Projection device and diffractive optical element

Abstract

A projection device (1) and a diffractive optical element (104). The projection device (1) comprises a laser light source, and a diffractive optical element (104), a magnifying lens (203'), a light homogenizing element (205), a total reflection prism (204) and a display element (201) which are successively provided along a light emitting path of the laser light source. The laser light source comprises three types of light emitting regions (101), and the diffractive optical element (104) comprises three diffraction regions provided corresponding to the three types of light emitting regions (101), the wavelengths of laser emitted from the three types of light emitting regions (101) being different. A light spot formed when a laser beam emitted from each light emitting region is diffracted by the diffractive optical element (104) and is then emitted to the display element (201) is a rectangular light spot (CB), the rectangular light spot (CB) being matched with an effective region of the display element (201), and the long-side direction of each rectangular light spot (CB) being parallel to the slow-axis direction of the laser beam emitted from a light emitting region.

Description

Projection device and diffractive optical element

[0001] Cross-reference to Related Applications

[0002] This application claims priority to the Chinese Patent Application No. 202410639040.4, filed on May 22, 2024, and entitled “Laser projection device and diffractive optical element”, the entire contents of which are incorporated herein by reference; and this application claims priority to the Chinese Patent Application No. 202410939717.6, filed on July 12, 2024, and entitled “Projection device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of projection technology, in particular to a projection device and a diffractive optical element. BACKGROUND

[0004] Laser projection display technology is also known as laser projection technology or laser display technology, which is a technology for projecting display by using laser as light source. Laser projection can most realistically reproduce the rich and bright colors of the objective world, and provide more powerful expression. Its color gamut coverage rate can reach more than 90% of the color space that can be recognized by the human eye, which is more than twice the color gamut coverage rate of traditional display.

[0005] At present, the laser projection system usually sets an illumination system on the light emitting side of the laser light source to shape and homogenize. The illumination system usually includes a light pipe or compound eye to homogenize the light, and then a relay system is used to shape the light spot. The complex structure of the illumination system leads to a large volume of the entire optical engine, which cannot meet the requirements of miniaturization of the optical system, and the complex optical system also leads to low light efficiency of the optical engine. SUMMARY

[0006] The present application provides a projection device, comprising:

[0007] a laser light source for emitting three-color laser light; the laser light source comprises three types of light emitting areas, and the laser light emitted by the three types of light emitting areas has different wavelengths;

[0008] a diffractive optical element located on the light emitting side of the laser light source, the diffractive optical element comprising three diffractive regions, one of the diffractive regions corresponding to one type of light emitting area;

[0009] a magnification lens located on the light emitting side of the diffractive optical element for changing the size of the laser light spot;

[0010] a light homogenizing element located on the light emitting side of the magnification lens for homogenizing the laser light beam;

[0011] a display element, located on a side of the homogenizing element away from the magnification lens, for modulating the incident laser beam to form a display image;

[0012] a total reflection prism, located between the magnification lens and the display element; the total reflection prism is used for reflecting the light emitted by the magnification lens to the display element, and transmitting the light emitted by the display element;

[0013] wherein the laser beam emitted by the light emitting area forms a rectangular spot when diffracted by the diffractive optical element and incident on the display element, and the long side of the rectangular spot is parallel to the slow axis direction of the laser beam emitted by the light emitting area.

[0014] Embodiments of the present application also provide a diffractive optical element, comprising:

[0015] a substrate;

[0016] a plurality of diffraction regions located on the substrate;

[0017] the diffraction region comprises a plurality of microstructures, the heights of the plurality of microstructures are not completely same; the microstructures are in a stepped shape, and the heights of the single-step of the microstructures in different diffraction regions are same.

[0018] Embodiments of the present application also provide a method for determining the height of a step of a diffractive optical element, comprising:

[0019] determining the phase corresponding to the diffractive optical element, the refractive index, and the wavelength of the incident laser;

[0020] based on the phase corresponding to the diffractive optical element, the refractive index, and the wavelength of the incident laser, determining the height of the single-step of the microstructure in the diffractive optical element;

[0021] wherein the diffractive optical element comprises a plurality of diffraction regions, and the heights of the single-step of the microstructure in different diffraction regions are same. BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 is a schematic diagram of the overall architecture of a projection device according to an embodiment of the present application;

[0023] FIG. 2 is a schematic diagram of the structure of a projection device according to an embodiment of the present application;

[0024] FIG. 3 is a schematic diagram of the arrangement of a laser chip according to an embodiment of the present application;

[0025] FIG. 4 is a schematic diagram of the arrangement of a laser chip according to another embodiment of the present application;

[0026] FIG. 5 is a schematic diagram of a laser spot emitted by a laser chip according to an embodiment of the present application;

[0027] FIG. 6 is a schematic diagram of a laser spot emitted by a laser according to an embodiment of the present application;

[0028] FIG. 7 is a schematic diagram of a laser spot emitted by a light emitting area according to an embodiment of the present application;

[0029] FIG. 8 is a schematic diagram of a correspondence between a light emitting area and a diffractive optical element according to an embodiment of the present application;

[0030] FIG. 9 is a schematic diagram of a spot variation according to an embodiment of the present application;

[0031] FIG. 10 is a schematic diagram of a correspondence between a display element and a rectangular spot according to an embodiment of the present application;

[0032] FIG. 11 is a schematic diagram of a correspondence between a display element and a rectangular spot according to an embodiment of the present application;

[0033] FIG. 12 is a schematic diagram of a correspondence between a display element and a rectangular spot according to an embodiment of the present application;

[0034] FIG. 13 is a schematic diagram of a spot variation according to an embodiment of the present application;

[0035] FIG. 14 is a schematic diagram of a correspondence between a light emitting area and a diffractive optical element according to an embodiment of the present application;

[0036] FIG. 15 is a schematic diagram of a correspondence between a light emitting area and a diffractive optical element according to an embodiment of the present application;

[0037] FIG. 16 is a schematic diagram of a side view of a diffractive optical element according to an embodiment of the present application;

[0038] FIG. 17 is a schematic diagram of a side view of a diffractive optical element according to an embodiment of the present application;

[0039] FIG. 18 is a schematic diagram of a top view of a diffractive optical element according to an embodiment of the present application;

[0040] FIG. 19 is a schematic diagram of a side view of a diffractive optical element including three sub-areas according to an embodiment of the present application;

[0041] FIG. 20 is a flowchart of a method for determining a step height of a diffractive optical element according to an embodiment of the present application;

[0042] FIG. 21 is a flowchart of a method for determining a step height of a diffractive optical element according to an embodiment of the present application;

[0043] FIG. 22 is a schematic diagram of a structure of a device for determining a step height of a diffractive optical element according to an embodiment of the present application;

[0044] FIG. 23 is a structural schematic diagram of a step height determination device of a diffractive optical element according to an embodiment of the present application;

[0045] FIG. 24 is a structural schematic diagram of a projection system according to an embodiment of the present application. DETAILED DESCRIPTION

[0046] For the purpose of making the purpose, implementation and advantages of the present application more clear, the following will combine the drawings in the exemplary embodiments of the present application to make a clear and complete description of the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only a part of the embodiments of the present application, but not all the embodiments.

[0047] The projection display is a method or device that controls a light source by a planar image information, and uses an optical system and a projection space to magnify and display an image on a projection screen. With the development of the projection display technology, the projection display is gradually applied to business activities, conference exhibitions, scientific education, military command, traffic management, centralized monitoring and advertisement entertainment and other fields, and its advantages such as a larger display picture size and clear display are also suitable for the requirements of large screen display.

[0048] The projection device can be based on a digital light processing (DLP) architecture, and a digital micromirror device (DMD) is used as a core device to produce an image by incident light of a projection light source on the DMD, and then the image light produced by the DMD is incident on a projection lens to form an image, and finally received by a projection screen.

[0049] FIG. 1 is a schematic diagram of the overall architecture of a projection device according to an embodiment of the present application.

[0050] As shown in FIG. 1, the projection device can include a projection light source 10, an illumination system 20 and a projection lens 30. The projection light source 10, the illumination system 20 and the projection lens 30 can also be collectively referred to as an optical engine.

