Laser projection device

Abstract

The application provides a laser projection device, a light source comprising a red laser component, a green laser component and a blue laser component, which respectively emit red laser, green laser and blue laser; the red laser component is arranged close to a light outlet of the light source; a static diffusion sheet is arranged in the light path of the combined blue laser and green laser or respectively for the blue laser and the green laser, so that the blue laser and the green laser are first diffused and then combined with the red laser beam; a converging lens group is arranged at the light outlet of the light source, which is used for reducing the spot of the combined three-color laser beam and then emitting the three-color laser beam from the light outlet of the light source; a diffusion wheel and a light receiving component are arranged between the converging lens and the light receiving component, which are used for diffusing the three-color laser beam in the converging state; and the light receiving component is a light guide pipe or a compound eye lens, which is used for homogenizing the three-color laser beam after diffusion. The laser projection device can present a projection picture with high brightness and good color.

Description

[0001] This application is a divisional application of Chinese Invention Application 201910538765.3 (2019-06-20), entitled "Laser Projection Device". Technical Field

[0002] This invention relates to the field of laser projection display technology, and more particularly to a laser projection device. Background Technology

[0003] Laser light sources possess advantages such as good monochromaticity, high brightness, and long lifespan, making them ideal light sources. With the increasing power of laser devices to meet the requirements of industrial applications, lasers are increasingly being used as lighting sources. For example, in recent years, lasers have been used as projection light sources in projection equipment, gradually replacing mercury lamps. Compared to LED light sources, lasers also offer advantages such as smaller optical spread and higher brightness.

[0004] Lasers are classified into blue lasers, red lasers, and green lasers according to the type of light emitted, emitting blue, red, and green laser light respectively. These classifications are based on different light-emitting mechanisms, such as... Figure 17 As shown, the red laser emitter chip has two emission points, but each chip corresponds to a collimating lens. Therefore, the collimating effect of one collimating lens on two emission points is worse than that of one collimating lens on one emission point. This causes the red laser to diverge at a larger angle than the other two colors after exiting the emission surface of the laser assembly. However, in practical applications, the optical path system is shared for all three colors of laser. During beam transmission, the optical lenses typically have their own light-gathering range or high light processing efficiency within a certain angle range. For red lasers, due to their faster divergence, beams over a large angle range are easily lost, resulting in higher light loss. This loss rate is difficult to estimate and cannot be solved by power compensation.

[0005] A solution is needed to address the problem of poor projection image quality caused by the large light loss of red laser in three-color laser applications, which leads to an imbalance in the system's color ratio. Summary of the Invention

[0006] This invention provides a laser projection device, including a three-color laser light source, which can present a high-brightness, high-color projection image.

[0007] This invention provides a laser projection device: a housing and a light source; the light source includes a red laser assembly and a green laser assembly installed side by side, and a blue laser assembly perpendicular to the red and green laser assemblies; a first beam combiner is disposed at the intersection of the blue and green lasers, the first beam combiner transmitting the blue laser and reflecting the green laser.

[0008] Furthermore, a second beam combiner is positioned at the intersection of the combined blue, green, and red lasers. This second beam combiner transmits the red laser and reflects the blue and green lasers to the third beam combiner.

[0009] The third beam combiner reflects the red, blue, and green lasers to the light source outlet; wherein the first, second, and third beam combiners are arranged in parallel.

[0010] Furthermore, the light reflectivity of both the first and second beam combiners is greater than their light transmittance.

[0011] Furthermore, the luminous power of the green laser component is lower than that of the red laser component and the blue laser component;

[0012] Furthermore, the spot size of the red laser reaching the second beam combiner is larger than the spot size of the blue and green lasers;

[0013] Furthermore, a homogenizing element and a converging lens group are sequentially arranged in the optical path from the third beam combiner to the light outlet of the light source;

[0014] Furthermore, a diffuser is provided in the optical path from the first beam combiner to the second beam combiner to diffuse the transmitted green and blue lasers;

[0015] Furthermore, the homogenizing element is a diffusion sheet with regularly arranged microstructures, or the homogenizing element is a two-dimensional diffraction element;

[0016] Furthermore, the three-color light source beam exits from the light source outlet and enters the light-collecting component via the diffuser wheel;

[0017] Furthermore, a half-wave plate is also provided in the optical path from the first beam combiner to the second beam combiner;

[0018] The half-wave plate is set to correspond to the wavelength of the green laser, or the half-wave plate is set to correspond to the wavelengths of both the green and blue lasers.

[0019] Furthermore, half-wave plates are respectively provided in the optical paths between the light-emitting surfaces of the blue laser component and the green laser component and the first beam combiner, with the half-wave plates corresponding to the blue laser wavelength and the green laser wavelength respectively.

[0020] Furthermore, the blue and green lasers have the same polarization direction, while the red laser has a different polarization direction than the two aforementioned colors.

[0021] Furthermore, the luminous power of the red laser component is 24W to 56W, the luminous power of the blue laser component is 48W to 115W, and the luminous power of the green laser component is 12W to 28W.

[0022] The laser projection device of one or more embodiments described above uses a three-color laser light source. The red laser is reflected twice and then output from the light source outlet. The blue laser is transmitted once and reflected twice, and the green laser is reflected twice and transmitted once before being output from the light source outlet. The red laser has the shortest optical path and undergoes the fewest total number of transmissions and reflections. Therefore, the red laser has less optical loss in the optical path, which is beneficial for maintaining the power ratio or color ratio of the three-color laser beam. The laser projection device described above can present a projection image with high brightness and good color. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of a laser projection device according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the optical principle of a light source in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the optical principle of another light source in an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of a light source structure in an embodiment of the present invention;

[0028] Figure 5 This is a structural diagram of an ultra-short throw projection screen according to an embodiment of the present invention;

[0029] Figure 6 for Figure 5 A graph showing the change in reflectivity of the projection screen to the projected beam;

[0030] Figure 7 This is a schematic diagram of a laser component assembly according to an embodiment of the present invention;

[0031] Figure 8 This is a front view of a laser assembly in an embodiment of the invention;

[0032] Figure 9 This is an exploded structural diagram of a laser component in an embodiment of the invention;

[0033] Figure 10 This is an exploded structural diagram of another laser component in an embodiment of the invention;

[0034] Figure 11 This is an exploded structural diagram of another laser component in an embodiment of the invention;

[0035] Figure 12 This is a schematic diagram of the structure of an MCL laser;

[0036] Figure 13 for Figure 12 Schematic diagram of the packaging structure of a laser circuit;

[0037] Figure 14 This is a schematic diagram of the heat dissipation system for the red laser component in an embodiment of the present invention;

[0038] Figure 15 This is a schematic diagram of the heat dissipation system assembly for the blue or green laser component in an embodiment of the present invention;

[0039] Figure 16 This is an exploded view of the heat dissipation system for the blue or green laser component in an embodiment of the present invention;

[0040] Figure 17 A schematic diagram of a red laser chip structure;

[0041] Figure 18 This is a schematic diagram of the optical path principle of a laser projection system according to an embodiment of the present invention;

[0042] Figure 19 This is a schematic diagram of the optical path principle of another laser projection system according to an embodiment of the present invention;

[0043] Figure 20 This is a schematic diagram of a diffuser sheet structure according to an embodiment of the present invention;

[0044] Figure 21 In an embodiment of the present invention, the laser beam passes through... Figure 20 The diagram shows the energy distribution behind the diffuser.

[0045] Figure 22 This is a schematic diagram of a light spot in the light path in an embodiment of the present invention;

[0046] Figure 23 This is a schematic diagram of the optical axis of a waveplate;

[0047] Figure 24 This is a schematic diagram illustrating the principle of a 90-degree change in the polarization of linearly polarized light.

[0048] Figure 25 This is a schematic diagram showing the polarization directions of P-beams and S-beams;

[0049] Figure 26 A schematic diagram showing the setup for waveplate rotation;

[0050] Figure 27 This is a schematic diagram of a laser projection optical path principle in an embodiment of the present invention;

[0051] Figure 28 This is a schematic diagram of another laser projection optical path principle in an embodiment of the present invention;

[0052] Figure 29 This is a schematic diagram of another laser projection optical path principle in an embodiment of the present invention;

[0053] Explanation of reference numerals in the attached figures:

[0054] 10 - Laser projection equipment; 101 - Housing;

[0055] 100-Light source, 102-Light source housing, 1021-Window, 104-Fixed bracket, 1041-Light-transmitting window, 1042-Third sealing element; 105-Sealing glass, 1051-First sealing element, 1052-Second sealing element, 106-First beam combiner, 107-Second beam combiner, 108-Third beam combiner, 109-Homogenizing element, 110-Blue laser assembly, 111-Converging lens assembly, 112-Diffuser, 120-Green laser assembly, 130-Red laser assembly, 121, 131, 141, 151, 140-Half-wave plate;

[0056] 1101 - Collimating lens group, 1102 - Metal substrate, 1103 - Laser pin, 1104a, 1104b - PCB board;

[0057] 200 - Optical mechanism, 250 - Light receiving component, 260 - Diffuser wheel;

[0058] 400 - Projection screen, 401 - Substrate layer, 402 - Diffusion layer, 403 - Uniform dielectric layer, 404 - Fresnel lens layer, 405 - Reflective layer;

[0059] 601-Heat fins, 602-Heat pipes, 603-Heat conduction block, 604-First fan, 605-Second fan, 606-Third fan, 607-Fourth fan, 610-Cold block, radiator-611, coolant supply-612, 613-Heat conduction block. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] Firstly, according to Figure 1The laser projection device shown herein will be used to explain the structure and operation of the laser projection device in this embodiment.

