Projection optical system and laser projection equipment

Abstract

The invention discloses a projection optical system and laser projection equipment. The projection optical system comprises a projection light source, a first illumination light path, a phase light modulation device, an optical coupling array, a second illumination light path, a display device and a lens. A laser light source emitted by the projection light source is shaped by the first illumination light path and then enters the phase light modulator for phase modulation, a modulated diffracted light beam enters the light coupling array, and the light coupling array not only can couple primary-order diffracted light into the second illumination light path, but also can couple secondary-order diffracted light into the second illumination light path. In addition, at least one level of high-order diffraction light can be coupled into a second illumination light path, so that more diffraction light can be used for a subsequent imaging light path, and the optical efficiency is improved. The energy distribution of the diffracted light beam entering the second illumination light path is modulated according to the brightness distribution of the to-be-displayed image, and after amplitude modulation is carried out through the display device, the brightness-darkness contrast in the displayed image can be remarkably improved, and the display requirement of HDR is met.

Description

Technical Field

[0001] This application relates to the field of projection display technology, and in particular to a projection optical system and a laser projection device. Background Technology

[0002] LCD displays use light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs) as backlights. The backlight can be divided into multiple zones, and the brightness of the light source in each zone can be controlled independently. This allows the light intensity of each backlight zone to be controlled according to the brightness distribution of the displayed image, thereby improving the contrast of the displayed image.

[0003] Laser projection systems use laser light sources, which consistently output illumination with a fixed beam size and as a single beam. Therefore, they cannot be divided into zones, unlike LCD displays which can affect image contrast. To achieve a backlight zoning effect similar to that of LCD displays, phase light modulation (PLM) devices can be incorporated into the projection system. These devices utilize light diffraction to modulate the phase distribution of the laser beam, ultimately achieving a backlight zoning effect and significantly improving dynamic contrast.

[0004] Due to limitations in pixel size and fill rate of PLM devices, some incident light in the output light field distribution of a PLM is diffracted to higher orders. These higher-order diffracted lights cannot enter the subsequent optical system, resulting in some energy loss and a loss of optical efficiency. Summary of the Invention

[0005] This application provides a projection optical system, including: Projection light source, used to emit three primary color lasers; The first illumination optical path is located on the light-emitting side of the projection light source and is used to shape the laser beam emitted from the projection light source. A phase-modulated light device, located on the light-emitting side of the first illumination optical path, is used to perform phase modulation on the incident laser beam according to the image to be displayed; The second illumination optical path is located on the light-emitting side of the phase light modulation device and is used to shape the incident laser beam. An optical coupling array, located between the phase light modulator and the second illumination optical path, is used to couple the primary diffracted light and at least one first-order higher-order diffracted light emitted from the phase light modulator to the second illumination optical path. A display device, located on the light-emitting side of the second illumination optical path, is used to modulate the amplitude of the incident laser beam according to the image to be displayed, forming an image beam for projection imaging; and The lens, located on the light-emitting side of the display device, is used to project and image the image beam.

[0006] In some embodiments of this application, the optical coupling array includes multiple optical coupling units, each of which is arranged in a circle and has a hollow structure at its center. The primary diffracted light emitted from the phase modulation device passes through the hollow structure and enters the second illumination optical path; at least one higher-order diffracted light emitted from the phase modulation device enters the optical coupling unit at the corresponding position and is coupled to the second illumination optical path by the optical coupling unit.

[0007] In some embodiments of this application, each of the optical coupling units is arranged symmetrically along the side and diagonal of the phase light modulation device.

[0008] In some embodiments of this application, the optical coupling unit is a total internal reflection prism, which includes an incident surface, a total internal reflection surface, and an exit surface. At least one first-order diffracted light emitted from the phase light modulation device is incident on the incident surface into the interior of the total internal reflection prism, incident on the total internal reflection surface, reflected by the total internal reflection surface to the emitting surface, and emitted through the emitting surface into the second illumination light path.

[0009] In some embodiments of this application, the incident surface of the total internal reflection prism is parallel to the optical axis of the second illumination path; the angle between the incident surface and the total internal reflection surface satisfies: ; in, This indicates the angle between the incident surface and the total reflection surface. This represents the angle of incidence when the higher-order diffracted light is incident on the incident surface. The value represents the F-number of the higher-order diffracted light incident on the total internal reflection prism, and n represents the refractive index of the total internal reflection prism.

[0010] In some embodiments of this application, the optical coupling unit is a concave reflector; the slope change of the region of the concave reflector near the phase light modulation device is less than the slope change of the region near the second illumination optical path.

[0011] In some embodiments of this application, the optical coupling unit is a plane mirror; the plane mirror is tilted relative to the optical axis of the second illumination optical path, and the tilt angle of the plane mirror is such that at least one first-order higher-order diffracted light is reflected towards the second illumination optical path.

[0012] In some embodiments of this application, the divergence angle of the higher-order diffracted light coupled by the optical coupling array satisfies: ; in, This represents the angle between the edge rays of the higher-order diffracted light coupled by the optical coupling array and the optical axis of the second illumination optical path. The f-number represents the lens number, r represents the aperture of the lens closest to the optical coupling array in the second illumination optical path, and f represents the focal length of the lens.

