light source onto multiple tracks.

[0020] This allows the position of an object to be detected by utilizing the wavelength selection effect of diffraction. Also, since there is no need to separate light wavelengths in the light emitting section, the number of optical components can be reduced. This allows the size of the light emitting section to be reduced, and the amount of space it occupies can be reduced.

[0021] Furthermore, each diffraction element may have a single diffraction grating period, the diffraction grating period of the diffraction elements being the same on the same track and different for each track, and the pattern of the presence or absence of diffraction elements on multiple tracks may be set according to position coordinates.

[0022] This makes it easier to position the diffractive elements.

[0023] Alternatively, at least one track may have at least one diffractive element arranged thereon, the diffractive element having a plurality of grating periods.

[0024] This allows the number of diffractive elements to be reduced.

[0025] Alternatively, the diffractive elements may be arranged such that the presence or absence of a diffraction grating period differs by only one diffraction grating period at adjacent position coordinates.

[0026] This makes it easier to determine reading errors and correct abnormal values, improving the accuracy of position detection.

[0027] In the optical system according to the above aspect, the optical element is a light-emitting element that receives light and emits light, the pattern of wavelengths of light emitted by the light-emitting elements in the multiple tracks is set according to position coordinates, the light source emits light having a single wavelength, and the light emitting unit irradiates the light emitted by the light source onto the multiple tracks.

[0028] This allows the position of an object to be detected by utilizing the light-emitting effect. Furthermore, since the light emitting unit handles light of a single wavelength, there is no need to include optical components for wavelength branching, and the number of optical components is reduced. This reduces the size of the light emitting unit, making it possible to reduce the amount of space it occupies. Furthermore, since the incident angle and exit angle with respect to the light-emitting element are arbitrary, there are no restrictions on the placement positions of the light emitting unit and the light collecting unit. As a result, the degree of freedom in device design can be increased.

[0029] Each light-emitting element emits light of a single wavelength, and the wavelength of light emitted by the light-emitting elements is the same on the same track but different for each track, and the pattern of the presence or absence of light-emitting elements on multiple tracks may be set according to position coordinates.

[0030] This makes it easier to arrange the light emitting elements.

[0031] The light emitting element may also be a phosphor.

[0032] Furthermore, at least one track may have at least one light emitting element disposed thereon that emits light of multiple wavelengths.

[0033] This allows the number of light emitting elements to be reduced.

[0034] The light emitting element may also be a laser excited by light.

[0035] Furthermore, the light emitting elements may be arranged such that the presence or absence of the wavelength of light emitted at adjacent position coordinates differs by only one wavelength.

[0036] This makes it easier to determine reading errors and correct abnormal values, improving the accuracy of position detection.

[0037] In the optical system according to the above aspect, the first direction may be a direction in which the object moves.

[0038] This makes it possible to detect the position of an object moving in the first direction.

[0039] A method for optically detecting the position of an object according to an aspect of the present disclosure includes arranging optical elements that have a reflective, diffractive, or luminescent effect on the surface of the object in a line in a first direction and a second direction perpendicular to the first direction, the rows aligned in the first direction being tracks, and the rows aligned in the second direction corresponding to position coordinates, a light emitting unit irradiating light onto multiple tracks based on light emitted by a light source, a light collecting unit receiving light from the multiple tracks, and a position detection unit reading the wavelengths of the light received by the light collecting unit and detecting the position coordinates at which the light was irradiated from the combination of wavelengths read, and the optical elements are arranged so that the combination of wavelengths of light received by the light collecting unit differs depending on the position coordinates.

[0040] According to this configuration, optical elements that exhibit reflective, diffractive, or luminescent properties are arranged in a row direction (tracks) and a column direction (position coordinates) on the surface of an object. A light emitting unit irradiates multiple tracks with light based on light generated by a light source, a light collecting unit receives light from the multiple tracks, and a position detecting unit reads the wavelengths of the light received by the light collecting unit and detects the position coordinates where the light is irradiated from the combination of read wavelengths. The optical elements are arranged so that the combination of wavelengths of light received by the light collecting unit differs depending on the position coordinates. This eliminates the need for the processes of imaging → photography → image analysis, and allows the position coordinates where the light is irradiated to be detected from the combination of read wavelengths, making it possible to detect the position of an object with a simple configuration.

[0041] In the position detection method according to the above aspect, the optical element may be a reflective element that reflects light, and a pattern of the presence or absence of reflective elements in the multiple tracks may be set according to position coordinates, and the light emitting unit may irradiate the multiple tracks with light having different wavelengths based on light having multiple wavelengths generated by the light source.

[0042] This makes it possible to detect the position of an object by utilizing the reflection effect.

[0043] In the position detection method according to the above aspect, the optical element may be a diffraction element that diffracts light, and the diffraction grating period pattern of the diffraction element in each track may be set according to position coordinates, and the light emitting unit may irradiate the plurality of tracks with light having a plurality of wavelengths generated by the light source.

[0044] This makes it possible to detect the position of an object by utilizing the wavelength selection effect caused by diffraction.

[0045] In the position detection method according to the above aspect, the optical element may be a light-emitting element that receives light and emits light, and the pattern of wavelengths of light emitted by the light-emitting elements in each track may be set according to position coordinates, and the light emitting unit may irradiate light having a single wavelength emitted by the light source onto multiple tracks.

[0046] This allows the position of the object to be detected by utilizing the light emitting effect.