[0051] Among them, the projection light source 10 is used to provide illumination light, and the color gamut, overall brightness and other characteristics of the projection image are affected by the projection light source 10. In a specific implementation, the projection light source 10 can use a mercury lamp, a light emitting diode (LED) or a laser light source.

[0052] The illumination system 20 is located on the light exit side of the projection light source 10, and is used to shape and homogenize the light beam emitted by the projection light source 10. In addition, as shown in FIG. 1, the illumination system 20 includes a display element 201, which can use the above-mentioned DMD, and can modulate the incident light beam to form a display image.

[0053] The projection lens 30 is located at the light exit side of the illumination system 20, specifically at the light exit side of the display element 201, and is used to project and image the image formed by the display element 201 to form an image of a size suitable for human eyes to view on a projection surface.

[0054] When the display element 201 is a DMD, the size and incident angle of the incident light beam have special requirements, and therefore the light beam emitted by the projection light source 10 needs to be shaped, homogenized, and the like before being incident on the display element 201. As shown in FIG. 1, in order to achieve the shaping, homogenization, and the like of the light beam, a light beam adjustment lens group 103, a light homogenizing element 202, a focusing lens group 203, and the like need to be provided.

[0055] The light beam adjustment lens group 103 can be a telescope lens group and can perform beam shrinking processing on the incident light beam; the light homogenizing element 202 can be a light pipe or an ommatidium lens group, and in FIG. 1, the light homogenizing element 202 is taken as an example of an ommatidium lens group, which is used to homogenize the incident light beam. In order to meet the requirements of the spot size and incident angle of the display element 201, the focusing lens group 203 needs to be provided to focus the light beam, and the focused projection light beam can be incident on the display element 201 for modulation.

[0056] As shown in FIG. 1, in order to make the spot incident on the DMD meet the requirements, a plurality of lens groups and light homogenizing elements need to be provided in the optical path, which causes the volume of the entire optical engine to be large and cannot meet the requirements of miniaturization of the optical system.

[0057] Therefore, in the projection device, a diffractive optical element is provided, and the small size and high efficiency of the diffractive optical element can be used to omit the plurality of lens groups and light homogenizing elements provided in the optical path, thereby reducing the volume of the projection device.

[0058] Specifically, as shown in FIG. 2, the projection device includes a laser light source, a diffractive optical element 104, a magnification lens 203', a light homogenizing element 205, a total reflection prism 204, a display element 201, and a projection lens 30.

[0059] The laser light source has the advantages of good monochromaticity, high brightness, and long service life, and is a relatively ideal light source. With the improvement of the power of the laser, the requirements of industrial application are met, and the laser is gradually used as a light source for illumination. In the projection device, the laser is used as a projection light source, gradually replacing the mercury lamp illumination, and compared with the LED light source, the laser is widely used due to the advantages of small optical expansion and high brightness.

[0060] In the embodiments of the present application, the laser light source is combined with the diffractive optical element 104. Since the diffractive optical element 104 is sensitive to the wavelength and the incident angle of the incident light, and the laser has a narrow half-peak width and high collimation, the laser light source is more suitable for use.

[0061] As shown in FIG. 2, the laser light source can emit three-color laser light, which can be divided into three types of light-emitting regions 101, namely a first light-emitting region 101-1, a second light-emitting region 101-2, and a third light-emitting region 101-3. The three types of light-emitting regions are used to emit laser light of different wavelengths. Among them, the three types of light-emitting regions 101 can be different regions in a laser light source that can emit three-color laser light, or three laser light sources that emit laser light of different colors, which are not limited here.

[0062] The diffractive optical element 104 is arranged on the light-emitting side of the three types of light-emitting regions 101. The diffractive optical element 104 includes three diffraction regions, which are arranged one-to-one with the three types of light-emitting regions 101.

[0063] The diffractive optical element (DOE for short) is an optical element that can change the propagation characteristics of light. The diffractive optical element 104 has a relatively thin thickness, and has microstructures on at least one of its side surfaces. The size of the microstructures is usually on the order of microns. These microstructures can change the phase of the incident light, thereby changing the propagation path of the light on a microscopic scale, and achieving beam shaping and homogenization.

[0064] The principle of beam shaping of the diffractive optical element 104 is mainly based on the diffraction and interference of light. When the light beam passes through the diffractive optical element 104, the microstructures of the diffractive optical element 104 will change the propagation direction of the light. When different light waves meet in space, they will interfere with each other. By precisely designing the microstructures of the diffractive optical element 104, the effects of diffraction and interference can be controlled, thereby achieving beam shaping.

[0065] Since the diffractive optical element 104 is arranged on the light-emitting side of the light-emitting region of the laser light source, it can achieve the effects of beam shaping and homogenization on the incident laser light beam. Therefore, it is not necessary to arrange more optical elements in the projection device to shape and homogenize the laser light beam. As shown in FIG. 2, the laser light beams emitted by the three types of light-emitting regions 101 of the laser light source are combined after diffraction by the diffractive optical element 104. The combined light beam only needs to be focused on the display element 201 by the magnification lens 203', and the projection lens projects and images the display image modulated by the display element 201, thereby obtaining a larger size projection image.

[0066] As shown in FIG. 2, the laser light source diffracts and shapes the laser light of different wavelengths before the light is combined, and only needs to adjust the size of the combined light beam after the light is combined to meet the illumination requirements of the display element. The optical path of the optical engine can omit multiple sets of lenses and light homogenizing elements and other optical devices, reducing the overall size of the optical engine and making the optical path more compact, which can meet the miniaturization design of the projection device.

[0067] In specific implementation, the laser light source can use a three-color laser that emits three primary color lasers, and can also use a dual-color laser that emits red and green dual-color lasers, green and blue dual-color lasers, etc., which are not limited in the present application.

[0068] The embodiments of the present application take a laser light source using a laser that can emit three primary color lasers as an example for illustration. As shown in FIGS. 3 and 4, the laser light source can include a plurality of laser chips arranged in an array, which are divided into a plurality of first laser chips a1, a plurality of second laser chips a2, and a plurality of third laser chips a3. Among them, the first laser chips a1 are located in the first light emitting area 101-1, the second laser chips a2 are located in the second light emitting area 101-2, and the third laser chips a3 are located in the third light emitting area 101-3.

[0069] In some embodiments, as shown in FIG. 3, the laser light source can use an MCL laser, and the first laser chips a1, the second laser chips a2, and the third laser chips a3 are arranged in a 4x7 matrix along the first direction x and the second direction y. The number of first laser chips a1 and the number of second laser chips a2 are both less than the number of third laser chips a3, the first laser chips a1 are arranged in a row along the first direction x, the second laser chips a2 are arranged in a row along the first direction, and the third laser chips a3 are arranged in two rows along the first direction.

[0070] In some embodiments, as shown in FIG. 4, the laser light source can use an NUBB laser or an NUMB laser, and the first laser chips a1, the second laser chips a2, and the third laser chips a3 are arranged in an array along the first direction x and the second direction y. The number of first laser chips a1 and the number of second laser chips a2 are both less than the number of third laser chips a3, the first laser chips a1 and the second laser chips a2 are arranged in a row along the first direction x, and the third laser chips a3 are arranged in a row along the first direction.

[0071] The above lasers are all semiconductor lasers. Due to material and efficiency problems, a larger number of red laser chips are usually required, so the above third laser chips a3 can be red laser chips, the second laser chips a2 can be green laser chips, and the first laser chips a1 can be blue laser chips.

[0072] It is worth noting that the arrangement of the laser chips shown in FIG. 3 and FIG. 4 is only for example, in actual application, the types of laser chips contained in the laser, the wavelength of the laser emitted by each laser chip, and the number and arrangement of each laser chip are not limited.

[0073] As shown in FIG. 5, the laser chip a can be composed of a plurality of semiconductor layers arranged in a stack, and the laser beams emitted thereby have different divergence angles in different directions, so that the laser beams form an elliptical laser spot B in the far field, the long axis direction of the ellipse corresponds to the plane parallel to the stacking structure of the laser chip (i.e. the plane formed by the first direction x and the second direction y), and the short axis direction of the ellipse corresponds to the stacking direction of the laser chip (i.e. the third direction z in FIG. 5), the divergence angle of the laser emitted by the laser chip a in the direction parallel to the plane of the stacking structure is greater than the divergence angle in the stacking direction. Therefore, the long axis direction of the ellipse can be referred to as the fast axis direction k1 of the laser, and the short axis direction of the ellipse can be referred to as the slow axis direction k2 of the laser.

