Diffractive optical element, optical assembly comprising the same, and reference line projection device

Abstract

The present application relates to a kind of diffractive optical elements for projecting reference line, the diffractive optical element includes multiple microstructure pattern units arranged periodically in two-dimensional array, the phase distribution of each microstructure pattern unit is configured to receive laser and modulate the laser projection reference line, wherein the field of view angle of the diffractive optical element in at least one direction is greater than or equal to 90 degrees.The present application also relates to an optical assembly comprising the diffractive optical element.The present application proposes a kind of diffractive optical element (DOE), instead of traditional refractive optical element, forms the required laser reference line.Because DOE has extremely high design freedom, target light field is not limited to a word line, cross line, more complex laser reference line, such as grid line, can also be designed.For the case that laser standard line is cross line, only a piece of DOE needs to be designed to achieve, without needing to be aligned and installed in vertical direction like two refractive optical elements.

Description

Technical Field

[0001] The present invention generally relates to the field of optical technology, and more particularly to a diffractive optical element for projecting a reference line, an optical component including the diffractive optical element, and a reference line projection device. Background Art

[0002] Laser line projectors are widely used in the construction industry to project laser reference lines to improve construction accuracy. Common laser line projectors on the market currently include straight lines and cross lines. These are usually implemented by first collimating the divergent light emitted by the laser diode, and then using a refractive optical element (ROE), such as a cylindrical lens, to form the desired light field (reference line). Existing laser line projectors that utilize refractive optical elements to implement cross lines have the problem of vertical alignment of two perpendicular cylindrical lenses, making installation difficult and having poor impact resistance.

[0003] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the existing technologies in this field. Summary of the Invention

[0004] In view of at least one drawback of the prior art, the present invention provides a diffractive optical element, an optical assembly including the diffractive optical element, and a reference line projection device.

[0005] According to one aspect of the present invention, a diffractive optical element for projecting a reference line is provided, wherein the diffractive optical element comprises a plurality of microstructure pattern units periodically arranged in a two-dimensional array, wherein the phase distribution of each of the microstructure pattern units is configured to receive a laser and modulate the laser to project the reference line, wherein the field of view angle of the diffractive optical element in at least one direction is greater than or equal to 90 degrees.

[0006] According to another aspect of the present invention, the reference line includes a horizontal reference line and a vertical reference line, and the field angles of the diffractive optical element in the horizontal direction and the vertical direction are both greater than or equal to 90 degrees.

[0007] According to another aspect of the present invention, the field angles of the diffractive optical element in the horizontal and vertical directions are both greater than or equal to 110 degrees.

[0008] According to another aspect of the present invention, a period size of the microstructure pattern units is smaller than a size of an incident light field of the laser on the diffractive optical element.

[0009] According to another aspect of the present invention, the incident light field may cover at least two of the microstructure pattern units.

[0010] According to another aspect of the present invention, the diffractive optical element is configured so that: the incident light field irradiated on the plurality of the microstructure pattern units forms a dotted baseline after diffraction modulation of the microstructure pattern units and interference modulation between the plurality of the microstructure pattern units.

[0011] According to another aspect of the present invention, the period of the microstructure pattern unit is 100um*100um to 2mm*2mm, and the size of the incident light field is 500um*500um to 5mm*5mm, wherein preferably, the period of the microstructure pattern unit is 500um*500um to 1mm*1mm, and the size of the incident light field is 1mm*1mm to 3mm*3mm.

[0012] The present invention further provides an optical assembly for projecting a reference line, comprising:

[0013] a laser light source configured to emit laser light; and

[0014] A diffractive optical element as described above.

[0015] According to another aspect of the present invention, the laser light source is a divergent light source, the diffraction optical element is designed for collimated light, and the optical component further includes a collimating lens located between the laser light source and the diffraction optical element, thereby shaping the laser light emitted by the laser light source into collimated light.

[0016] According to another aspect of the present invention, the laser light source is a divergent light source, and the diffractive optical element is designed for the divergent light source.

[0017] The present invention also provides a reference line projection device, comprising the optical component described above.