[0013] In some embodiments of this application, the spacing between the optical coupling array and the second illumination optical path satisfies the following: ; Wherein, d represents the distance between the optical coupling array and the second illumination optical path, and f represents the focal length of the lens in the second illumination optical path that is closest to the optical coupling array.

[0014] This application also provides a laser projection device, including: case; A projection optical system is located within the housing, and the projection optical system is any of the projection optical systems described above.

[0015] The projection optics system and laser projection device provided in this application include a projection light source, a first illumination optical path, a phase light modulator, an optical coupling array, a second illumination optical path, a display device, and a lens. The laser light emitted from the projection light source is shaped by the first illumination optical path and then enters the phase light modulator for phase modulation. The modulated diffracted beam then enters the optical coupling array. The optical coupling array can couple not only the principal order diffracted light into the second illumination optical path but also at least one higher order diffracted light, thereby allowing more diffracted light to be used in the subsequent imaging optical path, improving optical efficiency. The energy distribution of the diffracted beam entering the second illumination optical path is modulated according to the brightness distribution of the image to be displayed. After amplitude modulation by the display device, the contrast between bright and dark areas in the displayed image can be significantly improved, meeting the display requirements of HDR. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the projection system provided in an embodiment of this application; Figure 2 This is one of the schematic diagrams of the architecture of a projection optical system in related technologies; Figure 3 This is the second schematic diagram of the architecture of a projection optical system in related technologies; Figure 4 This is a schematic diagram of the energy distribution of diffracted light provided in an embodiment of this application; Figure 5 This is one of the schematic diagrams of the architecture of the projection optics system provided in the embodiments of this application; Figure 6 This is one of the structural schematic diagrams of a laser provided in the embodiments of this application; Figure 7 This is a second schematic diagram of the laser structure provided in the embodiments of this application; Figure 8 This is a schematic diagram of the combined light from the projection light source provided in an embodiment of this application; Figure 9 A schematic diagram illustrating the phase modulation principle of the phase optical modulation device provided in this application embodiment; Figure 10 A flowchart of phase processing provided for embodiments of this application; Figure 11 This is one of the structural schematic diagrams of the optical coupling array provided in the embodiments of this application; Figure 12 For along Figure 11 A schematic diagram of the cross-sectional structure of the optical coupling unit in the I-I' direction; Figure 13 This is a second schematic diagram of the structure of the optical coupling array provided in the embodiments of this application; Figure 14 For along Figure 13 A schematic diagram of the cross-sectional structure of the optical coupling unit in the I-I' direction; Figure 15 This is the third schematic diagram of the structure of the optical coupling array provided in the embodiments of this application; Figure 16 For along Figure 15 A schematic diagram of the cross-sectional structure of the optical coupling unit in the I-I' direction; Figure 17 This is a second schematic diagram of the architecture of the projection optics system provided in the embodiments of this application. Detailed Implementation

[0018] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction described in this application are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this application. The accompanying drawings of this application are for illustrating relative positional relationships only and do not represent actual scale.

[0019] Projection display technology is a technique that uses optical systems and projection space to magnify and display images. The projection system ultimately displays the image using an optical imaging system. With the continuous development of projection technology, laser projection systems, with their unique advantages, have been widely used in large-screen displays, laser TVs, digital cinemas, and portable projection displays. Laser projection displays can display more realistic and vibrant dynamic images on ultra-large screens, achieving a visually stunning effect that other display technologies cannot achieve.

[0020] Projection systems can be divided into front projection systems and rear projection systems. In a front projection system, the projector and the viewer are located on the same side of the projection screen. The projector emits projection light onto the screen, and the light is reflected back to the viewer, thus displaying the projected image. In a rear projection system, the projector and the viewer are located on opposite sides of the screen. The projector emits projection light onto the screen, and the screen transmits the light back to the viewer, thus displaying the projected image.

[0021] The present invention will be described using a front-projection system as an example. Figure 1 This is a schematic diagram of the projection system provided in an embodiment of the present invention.

[0022] like Figure 1 As shown, a front-projection system may include a projection device 100 and a projection screen 200.

[0023] The projection screen 200 is located on the light-emitting side of the projection device 100. The audience faces the projection screen 200. The projection device 100 emits projection light, which enters the projection screen 200 and is reflected back to the audience's location, so that the audience can see the projected image.

[0024] Figure 2 This is a schematic diagram of the overall architecture of a projection optics system. Figure 2As shown, the projection device may include: a projection light source 11, an illumination light path s, a display device 12, a total reflection prism group 13, and a lens 14.

[0025] The projection light source 11 is used to provide illumination, and the color gamut, overall brightness, and other characteristics of the projected image are all affected by the projection light source 11. In specific implementations, the projection light source 11 can be a mercury lamp, a light-emitting diode (LED), or a laser light source.

[0026] The illumination light path s is located on the light-emitting side of the projection light source 11 and is used to shape and homogenize the light beam emitted from the projection light source 11.

[0027] The display device 12 is used to modulate the amplitude of the incident illumination beam according to the image data of the image to be displayed, thereby generating an image beam.

[0028] Lens 14 is located on the light-emitting side of display device 12 and is used to project the image beam emitted by display device 12 to form an image on the projection surface (such as projection screen 200) that is suitable for human eye viewing.