[0074] As shown in FIG. 6, the laser does not directly emit laser from the laser chip a, but a reflecting prism f is arranged on the light-emitting side of the laser chip a, and the laser emitted by the laser chip a is incident on the reflecting prism f and reflected by the reflecting prism f to the light-emitting port of the laser. In addition, the laser also has a plurality of collimating lenses t corresponding to the laser chip a one-to-one on the light-emitting port, and the collimating lenses t are used to collimate the laser beams reflected by the reflecting prism f. Since the laser has a larger divergence angle in the fast axis direction k1, the collimating lenses t are usually designed for the divergence angle of the laser in the fast axis direction k1, which makes the divergence angle of the laser beam in the fast axis direction k1 after passing through the collimating lenses t smaller than the divergence angle in the slow axis direction k2.

[0075] In combination with FIG. 3 and FIG. 4, the same type of laser chip is usually arranged along the first direction x, so that the slow axis direction of the laser emitted by the light-emitting port of the laser is parallel to the first direction x, and the fast axis direction is parallel to the second direction y.

[0076] Taking the laser shown in FIG. 3 as an example, the lasers emitted by the three types of light-emitting areas can form a laser spot array as shown in FIG. 7 at the position of the light-emitting port. Among them, the laser beams emitted by the first laser chip a1 form a first laser spot B1 at the light-emitting port, the laser beams emitted by the second laser chip a2 form a second laser spot B2 at the light-emitting port, and the laser beams emitted by the third laser chip a3 form a third laser spot B3 at the light-emitting port. Then, taking each light-emitting area as a whole, the lasers emitted by the first light-emitting area 101-1 form a first laser spot array BL1 at the light-emitting port, the lasers emitted by the second light-emitting area 101-2 form a second laser spot array BL2 at the light-emitting port, and the lasers emitted by the third light-emitting area 101-3 form a third laser spot array BL3 at the light-emitting port. Each laser spot array as a whole can be regarded as a larger size spot. Since each laser spot has a larger divergence angle along the slow axis direction (i.e., the first direction x) and a smaller divergence angle along the fast axis direction (i.e., the second direction y), the laser spot array (the whole spot) formed at the light-emitting port of the laser has a larger divergence angle along the first direction x than along the second direction y, and the spot formed by the laser spot array has a larger size along the first direction x than along the second direction y.

[0077] The etendue is related to the beam area and the beam solid angle. The larger the beam solid angle is, the larger the divergence angle of the beam is. The larger the beam area is, the larger the spot size is. For the laser used in the embodiments of the present application, the laser spot formed by the lasers emitted by each light-emitting area has not only a larger divergence angle along the first direction x than along the second direction y, but also a larger spot size along the first direction x than along the second direction y. Therefore, the etendue of the beam emitted by the laser along the first direction x is larger than that along the second direction y.

[0078] As shown in FIG. 8, the three diffraction areas corresponding to the three types of light-emitting areas 101 are a first diffraction area 104-1, a second diffraction area 104-2, and a third diffraction area 104-3. Among them, the first diffraction area 104-1 is arranged corresponding to the first light-emitting area 101-1, the second diffraction area 104-2 is arranged corresponding to the second light-emitting area 101-2, and the third diffraction area 104-3 is arranged corresponding to the third light-emitting area 101-3. The laser beams emitted by each light-emitting area still have a certain divergence angle. With the increase of the optical path, the divergence degree of the laser beam is larger, and the size of the formed spot is also larger. Therefore, in the embodiments of the present application, the diffractive optical element can be arranged close to the corresponding light-emitting area, so that the size of the diffractive optical element is not too large.

[0079] As shown in FIG. 9, for each light emitting area 101, the corresponding diffraction area of the diffractive optical element 104 can shape the laser beam emitted by the corresponding light emitting area and image the emitted light spot at the position of the display element 201. The light spot formed by the light spot emitted by the diffractive optical element 104 being imaged at the position of the display element is referred to as the imaging light spot of the diffractive optical element. The imaging light spot of the diffractive optical element 104 has the same shape as the effective area of the display element 201, and when the display element 201 is a DMD, the imaging light spot of the diffractive optical element 104 is a rectangular light spot CB with an aspect ratio of 16:9. The imaging light spot of the diffractive optical element 104 being a rectangular light spot means that the optical expansion of the light beam emitted by the diffractive optical element 104 in the long direction of the rectangular light spot CB is greater than the optical expansion in the short direction of the rectangular light spot CB. In order to make the optical expansion of the laser, the diffractive optical element and the display element more matched, the microstructure of the diffractive optical element can be designed so that the long side of the rectangular light spot CB imaged at the position of the display element 201 is parallel to the slow axis direction of the laser beam emitted by the light emitting area 101, and the short side of the rectangular light spot CB is parallel to the fast axis direction of the laser beam emitted by the light emitting area 101. In this way, not only the diffraction efficiency of the diffractive optical element can be improved, but also the optical efficiency of the optical system can be improved.

[0080] As shown in FIG. 2, the laser beams emitted by the three types of light emitting areas 101 of the laser light source are incident on the light combining assembly 102 after passing through the corresponding diffraction areas.

[0081] Still taking the laser shown in FIG. 3 as an example, when the laser shown in FIG. 3 is combined, the light combining assembly 102 can include a first light combining piece 102-1, a second light combining piece 102-2 and a third light combining piece 102-3. Among them, the first light combining piece 102-1 is arranged corresponding to the first light emitting area 101-1, the second light combining piece 102-2 is arranged corresponding to the second light emitting area 101-2, and the third light combining piece 102-3 is arranged corresponding to the third light emitting area 101-3. The first light combining piece 102-1 is used to reflect the laser emitted by the first light emitting area 101-1 to the second light combining piece 102-2, the second light combining piece 102-2 is used to combine the laser emitted by the first light emitting area 101-1 with the laser emitted by the second light emitting area 101-2 and emit to the third light combining piece 102-3, and finally the third light combining piece 102-3 combines the laser emitted by the first light emitting area 101-1, the laser emitted by the second light emitting area 101-2 and the laser emitted by the third light emitting area 101-3.

[0082] The laser beams emitted by each light emitting area 101 of the laser light source are shaped by the corresponding diffraction area before being incident on the light combination assembly 102, so that the laser light spots incident on the light combination assembly 102 are all rectangular light spots, and the long sides of the three rectangular light spots are parallel to each other, and the short sides of the three rectangular light spots are parallel to each other. The light combination assembly 102 combines the three-color laser light along the second direction y, and the combined three-color rectangular light spots overlap together, and the centers of the three-color rectangular light spots coincide.

[0083] As shown in FIG. 2, the three-color laser beams after light combination pass through the magnification lens 203', and are focused at the position of the display element 201. A light homogenizing element 205 and a total reflection prism 204 are further arranged between the magnification lens 203' and the display element 201.

[0084] The magnification lens 203' is used to adjust the size of the light combination spot, so that it is more suitable for the size of the effective area of the display element 201. The magnification lens 203' can be a convex lens or a concave lens according to different specifications of the display element 201, which is not limited here.

[0085] In some embodiments, the light homogenizing element 205 can be a diffusion sheet, which is located between the magnification lens 203' and the total reflection prism 204, and is used to homogenize the incident laser beams. The diffusion sheet is located close to the total reflection prism 204, and can be in a static state or a motion state. The diffusion sheet can be a flat plate with dispersed diffusion particles, which has a scattering effect on the incident light, and can make the polarization direction of the outgoing laser present in a disordered state by high-frequency motion, thereby improving the problem of laser speckle. The diffusion sheet can move along the long side direction of the rectangular light spot, or can perform flip motion along the diagonal direction, which is not limited here.

[0086] The total reflection prism 204 can separate the illumination beam and the imaging beam. The total reflection prism 204 reflects the outgoing light of the magnification lens 203' to the display element 201, and transmits the outgoing light of the display element 201 modulated to the projection lens 30 for projection imaging.