[0062] Figure 1 A schematic diagram of a laser projection device is shown. The laser projection device 10 includes a housing 101 and, according to optical functions, a light source 100, an optical engine 200, and a lens 300. These optical components are enclosed by corresponding housings to achieve certain sealing or airtightness requirements. For example, the light source 100 is airtight, which can effectively prevent light decay. The light source 100, optical engine 200, and lens 300 are mounted in the housing 101. The optical engine 200 and lens 300 are connected and arranged along a first direction of the housing 101. Figure 1 As shown, the first direction can be the width of the entire device, or, depending on the usage, the first direction can be opposite to the user's viewing direction. A light source 100 is disposed within the space enclosed by the optical engine 200, the lens 300, and a portion of the device housing 101. The light source 100 is a pure tri-color laser light source, emitting red, blue, and green laser light.

[0063] Therefore, in this example, the light source 100 is used to provide illumination for the optomechanism 200. Specifically, the light source 100 provides illumination beams to the optomechanism 200 by sequentially and synchronously outputting three primary color illumination beams.

[0064] Light source 100 can also be a non-sequential output, with overlapping output periods of different primary colors. For example, red and green can overlap in output periods, increasing the proportion of yellow in the beam cycle, which is beneficial to improving image brightness. Alternatively, red, green, and blue can be lit simultaneously in some periods, and the three colors can overlap to form white, which can improve white field brightness.

[0065] Furthermore, when other types of light modulation components are used, in order to cooperate with the three-chip LCD light valve, the three primary colors of the light source can be simultaneously illuminated to output mixed white light. However, in this example, although the light source 100 outputs the three primary colors of light sequentially, according to the principle of three-color mixing, the human eye cannot distinguish the color of the light at any given moment; what is perceived is still mixed white light. Therefore, the output of the light source 100 is usually also referred to as mixed white light.

[0066] The light source includes a housing and blue, green, and red laser components mounted on different sides of the housing, emitting blue, green, and red laser light respectively. The green and red laser components are mounted side-by-side on the same side and are spatially perpendicular to the blue laser component. That is, the side of the housing containing the green and red laser components is perpendicular to the side containing the blue laser component, and both sides are perpendicular to the bottom surface of the housing or the bottom surface of the entire housing.

[0067] See Figure 2 The diagram illustrates one possible optical path for light source 100. The beam emitted by the red laser component undergoes two reflections before exiting the light source. The beam emitted by the green laser component undergoes two reflections and one transmission before exiting the light source. The beam emitted by the blue laser component undergoes two transmissions and one reflection before exiting the light source. It is evident that, in the above diagram, the red laser has the shortest optical path and the fewest total number of transmissions and reflections.

[0068] Each of the three-color laser components outputs a rectangular beam, and each is vertically mounted on the side of the light source housing 102 along the long side of its respective rectangular beam. In this way, the laser beams output by the three-color laser components will not form a cross-shaped beam when combined, which is beneficial for reducing the size of the combined beam and achieving higher homogeneity.

[0069] like Figure 4 As shown, the light source housing 102 includes multiple sides, a bottom surface, and a top cover. Multiple optical lenses in the light source 100 are disposed on the bottom surface of the light source housing 102. Multiple windows 1021 are provided on the sides of the light source housing 102 to mount the aforementioned multiple laser components. The light beam emitted by any of the aforementioned laser components of any color enters the internal cavity of the light source 100 through the corresponding mounting window and forms a light transmission path through the multiple optical lenses.

[0070] Furthermore, a pressure balancing device is installed on the bottom or top cover of the light source housing. This pressure balancing device can be a filter valve, used to connect the inner cavity of the light source to the outside, enabling airflow exchange. When the temperature of the inner cavity rises, the internal airflow flows outward; when the temperature cools down, external airflow can enter the inner cavity. Since the filter valve can be an airtight, waterproof filter membrane, it can filter out particles, dust, and other contaminants within a certain diameter range, keeping the inner cavity clean. Alternatively, the pressure balancing device can be a retractable airbag made of elastic rubber, which increases in volume to alleviate pressure buildup in the inner cavity. Both of these pressure balancing devices can be used as pressure relief devices. When the temperature of the inner cavity rises too high, pressure can be released outward by connecting the airbag or by increasing the volume of the sealed space within the inner cavity through a gas-containing structure, thus balancing the pressure and improving the reliability of the optical components within the light source.

[0071] Since the assembly structure of the three-color laser components and the light source housing is basically the same, in order to simplify the explanation of the connection relationship between the laser components and the light source housing, the following explanation will take the assembly structure of any one of the color laser components as an example.

[0072] The aforementioned three-color laser components are all MCL-type laser components, which encapsulate multiple light-emitting chips on a single substrate to form a surface light source output. For example... Figure 12 , Figure 13 The MCL laser shown includes a metal substrate 1102 on which multiple light-emitting chips (not shown) are packaged. These chips can be connected in series or driven in parallel rows or columns. The chips can be arranged in a 4x6 array, or other array arrangements such as 3x5, 2x7, 2x6, or 4x5. Different array numbers result in different overall luminous power. Pins 1103 extend from both sides of the metal substrate 1102. Electrical connections to these pins drive the light-emitting chips to emit light. A collimating lens group 1101 is also provided on the emitting surface of the MCL laser. This collimating lens group 1101 is typically fixed with adhesive. The collimating lens group 1101 includes multiple collimating lenses, each corresponding to a specific emitting position of the chip, to collimate the laser beam.

[0073] like Figure 13As shown, the MCL laser assembly also includes PCBs 1104a and 1104b disposed on the outer periphery of the MCL laser. PCBs 1104a and 1104b are parallel to or located in the same plane as the laser's light-emitting surface to drive the laser pins 1103 and provide drive signals to the laser. As shown, the circuit board has a flat structure, with pins 1103 on both sides of the laser. The pins 1103 are soldered or plugged into the circuit boards 1104a and 1104b on the side that are almost parallel to the plane where the laser is located. 1104a and 1104b can be integrally formed and surround the outside of the laser assembly substrate 1102, or 1104a and 1104b can be two independent circuit boards that enclose the laser assembly. In this way, the packaged laser assembly is also basically a flat structure, which is convenient for installation, saves space, and facilitates the miniaturization of the light source device.

[0074] Figure 7 and Figure 8 These are schematic diagrams of the assembly structure of any color laser component and its mounting bracket, as well as exploded structural diagrams.

[0075] like Figure 4 As shown, any color laser assembly is mounted on the window 1021 of the corresponding light source housing via a mounting bracket 104. The mounting bracket 104 and the light source housing 102 are secured with screws, thereby fixing the laser assembly at the window 1021 position. Any color laser assembly includes an MCL type laser assembly and a mounting bracket.

[0076] Each color laser component is secured to the mounting bracket with screws. Specifically, the metal substrate of the MCL laser has mounting holes that allow it to be secured to the mounting bracket.

[0077] like Figure 9 As shown, the mounting bracket 104 is a sheet metal part with a light-transmitting window 1041. The front of the light-transmitting window 1041 is mounted near the window 1021 of the light source housing 102, while the laser assembly of any color is mounted on the mounting position on the back of the light-transmitting window 1041. Furthermore, to improve the sealing of the mounting structure, a third sealing element 1042 is provided at the mounting position on the back of the light-transmitting window 1041. The third sealing element 1042 is a frame-shaped rubber part with folded edges, which can be fitted onto the front of the MCL laser to fix the MCL laser assembly to the mounting position. The third sealing element 1042 also acts as a buffer, preventing damage to the collimating lens group on the surface of the MCL laser due to hard contact with the sheet metal part.

[0078] The MCL laser assembly consists of an MCL laser and a corresponding PCB board 1104. After being fixed to the mounting bracket 104, the MCL laser assembly becomes an assembly unit and is installed together at the window 1021 position corresponding to the light source housing 102. Specifically, the window 1021 has studs around it, and screws are driven into the studs around the window by passing through the studs of the mounting bracket.

