Design method for diffractive optical elements, diffractive optical elements and projection apparatus

Abstract

The application provides a design method for a diffractive optical element, the diffractive optical element, a projection device and an intelligent door lock. The design method comprises the following steps: obtaining a processed target light field image according to an original pattern to be projected; obtaining a geometric relationship between an exit light beam and the diffractive optical element relative to a projection surface, including an inclination angle of the exit light beam relative to the projection surface and a vertical distance of the diffractive optical element relative to the projection surface; performing spatial conversion on the target light field image to obtain a converted light field image, the converted light field image being a light field image formed by the exit light beam in a plane perpendicular to the exit light beam; and calculating a phase diagram of the diffractive optical element according to the converted light field image. The embodiment of the application can make the image formed by the exit light beam of the diffractive optical element on the projection surface consistent with the original image, avoid the deformation or the decrease in the clarity of the projected image, and provide a structural basis for reducing the volume of the projection device and optimizing the installation conditions of the projection device.

Description

Technical Field

[0001] This invention relates to the field of optical projection equipment technology, and in particular to a design method for diffractive optical elements, diffractive optical elements and projection devices. Background Technology

[0002] Projection devices that project preset patterns onto specific locations, such as the ground or a wall, can be applied in various fields such as advertising and signage. Existing projection equipment mainly includes two structural forms. One is to make a light-shielding sheet from materials such as film, cut the light-shielding sheet according to the design, and use a lens group to magnify and form a preset pattern on the projection surface. The other is to project the preset pattern using a microlens array or diffractive optical element designed according to the target pattern.

[0003] Projection devices with light-shielding structures are relatively large. Due to limitations in the manufacturing precision of the light-shielding sheets, it is difficult to further reduce the size of the projection device, making it unsuitable for scenarios requiring miniaturization. They are typically placed in fixed locations, such as commercial advertising projections mounted on exterior walls. Projection devices using microlens arrays or diffractive optical elements have even smaller structural dimensions, but these smaller devices are closer to the supporting structure, making the projected image more susceptible to obstruction. Figure 1 As shown, when the projection device is tilted, the edges of the projected pattern will be distorted, affecting the visual effect.

[0004] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0005] To address one or more deficiencies in the prior art, the present invention provides a design method for a diffractive optical element configured to receive an incident light beam and to obliquely project a modulated outgoing light beam toward a projection surface. The design method includes:

[0006] The projection surface is not perpendicular to the emitted light beam;

[0007] Based on the original pattern to be projected, a processed target light field image is obtained, and the target light field image is formed on the projection surface;

[0008] Obtain the geometric relationship between the emitted beam and the diffractive optical element relative to the projection plane;

[0009] Based on the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, the target light field image is spatially transformed to obtain a transformed light field image, wherein the transformed light field image is the light field image formed by the outgoing light beam in a plane perpendicular to the outgoing light beam;

[0010] The phase diagram of the diffractive optical element is calculated based on the converted light field image;

[0011] The geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface includes the tilt angle of the outgoing beam relative to the projection surface and the vertical distance of the diffractive optical element relative to the projection surface. The vertical distance of the diffractive optical element relative to the projection surface is based on the incident position of the incident beam on the diffractive optical element or the exit position of the outgoing beam on the diffractive optical element.

[0012] According to one aspect of the invention, the step of performing spatial transformation includes:

[0013] The boundary features of the converted light field image are calculated based on the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, as well as the boundary features of the target light field image.

[0014] Define spatial transformation rules, and transform the pixels in the target light field image to the pixels in the transformed light field image according to the spatial transformation rules.

[0015] According to one aspect of the present invention, the spatial transformation rule takes the center of the target light field image or the vertical projection position of the exit position of the diffractive optical element on the projection plane as the origin of the coordinate system, takes the pixel points in the target light field image as the coordinate step size, and transforms the pixels in the target light field image into the transformed light field image according to the coordinate correspondence between the target light field image and the transformed light field image.

[0016] According to one aspect of the present invention, wherein the boundary of the target light field image is rectangular and the boundary of the transformed light field image is trapezoidal, and the step of converting pixels in the target light field image to pixels in the transformed light field image includes: performing coordinate transformation on the pixels row by row in a direction perpendicular to the height of the trapezoid.

[0017] According to one aspect of the invention, the step of converting pixels in the target light field image to pixels in the converted light field image includes:

[0018] The pixels in the transformed light field image are sampled and / or interpolated.

[0019] According to one aspect of the invention, the step of decimating and / or interpolating the pixels in the transformed light field image includes:

[0020] Based on the difference in the number of pixels in the same direction between the target light field image and the converted light field image, the converted light field image is sampled and / or interpolated according to a preset rule or algorithm.

[0021] According to one aspect of the invention, the converted light field image is located on a plane perpendicular to the principal ray of the outgoing light beam, and the algorithm for interpolating pixels in the converted light field image includes one or more of nearest neighbor interpolation, bilinear interpolation, and cubic convolution.