[0087] Both the diffraction optical element 104 and the magnification lens 203' have imaging effects. When designing the diffraction optical element 104, the laser beams emitted by each light emitting area 101 of the laser light source are desirably diffraction by the corresponding diffraction area, and can be sufficiently homogenized to form a clear rectangular light spot at the position of the display element 201, which completely coincides with the effective area of the display element 201.

[0088] However, in actual application, the diffraction efficiency of the diffractive optical element 104 cannot reach 100%, and the laser beam after passing through the diffractive optical element still has a certain divergence angle. In addition, considering the tolerance in the optical path, in the design of the three diffraction regions, the application can make the three types of light beams of the three light emitting regions 101 after passing through the three diffraction regions be rectangular light spots at the imaging spot position of the display element 201, and the sizes of the three rectangular light spots can be slightly larger than the effective area of the display element 201.

[0089] In some embodiments, as shown in FIG. 10, the area of the imaging spot (rectangular light spot CB) of the diffractive optical element can be 10%-20% larger than the area of the effective area 201a of the display element. At the same time, the centers of the imaging spots of the three diffraction regions coincide, and have an overlapping area, and the overlapping area can cover the effective area of the display element 201, so as to ensure that the energy distribution and color distribution of the three-color laser beams incident on the display element 201 are uniform.

[0090] For a semiconductor red laser chip, the emitted laser beam has two light emitting points. After being diffracted by the corresponding diffraction region and incident on the display element, two light spots CB1 and CB2 are formed as shown in FIG. 11, and the sizes of the two light spots are different, which makes the light intensity distribution in the effective area 201a of the display element uneven, and affects the display effect.

[0091] In order to overcome this problem, as shown in FIG. 12, the diffraction region corresponding to the red laser chip can be specially designed, the distribution of the microstructure is changed, so as to change the phase distribution of the incident laser, increase the diffraction angle of the diffracted light beam parallel to the long side direction of the rectangular light spot, and increase the length of the long side of the rectangular light spot formed by the red laser beam output by the diffractive optical element and incident on the display element. Thus, the lengths of the long sides of the light spots CB1 and CB2 formed by the two light emitting points are increased, the length of the overlapping area of the two light spots is increased, and the overlapping area can cover the effective area 201a of the display element, so as to overcome the problem of uneven energy distribution of the red laser light spot incident on the effective area 201a of the display element.

[0092] The three-color laser beams after being combined still have a certain divergence angle, and cannot obtain the clearest imaging when incident on the display element 201 as the optical path increases. Therefore, a magnification lens 203' is arranged between the light combination assembly 102 and the display element 201. The display element 201 can be located within a range of 5mm before and after the focal plane of the magnification lens 203'. After passing through the magnification lens 203', the imaging of the light beam incident on the display element 201 is a rectangular light spot with clear boundaries and uniform energy distribution. The diffusion sheet can be located within the focal length range of the magnification lens 203', and is used to further homogenize the combined light beam before the light beam is incident on the display element 201.

[0093] The following describes the variation of the spot divergence, spot size and spot shape of the laser light emitted from the laser and passing through the optical elements in the optical path of the optical engine shown in Fig. 2 in combination with Fig. 13. Fig. 10 takes the optical path of one type of light emitting region 101 of the laser light source as an example, and the optical paths of other light emitting regions are similar and can be referred to each other.

[0094] When the laser shown in Fig. 3 is used, as shown in Fig. 13, the laser light emitted from the light emitting region 101 forms 1x7 elliptical spots at a position (1) before the incident diffractive optical element 104, each of which is a spot formed by the laser beam emitted from each laser chip at the position of the light emitting port of the laser. The emitted light of the light emitting region 101 can be regarded as a laser beam with a certain width, and the emitted light of each laser chip in the light emitting region 101 can be regarded as a sub-beam. The sub-beams emitted from the light emitting region 101 are separated from each other, and the divergence angle along the slow axis direction k2 is greater than that along the fast axis direction k1. The energy distribution of the sub-beams is Gaussian distribution.

[0095] When the 1x7 sub-beams emitted from the light emitting region 101 are incident to the diffractive optical element 104 and are diffracted by the diffractive optical element 104, the energy distribution of each sub-beam is homogenized, and the principal axes of the sub-beams emitted from the diffractive optical element 104 are parallel to each other, forming 1x7 rectangular spots separated from each other at the exit position (2) of the diffractive optical element 104. After being diffracted by the diffractive optical element 104, the divergence angles of each sub-beam along the fast axis direction k1 and the slow axis direction k2 are both reduced, but after a certain optical path, the size of the rectangular spot formed at the position (2) is greater than that of the elliptical spot formed at the position (1).

[0096] After the sub-beams emitted from the diffractive optical element 104 are combined by the light combining assembly 102, 1x7 rectangular spots separated from each other are formed at a position (3) between the light combining assembly 102 and the magnification lens 203' before the incident magnification lens 203'. The principal axes of the sub-beams are still parallel to each other after the light combining, and the divergence angles are unchanged, but the size of the rectangular spot is increased after a certain optical path.

[0097] When the combined sub-beams are incident to the magnification lens 203', they are focused by the magnification lens 203'. The principal axes of the sub-beams are no longer parallel, and during the propagation of the sub-beams to the display element 201 through the magnification lens 203', the sub-beams converge or diverge and gradually approach each other, and finally merge into a rectangular spot with clear outline at the corresponding position (4) of the light entrance surface of the display element 201. The energy distribution of the rectangular spot is uniform, satisfying the flat-top distribution.

[0098] Finally, the display element 201 modulates the incident light beams to form a display image, and the modulated light is emitted to the projection lens 30. At the position (5) in the far field, the previously combined sub-beams gradually separate as the propagation distance increases, so that the profile of the light spot gradually becomes blurred and the sharpness deteriorates. At this time, a reasonable optical design of the projection lens is also needed to obtain a clear projected image on the projection surface.

[0099] The above change processes of the light beams and the light spots are only for one type of the light emitting area 101, and the change processes of the light beams and the light spots of the other two types of the light emitting area are similar. It is worth noting that, because the divergence angles and the spot sizes of the red, green and blue laser beams are different when emitted, the three color rectangular light spots with clear profiles and uniform energy distribution can be obtained at the light entrance surface of the display element 201, but the sizes of the three color rectangular light spots are different, and in general, the size of the red light spot is larger than that of the green light spot, and the size of the green light spot is larger than that of the blue light spot. However, as long as the centers of the three color rectangular light spots coincide and can all cover the effective area of the display element, a colorless image display can be obtained.

[0100] In the embodiments of the present application, when the three types of the light emitting areas of the laser light source are different areas of the same laser, the diffractive optical element can also be one element, and the different light emitting areas are designed separately. When the three types of the light emitting areas of the laser light source are three lasers emitting different wavelengths, three diffractive optical elements can be applied.

[0101] Because the projection device uses a laser light source, and the laser has strong coherence, the problem of laser speckle is prone to occur. The diffractive optical element is arranged in the laser light source in the embodiments of the present application, and the diffractive optical element can modulate the phase of the light. Therefore, the diffractive optical element can be designed to have an additional phase adjustment function in addition to the above modulation function of the incident light beams, so as to improve the problem of laser speckle.

[0102] In some embodiments, as shown in FIG. 14, the diffractive optical element includes a first area 104a and a second area 104b, and the laser light emitted by the light emitting area 101 passes through the first area 104a and the second area 104b of the corresponding diffractive optical element, and the phases of the laser light passing through the first area 104a and the second area 104b are different by an odd multiple of π.

[0103] The laser light emitted by the laser light source is generally polarized light. For example, the laser light emitted by a red laser light chip is p-polarized light, and the laser light emitted by a green laser light chip and a blue laser light chip is s-polarized light. The polarization direction and phase of the laser light emitted by the same laser light chip are the same, and therefore the laser light has strong coherence and is prone to speckle during projection display. To improve this problem, the diffractive optical element can be divided into two regions when designing the diffractive optical element. The phase distribution of the diffractive optical element needs to meet the requirements of shaping the incident laser light beam into a rectangular light spot of a set size and uniform energy distribution, and also needs to make the phase of the light emitted by the two regions differ by an odd multiple of π. In this way, the polarization direction of the laser light emitted by the first region can be perpendicular to the polarization direction of the laser light emitted by the second region. If the areas of the first region and the second region are the same, the polarization direction of the light emitted by one half of the diffractive optical element can be perpendicular to the polarization direction of the light emitted by the other half of the diffractive optical element. In this way, the coherence of the laser light can be reduced to the greatest extent, thereby improving the formation of laser speckle.