[0047] (Embodiment) Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0048] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0049] (First Example) Figure 1 shows the configuration of the first embodiment. The configuration in Figure 1 detects the position of an object OB moving in the direction of travel. The object OB is, for example, an electronic circuit board. In this embodiment, reflection is used to detect the position.

[0050] <Configuration> A plurality of reflective elements 1 are arranged two-dimensionally on the surface of the object OB. The reflective elements 1 are an example of an optical element in the present disclosure and perform a reflective function. The reflective elements 1 are, for example, 1 μm × 1 μm aluminum thin films (0.1 μm thick). Regarding the arrangement of the reflective elements 1, the alignment parallel to the direction of travel of the object OB (the column direction, corresponding to the first direction) is referred to as a "reflective track," and the alignment perpendicular to the direction of travel (the row direction, corresponding to the second direction) is referred to as a "position coordinate." Here, "perpendicular" includes cases where the angle between the first direction and the second direction is between 80 degrees and 100 degrees. In FIG. 1, there are five columns of reflective tracks T1 to T5 and 13 rows of position coordinates X1 to X13, so there are a maximum of 65 (= 5 × 13) locations where reflective elements 1 can be formed.

[0051] However, reflective elements 1 are not present in all locations, and some are missing. This is because, as will be described later, the presence or absence of reflective elements 1 is used to detect the position of the object OB. In other words, the way in which reflective elements 1 are "missing" makes it possible to quantify the position based on the wavelength combination of the collected light. In addition, it is desirable that areas without reflective elements 1 be coated with a low-reflection film, or have a light absorber / scatterer formed to reduce the surface reflection of light.

[0052] The multi-wavelength light source 11 has a function of outputting light of multiple wavelengths to the optical fiber 12. The multi-wavelength light source 11 has, for example, multiple light-emitting diodes having different emission wavelengths, or laser diodes or superluminescent diodes having different oscillation wavelengths. The light from these light sources is combined by a lens or the like and guided to the optical fiber 12. Light having wavelengths equal to or greater than the number of reflection tracks output from the multi-wavelength light source 11 propagates through the optical fiber 12. In this embodiment, the light output from the multi-wavelength light source 11 has five wavelengths (for example, 405 nm, 430 nm, 520 nm, 600 nm, and 640 nm).

[0053] The light emitting unit 13 is provided on the opposite side of the optical fiber 12. The light emitting unit 13 separates the light propagating through the optical fiber 12 into different optical paths according to wavelength using an internal prism, diffraction grating, etc. The light emitted from each optical path is incident on each of the reflection tracks T1 to T5 in a one-to-one relationship. In this embodiment, light a to e with wavelengths of 405 nm, 430 nm, 520 nm, 600 nm, and 640 nm are incident on the reflection tracks T5, T4, T3, T2, and T1, respectively. Optical paths independent from each other are formed inside the light emitting unit 13 or at the exit (window), and optical elements such as lenses and mirrors are present to prevent crosstalk.

[0054] The light collecting unit 21 guides the light reflected by the reflecting element 1 to the optical fiber 22. Inside the light collecting unit 21, there are lenses, mirrors, etc. for collecting light. However, imaging function is not required. The other end of the optical fiber 22 is connected to the spectrometer 23. The light emitted from the optical fiber 22 into the spectrometer 23 is split into individual wavelengths by a diffraction grating or the like inside the spectrometer, and irradiates the light receiving elements on the optical path of each wavelength. This irradiation generates an electromotive force in the light receiving elements. The electromotive force of each light receiving element is input to the analyzing device 24 and converted into position information within the analyzing device 24. The spectrometer 23 and the analyzing device 24 correspond to the position detecting unit in this disclosure.

[0055] As shown in Fig. 2, in the reflection process, the incident angle and the outgoing angle are equal (α = β). In the configuration of Fig. 1, the angle between the light traveling from the light emitting unit 13 toward the object OB and the normal to the surface of the object OB is the incident angle α with respect to the reflective element 1. The light reflected by the reflective element 1 propagates in the direction of the outgoing angle β (= α). Therefore, the light collecting unit 21 is positioned at a position on the outgoing angle β.

[0056] Now, let us assume that there are N reflective tracks, and that N types of wavelength light are irradiated onto each reflective track. Each reflective track at each position coordinate has two types of information: presence / absence of reflective element 1. Therefore, the position coordinate can be up to 2 N In the configuration of FIG. 1, there are five reflection tracks T1 to T5, so 32 (=2 5)It is possible to indicate the type of position.

[0057] <Operation> The multi-wavelength light source 11 is turned on and starts emitting light. The light output from the multi-wavelength light source 11 travels through the optical fiber 12 towards the light emitting unit 13. From the light emitting unit 13, lights a to e of N (here 5) types of wavelengths are irradiated onto the respective reflection tracks T1 to T5.

[0058] The object OB starts to move in the traveling direction. Then, starting from the row of the position coordinate X1, in the order of X1 → X2 → X3 →..., light is reflected from the reflection element 1 arranged in that row. The reflected light is collected by the condenser 21, propagated through the optical fiber 22, and split by the spectroscope 23.