[0079] Because the light source 100 contains multiple optical lenses, which are precision components, and the energy density during beam transmission is very high, if the internal environment is not clean, dust particles will accumulate on the surface of the precision lenses, causing a decrease in light processing efficiency, which in turn leads to light decay in the optical path, and consequently, a decrease in the overall brightness of the laser projection device. In this example, dust prevention measures inside the light source can mitigate the aforementioned light decay problem. Specifically, for example... Figure 10 As shown, a sealing glass 105 is also provided at window 1021. The sealing glass 105 isolates the inner cavity of the light source from the laser assembly installed at window 1021, preventing external dust and other contaminants from entering the inner cavity of the light source through the window opening. The sealing glass 105 can be disposed on the surface of the inner cavity of the light source, for example, by bonding, or it can be disposed on the side of the light source housing near the laser assembly, for example, by providing mounting positions on the outer surface of the light source housing, and then sequentially installing the laser assembly and the sealing glass on the outside of the window of the light source housing.

[0080] like Figure 10 As shown in the exploded view, for ease of installation of the sealing glass, in this example, the sealing glass 105 is installed on the side of the window 1021 near the laser assembly. The front of the mounting bracket 104 also has a first receiving groove for receiving the first seal 1051, and a second receiving groove at the window 1021 of the light source housing for receiving the second seal 1052. The sealing glass 105 is located between the first sealing member 1051 and the second sealing member 1052. Specifically, the second sealing member 1052 is placed in the second receiving groove at the window 1021. The second sealing member 1052 is provided with a fixing groove that matches the sealing glass 105. The sealing glass 105 is placed in the fixing groove, and the first sealing member 1051 is installed into the first receiving groove of the light-transmitting window 1041 of the fixing bracket by interference fit. Then, any color laser assembly composed of the fixing bracket and the MCL laser assembly is installed at the window 1021 of the light source housing. The first sealing member 1051 and the sealing glass 105 make extrusion contact. As the laser assembly is fixed, the sealing glass 105 is also fixed between the first sealing member 1051 and the second sealing member 1052.

[0081] Furthermore, in the above examples, the MCL type laser assembly of any color is fixed to the mounting bracket by shoulder screws, and a shock-absorbing component is provided between the shoulder screws and the mounting bracket to reduce the transmission of noise generated by the laser during high-frequency driving.

[0082] The assembly structure of the laser component and the light source housing has been described above. The laser component is mounted on the light source housing and emits a laser beam under the control of a drive signal, forming an optical path output internally, which, in conjunction with the optomechanical system and lens, performs projection imaging.

[0083] In the laser projection device provided in this embodiment, such as Figure 2 In the schematic diagram of the light source optical path shown, a first beam combiner 106 is set at the intersection of the blue laser and the green laser. The first beam combiner transmits the blue laser and reflects the green laser. A second beam combiner is set at the intersection of the combined blue laser, the green laser and the red laser. The second beam combiner reflects the red laser and transmits the blue and green lasers to a third beam combiner. The third beam combiner reflects the red laser, the green laser and the red laser to the light source output.

[0084] Specifically, the optical axis of the beam emitted from the blue laser component is perpendicular to the optical axis of the light source's outlet, while the optical axes of the beams emitted from the green and red laser components are parallel to the optical axis of the light source's outlet. The green laser emitted from the green laser component 120 is reflected by the first beam combiner 106 and then incident on the second beam combiner 107. The blue laser emitted from the blue laser component 110 is transmitted through the first beam combiner 106, and the blue and green lasers can be combined and output through the first beam combiner 107.

[0085] The blue and green laser beams, combined by the first beam combiner 106, have output directions perpendicular to and intersect with the red laser beam emitted by the red laser assembly 130. A second beam combiner 107 is positioned at the intersection of the three beams. The second beam combiner 107 reflects the red laser beam and transmits the green and blue laser beams. The three laser beams are combined into a single beam that enters the third beam combiner 108. The third beam combiner 108 reflects the three laser beams to the homogenizing element 109, and after being reduced in size by the converging lens group 111, the beam exits from the light source outlet.

[0086] like Figure 4 In the illustrated light source structure diagram, the green laser assembly 120 and the red laser assembly 130 are mounted side-by-side on one side of the light source housing, while the blue laser assembly 110 is mounted on the other side of the light source housing 102. The two sides of the light source housing are perpendicular to each other. All three laser assemblies output rectangular light spots and are vertically mounted on the side of the light source housing along the long side of their respective rectangular light spots.

[0087] Within the internal cavity of the light source, multiple beam combiners and a converging mirror assembly are also installed. Specifically, the first beam combiner is located between the blue laser assembly and the green laser assembly, at their intersection. The second beam combiner is tilted towards the emitting surface of the red laser assembly, transmitting the red laser and reflecting the blue and green lasers. The first, second, and third beam combiners are arranged approximately in parallel. Specifically, the first, second, and third beam combiners are fixed to the bottom surface of the light source housing by a base, and considering assembly tolerances, the angles of the first, second, and third beam combiners can be finely adjusted, for example, within ±3 degrees.

[0088] The third beam combiner is positioned close to the converging lens group to output the combined three-color laser beam to the converging lens group.

[0089] Among them, the third beam combiner is a reflecting mirror, while the first and second beam combiners are both dichroic filters.

[0090] Furthermore, the light reflectivity of both the first and second beam combiners is greater than their light transmittance. For example, the light reflectivity of the two beam combiners can reach 99%, while the transmittance is usually between 95% and 97%.

[0091] The three-color laser components provided in this example are all MCL type lasers, such as... Figure 12 As shown, an MCL laser comprises multiple light-emitting chips packaged on a metal substrate. Due to different light-emitting principles, the light-emitting power of different colored chips varies. For example, the light-emitting power of each green chip is approximately 1W, while the light-emitting power of each blue chip is over 4W. When the three-color lasers use the same number of chips arranged, such as a 4x6 package type, the overall light-emitting power also differs. For instance, the light-emitting power of the green laser assembly is less than that of the red laser assembly and also less than that of the blue laser assembly; the light-emitting power of the red laser assembly is less than that of the blue laser assembly.

[0092] Meanwhile, in the above embodiments, the red laser component, the blue laser component, and the green laser component are packaged with the same array of light-emitting chips, such as a 4x6 array. However, due to the different light-emitting principle of red laser, such as... Figure 17As shown, a single light-emitting chip contains two light-emitting points. This results in a larger divergence angle for the red laser along both the fast and slow axes compared to the blue and green lasers. During optical transmission, for the same optical lens, the red laser, due to its larger divergence angle, has a better light-gathering range or superior light processing performance within a certain angle range. Consequently, the longer the optical path or distance traversed by the red laser, the more severe its divergence becomes, leading to lower light processing efficiency for the red laser by subsequent optical lenses. Although the luminous power of the red laser assembly is greater than that of the green laser, the optical loss rate of the red laser is greater than that of the green and blue lasers after traversing the same optical path length.

[0093] like Figure 2 In the illustrated optical path, the blue laser, after being emitted along the emitting surface of the blue laser assembly, undergoes two transmissions and one reflection, and then exits from the light source outlet after passing through the homogenizing element 109 and the converging lens group 111. For the green laser, it undergoes two reflections and one transmission before entering the homogenizing element 109 and the converging lens group 111 and exiting from the light source outlet. The red laser, however, undergoes two reflections before entering the homogenizing element 109 and the converging lens group 111 and exiting from the light source outlet. It is evident that before exiting from the light source outlet, the optical path of the red laser is shorter than that of the blue and green lasers, thus reducing the optical loss generated during the transmission of the red laser. Furthermore, without considering the impact of light path on light loss, the light energy of the red laser after transmission through the second beam combiner and reflection through the third beam combiner can reach approximately 99% * 99% = 98%. It should be noted that the calculation of the light energy efficiency of the red laser here does not consider the large divergence angle of the red laser and the existence of large-angle light loss; it only considers the influence of the transmittance and reflectance of the optical lenses.

[0094] Blue laser light undergoes two transmissions and two reflections. Considering only the effect of transmittance on light loss, the light energy output from the first and second beam combiners, and reflected by the third beam combiner, is approximately 97% * 97% * 99% = 93%. Green laser light, after reflection from the first, second, and third beam combiners, outputs approximately 97% * 99% * 99% = 95% from the third beam combiner. In practical applications, blue lasers can have higher luminous power, and the human eye's visual function for blue is relatively low. Therefore, red laser light suffers the least transmittance loss through the lenses and has the shortest optical path. Thus, red laser light has the least light loss in its optical path.

[0095] Based on the aforementioned laser source layout, the different optical characteristics of each color laser can effectively balance the losses of each color laser beam during transmission, reducing the light loss caused by the easily lost characteristics of the red laser in the optical path. This ensures that the power ratio of the three lasers is close to the preset value, without significant imbalance, and also helps to achieve the theoretically designed color ratio and desired white balance. Furthermore, when the three lasers are combined and output from the third beam combiner, they all experience the same optical path, making it easier to achieve consistent light loss and reducing imbalance and inconsistency.