[0104] In some embodiments, as shown in FIG. 15, the diffractive optical element includes a first region 104a and two second regions 104b, and the two second regions 104b are respectively located on both sides of the first region 104a along a first direction x (the long side direction of the rectangular light spot). The second region 104b is divided into two parts, and the design on both sides of the first region 104a is symmetrical. In this way, the phase adjustment of the emitted laser light can be symmetrically distributed, thereby better improving the problem of laser speckle.

[0105] In some embodiments, a driving device can also be provided in the projection device. The driving device is connected to the diffractive optical element, and the driving device can drive the diffractive optical element 104 to vibrate along the first direction x (the long side direction of the rectangular light spot). For example, the diffractive optical element can perform high-frequency reciprocating motion along the first direction x. In this way, the light emitted by the diffractive optical element can form an imaging light spot each time. The imaging light spots after multiple vibrations are superimposed together, which can be regarded as homogenizing the light spot. In this way, the phase distribution of the emitted light in space can also be made more uniform, thereby improving the problem of laser speckle.

[0106] In some embodiments, the diffractive optical element can also be designed such that the polarization direction of the laser light emitted by the light emitting region 101 is in a disordered state after the laser light passes through the corresponding diffractive optical element 104. That is, after the phase distribution of the diffractive optical element meets the specific shaping and homogenization effect, a random phase is added in the diffractive optical element. In this way, the polarization direction of the emitted light becomes disordered, the strong coherence of the laser light is destroyed, and the purpose of speckle elimination is achieved.

[0107] The microstructure of the surface of the diffractive optical element 104 is made by a semiconductor processing technology. The morphology, size and refractive index of the surface of the diffractive optical element 104 will affect the phase of the light. In order to obtain an imaging with uniform energy distribution and clear profile at the position of the display element 201, the phase of the diffractive optical element needs to be finely designed according to the input parameters of the incident light beam and the output parameters of the exit light beam.

[0108] The input parameters of the incident light beam can include wavelength, beam quality, beam waist radius and light intensity distribution when the laser beams emitted by each laser chip are incident on the corresponding region of the corresponding diffractive optical element, and the output parameters of the exit light beam can include the size of the light spot, the exit distance, the diffraction order and the light intensity distribution when the laser beam is incident on the position of the display element.

[0109] The design of the diffractive optical element can use GS algorithm, Y-G algorithm, etc. to calculate the phase of the diffractive optical element. It is known from the periodicity of the phase that the phase of the diffractive optical element can be compressed to [0, 2π]. However, due to the limitation of the current processing capability, it is impossible to process microstructures with continuous phase, so the continuous phase can be subdivided into stepped microstructures with different heights.

[0110] The design idea of the GS algorithm for designing the phase distribution of the diffractive optical element is described below. When the amplitude distribution of the input field (incident laser beam) and the target field (laser beam at the position of the display element) is known, the initial phase can be selected as a random phase. Fourier transform is performed on the initial phase and the amplitude of the input field to obtain the complex amplitude in the frequency domain; the phase in the frequency domain complex amplitude is extracted, and the amplitude of the target field is added; inverse Fourier transform is performed on the obtained complex amplitude to obtain the complex amplitude in the spatial domain, and the phase in the complex amplitude is extracted, and the amplitude of the input field is added to obtain a new complex amplitude; Fourier transform is performed on the new complex amplitude to obtain the complex amplitude in the frequency domain. The phase of the finally extracted complex amplitude in the spatial domain is the phase of the diffractive optical element.

[0111] In addition, other algorithms can also be used to design the phase of the diffractive optical element. The embodiments of the present application only take the GS algorithm as an example, and in actual application, a reasonable way can be selected to design the diffractive optical element according to the requirements.

[0112] Since the diffractive optical element has strong wavelength sensitivity, it is usually necessary to design corresponding diffractive optical elements for three-color lasers respectively. As shown in FIG. 16, a red laser R, a green laser G and a blue laser B need to be separately provided with a diffractive optical element, which not only increases the cost of the mold of the diffractive optical element, but also increases the system tolerance, thereby making the assembly of the projection device more difficult.

[0113] The projection device provided in the embodiments of the present application includes a substrate and a plurality of diffraction regions on the substrate, as shown in FIG. 17 and FIG. 18. Each diffraction region includes a plurality of microstructures. As shown in FIG. 17, the microstructures are in a stepped structure, and the heights of the microstructures are not completely the same.

[0114] In the embodiments of the present application, different diffraction regions correspond to different light emitting regions of the laser light source, and the heights of the single steps in the microstructures included in different diffraction regions are the same, so that different diffraction regions can be arranged on the same substrate. Therefore, it is not necessary to arrange independent diffraction optical elements for each color of laser light, which effectively reduces the system tolerance, thereby reducing the assembly difficulty, improving the assembly portability, and reducing the cost of the diffraction optical element mold.

[0115] It should be noted that FIG. 17 and FIG. 18 are schematic diagrams of the overall structure of the diffraction optical element, and do not show the plurality of diffraction regions.

[0116] In some embodiments, the laser light emitted by the laser light source includes first laser light and second laser light, wherein the colors of the first laser light and the second laser light are different, and the wavelength of the first laser light is greater than the wavelength of the second laser light. Then, the height of the highest microstructure in the diffraction region corresponding to the first laser light is greater than the height of the highest microstructure in the diffraction region corresponding to the second laser light.

[0117] The height of the highest microstructure in the diffraction region can be calculated by the following formula: Δ=φ / k=φ*λ / 2π=(n-1)h (1)

[0118] Based on the above formula (1), the following can be obtained:

[0119] In the above formula (1) and formula (2), Δ represents the optical path difference, φ represents the phase of the diffraction optical element, λ represents the wavelength of the laser light incident to the diffraction optical element, k=2π / λ represents the wave number, n is the refractive index of the diffraction optical element, and h is the maximum height of the microstructure in the diffraction region.

[0120] Based on the above formula, when the phase φ and the refractive index n of the diffraction optical element are constant, the height h of the highest microstructure gradually increases with the increase of the wavelength λ of the incident laser light. It can be known that the diffraction optical element has strong wavelength sensitivity. Therefore, when the wavelength of the first laser light is greater than the wavelength of the second laser light, the height of the highest microstructure in the diffraction region corresponding to the first laser light is greater than the height of the highest microstructure in the diffraction region corresponding to the second laser light.

[0121] Since different colors of laser correspond to different wavelengths, the plurality of diffraction regions included in the diffractive optical element correspond to different colors of laser one by one. Taking the example of a laser light source emitting red, green and blue three-color laser, the diffractive optical element can include three diffraction regions corresponding to red laser, green laser and blue laser respectively, and the maximum height of the microstructure in the three diffraction regions is different.

[0122] Taking any diffraction region as an example, if the number of steps contained in the microstructure is defined as m, for example, 18-step microstructure contains 18 steps. At this time, in this diffraction region, the step height can be in turn 0, h / m, …, m*h / m from low to high.

[0123] Still taking the example of a laser light source emitting red, green and blue three-color laser, the maximum height of the microstructure in the diffraction region corresponding to the red laser is denoted as hR, and the number of steps contained is denoted as mR. The maximum height of the microstructure in the diffraction region corresponding to the green laser is denoted as hG, and the number of steps contained is denoted as mG. The maximum height of the microstructure in the diffraction region corresponding to the blue laser is denoted as hB, and the number of steps contained is denoted as mB. Since the wavelength of red laser is greater than that of green laser, and the wavelength of green laser is greater than that of blue laser, hR>hG>hB. At this time, the target height of the single-step microstructure in the diffraction region corresponding to red, green and blue three-color laser is HR / mR, HG / mG and hB / mB respectively.

[0124] In order to make the height of the single-step microstructure in the diffraction region corresponding to red, green and blue three-color laser the same, the target height of the single-step microstructure in any diffraction region can be selected as the height of the single-step microstructure in the diffractive optical element. At this time, the steps of the three diffraction regions included in the diffractive optical element can be aligned and processed on the same substrate, as shown in FIG. 19, which is a side view of a diffractive optical element including three diffraction regions provided by an embodiment of the present application.