[0022] According to one aspect of the invention, the process of interpolating pixels in the transformed light field image includes:

[0023] The pixel coordinates in the transformed light field image are transformed in reverse to obtain the corresponding coordinates in the target light field image;

[0024] The pixel coordinates in the transformed light field image are rounded to their corresponding coordinates in the target light field image according to a preset rounding algorithm;

[0025] The pixel value corresponding to the rounded coordinate position in the target light field image is inserted into the pixel coordinate position in the transformed light field image.

[0026] According to one aspect of the present invention, the preset rounding algorithm includes:

[0027] The rounding method is selected based on the corresponding coordinate values ​​of the pixel coordinates in the transformed light field image in the target light field image and / or the pixel changes of adjacent coordinates in the target light field image.

[0028] According to one aspect of the invention, the incident light beam of the diffractive optical element is perpendicular to the diffractive optical element; when the incident light beam is divergent, the optical axis of the divergent light is perpendicular to the diffractive optical element.

[0029] According to one aspect of the present invention, the step of converting pixels in the target light field image to pixels in the converted light field image includes: determining the position of the coordinate origin; the step of calculating the phase map of the diffractive optical element based on the converted light field image includes: calculating the phase map using a 4-step or 8-step method.

[0030] According to one aspect of the invention, the invention also includes a diffractive optical element designed and fabricated using the design method described above, wherein the outgoing beam of the diffractive optical element forms a target light field image on the projection surface, and the outgoing beam of the diffractive optical element is not perpendicular to the projection surface.

[0031] According to one aspect of the invention, the invention further includes a projection device in which the projection surface is not perpendicular to the emitted light beam, the projection device comprising:

[0032] shell;

[0033] A light emitter, disposed within the housing, configured to emit a light beam; and

[0034] A diffractive optical element is designed and manufactured according to the aforementioned design method, so that the diffractive optical element can project the original pattern to be projected onto the projection surface to form a target light field image; the diffractive optical element is disposed downstream of the light source, the light beam is perpendicularly incident on the diffractive optical element, and the outgoing light beam is obliquely irradiated onto the projection surface; the outgoing surface of the diffractive optical element is parallel to the projection surface or inclined at a preset angle.

[0035] According to one aspect of the present invention, the exit surface of the diffractive optical element is inclined at a preset angle relative to the projection surface, and the incident beam of the diffractive optical element has a preset angle with the projection surface.

[0036] According to one aspect of the invention, the diffractive optical element is an eccentric structure, the exit surface of the diffractive optical element is arranged parallel to the projection surface, and the incident light of the diffractive optical element is perpendicular to the projection surface.

[0037] According to one aspect of the invention, the projection device further includes:

[0038] A collimating lens is disposed between the light emitter and the diffractive optical element, and the collimating lens and the diffractive optical element are arranged in parallel.

[0039] According to one aspect of the invention, the projection device further includes:

[0040] An adjustment structure is provided, in which the collimating lens is disposed. The adjustment structure is movably connected to the housing to change the distance between the collimating lens and the light emitter.

[0041] According to one aspect of the invention, the light emitter is a semiconductor laser.

[0042] According to one aspect of the invention, the invention also includes a smart lock, the smart lock including the projection device as described above.

[0043] Compared with existing technologies, embodiments of the present invention provide a design method for diffractive optical elements. Addressing the problem that the projected image obtained on the projection surface does not correspond to the desired target image when the outgoing beam of the diffractive optical element is not perpendicular to the projection surface, the present invention obtains a processed target light field image using the original pattern. Based on the geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface, the target light field image is spatially transformed to obtain a transformed light field image. The phase map of the diffractive optical element is calculated using the transformed light field image. This ensures that the image formed by the beam projected by the diffractive optical element illuminating the projection surface matches the desired original image, avoiding image distortion or decreased clarity. It also provides a structural basis for reducing the size of the projection device and optimizing its installation conditions. The present invention also includes an embodiment of a diffractive optical element designed and manufactured using the aforementioned design method, as well as embodiments of a projection device and a smart door lock. The diffractive optical element designed and manufactured using the aforementioned design method ensures clear and accurate projected images and effectively reduces the structural volume of the projection device and smart door lock, optimizing the installation conditions of the projection device. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0045] Figure 1 This is a schematic diagram of the projection beam being blocked in the prior art;

[0046] Figure 2 This is a flowchart illustrating a design method for a diffractive optical element in one embodiment of the present invention;

[0047] Figure 3 This is a flowchart illustrating a design method including a spatial transformation process in one embodiment of the present invention;

[0048] Figure 4 This is a flowchart illustrating a design method for performing pixel sampling and / or interpolation on a converted light field image, as described in one embodiment of the present invention.