[0018] This invention employs a diffractive optical element (DOE) to replace the traditional ROE element to form the required laser reference line. Because the DOE offers a high degree of design freedom, the target light field is not limited to a straight line or a crosshair; more complex laser reference lines, such as a grid, can be designed. For laser reference lines that are crosshairs, a single DOE is sufficient, eliminating the need for vertical alignment required for two refractive optical elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0020] Figure 1A schematic diagram of an optical assembly for projecting a reference line according to one embodiment of the present invention is shown;

[0021] Figure 2 A schematic diagram showing a diffractive optical element according to the present invention and a partial phase distribution of one of the microstructure pattern units;

[0022] Figure 3A and 3B Two embodiments of the baseline are shown in FIG;

[0023] Figure 4 The reference line projected by a single microstructure pattern unit and its local magnified image are shown;

[0024] Figure 5 shows a reference line projected according to one embodiment of the present invention and a partially enlarged view thereof; and

[0025] Figure 6 FIG. 4 is a schematic diagram showing an optical component for projecting a reference line according to another embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0027] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the aforementioned features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0028] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical, electrical, or intercommunication connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0029] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may also include the first and second features not being in direct contact but being in contact via another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a lower level than the second feature.

[0030] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0031] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] Figure 1 A schematic diagram of an optical assembly 10 for projecting a reference line according to an embodiment of the present invention is shown below. Figure 1 Detailed description.

[0033] like Figure 1As shown, optical assembly 10 includes a laser light source 11, a collimating lens 12, and a diffractive optical element 13. Laser light source 11 is, for example, a laser diode LD, which emits a laser beam when driven. The laser beam from laser light source 11 is incident on collimating lens 12, where it is shaped and modulated into a parallel beam, which then enters diffractive optical element 13 downstream in the optical path.

[0034] Figure 2 FIG. 5 shows a schematic diagram of a diffractive optical element according to the present invention and a partial phase distribution of one of the microstructure pattern units. Figure 2 As shown on the left, the diffractive optical element 13 of the present invention includes a plurality of, for example, G*H, microstructure pattern units, which are periodically arranged in a two-dimensional array, wherein each microstructure pattern unit has the same phase distribution pattern. Figure 2 The right side also shows a partial phase distribution pattern of a microstructure pattern unit of the diffractive optical element. As shown in the figure, the diffractive optical element is an 8-step element. Different grayscales in the figure represent different step heights, that is, different phases. Each microstructure pattern unit on the diffractive optical element 13 can change the phase distribution of the wavefront of light incident on it, thereby modulating the transmission of light so that the output light beam conforms to the preset light intensity distribution and light field pattern. In the present invention, the phase distribution of each microstructure pattern unit is configured to receive laser light and modulate the laser light to project the reference line. Figure 3A and 3B Two embodiments of the baseline are shown in FIG. Figure 3A The reference lines in the chart are cross-shaped, including horizontal and vertical reference lines. Figure 3B The reference lines in the embodiment are in a grid pattern, with multiple horizontal and vertical reference lines intersecting to form a grid. It will be readily understood by those skilled in the art that the scope of protection of the present invention is not limited to a specific type of reference line, and may also be a straight line, for example, including only horizontal or vertical reference lines.

[0035] The diffractive optical element 13 according to the present invention has a field angle greater than or equal to 90 degrees in at least one direction. Figure 1 FIG. 1 is a schematic diagram of an optical assembly 10. As shown in the figure, the diffractive optical element 13 has a horizontal field angle θ of greater than or equal to 90 degrees. Additionally or alternatively, the diffractive optical element 13 also has a vertical field angle of greater than or equal to 90 degrees. Furthermore, according to a preferred embodiment of the present invention, the diffractive optical element 13 has a horizontal and vertical field angle of greater than or equal to 110 degrees.

[0036] Compared with conventional diffraction optical elements, the projection area of ​​the diffraction optical element of the present invention is relatively large, that is, the field of view angle is relatively large. The field of view angle of conventional diffraction optical elements is generally relatively small, for example, less than 60 degrees, and can be designed according to the paraxial approximation principle. However, since the laser line projector requires that a reference line as long as possible be projected within a smaller projection distance range, the field of view angle of the diffraction optical element used for the laser line projector is required to be as large as possible, for example, greater than or equal to 90 degrees, and even preferably greater than or equal to 110 degrees. In the case of a relatively large field of view angle, the target pattern designed by the conventional design method is unevenly distributed on the plane, with the middle bright and the surrounding dark. Taking the reference line of the laser line projector as an example, the part of the line near the center of the projection area is relatively bright, and the brightness of the line gradually darkens as it extends to the edge of the projection area. This is because the brightness distribution of the target pattern designed by the conventional design method on the spherical surface is uniform, but it will be distorted when projected onto a plane, and the edge pixels are elongated, resulting in reduced brightness. To address this problem, the diffractive optical element of the present invention performs distortion correction during the design process, that is, brightness compensation is performed on the edge area of ​​the reference line, thereby ensuring that the reference line appears as a straight line with relatively uniform brightness within a larger field of view.