[0029] The display device 12 can be a digital micromirror device (DMD). When the display device 12 uses a DMD, there are special requirements for the size and angle of the incident beam. Therefore, the beam emitted from the projection light source 11 needs to be shaped and homogenized before it enters the display device 12. For example Figure 2 As shown, to achieve beam shaping and homogenization, the illumination optical path s needs to include a beam adjustment lens group s01, a homogenizing element s02, and a focusing lens group s03. The beam adjustment lens group s01 can be a telescopic lens group to reduce the incident beam; the homogenizing element s02 can be a light guide or a compound eye lens group. Figure 2 The diagram illustrates a homogenizing element s02 using a compound eye lens group as an example. The homogenizing element s02 is used to homogenize the incident light beam. In order to meet the light spot size and incident angle of the incident display device 12, a focusing lens group s03 is also required to focus the light beam. After focusing, the projected light beam is totally reflected by the total internal reflection prism group 13 and modulated to the display device 12.

[0030] Currently, mainstream displays typically use LCDs. LCDs are non-self-emissive displays and require LEDs or OLEDs as backlights. The backlight of an LCD can be divided into multiple zones, and the brightness of the light source in each zone can be controlled independently. This allows the light intensity of each backlight zone to be controlled according to the brightness distribution of the displayed image, thereby improving the contrast of the displayed image.

[0031] For projection optics systems, the projection light source 11 always provides illumination output according to a certain beam size and as a whole beam. Therefore, it cannot be divided into zones and cannot affect image contrast like an LCD monitor. The light in the black areas of the displayed image is reflected into the inactive area by the DMD, resulting in light power loss, making it difficult to meet the display requirements of High Dynamic Range (HDR).

[0032] In order to enable the projection optics system to achieve an effect similar to backlight zoning, such as Figure 3 As shown, a phase light modulation (PLM) device 15 can be set in the projection optical system to modulate the phase distribution of the illumination beam by light diffraction, thereby achieving the effect of backlight zoning and significantly improving dynamic contrast.

[0033] However, due to limitations in pixel size and fill rate of PLM devices, the light field distribution output by PLM devices, such as... Figure 4 As shown, it includes both principal diffracted light (MB) and higher-order diffracted light (NB). The subsequent optical system is designed based on the principal diffracted light. These higher-order diffracted lights cannot enter the subsequent optical system, resulting in some energy loss and optical efficiency loss.

[0034] In view of this, embodiments of this application provide a projection optical system that can collect higher-order diffracted light into the subsequent imaging optical path, thereby improving optical efficiency.

[0035] like Figure 5 As shown, the projection optical system provided in this application embodiment includes: a projection light source 11, a first illumination optical path s1, a phase light modulation device 15, an optical coupling array 30, a second illumination optical path s2, a display device 12, a total reflection prism group 13, and a lens 14.

[0036] The projection light source 11 can be a laser light source, which is used to emit three primary color lasers. In specific implementations, the laser light source may include one or more lasers that can emit three color lasers, or it may include multiple lasers that emit monochromatic lasers; this is not limited here.

[0037] Taking the example that each laser can emit three colors of laser light, a laser is usually packaged with multiple laser chips in a single package structure to emit laser light of different wavelengths.

[0038] like Figure 6 and Figure 7As shown, the laser 111 may include multiple laser chips, which are divided into a first laser chip 111r, a second laser chip 111b, and a third laser chip 111g. The lasers emitted by the first laser chip 111r, the second laser chip 111b, and the third laser chip 111g have different wavelengths.

[0039] In some embodiments, such as Figure 6 As shown, the number of first laser chips 111r is greater than the number of second laser chips 111b, and also greater than the number of third laser chips 111g. The first laser chips 111r are arranged in two rows, the second laser chips 111b are arranged in one row, and the third laser chips 111g are arranged in one row. The three types of laser chips are arranged in a 4×7 array.

[0040] In some embodiments, such as Figure 7 As shown, the number of first laser chips 111r is greater than the number of second laser chips 111b, and also greater than the number of third laser chips 111g. Four first laser chips 111r are arranged in one row, and two second laser chips 111b and three third laser chips 111g are arranged in another row.

[0041] Optionally, the first laser chip 111r can be a red laser chip that emits red laser light; the second laser chip 111b can be a blue laser chip that emits blue laser light; and the third laser chip 111g can be a green laser chip that emits green laser light.

[0042] It is worth noting that, Figure 6 and Figure 7 The arrangement of laser chips shown is for illustrative purposes only. In actual applications, the types of laser chips included in laser 111, the wavelength of laser emitted by each laser chip, the number of each laser chip, and the arrangement are not limited.

[0043] The laser source also includes a beam combining component 112, located on the light-emitting side of the laser 111, for combining the three-color laser light emitted from the laser 111. This is assuming the laser source includes only one... Figure 6 Taking the laser shown as an example, the specific structure of the light combining component 112 will be illustrated. Figure 8 As shown, the light combining component 112 may include a first light combining member 112a, a second light combining member 112b, a third light combining member 112c, and a fourth light combining member 112d.

[0044] The first light combiner 112a and the second light combiner 112b are located on the light-emitting side of the two rows of first laser chips 111r, respectively. The third light combiner 112c is located on the light-emitting side of the second laser chip 111b, and the fourth light combiner 112d is located on the light-emitting side of the third laser chip 111g.