[0049] Figure 5 This is a schematic diagram illustrating spatial transformation of a target light field image in one embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of spatial transformation of a target light field image in another embodiment of the present invention;

[0051] Figure 7 This is a cross-sectional view of the projection device in one embodiment of the present invention;

[0052] Figure 8 This is a schematic diagram of the beam emitted by the projection device in one embodiment of the present invention;

[0053] Figure 9 This is a schematic diagram of the beam emitted by the projection device in another embodiment of the present invention;

[0054] Figure 10A and Figure 10B This is a schematic diagram of the installation method of the projection device in the smart door lock and the emitted light beam in different embodiments of the present invention. Detailed Implementation

[0055] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0056] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the 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 indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0059] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0060] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0061] Figure 2 The following illustrates a detailed flow of a design method 100 for a diffractive optical element according to an embodiment of the present invention, in conjunction with... Figure 2 The design method 100 for diffractive optical elements is described in detail.

[0062] Design method 100 is used to design the characteristic microstructure of a diffractive optical element to meet the usage requirements of the diffractive optical element. In this embodiment, the diffractive optical element is configured to receive an incident light beam and modulate the incident light beam using its characteristic microstructure, so that the modulated outgoing light beam is obliquely projected onto the projection surface. In this embodiment, the outgoing light beam of the diffractive optical element is not perpendicular to the projection surface, but illuminates the projection surface at a preset angle, and forms a preset image on the projection surface, such as a pattern, text, or stripes. The diffractive optical element in this embodiment changes the position of the preset image formed on the projection surface, which can be used to avoid the obstruction of the outgoing light beam by other structures and overcome the problem of image distortion on the projection surface under oblique incidence.

[0063] Preferably, the incident beam of the diffractive optical element is perpendicular to the diffractive optical element. When the incident beam is divergent, the optical axis of the divergent beam is perpendicular to the diffractive optical element. In this embodiment, the diffractive optical element is disposed in the projection device. The projection device has a small structural size. Maintaining the incident beam perpendicular to the diffractive optical element can further control the structural size of the projection device and reduce the light field changes caused by the oblique incident beam, thus simplifying the design calculation of the diffractive optical element.

[0064] In step S101, a processed target light field image is obtained based on the original pattern to be projected. This target light field image is an image formed on the projection surface that can be observed by the user. For example, the original pattern to be projected may be a specific promotional image, logo, or prompt text. Based on the original pattern, the emitted light field of the diffractive optical element can be obtained, and the image formed by the emitted beam on the projection surface is the target light field image. In practical applications, the target light field image formed after modulation by the diffractive optical element may not be exactly the same as the original pattern to be projected. For example, there may be changes in resolution, or continuous pattern lines may be replaced by intermittent dot matrix. Therefore, it is necessary to comprehensively consider the imaging characteristics of the diffractive optical element and the corresponding light source characteristics to process the original pattern to obtain a target light field image that can be projected onto the projection surface using the diffractive optical element. Additionally, when the original pattern is a color image, it can be converted to a grayscale image as needed to serve as the target light field image.

[0065] Compared with traditional light-blocking projection devices, diffractive optical elements have different imaging principles. Therefore, the processing method of forming the light field of the original pattern to be projected by directly cutting out the light-transmitting part cannot be applied to the design of diffractive optical elements. Therefore, it is necessary to preprocess the original pattern to be projected in order to obtain the target light field image that can be realized by the light field emitted by the diffractive optical element.

[0066] In step S102, the geometric relationship between the emitted beam and the diffractive optical element relative to the projection surface is obtained. Specifically, in this embodiment, the geometric relationship between the emitted beam and the diffractive optical element relative to the projection surface includes the tilt angle of the emitted beam relative to the projection surface and the vertical distance of the diffractive optical element relative to the projection surface. The tilt angle between the emitted beam and the projection surface is obtained according to the design of the corresponding projection device (e.g., according to the installation angle of the projection device). In this embodiment, the emitted beam illuminates the projection surface at a preset angle. For cases where the emitted beam is divergent, the tilt angle between the emitted beam and the projection surface can be based on the optical axis of the emitted beam's light field. The vertical distance of the diffractive optical element relative to the projection surface is specifically calculated based on the incident position of the incident beam on the diffractive optical element or the exit position of the emitted beam on the diffractive optical element, using the vertical projection of the incident or exit position onto the projection surface. The projection device is usually set in a fixed position or can move synchronously with the mounting surface. The relative positional relationship between the projection device and the projection surface is determined at the beginning of the design. Preferably, the angle at which the emitted light beam hits the projection surface and the vertical distance between the diffractive optical element and the projection surface are design values. When the projection device is working normally, the values ​​of the above design values ​​remain fixed or fluctuate within a small range.

[0067] Of course, the geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface can also be represented in other ways. For example, when the outgoing beam is perpendicular to the diffractive optical element and the diffractive optical element is tilted relative to the projection surface, the complementary angle between the outgoing surface of the diffractive optical element and the projection surface can also be used to represent the angle between the outgoing beam and the projection surface. Alternatively, after the vertical distance between the diffractive optical element and the projection surface and the center of the target light field image are determined, the angle between the outgoing beam and the projection surface can also be calculated using distance and trigonometric functions. This invention does not limit the type of geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface that is directly obtained. Based on simple mathematical principles, mutual conversion can be achieved to meet the calculation requirements.

