KR20240013543A - Lighting apparatus for machine vision - Google Patents

Abstract

The present invention relates to a lighting device for machine vision that emits a beam in various radiation patterns by passing light reflected from a light guide plate through a diffraction grating array with a controlled grating period and grating direction, comprising: a light source; a light guide that totally reflects light emitted from the light source; a coupler that guides light emitted from the light source to the light guide plate; and a light extraction unit formed on one side of the light guide unit, in which diffraction gratings formed in minute regions having the same or different lattice constants are arranged, and extract light totally reflected from the light guide plate; a grating period of the diffraction grating; Alternatively, the radiation pattern of light emitted through the light extraction unit may be adjusted depending on the grid direction.

Description

Lighting device for machine vision{LIGHTING APPARATUS FOR MACHINE VISION}

The present invention relates to a lighting device for machine vision, and more specifically, to a lighting device for machine vision that emits a beam in an arbitrarily designed radiation pattern by implementing a local grating array on a light guide plate. .

Machine vision acquires images of products through hardware such as cameras, optical systems, and lighting devices installed on the production line, and performs image processing through software to analyze and inspect the acquired images to improve the quality of the products produced. It refers to a management technology and is used to inspect final products in various manufacturing industries.

Among the components of machine vision, in the case of lighting devices that irradiate light to the inspection object, the inspection accuracy of the inspection object may vary depending on the irradiation efficiency, so coaxial lighting, oblique lighting, and dark field ( Various types of lighting devices, such as dark-field lighting and dome lighting, have been developed.

Among them, as shown in FIG. 1, dome-shaped lighting has the effect of preventing shadows from forming on an object (subject of inspection) by radiating light from multiple directions at once to the object (subject to be inspected), as if outdoors on a cloudy day. In addition, it has the effect of increasing contrast by averaging diffuse reflections on surfaces with high diffuse reflections, such as rough processed metal surfaces.

Meanwhile, the existing dome-type lighting had the problem of being unable to be placed in narrow production lines due to its large volume. To solve this problem, as shown in FIG. 2, a flat dome light was developed that has the same radiation pattern as the existing dome type light but has a significantly smaller volume by arranging a random scattering structure on the light guide plate.

However, the random scattering structure on the light guide plate changes the angular characteristics of the radiation pattern depending on the shape of the scatterer, and the output distribution of the radiation pattern can be adjusted by adjusting the area of the individual scatterer and the density distribution of the scatterer per unit area. Basically, due to random scattering characteristics, there are limitations in precise control of the radiation pattern and high efficiency.

Korean Patent No. 10-1931166

The object of the present invention is to provide a lighting device for machine vision that has a small volume, such as a flat dome lighting, while controlling the radiation pattern precisely and at the same time has high energy efficiency.

A lighting device for machine vision according to the present invention to achieve the above problem includes a light source; a light guide that totally reflects light emitted from the light source; a coupler that guides light emitted from the light source to the light guide plate; and a light extraction unit formed on one side of the light guide unit, arranged with a plurality of diffraction gratings formed in micro regions having the same or different lattice constants, and extracting light totally reflected from the light guide plate; The radiation pattern of light emitted through the light extraction unit is adjusted according to the grid period or grid direction.

In one embodiment of the present invention, the light source is a point light source or a line light source.

Additionally, in one embodiment of the present invention, the light source is characterized as being a short-wavelength or multi-wavelength light source.

Additionally, in one embodiment of the present invention, the coupler is characterized as being at least one of a butt coupler, a prism, or a coupler with an inclined surface.

In addition, in one embodiment of the present invention, the coupler having the prism or inclined surface is characterized in that it is a reflection or transmission type of light.

In addition, in one embodiment of the present invention, a collimator that directs light incident on the coupler from the light source in parallel is further included.

Additionally, in one embodiment of the present invention, the inclined surface is characterized in that it has a curved shape.

In addition, in one embodiment of the present invention, a collimator that directs the light reflected from the coupler in parallel is further included.

Additionally, in one embodiment of the present invention, the light guide part and the light extraction part are characterized in that they are formed in a plate shape.

Additionally, in one embodiment of the present invention, the light guide part and the light extraction part are characterized in that they are formed in a curved shape.