[0037] Furthermore, due to the relatively large field of view of the diffractive optical element to be designed, the phase distribution of the diffractive optical element obtained using conventional design methods contains many very small feature regions, such as tiny features of several hundred nanometers. These tiny feature phases contain high-frequency component information, which affects the wide-angle energy distribution of the target light field. However, due to limitations in processing technology, these tiny features are difficult to produce, resulting in deviations between the actual processed diffractive optical element morphology and the theoretical design morphology, and thus between the actual target light field and the preset target light field. Taking into account existing processing technology, the inventors of the present invention imposed feature size restrictions during the diffractive optical element design process to ensure consistency between the production results and the design results.

[0038] In addition, due to the high coherence of laser, the target pattern formed by the diffraction optical element will have a more obvious speckle effect. For the design of the reference line of the laser line projector, the line will have irregular granular dark spots, which is not beautiful. Figure 4 shown. Figure 4The left side of the center shows a crosshair projected by a single microstructure pattern unit of a diffractive optical element, while the right side shows a magnified portion of the crosshair. A large number of irregular, granular dark spots can be seen, and the baseline is not clear or aesthetically pleasing. To address this issue, according to one embodiment of the present invention, the period size of the microstructure pattern units of the diffractive optical element can be adjusted so that the incident light field emitted by the laser light source illuminates multiple periods of the diffractive optical element. The diffraction images formed by the multiple periods on the diffractive optical element interfere with each other, causing the so-called continuous line originally formed by the diffraction of a single period to interfere into a dotted line distribution. This eliminates the obvious irregular speckle observed on the target pattern, improving the aesthetics of the crosshairs.

[0039] According to a preferred embodiment of the present invention, the period of the microstructure pattern unit is smaller than the size of the incident light field of the laser on the diffractive optical element 13. Preferably, the incident light field can cover at least two of the microstructure pattern units. Since the incident light field is irradiated on at least two microstructure pattern units, a dotted baseline is formed after diffraction modulation of the microstructure pattern units and interference modulation between the multiple microstructure pattern units, such as Figure 5 shown.

[0040] The period of a diffraction optical element refers to the basic unit of the phase distribution designed based on the incident light field and the target light field, i.e., the target pattern. The period size can be set according to specific design requirements. The period length can be, for example, several hundred microns to several millimeters, such as 200um to 5mm. The larger the period, the smaller the point spacing of the dotted lines formed by the interference between the periods. Conversely, the smaller the period, the larger the point spacing of the dotted lines formed by the interference between the periods. According to a preferred embodiment of the present invention, the period of the microstructure pattern unit is 100um*100um to 2mm*2mm, and the size of the incident light field is 500um*500um to 5mm*5mm. Preferably, the period of the microstructure pattern unit is 500um*500um to 1mm*1mm, and the size of the incident light field is 1mm*1mm to 3mm*3mm.

[0041] The processing accuracy of the diffractive optical element (i.e., the minimum characteristic size) determines the number of phase distributions within a single period of the diffractive optical element. When the period is constant, the smaller the minimum characteristic size, the greater the number of phase distributions, the higher the design flexibility of the diffractive optical element, and the ability to design more flexible and complex target patterns. However, due to the limitations of the processing technology level of the diffractive optical element, the minimum characteristic size is usually from a few hundred nanometers to a few microns, for example, 200nm to 5um. In a preferred embodiment of the present invention, the minimum characteristic size is 200nm, the period is 700um, and the incident light field size of the laser light source is 2mm.