[0096] The optical path formed by the arrangement of the lasers is L-shaped, which is relatively regular. This helps to reduce the length of the housing in one direction and is also beneficial for structural design. It allows for the reservation of regular space in the housing, making it easier to install heat dissipation devices.

[0097] The laser components mentioned above all adopt MCL type laser components. Compared with traditional BANK type laser components, MCL type laser components are significantly smaller in size. Therefore, in this embodiment, its structural volume is significantly reduced compared with the traditional use of BANK type laser components, which allows for more space to be reserved near the light source, providing convenience for heat dissipation design. For example, the placement of heat sinks and fans can be more flexible in terms of location selection. In addition, circuit boards and other structures may be set up, which also helps to reduce the length of the whole structure in a certain direction or the overall volume of the whole machine.

[0098] Furthermore, since the lens component is usually located next to the light source in the overall structure, and the light source is the heat source of the laser projection device, the L-shaped optical path arrangement mentioned above allows the laser component to be arranged as close as possible to one side of the overall housing, with a space reserved in the middle, which can also serve as an isolation space between it and the lens. This prevents the heat from the laser from emitting light from being rapidly transferred to the lens and other precision optical lenses, thus affecting the optical performance.

[0099] As Figure 2 Variations, and Figure 2 The difference in the optical path shown is that the positions of the blue laser component and the green laser component can also be interchanged, for example... Figure 3 As shown, the blue laser emitted by the blue laser component 110 is reflected by the first beam combiner 106, and then transmitted through the second beam combiner 107 and reflected by the third beam combiner 109 in sequence, with a light loss of about 5 percentage points. The light loss of the green laser is about 7 percentage points. By increasing the proportion of the green laser emission period in the circuit, the problem of relatively high green light loss caused by the above light source layout can be reduced or alleviated.

[0100] In the above embodiments, by setting the light path of the red laser to the shortest possible value, reducing the number of times the red laser is transmitted or reflected, or by setting the red laser to only pass through the reflected light path, the light transmission loss of the red laser can be reduced. This ensures that the light loss of the red laser before beam combining is minimized, which is beneficial for maintaining the power and color ratio of the three-color light source beams, making the system white balance close to the theoretical set value, and achieving a high projection image quality.

[0101] See Figure 2 and Figure 3 In the above-mentioned laser projection equipment application embodiment, the light source, after the three-color lasers are combined by the beam combiner, also needs to pass through the homogenizing element and the converging lens group to homogenize and shrink the beam, so as to improve the light collection efficiency and homogenization efficiency of the light receiving element in the subsequent optical engine.

[0102] Specifically, such as Figure 2 The light source 100 also includes a homogenizing element 109 and a converging lens group 111. The homogenizing element 109 is disposed between the third combining mirror 108 and the converging lens group 111. Specifically, the homogenizing element can be a diffuser sheet with regularly arranged microstructures, such as... Figure 20 As shown. Currently, the microstructure of commonly used diffusers is random and irregular. The homogenizing diffuser used in this light source architecture utilizes a regularly arranged microstructure, similar to the principle of beam homogenization by a compound eye lens, which can transform the energy distribution of the laser beam from a Gaussian type to a more uniform type. Figure 21 The shape shown is made of Figure 21 As shown, the energy near the central optical axis of the laser is greatly weakened and becomes smoother, and the divergence angle of the laser beam is also increased. Thus, the effect of energy homogenization is much better than that of commonly used diffusers with irregularly arranged microstructures.

[0103] The above-mentioned homogenizing diffusion sheet can have regularly arranged microstructures set on one side or on both sides.

[0104] After homogenization by the aforementioned homogenizing diffuser, the laser beam is then passed through a converging lens group to reduce the spot size. On the one hand, homogenizing the high-energy laser beam first can reduce the impact of uneven energy distribution on the downstream components. On the other hand, homogenizing first and then reducing the beam size can also reduce the difficulty of homogenizing the spot size again after beam reduction.

[0105] Furthermore, the homogenizing element 109 can also be a two-dimensional diffraction element, which can also achieve a better homogenization effect.

[0106] In this example, the converging lens assembly includes two convex lenses, such as a biconvex lens and a combination of a convex and concave lens. Both lenses are spherical lenses, although aspherical lenses could also be used. However, spherical lenses are easier to shape and control with precision than aspherical lenses, and their cost can be reduced. In this example, the converging lens assembly is used to converge the light beam. The focal point of the converging lens assembly is set at the light-receiving aperture of the downstream light-receiving element, meaning the focal plane of the converging lens assembly is located at the light-receiving surface of the light-receiving element, thus improving the light-receiving efficiency of the light-receiving element.

[0107] In one specific implementation, the converging lens assembly is located at the light-emitting port of the light source housing. Specifically, the rear lens or the entire lens assembly can be installed at the light-emitting port, and the housing around the light-emitting port is filled with sealing materials, such as sealing rubber rings. This ensures that while the converging lens assembly is fixed, the internal cavity of the light source remains airtight, preventing dust particles from being brought in during airflow exchange with the outside environment through the first light-emitting port, which acts as a light-transmitting window. Furthermore, directly fixing the converging lens assembly to the first light-emitting port position helps shorten the optical path and reduce the size of the light source housing.

[0108] The converging light beam emitted from the first light-emitting port of the light source is ultimately collected by the light-collecting component of the optomechanical illumination optical path. For example... Figure 18 The schematic diagram of the optical path shown illustrates this. In this example, the light-receiving component 250 is a light guide. The light guide has a rectangular light-incident surface and a light-exit surface. The light guide serves as both a light-receiving component and a light-homing component. The light-incident surface of the light guide is the focal plane of the converging lens group 111. The converging lens group 111 inputs the converged light beam into the light guide 250. The light beam undergoes multiple reflections inside the light guide and exits from the light-exit surface. Due to the homogenizing diffuser in the front-end optical path, and the homogenization effect further enhanced by the light guide, a better three-color mixing homogenization effect can be achieved, improving the quality of the illumination beam.

[0109] Since the light source is a pure three-color laser, speckle is a phenomenon unique to lasers. To obtain higher projection image display quality, speckle reduction processing of the three-color laser is required. In this example, a diffuser wheel 260, i.e., a rotating diffuser, is also provided between the converging lens group 111 and the light-collecting component 250. The diffuser wheel 260 is located in the converging optical path of the converging lens group 111, and the distance between the surface of the diffuser wheel 260 and the light-collecting component 250-light guide tube is approximately 1.5 to 3 mm. The diffuser wheel can diffuse the converging beam, increasing the divergence angle and random phase. Furthermore, since the human eye has different sensitivities to speckle of different colors of laser, the diffuser wheel can be divided into sections, such as a first section and a second section. The first section is used to transmit red laser, and the second section is used to transmit blue and green laser. The divergence angle of the first section is slightly larger than that of the second section. Alternatively, it can be divided into three zones, corresponding to red, green, and blue lasers respectively. Among these three zones, the divergence angles of the red laser zone are largest, while those of the blue laser zone are smallest. When the diffuser wheel has corresponding zones, its rotation period can be the same as the period of the light source. Typically, when the diffuser wheel is a single diffuser sheet, its rotation period is not specifically limited.

[0110] The light guide has a certain range of light-receiving angles. For example, light beams within a range of ±23 degrees can enter the light guide and be utilized by the downstream illumination path, while other large-angle beams become stray light and are blocked, resulting in light loss. Placing the light-emitting surface of the diffuser close to the light-inlet surface of the light guide can increase the amount of diffused laser beam collected into the light guide, thereby improving light utilization.

[0111] It should be noted that the aforementioned light-collecting component can also be a compound eye lens component.

[0112] Furthermore, as mentioned earlier, due to the homogenizing diffuser 109 set in the front-end optical path, the light beam is homogenized and then converged by the converging lens group 111 before being incident on the diffuser wheel 260. The laser beam first passes through a stationary diffuser and then through a moving diffuser. In this way, the laser beam is further homogenized by the stationary diffuser, which enhances the homogenization effect of the laser beam, reduces the energy ratio of the beam near the optical axis, thereby reducing the coherence of the laser beam and greatly improving the speckle phenomenon in the projected image.

[0113] In the light source provided in the above embodiments, the light beam is incident on the light guide tube for light collection and homogenization. The applicant measures the light spot distribution on the light-incident surface of the light guide tube, which shows a relatively obvious inner and outer ring color boundary phenomenon. For example, the converging light spot appears circular, with the outermost ring being red, followed by concentric rings of purple, blue, etc., moving inwards. Figure 22As shown, research revealed that, as mentioned earlier, the divergence angle of the red laser component, due to its different emission principle, is greater than that of the blue and green lasers. Although in this example, the three-color laser components use an array arrangement of the same number of chips and have the same physical size, the inherent characteristics of the red laser result in a larger spot size during transmission compared to the blue and green lasers. This phenomenon already exists during tri-color beam combining, and its divergence angle increases faster than that of the other colors as the optical path distance increases. This means that even though the tri-color beam combining undergoes homogenization, beam contraction, and possibly further diffusion and homogenization via a rotating diffuser, the red laser spot size will always remain larger. This phenomenon was also observed in the test spot at the light-incident surface of the light guide.