[0059] The analysis device 24 determines from the output of the spectroscope 23 which wavelength of light has arrived. Specifically, a threshold intensity Pth is determined in advance. For the light intensity P(Xi, λj) of the wavelength λj at the position coordinate Xi (in FIG. 1, i is 1 to 13) and the reflection track Tj (in FIG. 1, j is 1 to 5), If P(Xi, λj) ≥ Pth, there is reflection of track Tj at the position coordinate Xi If P(Xi, λj) < Pth, there is no reflection of track Tj at the position coordinate Xi and make a judgment. Thus, a digital value Ej corresponding to the presence or absence of reflection in the track Tj can be given to the position coordinate Xi. For example, let Ej = 1 when there is reflection and Ej = 0 when there is no reflection.

[0060] FIG. 3 is an example of obtaining the digital value of the position coordinate. In the example of FIG. 3, the intensities of lights a, b, d, and e exceed the threshold Pth, but the intensity of light c is below the threshold Pth. Therefore, the digital value of the position coordinate is "11011". The value of the position at the position coordinate Xi is

Equation

[0061] The order of the digital values ​​of the position coordinates does not need to correspond to the order of the actual positions. For example, the former can be in ascending order and the latter in descending order. For example, a lookup table or the like can be used to ensure a 1:1 correspondence between "digital values" and "actual positions."

[0062] Figure 4 shows an example of assigning digital values ​​to position coordinates. In Figure 4, there are three reflection tracks and eight position coordinates. In this case, as mentioned above, 8 (=2) values ​​are assigned depending on whether or not there is a reflection. 3 ) types of location information can be provided.

[0063] In FIG. 4(a), digital values ​​are assigned to position coordinates X1 to X8 in a monotonically increasing order (000 → 001 → 010 → 011 → ...). In this case, there is no regularity in the change in the presence or absence of reflection when the position coordinate changes; there may be one, two, or three changes. For example, when the position coordinate changes from X2 to X3, the presence or absence of reflection changes in the reflection tracks T1 and T2; when the position coordinate changes from X3 to X4, the presence or absence of reflection changes in the reflection track T1; and when the position coordinate changes from X4 to X5, the presence or absence of reflection changes in the reflection tracks T1, T2, and T3.

[0064] In Figure 4(b), digital values ​​are assigned to position coordinates X1 to X8 in a sequence known as a Gray code. In this case, the presence or absence of reflection always changes in only one reflection track when the position coordinate changes. For example, when the position coordinate changes from X2 to X3, the presence or absence of reflection changes only in reflection track T2; when the position coordinate changes from X3 to X4, the presence or absence of reflection changes only in reflection track T1; and when the position coordinate changes from X4 to X5, the presence or absence of reflection changes only in reflection track T3.

[0065] In the case of Figure 4(b), if there is a change in the presence or absence of reflection in two or more reflective tracks when the position coordinates change, it is clear that a reading error has occurred due to, for example, a sudden disturbance of external light. Therefore, the abnormal value can be eliminated. It is also possible to correct this abnormal value based on normal measurements before and after. In this way, using the Gray code to assign digital values ​​makes it easy to determine and correct errors, improving the accuracy of position detection.

[0066] To realize the allocation of FIG. 4(b), the reflective elements 1 should be arranged so that the presence or absence of a reflective element differs by only one track at adjacent position coordinates.

[0067] When using Gray code, the binary sequence is not monotonically increasing but is random, so the position coordinates calculated from the digital values ​​are also random. However, as mentioned above, it is possible to convert the "digital value" to the "actual position" in a 1:1 ratio using, for example, a lookup table.

[0068] In addition, for example, some of the reflection tracks may be used for the increment signal, which allows for higher measurement accuracy.

[0069] <Effects> According to this embodiment, the position of the object OB can be detected by utilizing the reflection effect. Furthermore, since the position of the object OB is detected from the presence or absence of reflected light of each wavelength, the accuracy of position detection does not depend on the shape of the reflected light. In other words, there is no need to determine whether the shape of the reflected light is a cross or a square, and light rays that give a so-called "blurred image" that is not focused at a single point may be used. Therefore, the process of imaging → photographing → image analysis is no longer necessary, and the degree of freedom in designing the alignment device (and the equipment using it) is improved.

[0070] (Second Example) 5 shows the configuration of the second embodiment. In contrast to the first embodiment, which utilizes reflection, the second embodiment utilizes wavelength selection due to diffraction.

[0071] <Configuration> FIG. 6 shows an example of the diffractive element 2 used in this embodiment. The diffractive element 2 is an example of an optical element in the present disclosure and exhibits diffractive properties. The diffractive element 2 shown in FIG. 6 has triangular projections and depressions periodically formed on a film made of, for example, SiO2, with a thickness of 0.5 μm and a size of 3 × 3 μm. The shape of the projections and depressions may be, for example, rectangular or sawtooth. Such a diffractive element 2 can be fabricated, for example, by nanoimprinting.

[0072] When light of wavelength λ enters a surface on which a diffraction grating with a period d (i.e., the period of the uneven shape is d) is formed at an incident angle α, the exit angle β from that surface satisfies the following equation.

number

[0073] In FIG. 5, a plurality of diffractive elements 2 are arranged two-dimensionally on the surface of the object OB. Regarding the arrangement of the diffractive elements 2, the arrangement in a direction parallel to the traveling direction of the object OB (column direction) is called a "diffractive track," and the arrangement in a direction perpendicular to the traveling direction (row direction) corresponds to a "position coordinate." In FIG. 5, as in the first embodiment, there are five columns of diffraction tracks T1 to T5 and 13 rows of position coordinates X1 to X13, so there are a maximum of 65 locations (= 5 × 13) where diffractive elements 2 can be formed. However, as with the reflective elements 1 in the first embodiment, some diffractive elements 2 are missing. Depending on how these diffractive elements 2 are "missing," it is possible to quantify positions based on the wavelength combination of the collected light, as in the first embodiment.