[0042] Figure 1 The laser light source 11 shown in the figure is a divergent light source, and the diffractive optical element 13 is designed for collimated light. Therefore, a collimating lens 12 needs to be provided between the laser light source 11 and the diffractive optical element 13 to shape the laser light emitted by the laser light source 11 into collimated light. It is easy for those skilled in the art to understand that the present invention is not limited to this. For example, the laser light source 11 can be a divergent light source, and the diffractive optical element is designed for a divergent light source, such as Figure 6 As shown schematically, the optical component 10' includes a laser light source and a diffractive optical element. The laser light source is a divergent light source, and the diffractive optical element is designed for the divergent light source. For example, a Fresnel diffraction lens with a function similar to a collimating lens can be designed to obtain a phase distribution pattern, and then a DOE for collimated light can be designed to obtain a corresponding phase distribution pattern, and then the two phase patterns can be superimposed. Therefore, the divergent laser beam can be directly received and modulated to project a phase distribution pattern corresponding to the phase distribution pattern. Figure 4 and Figure 5 Similar light field patterns. In addition, refer to Figure 1-Figure 5 Each technical feature of the described embodiment can be combined with Figure 6 In the embodiments, no creative effort is required.

[0043] On the other hand, designs targeting collimated light pose a high risk to human eye safety. After passing through the collimating lens, the LD forms a parallel laser beam with a very high power density. If the ROE is damaged, the parallel laser beam may directly hit the human eye, causing significant damage. Designs targeting divergent light, on the other hand, eliminate the collimation step and transmit the laser beam in a divergent manner. Therefore, the power density of the laser beam is lower at a certain distance from the laser source, reducing the risk to human eye safety. Under the same eye safety requirements, designs targeting divergent light can use higher-power LD light sources.

[0044] The present invention also relates to a reference line projection device, comprising the optical assembly 10 as described above.

[0045] The present invention provides a diffractive optical element (DOE) that replaces traditional ROEs to form the required laser reference lines. Because DOEs offer a high degree of design freedom, the target light field is not limited to straight lines or crosshairs; more complex laser reference lines, such as grid lines, can be designed. For laser reference lines that are crosshairs, a single DOE is sufficient, eliminating the need for vertical alignment required for two refractive optical elements.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diffractive optical element for projecting a reference line, characterized in that The diffractive optical element includes a plurality of microstructure pattern units periodically arranged in a two-dimensional array, wherein the phase distribution of each of the microstructure pattern units is configured to receive laser light and modulate the laser light to project the reference line, wherein the field of view angle of the diffractive optical element in at least one direction is greater than or equal to 90 degrees; The size of the period of the microstructure pattern unit is smaller than the size of the incident light field of the laser on the diffractive optical element; The diffractive optical element is configured such that: the incident light field irradiated on the plurality of the microstructure pattern units forms a reference line in the form of a dotted line after being diffracted and modulated by the microstructure pattern units and interferometrically modulated between the plurality of the microstructure pattern units, thereby suppressing granular dark spots on the reference line and improving the clarity of the reference line; The diffractive optical element is configured to perform brightness compensation on the edge area of ​​the reference line to correct the uneven distribution of the reference line on the plane, which is bright in the middle and dark around the edges, so that the reference line appears as a straight line with uniform brightness within the field of view.

2. The diffractive optical element according to claim 1, wherein The reference lines include a horizontal reference line and a vertical reference line, and the field angles of the diffractive optical element in the horizontal direction and the vertical direction are both greater than or equal to 90 degrees.

3. The diffractive optical element according to claim 2, wherein: The viewing angles of the diffractive optical element in the horizontal direction and the vertical direction are both greater than or equal to 110 degrees.

4. The diffractive optical element according to any one of claims 1 to 3, wherein: The incident light field may cover at least two of the microstructure pattern units.

5. The diffractive optical element according to any one of claims 1 to 3, wherein: The period of the microstructure pattern unit is 100um*100um to 2mm*2mm, and the size of the incident light field is 500um*500um to 5mm*5mm.

6. The diffractive optical element according to claim 5, wherein The period of the microstructure pattern unit is 500um*500um to 1mm*1mm, and the size of the incident light field is 1mm*1mm to 3mm*3mm.

7. An optical assembly for projecting a reference line, characterized in that The optical assembly comprises: a laser light source configured to emit laser light; and The diffractive optical element according to any one of claims 1 to 6.

8. The optical component according to claim 7, wherein The laser light source is a divergent light source, the diffractive optical element is designed for collimated light, and the optical component further includes a collimating lens located between the laser light source and the diffractive optical element, thereby shaping the laser light emitted by the laser light source into collimated light.

9. The optical component according to claim 7, wherein: The laser light source is a divergent light source, and the diffraction optical element is designed for the divergent light source.

10. A reference line projection device, characterized in that: The reference line projection device comprises an optical component as described in any one of claims 7-9.

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