A DMD projection method for compensating dispersion

Abstract

The present invention relates to a dispersion compensation DMD projection method, comprising the following steps: projecting a light beam containing different wavelengths emitted by a projection light source onto a dispersion prism, so that the light beams of different wavelengths are irradiated on the DMD at different incident angles; controlling the states of each micromirror on the DMD according to the desired projected pattern; the DMD reflects the light beams of different wavelengths projected onto the surface of the DMD, and the light beams of different wavelengths at different incident angles are reflected by the DMD and are emitted at the same exit angle; the light beams of different wavelengths at different incident angles reflected by the DMD form the desired multi-wavelength pattern for projection at the projection surface position after passing through the projection objective lens. Compared with the prior art, the present invention proposes a dispersion compensation technology for the first time, and uses a dispersion prism to offset the dispersion generated by the projection light beam and the dispersion caused by the diffraction effect of the DMD, which has the advantages of higher light extraction efficiency, high projection color reproduction, complete spectral information, and clearer patterns.

Description

Technical Field

[0001] The invention relates to the technical field of projection display, and in particular to a dispersion compensation DMD projection method. Background Art

[0002] With the continuous advancement of science and technology, projection display technology has never stopped its development. At present, the most mainstream products in the projection market are based on LCD projection technology, LCOS projection technology and DLP projection technology. Among them, DLP technology is based on reflective DMD. Compared with the transmission projection method, the light efficiency is further improved. At the same time, the high-frequency flipping of DMD can make DLP projection products have higher contrast, clearer images, and stronger color reproduction capabilities. It is widely used in digital film projection, large-screen display, lithography, medical imaging, 3D printing, projectors and other fields.

[0003] The principle of the existing DMD-based DLP projection system is that the projection light source is processed and incident on the DMD device. The DMD loads the required projection pattern through the micromirror switch, and then uses the projection objective lens to project the image onto the projection screen. With the increase in market requirements for DLP projection resolution, DMD chips with smaller micromirrors and more micromirrors are used in DLP projection systems. For example, the DLP9000X chip produced by TI has a resolution of up to 2560×1600 and a micromirror size of only 7.6μm. However, the use of DMD with high resolution and small micromirror size leads to serious diffraction effects during the use of DLP. Since the diffraction angle of the light beam is related to the wavelength of the light beam, when light beams of different wavelengths are irradiated to the DLP projection system, the light beams will produce severe dispersion. At the same time, the optical system is a frequency domain low-pass filtering system. If light beams of different wavelengths have different angles after being emitted from the DMD, it cannot be guaranteed that these light beams of different wavelengths can pass through the subsequent optical system, resulting in the loss of some wavelengths of light beams during the transmission of the optical system. In particular, in a microscopic projection system, since the entrance pupil size of the microscope objective is severely limited, the frequency band range of the system is much smaller than that of an ordinary projection system, which easily causes the outgoing light of different angles to be unable to pass through the microscope objective at the same time, resulting in the spectral components of the projected image on the projection surface being inconsistent with the projection light source, resulting in the loss and distortion of the image spectral information, and in severe cases, the projected image may be blurred. In addition, since light beams of different wavelengths cannot all pass through the subsequent low-pass optical system, light energy loss will occur.

[0004] In summary, there is currently no method that can solve the problems of spectral information loss and distortion of projection images, image blur, and low light energy utilization caused by multi-wavelength light beam dispersion under high-resolution, small micro-mirror size DMD projection technology. Summary of the invention

[0005] The purpose of the present invention is to provide a dispersion compensating DMD projection method in order to overcome the defects of the above-mentioned prior art, so as to solve the problems of color distortion and spectral information distortion of the projection image, image blur and low light energy utilization rate caused by the dispersion phenomenon of multi-wavelength light beams under the DMD projection technology with high resolution and small micromirror size.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A dispersion compensation DMD projection method comprises the following steps:

[0008] The light beams with different wavelengths emitted by the projection light source are projected onto the dispersion prism, so that the light beams with different wavelengths are irradiated onto the DMD at different incident angles;

[0009] The states of the micromirrors on the DMD are controlled according to the desired projection pattern; the DMD reflects the light beams of different wavelengths projected onto the surface of the DMD, and the light beams of different wavelengths with different incident angles are reflected by the DMD and emitted at the same emission angle;

[0010] Light beams of different wavelengths at different incident angles reflected by the DMD form a desired multi-wavelength pattern for projection at the projection surface after passing through the projection objective lens.