[0114] To improve the overlap of the three-color laser spots, the length of the light guide tube can be increased to improve the light mixing and homogenization effect, but this will increase the optical path length and the structural volume.

[0115] This example presents a solution, specifically, in the aforementioned Figure 2 Based on the provided optical path schematic, such as Figure 19 As shown, a diffuser 112 is placed in the optical path of the blue and green laser beams to first diverge the blue and green laser beams before combining them with the red laser beam. The diffuser 112 is positioned in the optical path between the first beam combiner 106 and the second beam combiner 107. Alternatively, stationary diffusers can be placed separately for the blue and green lasers, for example, in the optical paths between the emitting surfaces of the two color laser components and their corresponding beam combiners.

[0116] By placing a diffuser in the optical paths of the blue and green lasers, the blue and green laser beams can be expanded, for example, by setting a diffusion angle of 1 to 3 degrees. After passing through the diffuser, the expanded blue and green laser beams are then combined with the red laser. At this point, the spot sizes of the three lasers are roughly the same, and the overlap of the spots is improved. The higher overlap of the three-color spots also facilitates the homogenization and spot removal of subsequent optical paths, improving beam quality.

[0117] The laser emitted by the laser is linearly polarized light. During the emission of red, blue, and green lasers, the resonant cavity oscillates in different directions, resulting in the polarization direction of the red laser linearly polarized light being 90 degrees from that of the blue and green lasers. The red laser is P-polarized light, while the blue and green lasers are S-polarized light.

[0118] In the above embodiment, a red laser assembly, a blue laser assembly, and a green laser assembly are used, with the green laser assembly polarized at 90 degrees. The red laser is a p-ray, while the blue and green lasers are s-rays. The three-color beams projected by the laser projection device have different polarization directions.

[0119] In practical applications, laser projection devices are usually paired with projection screens that have high gain and contrast, such as optical screens, in order to better reproduce colors and contrast, so as to better reproduce high-brightness and high-contrast projected images.

[0120] An ultra-short throw projection screen, such as Figure 5 The image shows a Fresnel optical screen. Along the incident direction of the projection beam, it includes a substrate layer 401, a diffusion layer 402, a homogeneous medium layer 403, a Fresnel lens layer 404, and a reflective layer 405. The thickness of a Fresnel optical screen is typically between 1 and 2 mm, with the substrate layer 401 accounting for the largest proportion of the thickness. The substrate layer also serves as the supporting structure for the entire screen, possessing a certain degree of light transmittance and rigidity. The projection beam first passes through the substrate layer 401, then enters the diffusion layer 402 for diffusion, and then enters the homogeneous medium layer 403. The homogeneous medium layer is a uniformly transparent medium, for example, made of the same material as the substrate layer 401. The beam passes through the homogeneous medium layer 403 and is incident on the Fresnel lens layer 404. The Fresnel lens layer 404 converges and collimates the beam. The collimated beam is reflected by the reflective layer and then refracts back through the Fresnel lens layer 404, the homogeneous medium layer 403, the diffusion layer 402, and the substrate layer 401 before being incident on the user's eye.

[0121] During the research and development process, the applicant discovered that ultra-short-throw projection images using the aforementioned three-color laser light source exhibit localized color shifts, resulting in uneven color distribution phenomena such as "color spots" and "color blocks." This phenomenon is caused by two main reasons. Firstly, in currently used three-color lasers, the different colors of the laser beams have different polarization directions. Optical systems typically incorporate multiple optical lenses, such as lenses and prisms. These optical lenses themselves have different transmittance and reflectance for P-polarized and S-polarized light; for example, the transmittance of an optical lens for P-polarized light is relatively greater than that for S-polarized light. Secondly, due to the screen material structure, as the incident angle of the ultra-short-throw projection beam changes, the transmittance and reflectance of the ultra-short-throw projection screen itself exhibit significant changes for beams with different polarization directions. Figure 6As shown, for a red projection beam, when the projection angle is around 60 degrees, experiments show that the reflectivity of the projection screen for P-type red projection beams differs from that for S-type red projection beams by more than 10 percentage points. This means that the ultra-short throw projection screen has a higher reflectivity for P-type light than for S-type light. This results in more P-type light being reflected by the screen into the human eye, while the amount of S-type light reflected into the human eye is relatively reduced. This difference in transmission and reflection for light of the same color but different polarization directions also exists when the projection beam is of other colors. When the three primary colors of light are in different polarization states, after passing through the aforementioned projection optical system and projection screen, especially the relatively obvious difference in transmission and reflection on the projection screen, an imbalance in the luminous flux of different colors of light reflected into the human eye will occur, ultimately leading to color distortion in local areas of the projected image. This is particularly noticeable when displaying color images.

[0122] To address the aforementioned problems, improvements were made to the light source provided in the above embodiments, resulting in another embodiment of the light source structure.

[0123] In this embodiment, the blue laser assembly and the green laser assembly are arranged adjacent to each other. A phase delay plate is set in the output path of the blue laser and the green laser and before they are incident on the third beam combiner to change the polarization direction of the blue laser and the green laser so that they are the same as the polarization direction of the red laser, thus solving the color distortion phenomenon of the projected image caused by the different polarization directions.

[0124] First, let's introduce the working principle of a phase retardation plate. A phase retardation plate, corresponding to a specific color wavelength, affects the degree of phase change in the transmitted light beam by the thickness of the crystal growth. In this example, the phase retardation plate is a half-wave plate, also called a λ1 / 2 wave plate, which can change the phase of a light beam of the corresponding color wavelength by π (180 degrees) and rotate the polarization direction by 90 degrees, for example, changing P-beams to S-beams, or vice versa. Figure 23 As shown, the waveplate is a crystal with its own optical axis W, which is located in the plane of the waveplate. The waveplate is placed in the optical path and is perpendicular to the optical axis O of the light source. Therefore, the optical axis W of the waveplate is perpendicular to the optical axis O of the light source.

[0125] like Figure 24 As shown, a coordinate system is established with the optical axis W of the waveplate. The coordinate system formed by the P-polarized light along the optical axis W and the direction perpendicular to the optical axis W has components Ex and Ey, where Ex and Ey can both be expressed using the light wave formula. The P-light can be regarded as the spatial synthesis of two-dimensional waves with components Ex and Ey.

[0126] When P-beam passes through a waveplate, its phase changes by π, or 180 degrees. The phase constants of Ex and Ey both exhibit a change of π. For a light wave in its original polarization direction at a certain moment, after the 180-degree phase change of b0, c0, and a0, the light waves of the two directional components are superimposed, resulting in a change in their spatial polarization positions, forming b1, c1, and a1, thus becoming light in the S-polarization direction. The aforementioned spatial position changes of b0, c0, a0, and b1, c1, and a1 are merely illustrative examples.

[0127] After passing through a half-wave plate, the light that was originally polarized in the P direction becomes polarized in the S direction, such as Figure 25 As shown, the two polarization directions are perpendicular to each other.

[0128] Based on the above explanation, as Figure 27 The schematic diagram of the optical path shows phase retarders of corresponding wavelengths placed in the output paths of the blue and green laser components, respectively. Specifically, the phase retarders are half-wave plates. In this example, the center wavelength of the blue laser is approximately 465 nm, and the center wavelength of the green laser is approximately 525 nm. Figure 27 In the optical path diagram shown, half-wave plate 121 is located in the output path of the blue laser, and its center wavelength is set accordingly. Half-wave plate 131 is located in the output path of the green laser, and its center wavelength is set accordingly. This can change the polarization direction of both the green and blue lasers by 90 degrees, changing them from S-light to P-light.

[0129] Based on the above optical path principle, in one specific implementation, the half-wave plate can be set in the inner cavity of the light source, located between the light combining mirror corresponding to the laser assembly on the inner side of the light source housing, and the half-wave plate can be fixed by setting a lens base on the bottom surface of the light source housing.

[0130] Alternatively, the half-wave plate can be placed inside the window for the laser assembly on the light source housing, for example, by adhesive or by fixing it to the inside of the window.

[0131] Alternatively, the half-wave plate can be positioned between the laser assembly and the outer side of the light source housing window. For example, the half-wave plate can be attached to or fixed to the outer side of the window, and the laser assembly (including the mounting bracket) can be mounted on the mounting position on the outer side of the window via the mounting bracket.