Additionally, in one embodiment of the present invention, the exit angle of light emitted from the light guide through the light extraction unit is characterized in that it is derived from the relationship shown in the equation below.

<Equation>

Here, n ₁ is the refractive index of the light guide unit 30, n ₂ is the refractive index of the light extraction unit 40, n _air is the refractive index of external air, θ _inc is the angle of incidence at which light enters the light extraction unit 40, θ ₂ is the angle of the light at the light extraction unit 40, θ _ext is the emission angle from the light extraction unit 40, m is the diffraction order, λ is the wavelength of light, and Λ means the grating period.

In addition, in one embodiment of the present invention, the grating period and grating direction of each diffraction grating are adjusted so that the tilt angle and azimuth angle of the light passing through the plurality of diffraction gratings are the same or different from each other.

In addition, in one embodiment of the present invention, each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the light extraction unit is concentrated toward one object to be inspected.

In addition, in one embodiment of the present invention, each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the light extraction unit is concentrated toward two or more objects to be inspected.

In addition, in one embodiment of the present invention, each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the plurality of diffraction gratings is gathered into a plurality of cones.

According to the present invention, a lighting device for machine vision can be manufactured that has a small volume, can implement various radiation patterns according to control of the diffraction grating, and has high energy efficiency.

Figure 1 is a diagram showing a conventional dome-type lighting device for machine vision.
Figure 2 is a diagram showing a conventional flat dome lighting device for machine vision.
Figure 3 is a diagram showing a lighting device for machine vision according to an embodiment of the present invention.
Figure 4 is a diagram showing a butt coupler according to another embodiment of the present invention.
Figure 5 is a diagram for explaining the principle of total reflection.
Figure 6 is a diagram showing the total reflection phenomenon of light within the light guide.
Figure 7 is a diagram showing a state in which light emitted from a light source moves through a coupler and a light guide according to an embodiment of the present invention.
FIG. 8A is an enlarged view of portion X of FIG. 3.
FIG. 8B is a diagram showing the diffraction grating shown on the bottom of FIG. 8A.
Figure 9 is a diagram showing the diffraction phenomenon of light passing through a diffraction grating within the light guide.
Figure 10 is a diagram explaining the inclination angle and azimuth angle of light passing through a diffraction grating.
Figure 11 is a graph showing the radial direction of the beam through adjustment of the grating period of the diffraction grating in one embodiment of the present invention.
Figure 12 is a graph showing the diffraction efficiency at the target emission angle according to the thickness of the diffraction grating in one embodiment of the present invention.
Figure 13 is a diagram showing the radiation pattern of a lighting device for machine vision according to another embodiment of the present invention.
Figure 14 is a diagram showing a state in which the light guide part and the light extraction part are formed as curved surfaces in a lighting device for machine vision according to another embodiment of the present invention.
Figure 15 is a diagram showing a state in which light with different wavelengths is emitted from the light guide and irradiated to an object to be inspected in a lighting device for machine vision according to another embodiment of the present invention.

Hereinafter, with reference to the attached drawings, a lighting device for machine vision according to a preferred embodiment will be described in detail as follows. Here, the same symbols are used for the same components, and repetitive descriptions and detailed descriptions of known functions and configurations that may unnecessarily obscure the gist of the invention are omitted. Embodiments of the invention are provided to more completely explain the invention to those skilled in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Figure 3 is a diagram showing a lighting device for machine vision according to an embodiment of the present invention.

As shown in FIG. 3, a lighting device for machine vision according to an embodiment of the present invention includes a light source 10, a coupler 20, a light guide unit 30, and a light extraction unit 40.

The light source 10 is a source that radiates light to the object O, and there is no limit to the installation location or number of the light source 10 in the machine vision lighting device according to the present invention. The light source 10 may be a point light source or a line light source depending on the embodiment. At this time, if the light source 10 is a point light source, surface light emission can be induced by adjusting the azimuth angle in the coupler 20. Additionally, the light source 10 may be a short-wavelength or multi-wavelength light source depending on the embodiment. Additionally, in another embodiment, the light source 10 may be selected from point light sources, line light sources, short-wavelength light sources, and multi-wavelength light sources and configured in various combinations.