[0011] Furthermore, the light beams of different wavelengths form different incident angles after passing through the dispersion prism and illuminate the DMD. The DMD reflects the light beams of different incident angles respectively and emits them at the same output angle.

[0012] Furthermore, the method also includes: selecting a dispersion prism so that the dispersion angle distribution curve of the dispersion prism matches the diffraction angle distribution curve of the DMD for the light beam, so that light beams with different incident angles are emitted at the same exit angle after being reflected by the DMD, thereby realizing dispersion compensation caused by the diffraction effect of the DMD.

[0013] Furthermore, the method also includes: adding a 4F system between the dispersion prism and the DMD to process the light beams of different wavelengths emitted by the dispersion prism so that the light spot areas of the light beams of different wavelengths overlap after being incident on the DMD surface.

[0014] Furthermore, the 4F system includes a first lens group and a second lens group distributed in sequence, and the light beams of different wavelengths emitted by the dispersion prism are sequentially passed through the first lens group and the second lens group and then irradiated onto the DMD, so that the light spot areas of the light beams of different wavelengths overlap after being incident on the DMD surface.

[0015] Furthermore, the first lens group and the second lens group are both cylindrical lenses, and the projection light beam is adjusted to an elliptical shape by the cylindrical lenses, so that the ratio of the major axis to the minor axis of the projection light beam is consistent with the aspect ratio of the DMD, thereby improving the utilization rate of light energy.

[0016] Furthermore, the method also includes: by adding a beam expansion system between the projection light source and the dispersion prism, adjusting the aperture of the output beam of the projection light source so that the aperture of the beam projected onto the DMD is suitable for the target surface size of the DMD.

[0017] Furthermore, the dispersion prism is a curved prism, the light-emitting surface of the curved prism is a curved surface, and the coincidence degree between the dispersion angle distribution curve of the dispersion prism and the diffraction angle distribution curve of the DMD is improved by the curved prism.

[0018] Furthermore, the dispersion prism is a prism with a grating microstructure, and the overlap between the dispersion angle distribution curve of the dispersion prism and the diffraction angle distribution curve of the DMD is improved by etching a grating structure on the surface.

[0019] Furthermore, the projection light source is one of an LED light source, a laser light source, and a halogen lamp.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention proposes a dispersion compensation technology for the first time, using a dispersion prism to offset the dispersion generated by the projection light beam and the dispersion caused by the diffraction effect of the DMD device, thereby solving the problems of color distortion, spectral information loss, and image blur caused by the diffraction of the DMD device itself, as well as the problem of light energy loss caused by the inability of all light beams of different wavelengths to pass through the subsequent low-pass optical system due to the different emission angles of the DMD. The present invention has higher light extraction efficiency, high projection color reproduction, complete spectral information, and clearer patterns.

[0022] (2) The present invention is the first to use a prism with a curved surface and a grating microstructure for dispersion compensation, which can increase the overlap of the dispersion angle distribution curves of the dispersion prism and the DMD diffraction, thereby improving the compensation effect.

[0023] (3) The present invention adds a 4F system in front of the DMD, which can converge all the projection light beams to the same position on the DMD target surface, thereby improving the utilization rate of light energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a flow chart of a dispersion compensation DMD projection method provided in Example 1 of the present invention

[0025] Figure 2An optical schematic diagram of a projection device corresponding to a dispersion compensation DMD projection method provided in Example 1 of the present invention;

[0026] Figure 3 A schematic diagram of the structure of a projection device corresponding to a dispersion compensation DMD projection method provided in Example 1 of the present invention;

[0027] Figure 4 An optical schematic diagram of a projection device corresponding to a dispersion compensation DMD projection method provided in Example 2 of the present invention;

[0028] Figure 5 A schematic diagram of the structure of a projection device corresponding to a dispersion compensation DMD projection method provided in Example 2 of the present invention;

[0029] Figure 6 An optical schematic diagram of a projection device corresponding to a dispersion compensation DMD projection method provided in Example 3 of the present invention;

[0030] FIG. 7( a ) is a schematic diagram of a curved dispersion prism provided in Example 5 of the present invention;

[0031] FIG7( b ) is a schematic diagram of a dispersion prism with a grating microstructure provided in Example 6 of the present invention;