[0125] Correspondingly, as shown in FIG. 2, three light emitting regions can correspond to one diffractive optical element, and the three diffraction regions can be combined on the same substrate, which not only reduces the processing cost of the diffractive optical element mold, but also reduces the system tolerance and improves the assembly portability.

[0126] It should be noted that if the target height of the single-step microstructure in a certain diffraction region is selected as the height of the single-step microstructure in the diffractive optical element, since different diffraction regions correspond to different laser wavelengths, the target height of the single-step microstructure in different diffraction regions is different, and at this time, there is a certain deviation in the target height of the single-step microstructure in different diffraction regions.

[0127] In some embodiments, when the height of the single-step of the microstructure of the diffractive optical element is designed, the target height of the single-step of the microstructure of the diffractive region with the least difference from the target height of the single-step of the microstructure of the other diffractive regions can be taken as the height of the single-step of the microstructure of the diffractive optical element.

[0128] wherein the target height of the single-step of the microstructure in the diffractive region is the ratio of the maximum height of the microstructure in the diffractive region to the number of steps.

[0129] In some embodiments, the height of the single-step of the microstructure in the diffractive optical element is determined by traversing the highest microstructure and the number of steps it contains in each diffractive region, then determining the target height of the single-step of the microstructure in each diffractive region, and then selecting each diffractive region in turn, comparing the target height of the single-step of the selected diffractive region with the target height of the single-step of the other diffractive regions, and taking the target height of the single-step of the diffractive region with the least difference from the target height of the single-step of the other diffractive regions as the height of the single-step of the microstructure of the diffractive optical element.

[0130] For example, in the case where the number of steps contained in the m-step microstructure is m, the height of the single-step of the diffractive optical element needs to satisfy min{[h / m]-[HR / mR], [h / m]-[HG / mG], [h / m]-[hB / mB]}, wherein h / m represents the height of the single-step of the diffractive optical element, and HR / mR, HG / mG and hB / mB represent the target height of the single-step of the diffractive region corresponding to red, green and blue laser respectively.

[0131] Taking the target height of the single-step of the diffractive region with the least difference from the target height of the single-step of the other diffractive regions as the height of the single-step of the entire diffractive optical element, and the height of the single-step of the microstructure in all diffractive regions of the diffractive element being the same, can reduce the deviation of the height of the single-step of each diffractive region from its target height.

[0132] In some embodiments, if the number of steps contained in the m-step microstructure is defined as m, and based on the existing processing capability, the number of steps contained in the highest microstructure in the diffractive optical element ranges from greater than or equal to 3 and / or less than or equal to 19.

[0133] In some embodiments, the number of steps included in the m-order microstructure can also be defined as m-1, for example, the 18-order microstructure includes 17 steps. At this time, the step heights from low to high can be 0, h / (m-1), …, (m-1)*h / (m-1) in turn, wherein h / (m-1) represents the height of the single-step of the diffractive optical element. At this time, the target heights of the single-step in the diffraction regions corresponding to the red, green and blue lasers are hR / (mR-1), hG / (mG-1) and hB / (mB-1) respectively. At this time, the number of steps included in the highest microstructure included in the diffractive optical element ranges from greater than or equal to 4 and / or less than or equal to 20. The height of the single-step of the diffractive optical element needs to satisfy min{[h / (m-1)]-[HR / (mR-1)], [h / (m-1)]-[HG / (mG-1)], [h / (m-1)]-[hB / (mB-1)]}. The principle of determining the height of the single-step of the diffractive optical element is basically the same as that of determining the height of the single-step when the number of steps of the m-order microstructure is defined as m. For reference can be made to the above embodiments, which will not be described in detail here.

[0134] Based on the same inventive concept, the embodiments of the present application also provide a diffractive optical element, which comprises: a substrate and a plurality of diffraction regions located on the substrate, different diffraction regions being used for shaping and homogenizing lasers of different colors; each diffraction region comprises a plurality of microstructures, the heights of the plurality of microstructures being not completely the same, and the microstructures being in a stepped shape. The heights of the single-steps of the microstructures included in different diffraction regions are the same.

[0135] The specific structure of the diffractive optical element can be referred to the above embodiments, which will not be described in detail here.

[0136] FIG. 20 is a flow chart of a method for determining the step height of the diffractive optical element provided by the embodiments of the present application. As shown in FIG. 20, the method comprises the following steps:

[0137] S901: determining the phase corresponding to the diffractive optical element, the refractive index and the wavelength of the incident laser.

[0138] In some embodiments, the phase corresponding to the diffractive optical element can be [0, 2π].

[0139] The incident laser is the laser incident to the diffractive optical element. When the red, green and blue lasers are emitted by the laser light source, the incident laser includes the three-color lasers.

[0140] S902: determining the height of the single-step of the microstructure in the diffractive optical element based on the phase corresponding to the diffractive optical element, the refractive index and the wavelength of the incident laser.

[0141] The diffractive optical element includes a plurality of diffractive regions, and the heights of the single steps of the microstructures in different diffractive regions are the same.

[0142] In some embodiments, the maximum height of the microstructure in each diffractive region can be determined based on the phase corresponding to the diffractive optical element, the refractive index, and the wavelength of the incident laser light; and the height of the single step of the microstructure in the diffractive optical element can be determined based on the maximum height of the microstructure in each diffractive region.

[0143] In some embodiments, the maximum height of the microstructure in each diffractive region can be calculated based on the above formula (2). For example, based on the formula (2), the phase φ corresponding to the highest microstructure is 2π, and at this time, h = λ / (n-1), where h is the height of the highest microstructure in the diffractive region, and n is the refractive index of the diffractive optical element.

[0144] Suppose n = 1.458, and the wavelength of the red laser light is 643 nm, at this time, the height hR of the highest microstructure in the diffractive region corresponding to the red laser light is 643 / (1.458-1)≈1404 nm.

[0145] Similarly, the wavelength of the green laser light is 525 nm, at this time, the height hG of the highest microstructure in the diffractive region corresponding to the green laser light is 525 / (1.458-1)≈1146 nm.

[0146] The wavelength of the blue laser light is 465 nm, at this time, the height hB of the highest microstructure in the diffractive region corresponding to the blue laser light is 465 / (1.458-1)≈1015 nm.

[0147] FIG. 21 is a flowchart of a second method for determining the step height of the diffractive optical element according to an embodiment of the present application. As shown in FIG. 21, in some embodiments, when the height of the single step of the microstructure in the diffractive optical element is determined based on the maximum height of the microstructure in each diffractive region, the following process can be repeatedly performed until the diffractive region with the minimum difference of the target height is found:

[0148] S1001: Determine the number of steps included in the highest microstructure in each diffractive region.

[0149] If the number of steps included in the m-order microstructure is defined as m, at this time, the number of steps included in the highest microstructure in the diffractive optical element can range from greater than or equal to 3 and / or less than or equal to 19 as shown in the above embodiments.

[0150] Still taking the laser light source emitting red, green and blue three color laser as an example, from the above embodiment, it can be known that the height hR of the highest microstructure in the diffraction region corresponding to the red laser > the height hG of the highest microstructure in the diffraction region corresponding to the green laser > the height hB of the highest microstructure in the diffraction region corresponding to the blue laser. At the same time, since the height of the single-step of the microstructure needs to be the same, it can be determined that the number of steps included in the highest microstructure in the diffraction region corresponding to the red laser > the number of steps included in the highest microstructure in the diffraction region corresponding to the green laser > the number of steps included in the highest microstructure in the diffraction region corresponding to the blue laser.

[0151] Further, a group of values can be selected as the number of steps included in the highest microstructure in the diffraction region corresponding to the red, green and blue three color laser based on the range of the number of steps, such as 18, 15, 13, or 16, 12, 10, etc.

[0152] S1002: Determine the target height of the single-step of the microstructure in each diffraction region based on the height of the highest microstructure in each diffraction region and the number of steps included in the highest microstructure.

[0153] In an implementation scenario, the number of steps included in the highest microstructure in the diffraction region corresponding to the red, green and blue three color laser is 18, 15 and 13 respectively. For the diffraction region corresponding to the red laser, the height hR of the highest microstructure is 1404 nm, and at this time the target height of the single-step in this region is 1404 / 18 = 78 nm.