[0132] Alternatively, when a sealing glass is installed at the window, the half-wave plate can be positioned between the sealing glass and the light-emitting surface of the laser assembly. For example... Figure 11 The exploded view of the laser assembly structure shown shows that there is also a support platform (not shown in the figure) on the front of the light-transmitting window 1041 of the fixing bracket of the laser assembly. The half-wave plate 140 can be fixed to the support platform by adhesive. There are also receiving grooves around the support platform to accommodate the first sealing member 1051. Figure 9 A schematic diagram shows a half-wave plate mounted on the front of a fixed bracket. The half-wave plate 140 is mounted at the light-transmitting window 1041 of the fixed bracket and fixed by adhesive dispensing through the surrounding adhesive grooves. The length and width of the half-wave plate 140 range from 25 to 30 mm and 21 to 28 mm, respectively; the length and width of the light-transmitting window of the fixed bracket range from 20 to 24 mm and 18 to 20 mm, respectively. For example, in one embodiment, the half-wave plate is 30 mm * 28 mm, and the size of the light-transmitting window is 24 mm * 20 mm.

[0133] After the half-wave plate 140 is fixed to the mounting bracket 104, it, along with the MCL-type laser assembly mounted on the mounting bracket 104, is installed together with the mounting bracket 104 at the mounting position of the window 1021 of the light source housing 102. As mentioned above, the mounting position of the window 1021 of the light source housing is also provided with a second receiving groove for accommodating the second sealing member 1052. The sealing glass 105 is sandwiched between the first sealing member 1051 and the second sealing member 1052 on the laser assembly. Based on the above structure, after the laser beam is emitted from the light-emitting chip, it passes through the half-wave plate 140 and the sealing glass 105 in sequence before entering the inner cavity of the light source through the window 1021 of the light source housing.

[0134] In the aforementioned light source structure, half-wave plates of corresponding colors are installed on the mounting brackets of both the blue and green laser components. This causes a 90-degree change in the polarization polarity of the beams after passing through the corresponding half-wave plates. The green laser is already P-polarized when it enters the first beam combiner, and the blue laser is also already P-polarized when it enters the first beam combiner. Therefore, the beams output after the first beam combine the blue and green lasers are both P-polarized, which is the same polarization direction as the red laser. The second beam combiner outputs the three beams with the same polarization direction. After homogenization and beam contraction, the beams enter the optomechanical illumination path, are reflected by the DMD, and enter the lens, where they are projected onto the screen to form an image. Because the three colors have the same polarization direction, the uneven color distribution, such as "color spots" and "color blocks," in the projected image can be eliminated or greatly reduced.

[0135] As a variation of the above embodiment, in this example, the blue laser and green laser are first combined, and then combined with the red laser. In this case, the half-wave plate can also be placed in the optical path after the blue and green lasers are combined and before the red laser is combined. Specifically, as shown... Figure 28As shown, another light source optical path principle diagram is provided. The half-wave plate 141 can be placed between the first beam combiner 106 and the second beam combiner 107 to transmit the combined beam of the blue laser and the green laser emitted from the first beam combiner 106. Based on the above optical path principle, the green laser and the blue laser respectively output S-polarized light. The green S-polarized light is incident on the first beam combiner 106 and is reflected, while the blue S-polarized light is incident on the first beam combiner 106 and is transmitted. The first beam combiner 106 combines the blue laser and the green laser, both of which are S-polarized light, and then passes them through the half-wave plate 141. The half-wave plate 141 changes the polarization direction of the green laser and the blue laser before they are incident on the second beam combiner 107.

[0136] Specifically, the half-wave plate 141 can be set for the wavelength of one color, such as the wavelength of green laser. After passing through the half-wave plate, the polarization direction of the green laser rotates by 90 degrees, changing from the original S-polarization to P-polarization. After passing through the half-wave plate, the wavelength of the half-wave plate does not correspond to the blue wavelength setting, so the polarization direction of the blue laser does not deflect by 90 degrees, but is close to the P-polarization direction. Since the human eye has a lower visual function for blue and lower sensitivity to blue, visual discomfort is more obvious when there is color distortion, such as with red and green. Alternatively, the half-wave plate 141 can also be set for the middle value of the center wavelength of blue and green. In this way, the polarization direction change of green and blue lasers is not 90 degrees, but close to 90 degrees. Although neither blue nor green lasers deflect from S-polarization to P-polarization, neither is in the original S-polarization state. This can also improve the consistency of the light processing process of the three primary colors of red, green, and blue in the entire system, and can improve the technical problem of color unevenness such as "color spots" and "color blocks" in local areas of the projected image. The principle will not be elaborated here.

[0137] In the above example, the half-wave plate 141 can be fixed by a fixing base set on the bottom surface of the light source housing.

[0138] It should be noted that, in Figure 28 The method of setting up a half-wave plate shown is also applicable to... Figure 2 , Figure 3 , Figure 18 or Figure 19 The optical path architecture shown in the schematic diagram operates on the same principle as described above and will not be repeated here.

[0139] In optical systems, for different wavelengths, the transmittance and reflectance of the same optical lens for P-wave and S-wave light are roughly equivalent. Here, "optical lens" includes all the various optical lenses in the entire laser projection device, such as the converging lens group, the lens group in the illumination path of the optical engine section, and the refractive lens group in the lens section. Therefore, when the laser beam emitted from the laser source passes through the entire projection optical system, this difference in transmittance and reflection is the result of the superposition of the entire system and will be more pronounced.

[0140] Before adding a half-wave plate, especially when the primary colors are P- and S-polarized light, both the optical lenses of the optical system and the projection screen exhibit significant selective transmission of P- and S-light. For example, depending on the incident angle of the projection beam, the projection screen's transmittance for P-light (red light) is significantly greater than its transmittance for S-light (green and blue light). This causes localized color unevenness in the projected image, resulting in "color spots" or "color patches" on the screen.

[0141] In the aforementioned embodiments, by setting half-wave plates in the light output paths of the blue and green lasers, and by setting half-wave plates of corresponding wavelengths for the blue and green lasers respectively, the polarization directions of the blue and green lasers can be changed by 90 degrees. In this example, the polarization direction changes from S-polarization to P-polarization, which is consistent with the polarization direction of the red laser. Thus, when the blue and green lasers, which are now P-polarized, are reflected into the human eye through the same optical imaging system and projection screen, the transmittance of the P-polarized blue and green lasers in the optical lens is comparable to that of the P-polarized red laser. The consistency of the light processing is close, and the difference in reflectivity of the projection screen to the three primary colors is also reduced. The consistency of the light processing of the three primary colors in the entire projection system is improved, which can fundamentally eliminate the color deviation phenomenon of "color spots" and "color blocks" in local areas of the projected image and improve the display quality of the projected image.

[0142] Furthermore, by placing a half-wave plate in the combined optical path of the blue and green lasers, the polarization direction of either the green or blue laser can be changed by 90 degrees, or the polarization direction of both colors can be changed by a factor close to 90. This also reduces the polarization difference with the red laser (P-light). Based on this principle, the consistency of the entire system's processing of the three primary colors (red, green, and blue) can be improved, thus mitigating the technical problem of uneven color distribution, such as "color spots" or "color patches," in localized areas of the projected image.

[0143] Furthermore, since the transmittance of optical lenses in optical systems for P-polarized light is usually greater than that for S-polarized light, and the reflectance of the projection screen used in this example for P-polarized light is also greater than that for S-polarized light, by converting the blue and green lasers of S-polarized light into P-polarized light, so that the red, green, and blue lasers are all P-light, the light transmission efficiency of the projection beam in the entire system can be improved, the brightness of the entire projection screen can be increased, and the quality of the projection screen can be improved.

[0144] To address the technical problem of uneven color distribution, such as "color spots" and "color blocks" appearing on the projected image, this embodiment provides a laser projection device, which is applied to... Figure 29 The light source unit is shown. In this example, a half-wave plate corresponding to the red wavelength is provided before the red laser beam is combined with the blue and green laser beams. For example, half-wave plate 151 is provided between the red laser assembly 110 and the second beam combiner 107.

[0145] The half-wave plate configuration scheme can be found in the previous embodiment where half-wave plates are configured for the blue laser and the green laser respectively.

[0146] For example, a half-wave plate can be placed inside the cavity of the light source, in the optical path between the inner side of the light source housing and the third beam combiner. The half-wave plate can be fixed by setting a lens base on the bottom surface of the light source housing.

[0147] Alternatively, the half-wave plate can be placed inside the window for the red laser assembly on the light source housing, for example, by adhesive or by fixing it to the inside of the window.

[0148] Alternatively, the half-wave plate can be positioned between the red laser assembly and the outer side of the light source housing window. For example, the half-wave plate can be attached to or fixed to the outer side of the window, and the laser assembly (including the mounting bracket) can be mounted on the mounting position on the outer side of the window via the mounting bracket.

[0149] Alternatively, when a sealing glass is installed at the window, the half-wave plate can be positioned between the sealing glass and the light-emitting surface of the laser assembly. The specific installation method can also be referred to... Figure 11 The details of that will not be repeated here.