[0045] Among them, the first laser chip 111r emits red laser, the second laser chip 111b emits blue laser, and the third laser chip 111g emits green laser.

[0046] The first beam combiner 112a reflects the red laser emitted from the first row of first laser chips 111r towards the second beam combiner 112b. The second beam combiner 112b combines the red lasers emitted from the two rows of first laser chips 111r and emits them towards the third beam combiner 112c. The second beam combiner 112b can be a polarization beam combiner. In this case, a phase delay element needs to be set on the light-emitting side of the second row of first laser chips 111r to convert the red laser emitted from the second row of first laser chips 111r from p-polarized light to s-polarized light. By utilizing the property of the polarization beam combiner to transmit p-polarized light and reflect s-polarized light, the red p-polarized light emitted from the first row of first laser chips 111r and the s-polarized light converted from the second row of first laser chips 111r are combined.

[0047] The third light combiner 112c and the fourth light combiner 112d can be wavelength combining elements. In some embodiments, the third light combiner 112c and the fourth light combiner 112d can be dichroic filters or dichroic film layers. The third light combiner 112c can combine the red laser emitted from the first laser chip 111r with the blue laser emitted from the second laser chip 111b and output it to the fourth light combiner 112d. The fourth light combiner 112d can combine the red laser, the blue laser, and the green laser emitted from the third laser chip 111g.

[0048] Continue to refer to Figure 5 A first illumination optical path s1 is also provided on the light-emitting side of the projection light source 11. The first illumination optical path s1 is used to shape the laser beam emitted from the projection light source 11 before it is incident on the phase light modulation device 15. In some embodiments, such as Figure 5 As shown, the first illumination optical path s1 can be a collimating lens group composed of two lenses. The collimating lens group can be located on the light-emitting side of the light combining component of the projection light source 11 to collimate the incident laser beam. The collimated laser beam is then incident on the phase light modulation device 15, which helps to reduce the design difficulty of the phase light modulation device and improve the diffraction efficiency of the phase light modulation device.

[0049] The phase light modulator 15 is located on the light-emitting side of the first illumination light path s1. It is used to perform phase modulation on the incident laser beam according to the image to be displayed, so that the light intensity distribution of the modulated light on the incident surface of the display device 12 matches the brightness distribution of the image to be displayed. The area with higher brightness of the image to be displayed receives a greater light intensity illuminating the corresponding area of ​​the display device, and the area with lower brightness of the image to be displayed receives a smaller light intensity illuminating the corresponding area of ​​the display device, thereby improving the brightness contrast of the displayed image.

[0050] In practical implementation, the phase light modulation device 15 can be a transmissive device or a reflective device. The reflective phase modulation device can not only play the role of phase modulation of the incident beam, but also fold the optical path and reduce the length of the projection system in the same direction.

[0051] The phase modulation device 15 in this embodiment is a reflective device, such as... Figure 9 As shown, the phase light modulation device 15 may include: a plurality of dimming units u arranged in an array, each dimming unit u including: a driving component and a reflector mounted on the driving component; the driving component is used to drive the reflector to move in a direction perpendicular to the reflective surface of the reflector, thereby causing a phase change in the reflected light. Figure 9 As shown, based on the brightness distribution of the image to be displayed, the phase light modulator 15 pre-adjusts the intensity distribution of the light beam incident on the display device. Combined with the amplitude modulation of the incident beam by the display device, this allows for brighter areas to be displayed even brighter, and darker areas to be displayed even darker, thereby improving the contrast and enhancing the display effect. Simultaneously, the phase light modulator 15 can also redirect light rays that should be incident on areas with lower brightness to areas with higher brightness, thus preventing energy loss.

[0052] If the light beam emitted from the projection light source 11 and projected onto the phase modulation device 15 is called the laser beam, and the light beam incident on the display device 12 after phase modulation by the phase modulation device 15 is called the illumination beam, then the amplitude distribution of the illumination beam at the light-incident surface of the display device 12 after phase modulation by the phase modulation device 15 is the desired image. The complex amplitude distribution of the illumination beam at the light-incident surface of the display device 12 after phase modulation by the phase modulation device 15 is: ; in, This indicates the amplitude distribution of the laser beam at the light incident surface of the display device 12 after phase modulation by the phase light modulator 15. This represents the phase distribution of the laser beam at the incident surface of the display device 12 after phase modulation by the phase modulation device 15. Complex amplitude distribution. The desired distribution after phase modulation by the phase-modulated light device 15, therefore and All are known quantities, so the complex amplitude The quantity is known.

[0053] Once the structure of the laser source is determined, the amplitude and phase of the light rays at various positions in the laser beam provided by that source can be determined. In this case, the complex amplitude distribution of the laser beam provided by the laser source is as follows: ; in, This indicates the amplitude distribution of the laser beam provided by the laser source; This represents the phase distribution of the laser beam before phase modulation by the PLM. Because... and All of these can be obtained through measurement; therefore, the complex amplitude function The quantity is known.