[0032] Figure 8 It is an optical schematic diagram of a projection device corresponding to the dispersion compensation DMD projection method in Example 5 of the present invention;

[0033] Fig. 9 It is an optical schematic diagram of a projection device corresponding to the dispersion compensation DMD projection method in Example 6 of the present invention;

[0034] FIG10( a ) is a schematic diagram of an output image of a DMD (3) without dispersion compensation provided in Example 1 of the present invention;

[0035] FIG10( b ) is a schematic diagram of an output image of a DMD (3) for compensating for dispersion provided in Example 1 of the present invention;

[0036] Fig.11 is a graph showing the relationship between different wavelengths and the emission angles of the light beam after passing through the DMD (3) of the present invention;

[0037] FIG12( a ) is a diagram showing the relationship between different wavelengths and the emission angles of a light beam after passing through a dispersion prism provided in Example 1 of the present invention;

[0038] FIG12( b ) is a diagram showing the relationship between different wavelengths and the emission angles of a light beam after passing through a curved dispersive prism provided in Example 5 of the present invention;

[0039] In the figure, 1, projection light source, 2, dispersion prism, 21, plane prism, 22, curved prism, 23, prism with grating microstructure, 3, DMD, 4, projection objective, 5, projection image plane, 6, 4F system, 61, the first lens group of 4F system, 62, the second lens group of 4F system, 7, beam expansion system, 71, the front lens group of beam expansion system, 72, the rear lens group of beam expansion system. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0043] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0044] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0045] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0046] Example 1

[0047] like Figure 1 As shown, this embodiment provides a dispersion compensation DMD projection method, comprising the following steps:

[0048] S1: Projecting light beams containing different wavelengths emitted by the projection light source 1 onto the dispersion prism 2, so that the light beams of different wavelengths are irradiated onto the DMD 3 at different incident angles;

[0049] S2: Control the states of each micromirror on DMD3 according to the desired projection pattern; DMD3 reflects the light beams of different wavelengths projected onto the surface of DMD3, and the light beams of different wavelengths with different incident angles are reflected by DMD3 and emitted at the same emission angle, thereby achieving dispersion compensation;

[0050] Regarding the selection of DMD3 and dispersion prism 2, this solution selects dispersion prism 2 so that the dispersion angle distribution curve of dispersion prism 2 matches the diffraction angle distribution curve of DMD3 for the light beam.

[0051] Specifically, light beams of different wavelengths form different incident angles after passing through the dispersion prism 2 and illuminate the DMD3. DMD3 reflects the light beams with different incident angles respectively, as shown in Figure 12. Since the diffraction angle distribution curve of the light beam by DMD3 matches the dispersion angle distribution curve of the dispersion prism 2, the light beams with different incident angles will be emitted at the same exit angle, thereby achieving dispersion compensation.

[0052] S3: Light beams of different wavelengths at different incident angles reflected by DMD3 pass through projection objective lens 4 to form a desired multi-wavelength pattern at the projection surface.

[0053] The projection light source 1 can be selected from one of an LED light source, a laser light source, and a halogen lamp.

[0054] In this embodiment, the projection light source 1 is a two-color LED light source, and the dispersion prism 2 is a plane prism 21;

[0055] The working principle of this embodiment is as follows: the projection light source 1 emits light beams with wavelengths of 480nm and 632nm, which are projected onto the dispersion prism 2. The dispersion prism 2 has a low Abbe number, and light beams of different wavelengths are deflected at different angles after entering the prism, which can be used to compensate for the problem of non-overlapping projection patterns caused by the diffraction of the DMD 3.

[0056] Optionally, in this embodiment, the incident angle of the dispersion prism is 50°, and the wavelengths of 480nm and 632nm light beams after passing through the dispersion prism produce a 2° exit angle difference, and are finally irradiated on DMD 3; at the same time, the size of DMD 3 is 12.4mm×19.6mm, and the resolution is 1920×1080, which is used to load the required projection pattern and modulate the light beam with a 2° dispersion compensation angle irradiated on DMD 3. The spot utilization rate of the projection light beam on DMD 3 is ≥56%, and the dual-wavelength projection overlap area is >80%. The projection objective 4 projects the dispersion-corrected light beam modulated by DMD 3 onto the projection image plane 5 to form the modulated final projection image. Figure 3 It is a structural diagram of this embodiment.