[0154] For the diffraction region corresponding to the green laser, the height hG of the highest microstructure is 1146 nm, and at this time the target height of the single-step in this diffraction region is 1146 / 15 = 76.4 nm.

[0155] For the diffraction region corresponding to the blue laser, the height hB of the highest microstructure is 1015 nm, and at this time the target height of the single-step in this diffraction region is 1015 / 13 ≈ 78.1 nm.

[0156] S1003: Select any diffraction region to determine the difference degree of the target height of the single-step of the other diffraction regions and the target height of the single-step of the diffraction region.

[0157] If the target height of the single-step of a certain diffraction region is taken as the height of the single-step of the diffractive optical element, for the selected diffraction region, the target height of the single-step is consistent with the height of the single-step of the diffractive optical element, and there is no deviation. However, for other diffraction regions, the target height of the single-step will deviate from the height of the single-step of the diffractive optical element, and thus only the difference between the target height of the single-step of the other diffraction regions and the height of the single-step of the diffractive optical element needs to be considered.

[0158] In an implementation scenario, when determining the difference between the target height of the single-step of a certain diffraction region and the height of the single-step of the diffractive optical element, the difference between the target height of the single-step of the diffraction region and the height of the single-step of the diffractive optical element can be determined, and the ratio of the difference to the target height of the single-step of the diffraction region can represent the difference.

[0159] For example, if the target height (78 nm) of the single-step in the diffraction region corresponding to the red laser is taken as the height of the single-step of the diffractive optical element, for the diffraction region corresponding to the red laser, the target height of the single-step is consistent with the height of the single-step of the diffractive optical element, and there is no deviation.

[0160] However, for the diffraction regions corresponding to the green laser and the blue laser, the target height of the single-step will deviate from the height of the single-step of the diffractive optical element.

[0161] Specifically, for the diffraction region corresponding to the green laser, the target height of the single-step is 76.4 nm, and if the height of the single-step of the diffractive optical element is set to 78 nm, the difference between the target height of the single-step of the diffraction region corresponding to the green laser and the height of the single-step of the diffractive optical element is (78-76.4) / 76.4≈2.1%.

[0162] For the diffraction region corresponding to the blue laser, the target height of the single-step is 78.1 nm, and if the height of the single-step of the diffractive optical element is set to 78 nm, the difference between the target height of the single-step of the diffraction region corresponding to the blue laser and the height of the single-step of the diffractive optical element is (78.1-78) / 78≈0.1%.

[0163] Therefore, when the highest microstructure in the diffraction region corresponding to the red, green and blue lasers respectively includes 18, 15 and 13 steps, and the target height of the single-step of the diffraction region corresponding to the red laser is taken as the height of the single-step of the diffractive optical element, the overall difference between the target height of the single-step of the diffraction region corresponding to the blue and green lasers and the height of the single-step of the diffractive optical element is 2.1%+0.1%=2.2%.

[0164] In another implementation scenario, if the target height (76.4nm) of the single-step of the diffraction region corresponding to the green laser is taken as the height of the single-step of the diffractive optical element, the difference between the target height of the single-step of the diffraction region corresponding to the red and blue lasers and the height of the single-step of the diffractive optical element can be determined. Through calculation, the overall difference between the target height of the single-step of the diffraction region corresponding to the red and blue lasers and the height of the single-step of the diffractive optical element is (78-76.4) / 78+(78.1-76.4) / 78.1≈4.2%.

[0165] Similarly, in another implementation scenario, if the target height (78.1nm) of the single-step of the diffraction region corresponding to the blue laser is taken as the height of the single-step of the diffractive optical element, the difference between the target height of the single-step of the diffraction region corresponding to the red and green lasers and the height of the single-step of the diffractive optical element can be determined. Through calculation, the overall difference between the target height of the single-step of the diffraction region corresponding to the red and green lasers and the height of the single-step of the diffractive optical element is (78.1-78) / 78+(78.1-76.4) / 76.4≈2.35%.

[0166] In summary, when the highest microstructure in the diffraction region corresponding to the red, green and blue lasers respectively includes 18, 15 and 13 steps, and the target height of the single-step of the diffraction region corresponding to the red laser is taken as the height of the single-step of the diffractive optical element, the overall difference between the target height of the single-step of the diffraction region corresponding to the green and blue lasers and the height of the single-step of the diffractive optical element is the smallest.

[0167] S1004: Take the target height of the single-step of the diffraction region with the smallest difference as the height of the single-step of the microstructure in the diffractive optical element.

[0168] Further, based on the range of the number of steps, the number of steps contained in the highest microstructure is changed, the processes of S1001-S1003 are repeated until the target height of the single-step of a certain diffraction region is determined based on the target height of the single-step of the diffraction region, the overall difference between the target height of the single-step of the diffraction region and the target height of the single-step of other diffraction regions is minimized, and the target height of the single-step of the diffraction region is taken as the height of the single-step of the diffractive optical element. At this time, the number of steps contained in the highest microstructure in each diffraction region is also determined.

[0169] Therefore, the preparation of the diffractive optical element can be based on the height of the single-step.

[0170] The method for determining the height of the step of the diffractive optical element provided in the embodiments of the present application determines the height of the single-step of the diffractive optical element based on the phase, the refractive index and the wavelength of the incident laser, so that the heights of the single-steps of different diffraction regions are the same, and different diffraction regions can be arranged on the same substrate, without the need to arrange independent diffractive optical elements for each color of laser. This is beneficial to reduce the system tolerance, thereby facilitating the assembly difficulty and improving the assembly portability.

[0171] FIG. 22 is a structural schematic diagram of a device for determining the height of the step of the diffractive optical element provided in the embodiments of the present application. As shown in FIG. 22, the device includes a determining module 1101.

[0172] The determining module 1101 is configured to determine the phase corresponding to the diffractive optical element, the refractive index and the wavelength of the incident laser.

[0173] The determining module 1101 is further configured to determine the height of the single-step of the microstructure in the diffractive optical element based on the phase corresponding to the diffractive optical element, the refractive index and the wavelength of the incident laser; and the diffractive optical element includes a plurality of diffraction regions, and the heights of the single-steps of the microstructure included in different diffraction regions are the same.

[0174] The device for determining the height of the step of the diffractive optical element provided in the embodiments of the present application can execute the method for determining the height of the step of the diffractive optical element in the above-mentioned method embodiments, and has similar implementation principles and technical effects, which will not be described here. It should be noted that the division of each module shown in FIG. 22 is only a schematic, and the division of each module and the naming of each module are not limited in the present application.

[0175] FIG. 23 is a structural schematic diagram of the step height determination device of the diffractive optical element according to an embodiment of the present application. As shown in FIG. 23, the step height determination device of the diffractive optical element comprises a processor 1201 and a memory 1202. The memory 1202 stores codes, and the processor 1201 executes the codes stored in the memory 1202 to perform any one of the methods in the above embodiments.

[0176] The processor 1201 and the memory 1202 are connected through a bus 1203.

[0177] The specific implementation process of the processor 1201 can refer to the above-mentioned method embodiments, which have similar implementation principles and technical effects, and will not be described here in detail.

[0178] The present application also provides a computer readable storage medium, and the computer readable storage medium stores computer execution instructions. When the computer execution instructions are executed by a processor, the method of any one of the above embodiments is implemented.

[0179] The computer readable storage medium can include a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various storage program codes. Specifically, the computer readable storage medium stores program instructions, and the program instructions are used for the method in the above embodiments.

[0180] The present application also provides a program product, which includes execution instructions stored in a readable storage medium. At least one control module of the projection device can read the execution instructions from the readable storage medium, and the at least one control module executes the execution instructions to make the projection device implement the method provided by the various embodiments.

[0181] Based on the same inventive concept, the present application further provides a projection system. As shown in FIG. 24, the projection system comprises a projection device 1 and a projection screen 2.

[0182] The projection screen 2 is located on the light exit side of the projection device 1, and the audience faces the projection screen 2. The projection device 1 emits projection light, the projection light is incident on the projection screen 2, and the projection light is emitted to the direction of the audience through the projection screen 2, so that the audience can watch the projection image.