[0074] In this embodiment, diffractive elements 2 having the same period d are arranged on the same diffraction track, and diffractive elements 2 having different periods d are arranged on each of the diffraction tracks T1 to T5.

[0075] The multi-wavelength light source 11 has the same configuration as in the first embodiment, and light having wavelengths equal to or greater than the number of diffraction tracks propagates through the optical fiber 12. On the other hand, the light emitting unit 13A has a different configuration from the light emitting unit 13 in the first embodiment. That is, the light emitting unit 13A irradiates light of all wavelengths onto the diffraction tracks T1 to T5 without separating the light propagating through the optical fiber 12 into light beams of different wavelengths. For this reason, the light emitting unit 13A includes lenses, mirrors, and the like, but does not include optical components for splitting the light into light beams of different wavelengths.

[0076] The configurations of the light collecting unit 21, the spectroscope 23 and the analyzing device 24 are the same as those in the first embodiment.

[0077] <Operation> In this embodiment, light including five wavelengths (790 nm, 805 nm, 820 nm, 835 nm, and 850 nm) is irradiated onto the object OB from the light emitting unit 13A. The light emitting unit 13A is disposed so that the incident angle α is 45°. The light collecting unit 21 is disposed so that the output angle β is 60°.

[0078] FIG. 7(a) shows an example of the characteristics of the diffractive elements 2 arranged on each of the diffraction tracks T1 to T5. Diffractive elements 2 having the diffraction grating periods shown in the right column of FIG. 7(a) are arranged on the diffraction tracks T1 to T5. The only light that travels from each of the diffraction tracks T1 to T5 in the direction of the output angle β is light of the wavelengths in the center column of FIG. 7(a). In other words, even if light of multiple wavelengths is incident on each of the diffraction tracks T1 to T5, only light of one type of wavelength travels in the direction of the output angle β for each of the diffraction tracks T1 to T5, and light of other wavelengths travels in a different angle and does not enter the light-condensing unit 21.

[0079] For example, as shown in FIG. 7(b), even though light of many wavelengths shown in the leftmost column is incident on diffraction track T1, only light of wavelength 790 nm is directed in the direction of output angle β=60°. Light of other wavelengths is directed in the direction of β=63.6 to 80.2°. Because the light-collecting unit 21 is on the optical path of β=60°, only light of wavelength 790 nm enters the light-collecting unit 21 from diffraction track T1. The same is true for the other diffraction tracks T2 to T5; even though light of many wavelengths is incident at angle α, only light of wavelengths shown in the center column of FIG. 7(a) enters the light-collecting unit 21, which is located in the direction of output angle β.

[0080] In this way, light of a specific wavelength is incident on the light collecting unit 21 from each of the diffraction tracks T1 to T5. Therefore, light whose wavelength is selected depending on the presence or absence of the diffraction element 2 is propagated from the light collecting unit 21 to the spectrometer 23. The subsequent operation of converting the wavelength combination into a numerical value representing the position coordinate is the same as in the first embodiment.

[0081] <Effects> According to this embodiment, the position of the object OB can be detected by utilizing the wavelength selection effect of diffraction. Furthermore, since there is no need to separate wavelengths in the light emitting unit 13, the number of optical components provided in the light emitting unit 13 can be reduced. This allows the size of the light emitting unit 13 to be reduced, and the amount of space it occupies to be reduced. As a result, the degree of freedom in device design can be increased.

[0082] In this embodiment, to realize the digital value allocation of Fig. 4(b), the diffractive elements 2 are arranged so that the presence or absence of a diffraction grating period differs by only one diffraction grating period at adjacent position coordinates. For example, in the configuration of Fig. 5, the diffractive elements 2 are arranged so that the presence or absence of a diffraction grating period differs by only one track at adjacent position coordinates.

[0083] (Third Example) 8 shows the configuration of the third embodiment. In contrast to the first embodiment, which utilizes reflection, this embodiment utilizes fluorescence as the light-emitting effect.

[0084] Fluorescence occurs when high-energy light (short-wavelength light) is absorbed by a specific atom (or molecule) and the electrons inside the atom (or molecule) are excited to a higher energy level, and when the electrons transition to a lower energy level, the difference energy is released as light. Therefore, the output light of the phosphor is low-energy light (long-wavelength light).

[0085] <Configuration> FIG. 9 shows an example of the phosphor element 3 used in this example. The phosphor element 3 is an example of an optical element in the present disclosure and has a light-emitting effect. The phosphor element 3 is, for example, a film made of phosphor, 1 μm thick and 10 × 10 μm in size. When light with wavelength λ1 is incident on the phosphor element 3 at an arbitrary angle, light with wavelength λ2, which is larger than wavelength λ1, is emitted in all directions. Such a phosphor element 3 can be produced, for example, by screen printing.