The coupler 20 guides the light emitted from the light source to move to the light guide part 30 (referred to as a coupling) and is coupled to one side of the light guide part 30. In one embodiment of the present invention, the coupler 20 is a coupler having an inclined surface. At this time, the coupler 20 having an inclined surface may be a light transmissive or reflective type. For example, if a prism is used as the coupler 20 with an inclined surface, it may be referred to as a transmissive coupler, and if a mirror is used, it may be referred to as a reflective coupler. Depending on the configuration of each coupler, the position of the light source 10 may vary in order to guide light to the light guide 30.

Meanwhile, as shown in FIG. 4, in another embodiment of the present invention, the coupler 20 may be a butt coupler.

Meanwhile, according to one embodiment of the present invention, a collimator 50 may be further included to incident light emitted from the light source 10 into the coupler 20 in parallel. In one embodiment of the present invention, the collimator 50 is in the form of a lens and is located between the light source 10 and the coupler 20. Although the collimator 50 is not necessarily used in the present invention, it is preferably used for light control or efficiency.

Meanwhile, according to another embodiment, when the coupler 20 having a reflective inclined surface is formed as a curved surface, it can perform not only the function of a coupler but also the function of a collimator.

Figure 5 is a diagram for explaining the principle of total reflection, Figure 6 is a diagram showing the total reflection phenomenon of light within the light guide, and Figure 7 is a diagram showing the light emitted from a light source according to an embodiment of the present invention moving the coupler and the light guide. This is a drawing showing the state.

Light irradiated from the light source 10 by the coupler 20 is incident on the light guide part 30. At this time, a total reflection phenomenon occurs depending on the angle at which light is incident on the light guide unit 30.

Referring to FIG. 5, the total reflection phenomenon occurs when propagating from a medium with a high refractive index (n1) to a medium with a low refractive index (n2), and when incident conditions exceed a certain critical angle (θc), the light does not pass through the medium with a low refractive index and all A phenomenon of total reflection occurs. Here, the critical angle (θc) can be obtained as shown in Equation 1 below.

<Equation 1>

Referring to FIG. 6, if this critical angle (θc) condition is satisfied, the light incident on the light guide plate 30 with a high refractive index is not transmitted through the air with a low refractive index and is totally reflected within the light guide plate 30.

Referring to FIG. 7, the light guide portion 30 according to an embodiment of the present invention is made of acrylic material, the upper and lower walls are formed in a plate shape, and the light guide part 30 is surrounded by four sides to have an internal space. The refractive index (n _acryl ) of the light guide part 30 is 1.49, and the refractive index of air outside the light guide part 30 is approximately 1. Light irradiated from the light source 10 according to an embodiment of the present invention is reflected from the inclined surface of the coupler 20, and the inclined surface of the coupler 20 is adjusted so that the light incident on the light guide part 30 is greater than the critical angle θc. When the angle (θ slope) is adjusted, light is totally reflected within the light guide plate 30 according to the above-described principle of total reflection, and does not escape out of the light guide plate 30.

FIG. 8A is an enlarged view of part , and FIG. 10 is a diagram explaining the inclination angle and azimuth angle of light passing through the diffraction grating.

The light extraction unit 40 is formed on one side of the light guide unit 30. In one embodiment of the present invention, the light extraction part 40 is formed at the lower part of the light guide part 30 to face the upper part. The portion of the light extraction unit 40 where the diffraction grating is formed may be manufactured in the form of a film and then attached to the light guide unit 30, or may be manufactured by performing a nanoimprint process directly on the light guide unit 30.

As shown in FIGS. 8A and 8B, the light extraction unit 40 has a plurality of diffraction gratings 42 formed to have the same or different lattice constants for each microscopic region, and each diffraction grating 42 is arranged in a certain direction. do. Here, the lattice constant refers to a vector quantity that expresses both the lattice period (Λ) of the periodic pattern and the lattice direction. Figure 8b shows examples of nine diffraction gratings having the same or different lattice constants. Specific details about the diffraction grating will be described later.

Figure 9 is a diagram showing the relationship in which light is diffracted when it is emitted from the light guide unit 30 through the light extraction unit 40, and this relationship can be expressed as <Equation 2> below. <Equation 2> below explains the operating principle of the diffraction grating 42.