[0054] The phase modulation device 15 changes the phase distribution of the laser beam through phase modulation, and the new phase distribution of the illumination beam is obtained as follows: ; in, This indicates the amount by which the PLM changes the phase distribution of the laser beam; This indicates the position of each mirror in the PLM. Phase superposition of laser beams. The new complex amplitude distribution is then obtained as follows: ; After the laser beam is phase-modulated by the PLM, the complex amplitude distribution... With complex amplitude distribution The following conditions must be met: ; in, This represents the Fourier transform, i.e., the transformation of the complex amplitude distribution. After performing a Fourier transform, the complex amplitude distribution can be obtained. ; This represents the inverse Fourier transform, i.e., the transformation of the complex amplitude distribution. After performing the inverse Fourier transform, the complex amplitude distribution can be obtained. .

[0055] Therefore, through complex amplitude distribution With complex amplitude distribution The phase distribution that the PLM needs to be adjusted can then be derived. Therefore, based on the phase distribution that the PLM needs to be adjusted, the height of each mirror in the PLM on the reflecting surface perpendicular to the PLM can be determined.

[0056] Based on complex amplitude distribution With complex amplitude distribution The phase distribution that the PLM needs to adjust can be determined using phase recovery algorithms such as the Yang-Gu algorithm (YG algorithm), the Gerchberg-Saxton algorithm (GS algorithm), and the simulated annealing algorithm. .

[0057] Taking the GS algorithm as an example, such as Figure 10 As shown, the specific steps include: S1. Initialize random phase The measured spatial domain amplitude A forms a complex amplitude distribution. ; S2. Perform a Fourier transform on the complex amplitude f to obtain... Preserve the obtained phase The complex amplitude is obtained by combining the desired amplitude B. ; S3. Perform an inverse Fourier transform on the complex amplitude g to obtain... Preserve the obtained phase The measured spatial domain amplitude A is combined to form a new complex amplitude distribution f used in the next iteration; Repeat steps S2 and S3 above until the maximum number of iterations is met, and finally obtain the phase. This allows us to obtain the phase distribution that the phase modulation device 15 needs to adjust. .

[0058] When designing the phase distribution to be adjusted in the phase modulation device 15, the +1st or -1st order diffracted light is usually used as the principal order diffracted light. Higher order diffracted light refers to diffracted light of a higher order than the principal order. The energy of higher order diffracted light is lower than that of the principal order diffracted light, and the higher the order, the lower the energy. Therefore, when considering the collection of higher order diffracted light in this application, the main target is the first-order higher order diffracted light adjacent to the principal order diffracted light.

[0059] Specifically, such as Figure 5 As shown in the embodiment of this application, an optical coupling array 30 is also provided between the phase light modulator 15 and the second illumination optical path s2. The optical coupling array 30 is used to couple the primary diffraction light emitted from the phase light modulator 15 and at least one first-order higher-order diffraction light into the second illumination optical path.

[0060] Optical coupling arrays need to be based on, for example Figure 4The diffraction light energy distribution shown is designed such that the light spot in the central region is the principal order diffraction light with the strongest energy; the light spots around the central light spot are significantly less bright than the central light spot, and these surrounding light spots are higher order diffraction light. The function of the optical coupling array 30 is to transmit the principal order diffraction light and collect the higher energy orders among these higher order diffraction lights for subsequent projection imaging, thereby improving optical efficiency.

[0061] In specific implementation, such as Figure 11 As shown, the optical coupling array 30 includes multiple optical coupling units 301, each of which can be configured according to... Figure 4 The partitions shown are arranged in a circle, resulting in a hollow structure K at the center. The primary diffracted light emitted from the phase modulation device 15 passes through the hollow structure K and enters the second illumination optical path s2, while at least one higher-order diffracted light emitted from the phase modulation device 15 enters the corresponding optical coupling unit 301 and is coupled to the second illumination optical path s2 by the optical coupling unit 301.

[0062] Continue to refer to Figure 4 Typically, the phase light modulator 15 is rectangular, and its pixel units (such as mirrors) are arranged in an array along the long and short sides of the rectangle. Therefore, the order of the diffracted light emitted from the phase light modulator 15 is also symmetrically distributed along the long, short, and diagonal directions of the phase light modulator. Figure 11 As shown, when arranging the optical coupling units 301, each optical coupling unit 301 is arranged symmetrically along the sides (long and short sides) and diagonal of the phase light modulation device 15. Among them, Figure 11 The x-direction is parallel to the long side of the phase light modulator, the y-direction is parallel to the short side of the phase light modulator, and the direction intersecting the x-direction and y-direction is the diagonal direction of the phase light modulator.

[0063] In some embodiments, such as Figure 11 and Figure 12 As shown, the optical coupling unit 301 uses a total internal reflection prism. The total internal reflection prism is usually designed according to the incident direction and the exit direction of the first-order higher-order diffracted light.

[0064] Specifically Figure 12 For along Figure 11 A schematic diagram of the cross-sectional structure of the total internal reflection prism in the I-I' direction is shown below. Figure 12As shown, the total internal reflection prism can be classified as having an incident surface 3011, a total internal reflection surface 3012, and an exiting surface 3013. One of the first-order higher-order diffracted lights emitted from the phase light modulation device 15 enters the interior of the total internal reflection prism through the incident surface 3011, enters the total internal reflection surface 3012, is reflected by the total internal reflection surface 3012 to the exiting surface 3013, and exits into the second illumination light path through the exiting surface 3013.