[0150] The half-wave plate 151 corresponds to the wavelength setting of the red laser. Similarly, the polarization direction of the red laser can be rotated by 90 degrees through the half-wave plate, and the red laser light is changed from P-polarized light to S-polarized light.

[0151] It should be noted that the above-mentioned scheme of setting a half-wave plate for the red laser is also applicable to this invention. Figure 2 , Figure 3 , Figure 18 , Figure 19 The principle of the optical path shown in the diagram is the same as above and will not be repeated here.

[0152] In the above example, by setting a half-wave plate in the red laser output light path, the original P-polarized red laser light is converted into S-polarized light, which is consistent with the polarization direction of the blue and green lasers. In this way, the polarization direction of the three colors of the system is the same. Referring to the principle description of the previous embodiment, the difference in transmittance of the projection optical system for the red, blue, and green lasers that are all S-polarized light is reduced compared to when they are polarized light with different polarization directions. The reflectance of the ultra-short throw projection screen for the three colors of light that are all S-polarized light is also basically consistent, thereby improving the consistency of light processing for each primary color. This can eliminate or improve the phenomenon of uneven color such as "color spots" and "color blocks" in the projected image.

[0153] Furthermore, in the above embodiments, the laser emitting surface is rectangular, and correspondingly, the phase delay plate is disposed in the light output path of one or two colors, and its shape is also rectangular, wherein the long side and short side of the laser rectangular emitting area are parallel to the long side and short side of the phase delay plate rectangular receiving area, respectively.

[0154] Because laser beams contain high energy, optical lenses, such as lenses and prisms, experience temperature changes during operation. Internal stress is formed in these lenses during manufacturing, and this stress is released with temperature changes, resulting in stress birefringence. This stress birefringence causes different phase delays for different wavelengths of the beam, which can be considered a secondary phase delay. Therefore, in actual optical paths, the phase change of the beam is based on the combined effect of the stress birefringence of the half-wave plate and the optical lenses. The amount of delay inherent in these optical lenses varies depending on the system design. When applied, the technical solutions of the various embodiments described above can preferably correct for the secondary phase delay caused by the actual system, to approximate or achieve the theoretical value of a 90-degree change in beam polarization direction.

[0155] A half-wave plate has an optical axis in the plane in which its flat plate lies, such as Figure 23 As shown, the optical axis W of the half-wave plate is spatially perpendicular to the system optical axis O, and the optical axis of the half-wave plate is parallel to either its long or short side. In specific applications of the above embodiments, such as... Figure 26 As shown, the half-wave plate is configured to rotate along its long or short side by a preset angle, such as C degrees, as indicated by the dotted line in the figure. After this angle deflection, the optical axis of the half-wave plate also deflects by approximately ±C degrees, resulting in a change in the beam phase of approximately 180 degrees ± 2C degrees. This change, combined with the secondary phase delay of the system's optical lenses, ultimately alters the beam's polarization direction by approximately 90 degrees, close to the theoretical design value. In the various embodiments described above, C can be 10.

[0156] In one or more of the above embodiments, for laser projection light sources with three primary colors having different polarization directions, by setting a half-wave plate in the light output path of one or two colors in the laser projection device light source, the polarization direction of the corresponding transmitted one or two colors of light is changed, making it consistent with the polarization direction of other colors. The polarization polarity of the three primary colors of light output by the laser projection device is the same. Thus, when the laser beam emitted by the laser projection device light source passes through the same optical imaging system and is reflected into the human eye by the projection screen, the transmittance of the optical system for the three colors of laser is close, and the difference in reflectance of the projection screen for the three colors of laser is also reduced. The consistency of the light processing process of the three primary colors of light in the entire projection system is improved, which can fundamentally eliminate the phenomenon of uneven color such as "color spots" and "color blocks" appearing in local areas of the projected image, and improve the display quality of the projected image.

[0157] In laser projection equipment, the light source is the primary heat source. The high-density energy beam of the laser also generates heat when it shines on the surface of the optical lenses. The DMD chip, though only a few tenths of an inch in size, needs to withstand the beam energy required for the entire projected image, resulting in very high heat generation. On one hand, the laser has a set operating temperature to achieve stable light output, balancing lifespan and performance. On the other hand, the equipment contains multiple precision optical lenses, especially ultra-short-throw lenses, which contain multiple lenses. If the internal temperature of the entire equipment becomes too high, heat accumulation can cause "temperature drift" in the lenses, severely degrading image quality. Furthermore, components such as circuit boards, driven by electrical signals, also generate heat, and each electronic component has a set operating temperature. Therefore, good heat dissipation and temperature control are crucial for the normal operation of laser projection equipment.

[0158] Specifically, such as Figure 15 As shown and Figure 16 The heat-conducting block 603 conducts heat in contact with the heat sink of the green or blue laser component. The outer surface of the heat pipe 602 contacts the heat-conducting block to achieve heat transfer. One end of the heat pipe 602 that contacts the heat-conducting block 603 is the hot end, and the other end that contacts the heat dissipation fins is the cold end. The heat pipe is a closed system with liquid inside, and heat conduction is achieved through liquid-gas-liquid changes. The heat dissipation fins in contact with the cold end of the heat pipe are usually cooled by air, which also cools the cold end of the heat pipe, and the gas liquefies and flows back to the hot end of the heat pipe.

[0159] And, such as Figure 14As shown, the red laser component is connected to the cold head 610 for liquid cooling. In the liquid cooling circulation system, the cold head carries the heat from the heat source component back to the radiator, where it is cooled. The cooled coolant, such as water, then flows back to the cold head, and the cycle repeats to conduct heat to the heat source. The liquid cooling circulation system also includes a pump to keep the coolant flowing. In this example, the pump and cold head are integrated to reduce component size. The "cold head" mentioned below can refer to the integrated structure of the cold head and pump. Furthermore, the liquid cooling circulation system of the laser projection device in this example also includes a replenisher to replenish the liquid in the system, ensuring that the liquid pressure within the system is greater than the external pressure. This prevents external gases from entering the circulation system due to coolant evaporation or poor pipe joint sealing, which could cause noise or even cavitation damage to the device.

[0160] Compared to air-cooled systems, liquid cooling systems offer greater flexibility in that the volume of the cooling block and radiator is smaller than that of traditional heat sink fins, allowing for greater variety in their shape and structural placement. Since the cooling block and radiator are connected by pipes and form a single, continuous circulation system, the radiator can be positioned close to the cooling block or in other relative positions, depending on the available space in the laser projection equipment.

[0161] Within the space enclosed by the optical engine, lens, and another part of the main housing, there are also multiple circuit boards 500 and a second fan. The second fan is located close to the main housing, and there can be multiple second fans.

[0162] In laser projection equipment, the light source 100 is a laser source, and the different colored laser components it includes have different operating temperature requirements. Specifically, the red laser component operates at a temperature below 50℃, while the blue and green laser components operate at temperatures below 65℃. The DMD chip in the optical engine typically operates at around 70℃, and the lens temperature is usually controlled below 85℃. For the circuit board, the temperature control varies depending on the electronic components, typically ranging from 80℃ to 120℃. It is evident that because the optical and circuit components have different temperature tolerances—with the optical component generally having a lower tolerance than the circuit component—airflow from the optical component to the circuit component allows both parts to dissipate heat while maintaining their normal operation.

[0163] It should be noted that since the operating temperature of the red laser component is less than 50℃, for example, when controlled below 45℃, liquid cooling is used. The temperature difference between the surface of the radiator and the surface of the cooling head is controlled within the range of 1-2℃. That is, if the surface temperature of the cooling head is 45℃, the surface temperature of the radiator is 43℃-44℃. Here, the surface temperature of the cooling head refers to the temperature of the contact surface between the cooling head and the heat sink of the laser component. Specifically, the first fan draws in air at ambient temperature, typically 20-25℃, to cool the radiator, reducing its surface temperature to 43℃. The operating temperatures of the blue and green laser components are below 65℃, requiring the heat sink fins to reach a temperature of 62℃-63℃, with a temperature difference of 2-3℃ between the heat sink fins and the laser component's heat sink. As can be seen, the temperature of the radiator is lower than that of the heat sink fins; therefore, the radiator is positioned at the front of the heat dissipation path, before the heat sink fins. The airflow generated by the fan's rotation dissipates heat from the radiator and then blows back onto the heat sink fins, still dissipating heat from the fins.

[0164] Similarly, since the lens's operating temperature is controlled at 85℃ and the heat sink fins' temperature is 63℃, both still lower than the lens's operating temperature, the second airflow after passing through the heat sink fins is still a cold airflow relative to the lens, which can be used for heat dissipation. However, the operating temperature of the circuit boards is generally higher than the lens's operating control temperature. Therefore, the airflow after cooling the lens is also still a cold airflow relative to most of the circuit boards, and can continue to flow through multiple circuit boards for heat dissipation.