[0057] In this embodiment, a comparative experiment is conducted to verify the scheme without dispersion compensation and the scheme with dispersion prism 2 for dispersion compensation. As shown in FIG10( a ), the projection image of DMD 3 without dispersion compensation occurs. It can be seen that the projection image of light beams of different wavelengths produces serious dispersion, resulting in misalignment and blurring of the projection image. As shown in FIG10( b ), the projection image of DMD 3 with dispersion compensation occurs. Compared with FIG10( a ), it can be seen that the dispersion compensation scheme of this embodiment corrects the problems of color distortion, loss of spectral information, and image blurring of the projection image.

[0058] Example 2

[0059] This embodiment is substantially the same as Embodiment 1, except that Figure 4 and 5 As shown, the dispersion compensation DMD projection method of this embodiment also includes processing the light beams of different wavelengths emitted by the dispersion prism 2 by adding a 4F system 6 between the dispersion prism 2 and the DMD 3, so that the light spot areas of the light beams of different wavelengths overlap after being incident on the surface of the DMD 3, thereby improving the utilization rate of light energy. Its structure includes: a projection light source 1, a dispersion prism 2, a DMD 3, a projection objective 4, a projection image plane 5, and a 4F system 6. The light beams of different wavelengths emitted by the dispersion prism 2 are irradiated on the DMD 3 after passing through the 4F system 6, so that the surface of the DMD 3 is at a position where the overlap of light beams of different wavelengths is the highest, thereby improving the utilization rate of light energy.

[0060] Optionally, in this embodiment, the 4F system 6 includes two doublet lenses, both with a focal length of 150 mm and a total optical axis length of 600 mm. Figure 4 is an optical schematic diagram of this embodiment, Figure 5 It is a schematic diagram of the structure of this embodiment.

[0061] Specifically, the 4F system 6 includes a first lens group 61 and a second lens group 62 which are distributed in sequence. Light beams of different wavelengths emitted by the dispersion prism 2 pass through the first lens group 61 and the second lens group 62 in sequence and then irradiate the DMD3, so that the light spot areas of the light beams of different wavelengths overlap after being incident on the surface of the DMD3.

[0062] Preferably, the first lens group 61 and the second lens group 62 are both cylindrical lenses, and the projection beam is adjusted to an elliptical shape by the cylindrical lenses, so that the ratio of the major axis to the minor axis of the projection beam is consistent with the aspect ratio of the DMD3, thereby improving the utilization rate of light energy.

[0063] Example 3

[0064] This embodiment is substantially the same as the embodiment 1, except that the dispersion compensation DMD projection method of this embodiment further includes adjusting the exit beam aperture of the projection light source 1 by adding a beam expansion system 7 between the projection light source 1 and the dispersion prism 2, so that the beam aperture projected onto the DMD 3 is suitable for the target surface size of the DMD 3. Its structure includes: a projection light source 1, a dispersion prism 2, a DMD 3, a projection objective lens 4, a projection image plane 5, and a beam expansion system 7. The beam expansion system 7 is composed of a beam expansion system front lens group 71 and a beam expansion system rear lens group 72.

[0065] Optionally, in this embodiment, the focal length of the front lens group of the beam expansion system 7 is 20 mm, the focal length of the rear lens group is 40 mm, and the beam expansion ratio is 2.

[0066] Example 4

[0067] This embodiment is substantially the same as the embodiment 1, except that the dispersion compensation DMD projection method in this embodiment further includes: increasing the utilization rate of light energy by adding a 4F system 6 between the dispersion prism and the DMD 3, and adding a beam expansion system 7 between the projection light source and the dispersion prism to shape the projection light source. Its structure includes: a projection light source 1, a dispersion prism 2, a 4F system 6, a DMD 3, a projection objective lens 4, a projection image plane 5, and a beam expansion system 7.

[0068] Example 5

[0069] This embodiment is substantially the same as the embodiment 1, except that, as shown in FIG. 7( a ) and Figure 8As shown, in this embodiment, the dispersion prism 2 adopts a curved prism 22, and the overall structure includes a projection light source 1, a curved prism 22, a DMD3, a projection objective 4, and a projection image plane 5; and the schemes using a plane prism 21 and a curved prism 22 are experimentally compared, and the relationship between different wavelengths and the output angle after the light beam passes through the DMD 3 is analyzed; as shown in Figure 12(a), it is a relationship diagram between different wavelengths and the output angle after the light beam passes through the plane prism 21, and it can be seen that the wavelength and the output angle are nonlinearly related; as shown in Figure 12(b), it is a relationship diagram between different wavelengths and the output angle after the light beam passes through the curved prism 22, and it can be seen that the wavelength and the output angle are linearly related. Combining with the output light beam of DMD3 can improve the overlap of the dispersion curve and achieve a better compensation effect.