[0065] When designing the angles and refractive indices of each surface of a total internal reflection prism, it is necessary to reverse the propagation direction of the higher-order diffracted light incident on the obliquely incident total internal reflection prism so that the optical axis of the higher-order diffracted light emitted from the light-emitting surface is parallel to the optical axis of the principal and secondary diffracted light.

[0066] Specifically, the refractive index n of a total internal reflection prism is determined by the material. For example, when the total internal reflection prism uses H-ZBAF52 glass, n = 1.67. Different types of display devices typically require different illumination F-numbers F / #. For instance, when display device 12 uses a 0.23-inch DMD, the required illumination F-number is 1.8. Therefore, the F-number of the higher-order diffracted light to be recovered can be defined as... =1.8.

[0067] In air, the maximum lateral expansion angle of light originating from a finite-sized light source or diverging beam is considered to be the maximum lateral expansion angle of the diffracted light emitted from a phase-modulated light device, which can also be considered to originate from a finite-sized light source or diverging beam. =1.8, then = 15.52 degrees. Correspondingly, the aperture angle in the total internal reflection prism medium... .

[0068] If the refractive index of a total internal reflection prism is n, then the critical angle at which total internal reflection occurs when light incident on the prism reaches its interface is n. For example, when n=1.67, the critical angle for total internal reflection is... 36.78 degrees.

[0069] like Figure 12 As shown, the incident angle when the diffracted light is incident on the incident surface 3011 of the total internal reflection prism is... The angle of refraction after entering the total internal reflection prism is According to the principle of similar triangles, the angle between the incident surface and the total reflection surface of a total internal reflection prism is... The angle of incidence of the diffracted light refracted into the interior of the total internal reflection prism and incident on the total internal reflection surface 3012 is... According to the principle of total internal reflection: The diffracted light will undergo total internal reflection at the total internal reflection surface 3012. If the divergence angle of the diffracted light is considered, then the following must be satisfied: The angle of reflection of the diffracted light after being reflected by the total internal reflection surface 3012 is... The angle of incidence when the reflected ray is reflected to the light-emitting surface 3013 is The final exit angle when exiting the total internal reflection prism is .

[0070] According to the geometric relationships of triangles: , According to the law of refraction, we can obtain: Based on the above relationships, we can conclude that: ; in, Indicates the angle between the incident surface and the total internal reflection surface. This represents the angle of incidence when the higher-order diffracted light is incident on the incident plane. The F-number represents the higher-order diffracted light incident on the total internal reflection prism, and n represents the refractive index of the total internal reflection prism.

[0071] Based on the refractive index n of the total internal reflection prism, the F-number of the diffracted light, and the incident angle of the diffracted light. The apex angle of the total internal reflection prism is designed according to the above geometric and optical constraints. and bottom corner .

[0072] For example, if the refractive index of a total internal reflection prism is n=1.67, the base angle of the total internal reflection prism... =27 degrees, the angle of incidence when higher-order diffracted light is incident on the incident surface of a total internal reflection prism. =34 degrees, then the angle of refraction when the diffracted light is refracted into the interior of the total internal reflection prism =19.56 degrees. According to the phase triangle and the principle of corresponding angles, we know... =27 degrees, the incident angle of the diffracted light onto the total internal reflection surface is Based on the angular relationships of triangles, we can obtain: =46.56 degrees, =46.56 degrees. The angle of incidence when the reflected diffracted light exits the optical surface. At the same time, there is an angular relationship. , Therefore, we can conclude that: Ultimately, we can conclude that =21.70 degrees, =38.14 degrees. Therefore, the apex angle of the total internal reflection prism is... =24.86 degrees. This completes the design of the total internal reflection prism.

[0073] In some embodiments, such as Figure 13 and Figure 14As shown, the optical coupling unit 301 uses a concave mirror. The concave mirror not only reflects light but also images the incident light. Therefore, the concave mirror can convert higher-order diffracted light into light parallel to the principal order diffracted light, thereby further improving optical efficiency.

[0074] In specific implementation, such as Figure 14 As shown, the slope change of the region of the concave mirror (optical coupling unit 301) near the phase light modulation device is less than the slope change of the region near the second illumination optical path. That is, the slope change of the concave mirror along the propagation direction of higher order diffracted light becomes faster and faster, which can satisfy the light recovery of more higher order gradient diffraction angles.

[0075] In some embodiments, such as Figure 15 and Figure 16 As shown, the optical coupling unit 301 is a plane mirror. The plane mirror is tilted relative to the optical axis of the second illumination optical path. The tilt angle of the plane mirror is such that the incident light of at least one first-order higher-order diffracted light is reflected into light that propagates parallel to the optical axis of the second illumination optical path.

[0076] In practical implementation, the design angle of the plane mirror is similar to that of the total reflection surface of the total reflection prism. However, it is necessary to consider that the plane mirror may block light rays parallel to the optical axis of the principal diffracted light. Therefore, when installing and adjusting the plane mirror, the position of the plane mirror needs to be precisely aligned.