[0086] In FIG. 8, a plurality of phosphor elements 3 are two-dimensionally arranged on the surface of the object OB. Regarding the arrangement of the phosphor elements 3, the arrangement in the direction parallel to the traveling direction of the object OB (column direction) is called a "phosphor track," and the arrangement in the direction perpendicular to the traveling direction (row direction) corresponds to a "position coordinate." In FIG. 8, as in the first embodiment, there are five columns of phosphor tracks T1 to T5 and thirteen rows of position coordinates X1 to X13, so there are a maximum of 65 locations (= 5 × 13) where phosphor elements 3 can be formed. However, as with the reflective elements 1 in the first embodiment, some phosphor elements 3 are missing. Depending on the manner in which these phosphor elements 3 are "missing," it is possible to quantify positions based on the wavelength combination of the collected light, as in the first embodiment.

[0087] In this embodiment, five types of phosphor elements 3 (emitting light in blue, green, yellow, red, and near-infrared) are arranged. The same type of phosphor elements 3 are arranged on the same phosphor track. Different types of phosphor elements 3 are arranged on each of the phosphor tracks T1 to T5.

[0088] The excitation light source 31 outputs light of a single wavelength. However, the output light of the excitation light source 31 must have a wavelength that excites all types of phosphor elements 3 arranged on the object OB. An AlGaN ultraviolet LED (wavelength 380 nm) is used as the excitation light source 31, for example. The light emitting unit 32 is configured with an optical system including lenses and mirrors so that the output light of the excitation light source 31 is branched and the branched light is directed toward each of the phosphor tracks T1 to T5. The light emitting unit 32 has an extremely simple structure because it is not necessary to consider wavelength dispersion, etc.

[0089] The configurations of the light collecting unit 21, the spectroscope 23 and the analyzing device 24 are the same as those in the first embodiment.

[0090] <Operation> The excitation light of a single wavelength output from the excitation light source 31 is guided to the light emitting unit 32 through the optical fiber 12. The light emitting unit 32 splits the excitation light and irradiates each of the phosphor tracks T1 to T5. The phosphor elements 3 emit fluorescence of the respective colors in response to the excitation light that has reached the phosphor tracks T1 to T5.

[0091] In this way, light of a specific wavelength is incident on the light collecting unit 21 from each of the phosphor tracks T1 to T5. Therefore, light whose wavelength is selected depending on the presence or absence of the phosphor elements 3 is propagated from the light collecting unit 21 to the spectrometer 23. The subsequent operation of converting the wavelength combination into a numerical value representing the position coordinate is the same as in the first embodiment.

[0092] <Effects> According to this embodiment, the position of the object OB can be detected by utilizing the fluorescent effect as the light emitting effect. Furthermore, since the light emitting unit 32 handles light of a single wavelength, there is no need to include optical components for wavelength branching, and the number of optical components can be reduced. This reduces the size of the light emitting unit 32, and the amount of space it occupies. As a result, the degree of freedom in device design can be increased.

[0093] Furthermore, since the incident angle and the outgoing angle with respect to the phosphor element 3 are arbitrary, there are no restrictions on the placement positions of the light emitting section and the light collecting section as in the first and second embodiments, which also increases the degree of freedom in device design.

[0094] In this embodiment, to realize the digital value allocation of Fig. 4(b), the phosphor elements 3 may be arranged so that the presence or absence of emitted light wavelengths differs by only one wavelength at adjacent position coordinates. For example, in the configuration of Fig. 8, the phosphor elements 3 may be arranged so that the presence or absence of emitted light wavelengths differs by only one track at adjacent position coordinates.

[0095] (Fourth Example) 10 shows the configuration of the fourth embodiment. In contrast to the first embodiment, which utilizes a reflection effect, this embodiment utilizes a photo-excited laser oscillation effect as the light emission effect.

[0096] Generally, lasers are known to have the following mechanism: current is passed → population inversion (a state in which the number of high-energy electrons exceeds the number of low-energy electrons) occurs inside the material that makes up the laser → the light propagating through the material is amplified → laser oscillation occurs when this amplification becomes greater than the optical loss within the material. However, this population inversion can be achieved not only by current injection, but also by external light irradiation. In other words, laser oscillation can be obtained using external light as an excitation source. This is called optically pumped laser oscillation.

[0097] <Configuration> FIG. 11 shows an example of the light-emitting element 4 used in this example. The light-emitting element 4 is an example of an optical element in this disclosure and produces light. FIG. 11 shows a surface-emitting laser formed from a thin film of the alloy semiconductor AlGaAs. AlGaAs is an alloy semiconductor of AlAs and GaAs, and the band gap and refractive index can be changed by changing the AlAs composition. A so-called double heterostructure is formed by making the AlAs composition of the active layer smaller than the AlAs composition of the first and second cladding layers. External high-energy (short wavelength λ1) light generates electrons and holes in the active layer, and due to population inversion of the electrons and holes, the active layer has gain at approximately the energy of its forbidden band width. Placing this gain medium in a resonator produces laser oscillation with a wavelength λ2 (>λ1).

[0098] The configuration shown in Figure 11(a) has a distributed Bragg reflector (DBR) formed on the front and back surfaces using a dielectric multilayer film, forming a cavity between the front and back surfaces. For this reason, it is called a vertical cavity surface-emitting laser.

[0099] The configuration in Figure 11(b) has an uneven surface formed near the end face of a guide layer (for example, an AlGaAs layer with a higher AlAs composition than the active layer and lower than the cladding layer) formed on the surface. This uneven surface forms a diffraction grating. The resonator is formed by this diffraction grating and the opposite end face (which can be a cleaved surface). The diffraction grating is formed second-order (m = 2 in equation (1)) with respect to the emission wavelength. In this case, the first-order diffracted light is directed in the direction normal to the surface. For this reason, the laser is called a diffraction grating-coupled surface-emitting laser.