<Equation 2>

Here, n _acryl is the refractive index of the light guide unit 30, n _resin is the refractive index of the light extraction unit 40, n _air is the refractive index of external air, θ _inc is the angle of incidence at which light enters the light extraction unit 40, and θ2 is The angle of light at the light extraction unit 40, θ _ext , is the emission angle emitted from the light extraction unit 40, m is the diffraction order, λ is the wavelength of light, and Λ means the grating period.

Referring to FIG. 9, the refractive index of the resin of the diffraction grating portion is 1.5, which is greater than the refractive index of the light guide portion 30, which is 1.49. When light of wavelength λ, which is totally reflected in a medium with a high refractive index, such as the light guide part 30, encounters a part of the diffraction grating having an incident angle θ _inc and a grating period Λ, after passing through the diffraction grating 42, the <Equation 2 > It is diffracted at an angle of θ _ext and then emitted into the air.

As seen in the above-mentioned <Equation 2>, if you want to change the emission angle θ _ext of light that has the same wavelength and is incident at the same incident angle, you can adjust the grating period Λ.

Hereinafter, with reference to FIGS. 8B to 10, the inclination angle (θ) and azimuth angle (δ) when light L passes through the diffraction grating 42 will be described.

FIG. 10(a) is a diagram explaining the inclination angle θ of the emitted light L, and FIG. 10(b) is a diagram explaining the azimuth angle δ of the emitted light L. The inclination angle (θ) of the emitted light means the angle between the first reference line and the emitted light on the side (y-z plane) of the light extraction unit 40, and the azimuth angle (δ) of the emitted light is the light extraction unit 40. It means the angle between the second reference line and the emitted light on the lower or upper surface (x-z plane).

Referring to FIG. 8B, the size of the inclination angle θ of the emitted light L can be changed by changing the grating period Λ, as described above.

Azimuth (δ) refers to the grid direction. Diffraction grating A in FIG. 8B has a grating direction of approximately 45° relative to the z-axis line, diffraction grating B has a grating direction of approximately 90°, and diffraction grating C has a grating direction of approximately 135°. Of course, these angles may be displayed differently in azimuth depending on the set reference direction.

That is, in the present invention, it is possible to form a diffraction grating 42 having the same azimuth angle (δ) but different tilt angles (θ), and conversely, a diffraction grating 42 having the same tilt angle (θ) but different azimuth angles (δ) can be formed. It is possible to form

Meanwhile, in a diffraction grating, the fill factor, which is the ratio between the protruding portion and the grooved portion of the diffraction grating, is dependent on the amount of light or extraction efficiency. Therefore, when the filling ratio of the diffraction grating is changed, the amount of light or extraction efficiency changes accordingly. For example, fill ratio and extraction efficiency may have a monotonically increasing or decreasing relationship. Diffraction gratings C and D in FIG. 8B have the same azimuth angle (δ) and tilt angle (θ), but the amount of emitted light is different.

Meanwhile, as an example of the method for manufacturing a diffraction grating in the present invention, when two obliquely incident beams are gathered at a local position on a sample on which photoresist has been previously applied and interfere with each other, the photoresist is exposed according to the interference pattern. A local diffraction grating pattern can be formed, and at this time, a different type of diffraction grating pattern can be formed by changing the tilt angle or tilt direction (azimuth) of the two beams. This diffraction grating manufacturing method can be referred to as interference lithography technology. However, the manufacture of the diffraction grating is not limited to this, and known techniques can naturally be applied.

Meanwhile, according to another embodiment of the present invention, the collimator may also be placed inside the light guide part 30. If the light totally reflected inside the light guide 30 is collimated, beam control in the diffraction grating may become easier.

However, the collimation process within the light guide unit 30 is not necessarily an essential element. In other words, even for totally reflected light that is not collimated, various radiation patterns can be realized through an appropriate diffraction grating arrangement.

Figure 11 is a graph showing the radial direction of the beam through adjustment of the grating period of the diffraction grating in one embodiment of the present invention.

Figure 11 shows the emission angle ( Indicates a change in Extinction Angle.