[0077] Continue to refer to Figure 5 The principal diffracted light and at least one first-order higher-order diffracted light are collected and incident on the second illumination path, such as... Figure 5 As shown, the second illumination optical path s2 may include a first lens s21, a second lens s22, a third lens s23, and a fourth lens s24. The first lens s21 and the second lens s22 are used to adjust the size of the incident diffracted beam, while the third lens s23 and the fourth lens s24 are used to focus the diffracted beam toward the display device 12. A reflector s25 may also be provided in the second illumination optical path s2 to deflect the direction of the light path, thereby reducing the size of the optical system.

[0078] This application only illustrates the number and shape of lenses in the first illumination optical path s1 and the second illumination optical path s2. In practical applications, the number, type, and shape of lenses in the first illumination optical path s1 and the second illumination optical path s2 can be optimized according to the actual optical path design requirements, and no limitation is made here.

[0079] like Figure 5As shown, a total reflection prism group 13 is also provided between the second illumination light path s2 and the display device 12. The total reflection prism group 13 is used to reflect the light beam emitted from the second illumination light path s2 toward the display device 12. After the display device 12 modulates the amplitude of the incident light beam to form an image beam, the image beam passes through the total reflection prism group 13 and enters the lens 14.

[0080] The display device 12 can be a transmissive light modulator or a reflective light modulator. Figure 5 The display device 12 shown is a reflective light modulator, such as a liquid crystal on silicon (LCoS) or a digital micromirror device (DMD).

[0081] LCoS is a semiconductor technology that involves bonding a Complementary Metal Oxide Semiconductor (CMOS) substrate to a glass substrate containing transparent electrodes, followed by liquid crystal encapsulation. LCoS features high aperture ratio and high resolution for each pixel, enabling the formation of high-resolution images.

[0082] The DMD consists of many tiny mirrors, each of which can be individually driven to deflect. By controlling the deflection angle of the DMD, the brightness of the light incident on the lens 14 can be controlled.

[0083] In this embodiment of the invention, the display device 12 may employ a DMD. After the DMD modulates the amplitude of the incident light to form an image, it emits the light towards the lens 14, which then forms an image, thereby projecting the image to a suitable size for viewing.

[0084] It is understandable that the F-number of the illumination beam illuminating the display device 12 should be greater than the F-number of the lens, so as to collect all the light emitted from the display device into the lens for imaging. Therefore, in order to effectively utilize the higher-order diffracted light recovered by the optical coupling array 30, the F-number of the recovered higher-order diffracted light also needs to be greater than the lens's F-number of 4, so that it can be collected by the lens. If the divergence angle of the recovered higher-order diffracted light is... Then, the constraint relationship between it and the lens F-number should satisfy:

[0085] in, The angle between the edge rays of the higher-order diffracted light coupled by the optical coupling array 30 and the optical axis of the second illumination path is called the divergence angle. Indicates the F-number of the lens.

[0086] The divergence angle of the collected higher-order diffracted light also needs to be smaller than the aperture angle of the lens closest to the second illumination path (i.e., the first lens s21) so that the collected higher-order diffracted light can enter the first lens: ; in, denoted by r, which represents the angle between the edge ray of the higher-order diffracted light coupled by the optical coupling array 30 and the optical axis of the second illumination optical path; r represents the half-aperture of the lens (i.e., the first lens s21) closest to the optical coupling array in the second illumination optical path; and f represents the focal length of the lens.

[0087] The spacing between the optical coupling array and the second illumination optical path must also meet the following requirements: ; Where d represents the distance between the optical coupling array and the second illumination optical path, and f represents the focal length of the lens in the second illumination optical path that is closest to the optical coupling array.

[0088] The optical coupling array is positioned beyond one focal length of the first lens s21 to meet the imaging requirements of the first lens. Simultaneously, setting the distance between the optical coupling array and the first lens within the aforementioned range avoids setting the aperture of the first lens too large, thus preventing increased costs. In specific implementations, the distance between the optical coupling array and the first lens can be set to less than 10mm.

[0089] Phase-modulated light devices are diffractive elements, and their highest diffraction efficiency can only be achieved when incident at a set angle. Furthermore, due to the diffractive optical working principle of phase-modulated light devices, zero-order diffraction exists in the modulated beam. This zero-order diffraction creates an unmodulated bright spot at the center of the diffracted light, causing a decrease in uniformity and modulation accuracy, severely affecting the display effect.

[0090] To avoid the effects of zero-order diffraction, such as Figure 17 As shown, a total internal reflection prism group can be set between the phase light modulator 15 and the optical coupling array 30. In order to distinguish it from the total internal reflection prism group set near the display device, the total internal reflection prism group set near the display device is called the first total internal reflection prism group, and the total internal reflection prism group located between the phase light modulator 15 and the optical coupling array 30 is called the second total internal reflection prism group 16.