[0070] Example 6

[0071] This embodiment is substantially the same as the embodiment 1, except that, as shown in FIG. 7( b ) and Fig. 9 As shown, in this embodiment, the dispersion prism 2 adopts a prism 23 with a grating microstructure, and the overall structure includes a projection light source 1, a prism 23 with a grating microstructure, a DMD 3, a projection objective 4, and a projection image plane 5. The prism 23 with a grating microstructure improves the overlap between the dispersion angle distribution curve of the dispersion prism 2 and the diffraction angle distribution curve of the DMD 3 by etching a grating structure on the surface.

[0072] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A dispersion compensation DMD projection method, characterized in that: The following steps are involved: The light beams having different wavelengths emitted by the projection light source (1) are projected onto the dispersion prism (2), so that the light beams having different wavelengths are irradiated onto the DMD (3) at different incident angles; The states of the micromirrors on the DMD (3) are controlled according to the desired projection pattern; the DMD (3) reflects light beams of different wavelengths projected onto the surface of the DMD (3), and light beams of different wavelengths at different incident angles are reflected by the DMD (3) so as to be emitted at the same emission angle; Light beams of different wavelengths at different incident angles reflected by the DMD (3) pass through a projection lens (4) to form a desired multi-wavelength pattern at a projection surface position; The light beams of different wavelengths pass through the dispersion prism (2) to form different incident angles and illuminate the DMD (3), and the DMD (3) reflects the light beams of different incident angles respectively and emits them at the same output angle; The method further comprises: selecting a dispersion prism (2) so that the dispersion angle distribution curve of the dispersion prism (2) matches the diffraction angle distribution curve of the light beam by the DMD (3), so that light beams with different incident angles are emitted at the same emission angle after being reflected by the DMD (3), thereby achieving dispersion compensation caused by the diffraction effect of the DMD.

2. A dispersion compensation DMD projection method according to claim 1, characterized in that: The method further comprises: adding a 4F system (6) between the dispersion prism (2) and the DMD (3) to process light beams of different wavelengths emitted by the dispersion prism (2) so that the light spot areas of the light beams of different wavelengths overlap after being incident on the surface of the DMD (3).

3. A dispersion compensation DMD projection method according to claim 2, characterized in that: The 4F system (6) comprises a first lens group (61) and a second lens group (62) which are arranged in sequence. Light beams of different wavelengths emitted by the dispersion prism (2) pass through the first lens group (61) and the second lens group (62) in sequence and then irradiate the DMD (3), so that the light spot areas of the light beams of different wavelengths overlap after being incident on the surface of the DMD (3).

4. A dispersion compensation DMD projection method according to claim 3, characterized in that: The first lens group (61) and the second lens group (62) are both cylindrical lenses, and the projection light beam is adjusted into an elliptical shape by the cylindrical lenses, so that the ratio of the major axis to the minor axis of the projection light beam is consistent with the aspect ratio of the DMD (3), thereby improving the utilization rate of light energy.

5. The dispersion compensation DMD projection method according to claim 1, characterized in that: The method further comprises: adjusting the aperture of the output light beam of the projection light source (1) by adding a beam expansion system (7) between the projection light source (1) and the dispersion prism (2) so that the aperture of the light beam projected onto the DMD (3) is suitable for the target surface size of the DMD (3).

6. The dispersion compensation DMD projection method according to claim 1, characterized in that: The dispersion prism (2) is a curved prism (22), the light-emitting surface of the curved prism (22) is a curved surface, and the overlap between the dispersion angle distribution curve of the dispersion prism (2) and the diffraction angle distribution curve of the DMD (3) is improved by the curved prism (22).

7. The dispersion compensation DMD projection method according to claim 1, characterized in that: The dispersion prism (2) is a prism (23) with a grating microstructure, and the overlap between the dispersion angle distribution curve of the dispersion prism (2) and the diffraction angle distribution curve of the DMD (3) is improved by etching a grating structure on the surface.

8. The dispersion compensation DMD projection method according to claim 1, characterized in that: The projection light source (1) is one of an LED light source, a laser light source and a halogen lamp.

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