[0068] In step S103, based on the geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface, the target light field image is spatially transformed to obtain a transformed light field image, wherein the transformed light field image is the light field image formed by the outgoing beam in a plane perpendicular to the outgoing beam. In this embodiment, the outgoing beam is obliquely illuminating the projection surface. Due to different optical path distances, the divergence angle of the outgoing beam is different, and the outgoing light field will be deformed on the projection surface, resulting in the final image not corresponding to the original pattern to be projected. For example, when obliquely illuminating the projection surface, the near end has a shorter optical path, and with the same divergence angle, the length of the projected image becomes smaller, and correspondingly, the length of the projected image at the far end becomes larger. To address this issue, this embodiment proposes a spatial transformation of the target light field image, adjusting it to a transformed light field image in a plane perpendicular to the outgoing beam. This avoids the problem of edge distortion and allows it to directly correspond to the target light field image or the original pattern to be projected, reducing the computational difficulty of spatial transformation. The rules for spatial transformation are obtained based on the geometric relationship between the outgoing beam and the diffractive optical element relative to the projection plane, as obtained in step S102. Specifically, this may include coordinate correspondence rules determined based on geometric relationships, as well as optimization rules based on the imaging characteristics and design requirements of the diffractive optical element, etc., to spatially transform the target light field image. The specific process of spatial transformation will be described in subsequent preferred embodiments of this invention.

[0069] In step S104, the phase map of the diffractive optical element is calculated based on the converted light field image. After obtaining the phase map of the diffractive optical element, the corresponding mold can be processed to fabricate the diffractive optical element, or the diffractive optical element that meets the design requirements can be directly processed on the substrate. Preferably, in this step, a 4-step or 8-step phase map is used to calculate the phase map. The diffractive optical element adopts a multi-step design, and it is more difficult to design a 2-step diffractive optical element that meets the requirements of this invention. When designing the diffractive optical element, if the emitted light field image is a non-centrosymmetric pattern after deformation and conversion, a 2-step design will produce ghosting at a position symmetrical to the center point of the target pattern in the non-centrosymmetric pattern, affecting the visual effect of the final pattern presented on the projection surface. In practical applications, depending on the specific pattern to be projected, a 4-step or 8-step phase map is preferred to avoid the ghosting problem.

[0070] Figure 3 The present invention illustrates a specific flow of a design method 200 for a diffractive optical element according to a preferred embodiment of the present invention, which includes a process of spatially transforming a target light field image to obtain a transformed light field image. In the design method 200, steps S201, S202 and S205 are basically the same as steps S101, S102 and S104 of the design method 100 in the foregoing embodiment, and will not be described again here.

[0071] In step S203, the boundary features of the converted light field image are calculated based on the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, and the boundary features of the target light field image. The target light field image is an image formed on the projection surface, possessing known boundary features, obtained according to the design of the image to be projected. The boundary features of the target light field image include, for example, the boundary shape, range, and size of the image on the projection surface, and are set values. Furthermore, the boundary features in this embodiment are not limited to a range that completely fits the specific details in the image; they can also be a larger range that can cover all image information. For example, if the image formed by the target light field image on the projection surface is text, the boundary features of the target light field image can be set to a rectangle, square, circle, or other geometric shape that can cover all the text to simplify spatial transformation calculations.

[0072] When the outgoing light beam illuminates the projection surface at an angle, the image on the plane perpendicular to the outgoing light beam differs from the image on the projection surface. Specifically, the near end (closer to the outgoing light beam's exit point) contracts, while the far end (farther from the outgoing light beam's exit point) expands. Simultaneously, the distance between the near and far ends increases, and the larger the incident angle of the outgoing light beam on the projection surface, the more pronounced the edge distortion of the converted light field image. For example, in one specific embodiment of the invention, the boundary of the target light field image is rectangular. Based on the conversion rules obtained from the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, the boundary of the converted light field image is approximately trapezoidal, with stretching at the near end and contraction at the far end. Furthermore, inflection points, midpoints, and other feature points on the circumferential boundaries of the target light field image and the converted light field image can be used as references for positioning.

[0073] In this embodiment, contraction and expansion are relative concepts. The target light field image and the converted light field image include the diffusion angle characteristics of the emitted beam. For example, if the near edges of the target light field image and the converted light field image coincide, then the far edge of the converted light field image contracts relative to the far edge of the target light field image. Preferably, the center position of the converted light field image coincides with the center position of the target light field image, and the center positions of the target light field image and the converted light field image do not deform. Of course, other positions can be selected for locating the corresponding positions, and this is not limited in this invention. A similar method can be used to obtain the boundary features of the converted light field image for target light field images with other boundary shapes.