As shown in FIG. 11, the emission angle can be from 0° to 80° when the diffraction grating period (Λ) is 400 to 2800 nm. Here, the emission angle of 0° corresponds to vertical emission (see Figure 9). Therefore, according to the present invention, the radiation direction of the beam at a local location can be controlled by adjusting the diffraction grating period.

Figure 12 is a graph showing the diffraction efficiency at the target emission angle according to the thickness of the diffraction grating in one embodiment of the present invention, and shows the results calculated using a rigid coupled-wave analysis (RCWA) program.

Meanwhile, diffraction efficiency refers to the ratio of the amount (energy) of light diffracted to the amount (energy) of light incident on the light extraction unit 40. Factors that affect diffraction efficiency include the constituent materials of the diffraction grating, fill factor, thickness of the diffraction grating, and grating period. Using these factors, it is possible to control so that only a certain amount of incident light is diffracted. In the present invention, all of these factors can be controlled, but in particular, diffraction efficiency is controlled by adjusting the filling ratio or grating period.

As shown in FIG. 12, it can be seen that when the diffraction grating is formed with a uniform thickness of 200 nm, the diffraction efficiency according to the emission angle is calculated to be 11.7 to 40.0%. That is, according to the present invention, radiation efficiency can be controlled by adjusting the density per unit area of the diffraction grating at a local location. In this specification, the thickness of the diffraction grating can be determined by looking at the results shown in FIG. 12, taking into account the size of the diffraction grating according to the required diffraction efficiency.

Referring again to FIG. 3, according to the present invention, the light irradiated from the light source 10 is totally reflected within the light guide part 30 through the coupler 20, and has various radiation patterns through the light extraction part 40 to the object to be inspected. (O). At this time, various radiation patterns can be formed by adjusting the grating period and grating direction, which are the lattice constants of each two-dimensionally arranged diffraction grating. In other words, the grating constant of each diffraction grating can be adjusted so that light is directed to the object O according to the position or number of the object O.

Figure 13 is a diagram showing the radiation pattern of a lighting device for machine vision according to another embodiment of the present invention.

Figure 13 (a) shows a state in which the grating constant (grid period or grating direction) of each diffraction grating is controlled so that the radiation pattern of the emitted beam is directed toward the two objects, and Figure 13 (b) shows the state in Figure 13 It shows an embodiment that can be composed of various diffraction gratings to implement the radiation pattern shown in (a) (it does not show the diffraction grating at a specific position shown in (a) of FIG. 13).

In Figure 13 (a), assuming that the part where the light passing through the diffraction grating is concentrated on the left is the part where the first object is located, and the part where the light is concentrated on the right is the part where the second object is located, the grating among the diffraction gratings A diffraction grating with a smaller period is located closer to the inspected object, and a diffraction grating with a larger grating period is located further away from the inspected object. This can be fully understood by those skilled in the art by referring back to <Equation 2>, which defines the above-mentioned emission angle of light, by referring to the fact that the smaller the grid period, the smaller the emission angle and the closer it is to vertical.

As shown in (a) of FIG. 13, light passing through the diffraction grating is collected in an approximately cone shape on the surface on which the object to be inspected is placed. At this time, according to the present invention, the angle between the bus lines of the cone can be formed in various ways by adjusting the lattice constant of each diffraction grating.

Meanwhile, although not shown in (a) of FIG. 13, the diffraction gratings arranged in the x-axis direction (backward direction of the drawing) may be arranged with the grating direction changed to diffract light to the location of the object to be inspected.

Additionally, as described above, in order to determine diffraction efficiency, the thickness of the diffraction grating can be controlled (see FIG. 12) or the filling ratio can be controlled at a given diffraction grating thickness.

Meanwhile, the grating constant of each diffraction grating can be adjusted so that the point where light passing through each diffraction grating gathers has various shapes desired by the user, such as circular or square.

In (a) of FIG. 13, the grating constants of each diffraction grating are set so that the emitted light is directed toward two objects to be inspected, but each diffraction grating may be arranged to be directed toward one or three or more objects to be inspected.

Additionally, according to another embodiment of the present invention, light passing through a plurality of diffraction gratings may be controlled to be collected into a plurality of cones by adjusting the grating period and grating direction of each diffraction grating.