[0183] The projection system is referred to as a front projection system when the projection device 1 and the audience are located on the same side of the projection screen 2, and is referred to as a rear projection system when the projection device 1 and the audience are located on the two sides of the projection screen 2 respectively. In the front projection system, the projection device 1 emits projection light to the projection screen 2, and the projection screen 2 reflects the projection light to the audience, so that the audience can watch the projection image. In the rear projection system, the projection device 1 emits projection light to the projection screen 2, and the projection light is emitted to the audience through the projection screen 2, so that the audience can watch the projection image.

[0184] The projection device 1 can adopt any of the above projection devices, and the projection device includes a laser light source, a diffractive optical element, an illumination system and a projection lens. The laser light source includes three types of light-emitting regions, and the laser light emitted by the three types of light-emitting regions is of different wavelengths. The diffractive optical element includes three diffractive regions corresponding to the three types of light-emitting regions. The illumination system includes a magnification lens, a light homogenizing element, a total reflection prism and a display element. The display element can modulate the incident laser light to form a display image, and then the display image is incident to the projection lens for projection imaging.

[0185] The laser light emitted by each light-emitting region of the laser light source is of different wavelengths. When the laser light beams emitted by each light-emitting region are incident to the display element after being diffracted by the diffractive optical element, a rectangular spot is formed. The rectangular spot matches the effective area of the display element, and the long side direction of the rectangular spot is parallel to the slow axis direction of the laser light beams emitted by the light-emitting region. In this way, the optical etendue of the laser, the diffractive optical element and the display element can be matched more, which not only improves the diffraction efficiency of the diffractive optical element, but also improves the optical efficiency of the optical system.

[0186] The microstructure in each diffractive region of the diffractive optical element is a stepped microstructure, and the heights of the single steps of the microstructure in each diffractive region are the same. In this way, different diffractive regions can be arranged on the same substrate, and it is not necessary to arrange independent diffractive optical elements for laser light of each color. Therefore, the system tolerance is effectively reduced, the assembly difficulty is reduced, the assembly portability is improved, and the cost of the diffractive optical element mold is also reduced.

[0187] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all the changes and modifications falling within the scope of the present application.

Claims

1. A projection device, comprising: a laser light source configured to emit three-color laser light; the laser light source comprises three types of light emitting regions, the laser light emitted by the three types of light emitting regions having different wavelengths; a diffractive optical element located on an emitting side of the laser light source, the diffractive optical element comprising three diffractive regions, one of the diffractive regions corresponding to one type of light emitting region; a magnification lens located on an emitting side of the diffractive optical element, the magnification lens being configured to change the size of a laser light spot; a light homogenizing element located on an emitting side of the magnification lens, the light homogenizing element being configured to homogenize a laser light beam; a display element located on a side of the light homogenizing element away from the magnification lens, the display element being configured to modulate an incident laser light beam to form a display image; a total reflection prism located between the magnification lens and the display element, the total reflection prism being configured to reflect light emitted by the magnification lens to the display element and to transmit light emitted by the display element; wherein a laser light beam emitted by the light emitting region forms a rectangular light spot when the laser light beam is incident on the display element after being diffracted by the diffractive optical element, and a long side of the rectangular light spot is parallel to a slow axis direction of the laser light beam emitted by the light emitting region.

2. The projection apparatus of claim 1, wherein, The laser light beams emitted by the three diffractive regions form three rectangular light spots when the laser light beams are incident on the display element. Centers of the three rectangular light spots coincide and there is an overlapping region, the overlapping region covering an effective region of the display element.

3. The projection apparatus of claim 2, wherein, An area of the rectangular light spot formed by the laser light beam emitted by the diffractive optical element when the laser light beam is incident on the display element exceeds 10%-20% of an area of the effective region of the display element.

4. The projection apparatus of claim 1, wherein, The magnification lens is a convex lens or a concave lens. A distance between the display element and a focal plane of the magnification lens is less than or equal to ±5mm.

5. The projection apparatus of claim 4, wherein, The light homogenizing element is a diffusion sheet, the diffusion sheet being located close to the total reflection prism. The diffusion sheet is in a static state, or the diffusion sheet moves along a long side direction of the rectangular light spot. 6.The projection device of any one of claims 1-5, further comprising: a light combining assembly located on a side of the diffractive optical element away from the three types of light emitting regions, the light combining assembly being configured to combine three-color laser light beams.

7. The projection apparatus according to any one of claims 1 to 6, wherein, The diffractive optical element comprises a first region and a second region, and the laser light emitted by the light emitting region has a phase difference of an odd multiple of π after passing through the first region and the second region of the diffractive optical element.

8. The projection apparatus of claim 7, wherein, The diffractive optical element comprises one first region and two second regions, the two second regions being located on two sides of the first region along a slow axis direction of the laser light beam.

9. The projection apparatus of claim 8, wherein, The diffractive optical element is connected to a driving device, the driving device being configured to drive the diffractive optical element to vibrate along a long side direction of the rectangular light spot.

10. The projection apparatus according to any one of claims 1-6, wherein, The laser light emitted by the light emitting region has a disordered polarization direction after passing through the corresponding diffractive region.

11. The projection apparatus according to any one of claims 1-10, wherein, The diffractive optical element further comprises a substrate, and the plurality of diffractive regions are located on the substrate. The diffractive region comprises a plurality of microstructures, heights of the plurality of microstructures are not completely identical, and the microstructures are in a stepped shape, heights of single steps of the microstructures included in different diffractive regions are identical.

12. The projection apparatus of claim 11, wherein, The height of the single-step of the microstructure in the DOE is the target height of the single-step in the diffraction region corresponding to the light-out region; the target height of the single-step in the diffraction region corresponding to the light-out region is the minimum difference with the target height of the single-step in the diffraction region corresponding to the other light-out region. The target height of the single-step in the diffraction region is the ratio of the maximum height of the step-shaped microstructure in the diffraction region and the number of steps.

13. The projection apparatus according to claim 11 or 12, wherein, The highest step-shaped microstructure in the DOE includes the number of steps greater than or equal to 3 and / or less than or equal to 19.

14. The projection apparatus according to any one of claims 11 to 13, wherein, The laser emitted by the laser source includes the first laser and the second laser, and the wavelength of the first laser is greater than the wavelength of the second laser. The height of the highest step-shaped microstructure in the diffraction region corresponding to the first laser is greater than the height of the highest step-shaped microstructure in the diffraction region corresponding to the second laser.

15. A diffraction optical element, comprising: a substrate; a plurality of diffraction regions on the substrate; the diffraction regions include a plurality of microstructures, the heights of the microstructures are not completely the same; the microstructures are step-shaped, and the heights of the single-steps of the microstructures in different diffraction regions are the same.

16. A method for determining the height of the step of a diffraction optical element, comprising: determining the phase corresponding to the diffraction optical element, the refractive index, and the wavelength of the incident laser; based on the phase corresponding to the diffraction optical element, the refractive index, and the wavelength of the incident laser, determining the height of the single-step of the microstructure in the diffraction optical element; wherein the diffraction optical element includes a plurality of diffraction regions, and the heights of the single-steps of the microstructures in different diffraction regions are the same.

17. The method of claim 16, wherein, The method for determining the height of the single-step of the microstructure in the diffraction optical element based on the phase corresponding to the diffraction optical element, the refractive index, and the wavelength of the incident laser includes: based on the phase corresponding to the diffraction optical element, the refractive index, and the wavelength of the incident laser, determining the maximum height of the microstructure in each diffraction region; based on the maximum height of the microstructure in each diffraction region, determining the height of the single-step of the microstructure in the diffraction optical element.

18. The method of claim 17, wherein, The method for determining the height of the single-step of the microstructure in the diffraction optical element based on the maximum height of the microstructure in each diffraction region includes: determining the number of steps included in the highest microstructure in each diffraction region; based on the height of the highest microstructure in each diffraction region and the number of steps included in the highest microstructure, determining the target height of the single-step of the microstructure in each diffraction region; selecting any diffraction region, determining the difference degree of the target height of the single-step of the other diffraction regions and the target height of the single-step of the diffraction region; the target height of the single-step of the diffraction region with the minimum difference degree is the height of the single-step of the microstructure in the diffraction optical element.

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