[0074] In step S204, spatial transformation rules are defined, and pixels in the target light field image are transformed to pixels in the transformed light field image according to the spatial transformation rules. According to a preferred embodiment of the present invention, pixel transformation from the target light field image to the transformed light field image is completed using coordinate values ​​within the same coordinate system. Preferably, the position of the coordinate origin is first determined.

[0075] like Figure 5 As shown, in a specific embodiment of the present invention, the center position of the target light field image is taken as the origin (x0, y0), and the pixel points in the target light field image are taken as the coordinate step size, for example, in... Figure 5 In the image, the left side shows the target light field image, and the right side shows the transformed light field image. Based on the resolution of the target light field image, where pixels are evenly arranged, each pixel is used as a coordinate unit. The coordinates of all pixels in the target light field image are defined as (X...). n Y m Correspondingly, the pixels in the transformed light field image are defined as (x... n y m The center position of the transformed light field image corresponds to the pixel in the target light field image, and it also corresponds to the origin of the coordinate system.

[0076] Where x0 = 0, y0 = H*tan(θ), H is the perpendicular distance between the diffractive optical element and the projection plane, and θ is the incident angle of the outgoing beam within the projection plane. The correspondence between the coordinates in the target light field image and the transformed light field image is as follows:

[0077] Y=y,y0-h / 2≤y≤y0+h / 2;

[0078] X=(xb / 2)*b*h / [a*h+(ba)*y]+b / 2, x0-b / 2≤x≤x0+b / 2.

[0079] Where h is the length in the y-direction of the target light field image, i.e., the distance between the near and far ends; a is the length of the far end in the converted light field image; and b is the length of the near end in the converted light field image. In this embodiment, the near ends in the target and converted light field images are used as the reference, meaning that the near end lengths in both images are equal, both being b, during coordinate transformation. The length a of the far end in the converted light field image can be obtained through geometric calculation based on the numerical change in the y-direction. The above formula achieves a one-to-one correspondence between pixels in the target and converted light field images, obtaining the pixel value of the pixel in the converted light field image corresponding to the target light field image. Furthermore, the coordinates in the y-direction can be set to change uniformly, and the y-coordinates in the converted light field image can be calculated according to the same proportion.

[0080] The spatial transformation rules may differ in different embodiments of the present invention. For example, in another embodiment of the present invention, such as... Figure 6As shown, the left side is the target light field image, and the right side is the transformed light field image. The origin (x0, y0) is set to the vertical projection position of the diffractive optical element on the projection plane (e.g., the vertical projection distance of the exit position of the diffractive optical element on the projection plane). The pixel values ​​in the target light field image are used as the coordinate step size, based on the resolution of the target light field image. The pixels are uniformly arranged, and each pixel is considered a coordinate unit. For example, the X-coordinate increases with the pixel width, and the Y-coordinate increases with the pixel length. All pixels in the target light field image are defined as follows: (X0, y0) n Y m Correspondingly, the pixels in the transformed light field image are defined as (x... n y m The center position of the target light field image is (x0, y0+c), which corresponds to the pixel in the target light field image.

[0081] Where c is the distance between the center of the target light field image and the origin, which is also a set value. The coordinates of the center position in the transformed light field image are also (x0, y0+c). The correspondence between the coordinates in the target light field image and the transformed light field image is as follows:

[0082] Y=y,y0-h / 2+c≤y≤y0+h / 2+c;

[0083] X=(xb / 2)*b*h / [a*h+(ba)*y]+b / 2, x0-b / 2≤x≤x0+b / 2.

[0084] Where h is the length in the y-direction of the target light field image, i.e., the distance between the near and far ends; a is the length of the far end in the transformed light field image; and b is the length of the near end in the transformed light field image. Similarly, according to the calculation method in the aforementioned embodiment, the coordinate transformation ratios in the a, b, and y directions can be obtained. Based on the specific boundary features of the target light field image, different coordinate definitions can be selected to calculate the corresponding spatial transformation rules, thereby reducing computational load and improving efficiency and accuracy.

[0085] By using spatial transformation rules to establish the correspondence between pixel values ​​in the transformed light field image and the target light field image, the pixel values ​​of the pixels in the transformed light field image can be obtained. The phase map of the diffractive optical element that can generate the transformed light field image can then be calculated. After setting the diffractive optical element in a preset position, the image projected onto the projection surface is the target light field image.

[0086] Furthermore, according to a specific embodiment of the present invention, the boundary of the target light field image is rectangular, and the boundary of the converted light field image is trapezoidal due to the different optical paths at the near and far ends. In the process of converting pixels in the target light field image to pixels in the converted light field image, the coordinate transformation of the pixels is performed row by row in the direction perpendicular to the height of the trapezoid, that is, calculated row by row in the direction parallel to the near and far ends, so as to avoid deviation and distortion in the same straight line direction.

[0087] Figure 4 A preferred embodiment of the present invention illustrates a design method 300 for a diffractive optical element, which specifically includes a process of squaring and / or interpolating pixels in a converted light field image. In design method 300, steps S301, S302, S303, S304, and S306 are substantially the same as steps S201, S202, S203, S204, and S205 in the design method 200 for a diffractive optical element in the foregoing embodiment, and will not be described again.