In summary, the present invention makes it possible to form various radiation patterns by two-dimensionally arranging diffraction gratings with grating periods and grating directions in which the tilt and azimuth angles of light passing through a plurality of diffraction gratings are the same or different from each other.

Figure 14 is a diagram showing a state in which the light guide part and the light extraction part are formed as curved surfaces in a lighting device for machine vision according to another embodiment of the present invention.

As described above, in one embodiment of the present invention, the light guide part 30 and the light extraction part 40 are formed in a plate shape. However, as shown in FIG. 14, according to another embodiment of the present invention, the light guide portion 30 and the light extraction portion 40 may be formed in a curved shape to satisfy a suitable shape in a narrow production line situation. there is. As an example of the light extraction unit 40, a method of first forming a plurality of two-dimensionally arranged diffraction gratings into a film using imprinting technology and then attaching them to the curved light guide unit 30. This can be used.

Figure 15 is a diagram showing a state in which light with different wavelengths is emitted from the light guide and irradiated to an object to be inspected in a lighting device for machine vision according to another embodiment of the present invention.

Referring to FIG. 15, when the light source 10 is a multi-wavelength light source, it can be seen that each emitted light L passing through the light guide part 30 has various wavelengths. In one embodiment of the present invention, multi-wavelength emitted light (L) with various radiation patterns can be formed by adjusting the position, grating period, and grating direction of each diffraction grating.

The present invention has been described with reference to an embodiment shown in the attached drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. You will be able to. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

10: light source 20: coupler slope
30: light guide part 40: light extraction part
50: collimator

Claims (15)

light source;
a light guide that totally reflects light emitted from the light source;
a coupler that guides light emitted from the light source to the light guide plate; and
A light extraction unit is formed on one side of the light guide unit, has diffraction gratings formed in microscopic regions having the same or different lattice constants, and extracts light totally reflected from the light guide plate.
Characterized in that the radiation pattern of light emitted through the light extraction unit is adjusted according to the grating period or grating direction of the diffraction grating,
Lighting device for machine vision. According to claim 1,
A lighting device for machine vision, wherein the light source is a point light source or a line light source. According to claim 1,
A lighting device for machine vision, wherein the light source is a short-wavelength or multi-wavelength light source. According to claim 1,
A lighting device for machine vision, wherein the coupler is at least one of a butt coupler and a coupler with an inclined surface. According to claim 4,
A lighting device for machine vision, characterized in that the coupler having the inclined surface is a reflective or transmissive type of light. According to claim 1,
A lighting device for machine vision, characterized in that it further includes a collimator that directs light incident on the coupler from the light source in parallel. According to claim 1,
A lighting device for machine vision, wherein the inclined surface has a curved shape. According to claim 1,
A lighting device for machine vision, characterized in that it further includes a collimator that directs the light reflected from the coupler in parallel within the light guide. According to claim 1,
A lighting device for machine vision, wherein the light guide portion and the light extraction portion are formed in a plate shape. According to claim 1,
A lighting device for machine vision, wherein the light guide part and the light extraction part are formed in a curved shape. According to claim 1,
A lighting device for machine vision, characterized in that the exit angle of the light emitted from the light guide through the light extraction unit is derived from the relationship shown in the equation below.
<Equation>


Here, n ₁ is the refractive index of the light guide unit 30, n ₂ is the refractive index of the light extraction unit 40, n _air is the refractive index of external air, θ _inc is the angle of incidence at which light enters the light extraction unit 40, and θ2 is the The angle of light at the light extraction unit 40, θ _ext is the emission angle emitted from the light extraction unit 40, m is the diffraction order, λ is the wavelength of light, and Λ means the grating period. According to claim 1,
A lighting device for machine vision, wherein the grating period and grating direction of each diffraction grating are adjusted so that the inclination angle and azimuth angle of the light passing through the plurality of diffraction gratings are the same or different from each other. According to claim 1,
A lighting device for machine vision, wherein each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the light extraction unit is concentrated toward one object to be inspected. According to claim 1,
A lighting device for machine vision, wherein each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the light extraction unit is concentrated toward two or more objects to be inspected. According to claim 1,
A lighting device for machine vision, wherein each grating period and grating direction of the plurality of diffraction gratings are adjusted so that the light passing through the plurality of diffraction gratings is gathered into a plurality of cones.

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