[0100] The configuration shown in Figure 11(c) has recesses arranged two-dimensionally on the surface, and is called a photonic crystal surface-emitting laser. A resonator is formed by these two-dimensionally arranged recesses, and oscillates by forming a resonator that extends across the entire plane parallel to the surface. With appropriate design, laser light oscillated in the normal direction of the surface is emitted.

[0101] Such a light-emitting element can be fabricated by, for example, fabricating a vertical-cavity surface-emitting laser on a semiconductor wafer using metal-organic chemical vapor deposition, then removing the wafer and attaching it to the object to be measured.

[0102] In FIG. 10, a plurality of light-emitting elements 4 are arranged two-dimensionally on the surface of the object OB. The light-emitting elements 4 are capable of the optically excited laser oscillation described above. Regarding the arrangement of the light-emitting elements 4, the arrangement in the direction parallel to the traveling direction of the object OB (column direction) is called the "light-emitting track," and the arrangement in the direction perpendicular to the traveling direction (row direction) corresponds to the "position coordinate." In FIG. 10, as in the first embodiment, there are five columns of light-emitting tracks T1 to T5 and thirteen rows of position coordinates X1 to X13, so there are a maximum of 65 locations (= 5 × 13) where the light-emitting elements 4 can be formed. However, as with the reflective elements 1 in the first embodiment, some light-emitting elements 4 are missing. Depending on the manner in which the light-emitting elements 4 are "missing," it is possible to quantify the positions based on the wavelength combinations of the collected light, as in the first embodiment.

[0103] The light-emitting element 4 may have any of the configurations shown in Figures 11(a) to 11(c). In any case, no electrode for current injection is formed. Furthermore, it is desirable that the surface be treated with a low reflectance (such as an anti-reflective coating) for wavelength λ1 so that incident light (wavelength λ1) can easily enter the interior of the light-emitting element 4.

[0104] In this embodiment, five types of light emitting elements 4 (emitting light in blue, green, yellow, red, and near infrared) are arranged. The same type of light emitting elements 4 are arranged in the same light emitting track. Different types of light emitting elements 4 are arranged in each of the light emitting tracks T1 to T5.

[0105] The configurations of the excitation light source 31 and the light emitting section 32 are the same as those in Example 3. However, the output light of the excitation light source 31 must have a sufficient amount of light so that each light emitting element 4 is excited and reaches laser oscillation.

[0106] The configurations of the light collecting unit 21, the spectroscope 23, and the analyzer 24 are the same as those in the first embodiment. However, since the light emitting elements 4 emit light in the normal direction to the light emitting surface, it is desirable that the light collecting unit 21 be located almost directly above the portion of the substrate surface where the light from the light emitting unit 32 forms a spot.

[0107] <Operation> The excitation light of a single wavelength output from the excitation light source 31 is guided to the light emitting unit 32 through the optical fiber 12. The light emitting unit 32 branches the excitation light and irradiates each of the light emitting tracks T1 to T5. When the excitation light reaching the light emitting tracks T1 to T5 exceeds a laser threshold, the light emitting elements 4 oscillate at the respective wavelengths and emit laser light.

[0108] In this way, laser light of a specific wavelength is incident on the light collecting unit 21 from each of the light emitting tracks T1 to T5. Therefore, light whose wavelength is selected depending on the presence or absence of the light emitting elements 4 is propagated from the light collecting unit 21 to the spectrometer 23. The subsequent operation of converting the wavelength combination into a numerical value representing the position coordinate is the same as in the first embodiment.

[0109] <Effects> According to this embodiment, the position of the object OB can be detected by utilizing the optically excited laser oscillation effect as the light emission effect. Furthermore, since the light emitting unit 32 handles light of a single wavelength, there is no need to include optical components for wavelength branching or wavelength dispersion compensation elements, and the number of optical components can be reduced. This reduces the size of the light emitting unit 32, and the amount of space it occupies. As a result, the degree of freedom in device design can be increased.

[0110] Furthermore, compared to ordinary light, laser light has a higher intensity and higher directivity. Therefore, even if the light collecting unit 21 is located away from the object OB, the laser light can be detected. In other words, the degree of freedom in designing the arrangement of the light collecting unit 21 can be increased.

[0111] In this embodiment, to realize the digital value allocation of Fig. 4(b), the light emitting elements 4 may be arranged so that the presence or absence of the wavelength of light emitted at adjacent position coordinates differs by only one wavelength. For example, in the configuration of Fig. 10, the light emitting elements 4 may be arranged so that the presence or absence of the light at adjacent position coordinates differs by only one track.

[0112] As described above, according to this embodiment, optical elements that exhibit reflective, diffractive, or luminescent properties are arranged in a row direction (tracks) and a column direction (position coordinates) on the surface of the object OB. The light emitting unit irradiates each track with light based on light generated by a light source, the light collecting unit receives the light from each track, and the position detecting unit reads the wavelengths of the light received by the light collecting unit and detects the position coordinates where the light is irradiated from the combination of the read wavelengths. The optical elements are arranged so that the combination of wavelengths of light received by the light collecting unit differs depending on the position coordinates. This eliminates the need for the processes of imaging → photography → image analysis, and allows the position coordinates where the light is irradiated to be detected from the combination of read wavelengths, thereby enabling the position detection of the object with a simple configuration.