[0088] After converting the pixels in the target light field image to the pixels in the converted light field image, in step S305, the pixels in the converted light field image are sampled and / or interpolated. According to a specific embodiment of the present invention, when the number of pixels in the target light field image and the converted light field image in the same direction is different, the converted light field image is sampled and / or interpolated according to a preset rule and algorithm.

[0089] In different embodiments of the present invention, it is possible to select only sampling or only interpolation of the converted light field image, or to perform sampling and interpolation simultaneously at different positions of the converted light field image. Taking the boundary of the target light field image as a rectangle as an example, when the emitted light from the diffractive optical element does not rotate, the boundary of the converted light field image is trapezoidal. When the target light field image and the converted light field image are aligned at their near ends and correspond to each other in pixels, the far end of the converted light field image shrinks relative to the far end of the target light field image, which may cause overlap between the positions corresponding to the pixels of the target light field image in the converted light field image, and this overlap is more pronounced closer to the far end of the converted light field image. In this case, the pixels in the converted light field image can be sampled to extract some of the overlapping pixels. Specifically, sampling can be performed at fixed intervals or according to a preset filtering rule. However, due to the missing pixels, the resolution of the image finally formed on the projection surface may decrease.

[0090] When the target light field image and the transformed light field image are aligned at the far end and correspond in pixels, the near end of the transformed light field image is extremely stretched relative to the target light field image, resulting in gaps between adjacent pixels. To improve the resolution of the final image formed on the projection surface, interpolation can be performed between preset pixels to insert pixel values ​​calculated by an algorithm. For cases where the target light field image and the transformed light field image are aligned at different positions, both sampling and interpolation can be performed on the transformed light field image based on the pixel transformation results, with interpolation being preferred.

[0091] Specifically, the algorithms for interpolating pixels in the transformed light field image include one or more of the following: nearest neighbor interpolation, bilinear interpolation, and cubic convolution. To reduce computational complexity, nearest neighbor interpolation is preferred. Taking a pixel in the transformed light field image without a corresponding pixel value as an example, the pixel coordinates are inversely transformed to obtain the corresponding coordinates of the pixel in the target light field image. The inverse transformation of the pixel coordinates can be the same as the coordinate transformation in the spatial transformation rule used in this embodiment, but without rounding.

[0092] Then, according to a preset rounding algorithm, such as rounding up or rounding down, the coordinates of the pixels in the converted light field image obtained in the previous steps are rounded to the corresponding coordinates in the target light field image. According to a preferred embodiment of the present invention, the coordinates in the converted light field image and the target light field image are based on pixels as the step size. Therefore, in the target light field image, integer coordinates all have corresponding pixels. In subsequent steps, the pixel value of the pixel corresponding to the rounded coordinate position in the target light field image is inserted into the pixel coordinate position in the converted light field image. That is, the pixel position that needs to be interpolated is replaced by the neighboring pixel value, thereby improving the resolution of the image on the projection surface.

[0093] Furthermore, in the process of rounding the pixel coordinates in the converted light field image to the corresponding coordinates in the target light field image, the rounding rule can be selected based on the coordinate values ​​of the pixel coordinates in the converted light field image to the corresponding coordinate values ​​in the target light field image, and / or the pixel changes of adjacent coordinates in the target light field image. That is, rounding can be performed based on the rounding method of the numerical value, or it can be performed based on the characteristics of continuous pixel changes or abrupt changes.

[0094] The present invention also includes an embodiment of a diffractive optical element. The diffractive optical element in this embodiment is designed and fabricated using the design method in the foregoing embodiments. The diffractive optical element is used to form a target light field on the projection surface by the outgoing light beam. When the diffractive optical element is set in a preset position, its outgoing light beam is not perpendicular to the projection surface.

[0095] like Figure 7As shown, the present invention also includes an embodiment of a projection device 100, wherein the emitted beam of the projection device 100 is not perpendicular to the projection surface. The specific arrangement of the projection device 100 and the projection surface will be described in detail in subsequent embodiments.

[0096] In this embodiment, the projection device 100 includes a housing 110, a light emitter 120, and a diffractive optical element 130. The light emitter 120 is disposed inside the housing 110 and can emit a light beam. Preferably, the light emitter 120 is a semiconductor laser. In this embodiment, the diffractive optical element 130 is used to form a preset image on the projection surface. The projection device 100 can have a smaller overall structural size. Choosing a semiconductor laser for the light emitter 120 can further reduce the size of the projection device 100. The size of the semiconductor laser can be reduced to within 10×5×5mm. At the same time, compared with the commonly used 150mW LED (light-emitting diode) light source projection lamp, the semiconductor laser has lower power consumption, about 100mW, and the semiconductor laser has high luminous efficiency, which can form a clear image on the projection surface even in strong ambient light.