[0165] In this example, the radiator, heat sink fins, lens, and circuit board have gradually increasing operating temperature thresholds. The above-mentioned structural layout also facilitates the design of heat dissipation paths. The heat dissipation airflow can flow from components with lower operating temperature thresholds to components with higher operating temperature thresholds. Multiple heat source components can be cooled sequentially in one heat dissipation path, which can not only meet the heat dissipation needs of multiple heat source components, but also achieve high overall heat dissipation efficiency.

[0166] In another specific implementation, in order to enhance the heat transfer coefficient, the heat dissipation fins can be improved by structural modifications on the fin surface to increase the heat dissipation area or by increasing the airflow velocity, thereby increasing the heat dissipation capacity.

[0167] In the laser projection device provided in the above embodiments, the luminous power range of the red laser component can be 24W to 56W, the luminous power range of the blue laser component can be 48W to 115W, and the luminous power range of the green laser component can be 12W to 28W. Preferably, the luminous power of the red laser component is 48W, the luminous power of the blue laser component is 82W, and the luminous power of the green laser component is 24W. All three lasers use MCL-type laser components, which significantly reduce the size compared to BANK-type lasers while maintaining the same output luminous power.

[0168] As explained above, in laser projection equipment, the heat dissipation requirements for the light source 100 are the most stringent, making it the part with relatively low operating temperature control in the entire device. Specifically, the operating temperature of the red laser component is lower than that of the blue and green laser components. This is determined by the light-emitting principle of red lasers. Blue and green lasers are generated using gallium arsenide luminescent materials, while red lasers are generated using gallium nitride luminescent materials. Red lasers have lower luminous efficiency and generate more heat. The temperature requirements for red laser luminescent materials are also more stringent. Therefore, when dissipating heat from the light source component composed of three-color lasers, different heat dissipation structures need to be designed according to the temperature requirements of different laser components. This ensures that each color laser operates in an optimal state, improves the lifespan of the laser components, and makes their luminous efficiency more stable.

[0169] Air cooling can control the temperature difference between the hot and cold ends of the heat source to around 3°C, while liquid cooling can control the temperature difference more precisely and within a smaller range, such as 1-2°C. Liquid cooling is used for red laser components with lower operating temperature thresholds, while air cooling is used for blue and red laser components with relatively higher operating temperature thresholds. This allows for cooling at a lower cost while meeting the operating temperature requirements of red lasers, achieving a smaller temperature difference control, thus reducing the required fan speed. However, the components used in liquid cooling are more expensive than those used in air cooling.

[0170] Therefore, in the laser projection device in this example, the heat dissipation of the light source adopts a hybrid heat dissipation method of liquid cooling and air cooling, which can meet the operating temperature control of different laser components while being economical and reasonable.

[0171] Specifically, see Figure 14 The metal substrate on the back of the red laser assembly 110 is connected to the cold head via a first heat-conducting block 613. The area of ​​the first heat-conducting block 613 is larger than the area of ​​the heat-conducting surface of the cold head, and the area of ​​the first heat-conducting block is also larger than the area of ​​the heat-conducting surface of the heat sink on the back of the red laser assembly 110. This facilitates the rapid concentration of heat from the heat sink of the laser assembly and its transfer to the cold head, thereby improving heat transfer efficiency.

[0172] exist Figure 14 In the heat dissipation system structure shown, the outlet of the cold head 610 is connected to the inlet of the radiator 611 via a pipe, and the outlet of the radiator 611 is connected to the inlet of the cold head 610 via a pipe. In the liquid cooling circulation system formed by the cold head 610, the radiator 611, and the pipes, a coolant replenisher 612 is also provided. As mentioned earlier, the coolant replenisher 612 is used to replenish the system circulation with coolant. Therefore, the coolant replenisher can be installed in multiple locations throughout the circulation system. Depending on factors such as system structure and space, there can be one or more coolant replenishers; they can be connected to the pump or placed close to the radiator.

[0173] In this example, the blue laser assembly and the green laser assembly operate at the same temperature and share a single heat sink structure. Specifically, as shown... Figure 15 and Figure 16 As shown, the heat sinks on the back of the blue laser assembly 120 and the green laser assembly 130 are in contact with the heat pipe 602 via a heat-conducting block 603, with the heat pipe 602 extending into the heat sink fins 601. For different colored laser assemblies, for example, the heat-conducting block 603 is designated as the second heat-conducting block for the blue laser assembly and the third heat-conducting block for the green laser assembly. The second and third heat-conducting blocks can be two independent components, each conducting heat for a different laser assembly, or they can be a single structure. This facilitates installation and allows for temperature control when the heat dissipation requirements of the two laser assemblies are the same.

[0174] In this embodiment, multiple heat pipes are used, preferably with the same number of heat pipes corresponding to the blue and green laser components. In this example, the heat pipes are straight, and multiple heat pipes are used. Multiple through holes are opened inside the heat sink fins for inserting multiple heat pipes. The heat sink fins 601 are positioned close to the blue and green laser components, allowing the multiple heat pipes to be inserted directly into the heat sink fins without bending. The straight heat pipes facilitate the reduction of transmission resistance during gas-liquid changes inside the heat pipes, thereby improving heat conduction efficiency.

[0175] The aforementioned combined heat dissipation structure effectively cools the light source components, ensuring their proper operation. The light source emits three-color lasers, providing a high-quality illumination beam that projects a bright, high-color image. Because the three-color laser components are arranged in different spatial positions, multiple optical lenses are required within the light source cavity to combine the laser beams from different directions and perform homogenization and other light processing.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser projection device, characterized in that, It includes a light source, an optical engine, and a lens; the light source is used to provide illumination for the optical engine, and the lens is used for projection imaging; The light source includes a red laser assembly, a green laser assembly, and a blue laser assembly, which emit red laser, green laser, and blue laser respectively. The red laser assembly is positioned close to the light source outlet; the blue laser and the green laser are first combined and then combined with the red laser; the divergence angle of the fast and slow axes of the red laser emitted by the red laser assembly is greater than the divergence angles of the blue laser and the green laser emitted by the blue laser and the green laser, respectively. A stationary diffuser is provided in the optical path of the combined blue laser and the green laser, or, stationary diffusers are provided for the blue laser and the green laser respectively, so that the blue laser and the green laser are first diverged and then combined with the red laser; A converging lens group is provided at the light outlet of the light source to reduce the spot size of the combined three-color laser beam before it is emitted from the light outlet of the light source. Furthermore, the laser projection device is equipped with a diffusion wheel and a light-collecting element. The diffusion wheel is a rotating diffusion plate located between the converging lens group and the light-collecting component, and is used to diffuse the converged tri-color laser beam. The light-collecting component is a light guide or a compound eye lens, used to homogenize the diffused three-color laser beam.

2. The laser projection device according to claim 1, characterized in that, The stationary diffuser is used to diffuse blue laser and / or green laser at an angle of 1 to 3 degrees.

3. The laser projection device according to claim 1, characterized in that, The diffusion wheel has at least two zones; wherein the red laser zone has the largest divergence angle and the blue laser zone has the smallest divergence angle, or the red laser zone has the largest divergence angle and the blue and green laser zones have the same divergence angle.

4. The laser projection device according to claim 3, characterized in that, The rotation period of the diffusion wheel is consistent with the timing period of the primary color light of the light source.

5. The laser projection device according to claim 1, characterized in that, The focal point of the converging lens assembly is set at the light-receiving port of the light-receiving element at the rear end.

6. The laser projection device according to claim 1, characterized in that, The red laser has a different polarization direction from the blue laser and the green laser. A half-wave plate is provided in the optical path before the blue laser and the green laser combine with the red laser. The half-wave plate is located inside the window opened on the light source housing for the laser assembly.

7. The laser projection device according to claim 6, characterized in that, The half-wave plate is a single piece, placed in the optical path after the blue laser and green laser beams are combined and before the red laser beams are combined; or, the half-wave plate is two pieces, respectively placed corresponding to the blue laser and the green laser.

8. The laser projection device according to claim 1, characterized in that, The red laser has a different polarization direction from the blue laser and the green laser. A half-wave plate corresponding to the red wavelength is provided before the red laser beam is combined with the blue and green laser beams. The half-wave plate is provided inside the window opened on the light source housing for the red laser component, or the half-wave plate is provided in the inner cavity of the light source, located between the inner side of the light source housing and the beam combiner corresponding to the red laser component.

9. The laser projection device according to claim 1, characterized in that, The red, blue, and green lasers are combined and then pass through a homogenizing element, which includes a diffuser sheet with microstructures on one or both sides.

10. The laser projection device according to any one of claims 1-9, characterized in that, The red laser assembly, the green laser assembly, and the blue laser assembly all include a laser and a PCB board disposed on the outer periphery of the laser. The laser includes multiple light-emitting chips packaged on a substrate.

Images