[0113] (Modification of the second embodiment) FIG. 12 is an image of the diffraction element 2A used in this modified example. Generally, sine waves with different periods can be superimposed (combined). For example, in a certain coordinate system x, when a sine wave sin(2πx / d1) with a period d1 and a sine wave sin(2πx / d2) with a period d2 are superimposed with the same amplitude, the result is:

number

number

number

[0114] As shown in Figure 12, if we consider that a diffraction grating can be decomposed into multiple sine waves when subjected to Fourier expansion, diffraction gratings with periods d1, d2, ... can also be combined into one, as in equations (2) to (4). Using this concept, the configuration of the second embodiment can be configured so that one diffraction element has multiple diffraction grating periods and can select multiple wavelengths. This makes it possible to reduce the number of diffraction elements and the number of diffraction tracks.

[0115] FIG. 13 shows the configuration of this modified example. In the configuration of FIG. 13, there is only one diffraction track (T1). The diffraction elements 2A arranged on the diffraction track T1 have different combinations of diffraction grating periods depending on their position coordinates. Light including five wavelengths (790 nm, 805 nm, 820 nm, 835 nm, and 850 nm) is irradiated onto the diffraction track T1 from the light emitting unit 13B. The diffraction elements 2A selectively output light of the five wavelengths toward the light collecting unit 21 according to the combination of their own diffraction grating periods.

[0116] 13, there is only one row of diffraction tracks, but this is not limiting. By using the concept of this modified example, the number of diffraction tracks can be made smaller than the number of wavelengths used for position detection.

[0117] This modification improves the flexibility of device design by enabling the miniaturization of light emitting unit 13B and light collecting unit 21. In addition, the area on the surface of object OB where the diffractive elements are arranged can be reduced, improving the effective utilization of the surface of object OB.

[0118] (Modification of the third embodiment) FIG. 14 is an image diagram of a phosphor element 3A used in this modification. As shown in FIG. 14, it is generally possible to mix different phosphors to create a single phosphor. Therefore, in the configuration of the third embodiment, one phosphor element can be configured to emit light of multiple wavelengths. This makes it possible to reduce the number of phosphor elements and the number of phosphor tracks.

[0119] Fig. 15 shows the configuration of this modified example. In the configuration of Fig. 15, there is only one row of phosphor tracks (T1). The phosphor elements 3A arranged on the phosphor track T1 are configured to emit light of different combinations of wavelengths depending on their position coordinates. The output light of the excitation light source 31 is irradiated onto the phosphor track T1 from the light emitting section 32A. The phosphor elements 3A emit light of wavelengths according to the mixed phosphors.

[0120] 15, only one row of phosphor tracks is used, but the present invention is not limited to this. By using the concept of this modification, the number of phosphor tracks can be made smaller than the number of wavelengths used for position detection.

[0121] This modification allows for greater flexibility in device design, as it is possible to reduce the size of the light emitting unit 32A and the light collecting unit 21. In addition, it is possible to reduce the area on the surface of the object OB where the phosphor elements are arranged, thereby improving the effective use of the surface of the object OB.

[0122] (Application to mounting machines) 16 and 17 show an example of a configuration in which the above-described embodiment is applied to a mounting machine, where (a) is a side view and (b) is a top view. Here, an example of a configuration in which the third embodiment is applied is shown.

[0123] 16 and 17 mounts a semiconductor chip 42 on a substrate 41, which is an example of an object. A head 43 adsorbs the semiconductor chip 42 using a vacuum chuck or the like. Phosphor elements 3 are arranged on the surface of the substrate 41.

[0124] 17, the phosphor elements 3 are formed as a two-dimensional array of phosphor elements 3X for the X direction and phosphor elements 3Y for the Y direction. The emission wavelengths of the phosphor elements 3X and 3Y may be the same or different. In this example, the phosphor elements 3X emit reddish light (600 to 670 nm), and the phosphor elements 3Y emit blued light (400 to 500 nm).

[0125] As shown in Fig. 16, a head 43 of the mounting machine is provided with a laser light source 31 as an excitation light source for the phosphor. As shown in Fig. 17, the laser light source 31 includes a laser light source 31X for measurement in the X direction and a laser light source 31Y for measurement in the Y direction. The output characteristics (wavelength, optical output, transverse mode, polarization, modulation, etc.) of the laser light sources 31X and 31Y may be the same or may be adjusted to optimal characteristics for each direction. In this example, the same laser light source (AlGaN ultraviolet laser: wavelength 380 nm) is used.

[0126] A beam shaping lens is provided at the end of the laser light source 31 as a light emitting unit 32. This forms an elliptical spot that irradiates only phosphor elements at the same position coordinates, as shown in Fig. 17. The light distribution in the major axis direction of the ellipse is preferably uniform (a so-called top hat shape).