[0097] like Figure 7 As shown, in this embodiment, the diffractive optical element 130 is disposed downstream of the light source 120. The diffractive optical element 130 is designed and manufactured according to the design method for diffractive optical elements in the aforementioned embodiment. The diffractive optical element 130 can project the original pattern to be projected onto the projection surface, forming a target light field image on the projection surface. The light beam emitted by the light source 120 is perpendicularly incident on the diffractive optical element 130, and the outgoing light beam of the diffractive optical element 130 is obliquely irradiated onto the projection surface. However, the outgoing surface of the diffractive optical element 130 can be parallel to the projection surface or tilted at a preset angle.

[0098] Specifically, in one embodiment of the present invention, such as Figure 8 As shown, the diffractive optical element 130 can be configured as an eccentric structure. The exit surface of the diffractive optical element 130 is parallel to the projection surface, and the direction of its exit beam has a fixed tilt angle with the diffractive optical element 130. At the same time, the incident light of the diffractive optical element 130 is perpendicular to the projection surface.

[0099] like Figure 9As shown, in another embodiment of the present invention, the optical axis of the emitted light of the diffractive optical element 130 is perpendicular to the emission surface of the diffractive optical element 130, and the diffractive optical element 130 or the projection device 100 itself is inclined relative to the projection surface, and the emitted light of the diffractive optical element 130 is inclined relative to the projection surface at a preset angle. Of course, in different embodiments of the present invention, the diffractive optical element 130 may also be configured such that the optical axis of its emitted light has a non-perpendicular angle with the emission surface, and the emission surface of the diffractive optical element 130 is inclined relative to the projection surface.

[0100] Furthermore, such as Figure 7 As shown, according to a preferred embodiment of the present invention, the projection device 100 further includes a collimating lens 140 and an adjustment structure 150. The collimating lens 140 is disposed between the emitter 120 and the diffractive optical element 130, and is arranged parallel to the diffractive optical element 130. The collimating lens 140 can pre-modulate and collimate the emitted light from the emitter 120. The collimating lens 140 and the diffractive optical element 130 are arranged parallel to each other, and both the collimating lens 140 and the diffractive optical element 120 are perpendicular to the principal optical axis of the projection device 100.

[0101] According to a preferred embodiment of the present invention, the projection device 100 further includes an adjustment structure 150, wherein a collimating lens 140 is disposed within the adjustment structure 150. The adjustment structure 150 is movably connected to the housing 110. When the relative positional relationship between the adjustment structure 150 and the housing 110 is changed, the distance between the collimating lens 140 and the emitter 120 can be changed, thereby achieving focusing. Furthermore, the distance between the diffractive optical element 130 and the collimating lens 140 remains fixed. The diffractive optical element 130 is installed within the adjustment mechanism 150 and moves synchronously with the adjustment structure 150.

[0102] The present invention also includes an embodiment of a smart door lock 1, such as... Figure 10A and Figure 10B As shown, the projection device 100 in the aforementioned embodiment is installed inside the smart door lock 1 and can project a preset image toward the ground as a welcome light. According to a preferred embodiment of the present invention, the projection device 100 is configured to be approximately perpendicular to the projection surface to further reduce the space occupied by the projection device 100 in the smart door lock 1, and the diffractive optical element in the projection device 100 is configured such that the emitted light rays are inclined relative to the light-emitting surface of the diffractive optical element.

[0103] Figure 10A and Figure 10B The diagram illustrates two tilting methods for the emitted light from the projection device 100, both of which can be achieved using the diffractive optical elements described in the preceding embodiments. The emitted light from the projection device 100 can be tilted in a single direction, such as... Figure 10AAs shown, its tilt direction is roughly parallel to the vertical plane of smart door lock 1, but it can also be set to tilt in other directions, such as... Figure 10B As shown, the tilt direction of the emitted light also includes a horizontal component. When designing the projection device 100, by providing a fixed tilt angle for the emitted light, the characteristic microstructure of the corresponding diffractive optical element can be obtained according to the design method in the aforementioned embodiments.

[0104] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method for a diffractive optical element, the diffractive optical element being configured to receive an incident light beam and to obliquely project a modulated outgoing light beam toward a projection surface, the design method comprising: The projection surface is not perpendicular to the emitted light beam; Based on the original pattern to be projected, a processed target light field image is obtained, and the target light field image is formed on the projection surface; Obtain the geometric relationship between the emitted beam and the diffractive optical element relative to the projection plane; Based on the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, the target light field image is spatially transformed to obtain a transformed light field image, wherein the transformed light field image is the light field image formed by the outgoing light beam in a plane perpendicular to the outgoing light beam; The phase diagram of the diffractive optical element is calculated based on the converted light field image; The geometric relationship between the outgoing beam and the diffractive optical element relative to the projection surface includes the tilt angle of the outgoing beam relative to the projection surface and the vertical distance of the diffractive optical element relative to the projection surface. The vertical distance of the diffractive optical element relative to the projection surface is based on the incident position of the incident beam on the diffractive optical element or the exit position of the outgoing beam on the diffractive optical element. The steps for performing spatial transformation include: Based on the geometric relationship between the outgoing light beam and the diffractive optical element relative to the projection surface, and the boundary features of the target light field image, the boundary features of the converted light field image are calculated. Define spatial transformation rules, and transform pixels in the target light field image to pixels in the transformed light field image according to the spatial transformation rules; within the same coordinate system, use coordinate values ​​to complete the pixel transformation from the target light field image to the transformed light field image.