[0091] like Figure 17As shown, the second total internal reflection prism group 16 can totally reflect the laser beam emitted from the first illumination optical path s1 to the phase light modulator at an optimal angle, so that the phase light modulator can achieve the highest diffraction efficiency. When designing the phase of the phase light modulator 15, an additional beam tilt phase can be added to separate the diffracted beam and the zero-order beam, resulting in an angle between the diffracted beam emitted from the phase light modulator 15 and the zero-order beam. The diffracted beam, after passing through the second total internal reflection prism group 16, is incident on the optical coupling array 30, which couples the primary diffracted beam and at least one higher-order diffracted beam into the second illumination optical path. The zero-order beam, after passing through the second total internal reflection prism group 16, is deflected outside the imaging optical path, thereby avoiding the influence of the zero-order light spot on the projected image. The second total internal reflection prism group 16 can adjust the direction of the incident and emitted light of the phase light modulator, allowing the laser, phase light modulator, and display device in the projection light source to be arranged in parallel. This allows for a repositioning of the associated circuit boards, which helps to reduce the size of the projection device.

[0092] Based on the same inventive concept, this application also provides a laser projection device, which includes a housing and a projection optical system located within the housing. The projection optical system is the projection optical system provided in any of the above embodiments.

[0093] The projection optical system includes a projection light source, a first illumination optical path, a phase modulation device, an optical coupling array, a second illumination optical path, a display device, and a lens. The laser light emitted from the projection light source is shaped by the first illumination optical path and then enters the phase modulation device for phase modulation. The modulated diffracted beam then enters the optical coupling array. The optical coupling array can couple not only the principal order diffracted light into the second illumination optical path, but also at least one higher order diffracted light, thereby allowing more diffracted light to be used in the subsequent imaging optical path, improving optical efficiency. The energy distribution of the diffracted beam entering the second illumination optical path is modulated according to the brightness distribution of the image to be displayed. After amplitude modulation by the display device, the contrast between bright and dark areas in the displayed image can be improved, meeting the display requirements of HDR.

[0094] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0095] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A projection optical system, characterized in that, include: Projection light source, used to emit three primary color lasers; The first illumination optical path is located on the light-emitting side of the projection light source and is used to shape the laser beam emitted from the projection light source. A phase-modulated light device, located on the light-emitting side of the first illumination optical path, is used to perform phase modulation on the incident laser beam according to the image to be displayed; The second illumination optical path is located on the light-emitting side of the phase light modulation device and is used to shape the incident laser beam. An optical coupling array, located between the phase light modulator and the second illumination optical path, is used to couple the primary diffracted light and at least one first-order higher-order diffracted light emitted from the phase light modulator to the second illumination optical path. A display device, located on the light-emitting side of the second illumination optical path, is used to modulate the amplitude of the incident laser beam according to the image to be displayed, forming an image beam for projection imaging; and The lens, located on the light-emitting side of the display device, is used to project and image the image beam.

2. The projection optical system as described in claim 1, characterized in that, The optical coupling array includes multiple optical coupling units, which are arranged in a circle with a hollow center. The primary and secondary diffracted light emitted from the phase light modulator passes through the hollow structure and enters the second illumination optical path; At least one first-order diffracted light emitted from the phase modulation device is incident on the optical coupling unit at the corresponding position and coupled to the second illumination optical path by the optical coupling unit.

3. The projection optical system as described in claim 2, characterized in that, Each of the optical coupling units is arranged symmetrically along the side and diagonal of the phase light modulation device.

4. The projection optical system as described in claim 2, characterized in that, The optical coupling unit is a total internal reflection prism, which includes an incident light surface, a total internal reflection surface, and an exit light surface. At least one first-order diffracted light emitted from the phase light modulation device is incident on the incident surface into the interior of the total internal reflection prism, incident on the total internal reflection surface, reflected by the total internal reflection surface to the emitting surface, and emitted through the emitting surface into the second illumination light path.

5. The projection optical system as described in claim 4, characterized in that, The incident surface of the total internal reflection prism is parallel to the optical axis of the second illumination path; the angle between the incident surface and the total internal reflection surface satisfies: ； in, This indicates the angle between the incident surface and the total reflection surface. This represents the angle of incidence when the higher-order diffracted light is incident on the incident surface. The value represents the F-number of the higher-order diffracted light incident on the total internal reflection prism, and n represents the refractive index of the total internal reflection prism.

6. The projection optical system as described in claim 2, characterized in that, The optical coupling unit is a concave reflector; the slope change of the region of the concave reflector near the phase light modulation device is less than the slope change of the region near the second illumination optical path.

7. The projection optical system as described in claim 2, characterized in that, The optical coupling unit is a plane mirror; the plane mirror is tilted relative to the optical axis of the second illumination optical path, and the tilt angle of the plane mirror is such that at least one first-order higher-order diffracted light is reflected into the second illumination optical path.

8. The projection optical system as described in any one of claims 1 to 7, characterized in that, The divergence angle of the higher-order diffracted light coupled by the optical coupling array satisfies: ； in, This represents the angle between the edge rays of the higher-order diffracted light coupled by the optical coupling array and the optical axis of the second illumination optical path. The f-number represents the lens number, r represents the aperture of the lens closest to the optical coupling array in the second illumination optical path, and f represents the focal length of the lens.

9. The projection optical system as described in any one of claims 1 to 7, characterized in that, The spacing between the optical coupling array and the second illumination optical path satisfies the following: ； Wherein, d represents the distance between the optical coupling array and the second illumination optical path, and f represents the focal length of the lens in the second illumination optical path that is closest to the optical coupling array.

10. A laser projection device, characterized in that, include: case; A projection optical system is located within the housing, and the projection optical system is the projection optical system according to any one of claims 1 to 9.

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