[0127] The light collecting unit 21 collects the light from the phosphor elements 3X and 3Y and introduces it into the spectroscope 23. The operation of the spectroscope 23 and the analyzing device 24 is as described above. By allocating light of different wavelength bands in the X-axis direction and the Y-axis direction, it is possible to separate the light in the X-axis direction and the Y-axis direction for position detection even if light is collected by a single light collecting unit 21. In other words, the device can be made more compact. There is also no need to worry about the light from each direction becoming stray light (noise). It is also possible to provide dedicated light collecting units for the X-axis direction and the Y-axis direction, respectively. [Industrial Applicability]

[0128] The present disclosure enables optical position detection of an object with a simple configuration, and is therefore useful for, for example, miniaturizing electronic component mounters. [Explanation of symbols]

[0129] 1. Reflective elements (optical elements) 2,2A Diffractive elements (optical elements) 3,3A Phosphor element (optical element) 4. Light-emitting elements (optical elements) 11 Multi-wavelength light source 13,13A,13B Light emission section 21 Light collecting part 23 Spectrometer 24 Analyzer 31 Excitation light source 32,32A light emitting part

Claims

1. 1. An optical system for detecting the position of an object, comprising: Optical elements that exhibit a reflecting action, a diffracting action, or a luminous action are arranged on a surface of the object in a first direction and a second direction perpendicular to the first direction, and rows arranged in the first direction are tracks, and rows arranged in the second direction correspond to position coordinates; The optical system comprises: A light source and a light emitting unit that irradiates a plurality of tracks with light based on light generated by the light source; a light collecting unit that receives light from a plurality of tracks; a position detection unit that reads the wavelengths of the light received by the light collecting unit and detects the position coordinates of the light irradiated from the combination of the read wavelengths; The optical elements are provided so that the combination of wavelengths of light received by the light collecting unit varies depending on the position coordinates. Optical system.

2. 2. The optical system of claim 1, the optical element is a reflective element that reflects light, The pattern of the presence or absence of reflective elements in each track is set according to the position coordinates, the light source generates light having a plurality of wavelengths; The light emitting unit irradiates a plurality of tracks with light having different wavelengths based on the light generated by the light source. Optical system.

3. 3. The optical system of claim 2, The reflective elements are arranged so that the presence or absence of a reflective element differs by only one track at adjacent position coordinates. Optical system.

4. 2. The optical system of claim 1, the optical element is a diffractive element that diffracts light, The pattern of the diffraction grating period of the diffraction elements in each track is set according to the position coordinates, the light source generates light having a plurality of wavelengths; The light emitting unit irradiates the light emitted by the light source onto a plurality of tracks. Optical system.

5. 5. The optical system of claim 4, each diffractive element having a single grating period; the grating periods of the diffractive elements are the same in the same track and different from track to track; The pattern of the presence or absence of diffractive elements in the multiple tracks is set according to the position coordinates. Optical system.

6. 5. The optical system of claim 4, At least one track has at least one diffractive element disposed thereon, the diffractive element having a plurality of grating periods. Optical system.

7. 5. The optical system of claim 4, The diffractive elements are arranged such that the presence or absence of a diffraction grating period differs by only one diffraction grating period at adjacent position coordinates. Optical system.

8. 2. The optical system of claim 1, the optical element is a light-emitting element that receives light and emits light, a pattern of wavelengths of light emitted by the light-emitting elements in the plurality of tracks is set according to position coordinates; the light source generates light having a single wavelength; The light emitting unit irradiates the light emitted by the light source onto a plurality of tracks. Optical system.

9. 9. The optical system of claim 8, Each light-emitting element emits light of a single wavelength; The wavelengths of the light emitted by the light emitting elements are the same in the same track and are different for each track; The presence or absence of light emitting elements in multiple tracks is set according to the position coordinates. Optical system.

10. 9. The optical system of claim 8, The light-emitting element is a phosphor Optical system.

11. 11. The optical system of claim 10, At least one track has at least one light emitting element arranged thereon that emits light of a plurality of wavelengths. Optical system.

12. 9. The optical system of claim 8, The light-emitting element is a laser excited by light Optical system.

13. 9. The optical system of claim 8, The light emitting elements are arranged so that the presence or absence of the wavelength of light emitted at adjacent position coordinates differs by only one wavelength. Optical system.

14. 2. The optical system of claim 1, The first direction is a direction in which the object moves. Optical system.

15. 1. A method for optically detecting a position of an object, comprising: optical elements that exhibit a reflecting action, a diffracting action, or a luminous action are arranged on a surface of the object in a first direction and a second direction perpendicular to the first direction, the rows arranged in the first direction are defined as tracks, and the rows arranged in the second direction correspond to position coordinates; a light emitting unit irradiating light onto a plurality of tracks based on light generated by the light source; The light collecting section receives light from multiple tracks, a position detection unit that reads the wavelengths of the light received by the light collecting unit and detects the position coordinates of the light irradiated from the combination of the read wavelengths; The optical elements are provided so that the combination of wavelengths of light received by the light collecting unit varies depending on the position coordinates. Location detection methods.

16. 16. The position detection method according to claim 15, the optical element is a reflective element that reflects light, A pattern of the presence or absence of reflective elements in the plurality of tracks is set according to position coordinates, The light emitting unit irradiates a plurality of tracks with light having different wavelengths based on light having a plurality of wavelengths generated by the light source. Location detection methods.

17. 16. The position detection method according to claim 15, the optical element is a diffractive element that diffracts light, The pattern of the diffraction grating period of the diffraction elements in each track is set according to the position coordinates, The light emitting unit irradiates a plurality of tracks with light having a plurality of wavelengths generated by the light source. Location detection methods.

18. 16. The position detection method according to claim 15, the optical element is a light-emitting element that receives light and emits light, A pattern of wavelengths of light emitted by the light-emitting elements in each track is set according to position coordinates, The light emitting unit irradiates a plurality of tracks with light having a single wavelength generated by the light source. Location detection methods.

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