2. The design method according to claim 1, wherein the spatial transformation rule takes the center of the target light field image or the vertical projection position of the exit position of the diffractive optical element on the projection plane as the origin of the coordinate system, takes the pixel points in the target light field image as the coordinate step size, and transforms the pixels in the target light field image into the transformed light field image according to the coordinate correspondence between the target light field image and the transformed light field image.

3. The design method according to claim 1, wherein the boundary of the target light field image is rectangular, the boundary of the transformed light field image is trapezoidal, and the step of converting pixels in the target light field image to pixels in the transformed light field image includes: The coordinates of the pixels are transformed row by row in a direction perpendicular to the height of the trapezoid.

4. The design method according to claim 1, wherein the step of converting pixels in the target light field image to pixels in the converted light field image includes: The pixels in the transformed light field image are sampled and / or interpolated.

5. The design method according to claim 4, wherein the step of decimating and / or interpolating the pixels in the transformed light field image includes: Based on the difference in the number of pixels in the same direction between the target light field image and the converted light field image, the converted light field image is sampled and / or interpolated according to a preset rule or algorithm.

6. The design method according to claim 4, wherein the algorithm for interpolating pixels in the transformed light field image includes one or more of nearest neighbor interpolation, bilinear interpolation, and cubic convolution.

7. The design method according to claim 6, wherein the process of interpolating pixels in the transformed light field image includes: The pixel coordinates in the transformed light field image are transformed in reverse to obtain the corresponding coordinates in the target light field image; The pixel coordinates in the transformed light field image are rounded to their corresponding coordinates in the target light field image according to a preset rounding algorithm; The pixel value corresponding to the rounded coordinate position in the target light field image is inserted into the pixel coordinate position in the transformed light field image.

8. The design method according to claim 7, wherein the preset rounding algorithm includes: The rounding method is selected based on the corresponding coordinate values ​​of the pixel coordinates in the transformed light field image in the target light field image and / or the pixel changes of adjacent coordinates in the target light field image.

9. The design method according to any one of claims 1-8, wherein the incident beam of the diffractive optical element is perpendicular to the diffractive optical element; when the incident beam is divergent, the optical axis of the divergent beam is perpendicular to the diffractive optical element.

10. The design method according to any one of claims 1-8, wherein the step of converting pixels in the target light field image to pixels in the converted light field image comprises: Determine the position of the origin of the coordinate system; The step of calculating the phase map of the diffractive optical element based on the converted light field image includes: calculating the phase map using a 4-step or 8-step method.

11. A diffractive optical element, designed and manufactured using the design method as described in any one of claims 1-10, wherein the outgoing beam of the diffractive optical element forms a target light field image on a projection surface, and the outgoing beam of the diffractive optical element is not perpendicular to the projection surface.

12. A projection device in which the projection surface is not perpendicular to the emitted light beam, comprising: shell; A light emitter, which is disposed within the housing and configured to emit a light beam; and A diffractive optical element, designed and manufactured according to the design method of any one of claims 1-10, is provided to enable the diffractive optical element to project an original pattern to be projected onto a projection surface to form a target light field image; the diffractive optical element is disposed downstream of the light source, the light beam is perpendicularly incident on the diffractive optical element, and the outgoing light beam is obliquely irradiated onto the projection surface; the outgoing surface of the diffractive optical element is parallel to the projection surface or inclined at a preset angle.

13. The projection device according to claim 12, wherein the exit surface of the diffractive optical element is inclined at a preset angle relative to the projection surface, and the incident beam of the diffractive optical element has a preset angle with the projection surface.

14. The projection device according to claim 12, wherein the diffractive optical element is an eccentric structure, the exit surface of the diffractive optical element is arranged parallel to the projection surface, and the incident light of the diffractive optical element is perpendicular to the projection surface.

15. The projection device according to any one of claims 12-14, further comprising: A collimating lens is disposed between the light emitter and the diffractive optical element. The collimating lens and the diffractive optical element are arranged in parallel. The light beam emitted by the light emitter is collimated and then enters the diffractive optical element.

16. The projection device according to claim 15, further comprising: An adjustment structure is provided, in which the collimating lens is disposed. The adjustment structure is movably connected to the housing to change the distance between the collimating lens and the light emitter.

17. The projection device according to any one of claims 12-14, wherein the light emitter is a semiconductor laser.

18. A smart door lock, comprising a projection device as described in any one of claims 12-14.

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