WO2021037239A1

WO2021037239A1 - Projection optical system

Info

Publication number: WO2021037239A1
Application number: PCT/CN2020/112244
Authority: WO
Inventors: 杜鹏; 王则钦; 李屹
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2019-08-29
Filing date: 2020-08-28
Publication date: 2021-03-04
Also published as: CN112445050A; CN112445050B

Abstract

Disclosed is a projection optical system, comprising a light source (1), a light-splitting and -combining device (2), a first spatial light modulator (31), and a second spatial light modulator (32), wherein the light source (1) is used for emitting an illuminating beam that comprises a plurality of sub-beams; the light-splitting and -combining device (2) comprises a light-splitting surface (S1) and a light-combining surface (S2), and the plurality of sub-beams have different incident angles to the light-splitting surface (S1); and the incident angle of any sub-beam to the light-splitting surface (S1) is equal to or substantially equal to the incident angles of the first sub-beam and the second sub-beam, corresponding to the sub-beam, to the light-combining surface (S2). The light energy loss during the light splitting and combining of the illuminating beam can be reduced, thereby improving the output brightness of the system.

Description

A projection optical system

Technical field

This application relates to the field of optical technology, in particular to a projection optical system.

Background technique

In the field of low-end cinema projectors and high-end engineering projectors, users have a great demand for dual-chip optical engines. Compared with the three-chip high-end projector, the two-chip optical engine can achieve a 12-bit projection gray scale, and can reduce the cost; compared with the single-chip engineering projector, the two-chip optical engine can achieve Higher brightness and grayscale. Therefore, for the dual-chip optical engine system, only by achieving higher optical efficiency can its advantages be realized.

The inventor of the present application discovered in the long-term research and development process that, in the prior art, the incident light in the two-chip optical engine has a spectrum loss during the light splitting and combining process, so the separated red fluorescence and green fluorescence are more colored Well, it is close to the standard color coordinates of DCI-P3, so the number of red and green lasers added is limited, so that although the whole machine can achieve the color gamut standard of the projector, the brightness that can be achieved is limited.

Summary of the invention

The main technical problem solved by the present application is to provide a projection optical system that can reduce the light loss during light splitting and combining, so as to improve the output brightness of the projection optical system.

In order to solve the above technical problems, a technical solution adopted in this application is to provide a projection optical system, which includes: a light source, a light splitting and combining device, a first spatial light modulator, and a second spatial light modulator; wherein The light source is used to emit an illuminating beam, and the illuminating beam includes multiple sub-beams; the light splitting and combining device includes a light splitting surface and a light combining surface. The multiple sub-beams have different incident angles to the light splitting surface. The light splitting surface is used to divide each sub beam into the first sub Light beam and second sub-beam, the first sub-beam enters the first spatial light modulator, the second sub-beam enters the second spatial light modulator, the light combining surface is used to combine the first sub-beam emitted by the first spatial light modulator and The second sub-beam emitted by the second spatial light modulator is combined into an emergent light beam;

Wherein, the difference between the incident angle of any one of the sub-beams to the light-splitting surface and the incident angles of the first sub-beam and the second sub-beam corresponding to the sub-beams to the light-combining surface is less than a preset threshold.

Wherein, the light splitting and light combining device includes a first optical part and a second optical part that are adjacently arranged. One part of the surfaces adjacent to the first optical part and the second optical part is provided with a light splitting surface, and the other part is provided with a light combining surface. The optical part is used to guide the illumination beam to the beam splitter, and the second sub-beam is guided to the second spatial light modulator after M reflections, where M is an even number greater than or equal to 2; the second optical part is used to transfer the first The sub-beam is guided to the first spatial light modulator after N reflections, where N is an even number greater than or equal to 2.

Wherein, the first optical part includes a first prism and a second prism that are adjacently arranged, the surface adjacent to the first prism and the second prism is a first total reflection surface, and the first prism is opposite to the first total reflection surface The set surface is a second total reflection surface, and the second sub-beams are reflected to the second spatial light modulator after passing through the second total reflection surface and the first total reflection surface in sequence.

Wherein, the second optical part includes a third prism and a fourth prism that are adjacently arranged, the surface adjacent to the third prism and the fourth prism is the third total reflection surface, and the surface of the third prism opposite to the third total reflection surface It is the fourth total reflection surface, and the first sub-beam is reflected to the first spatial light modulator after passing through the fourth total reflection surface and the third total reflection surface in sequence.

Wherein, the light splitting and light combining device further includes a fifth prism, and the fifth prism includes a first surface adjacent to the second total reflection surface of the first prism, and a second surface perpendicular to the main optical axis of the illumination beam.

Among them, the illuminating light beam includes the first color light, the second color light and the third color light. The beam splitting surface transmits the first color light according to the wavelength characteristics, and reflects the second color light and the third color light. The light combining surface responds to the first color light according to the wavelength characteristics. The light transmits and reflects the second color light and the third color light.

Wherein, the projection optical system also includes an optical relay system, which is located between the light source and the light splitting and combining device, and is used for concentrating the illuminating light beam to a predetermined range.

Among them, the light source is a polarized light source.

Among them, the beam splitting surface divides each sub-beam into a first sub-beam and a second sub-beam according to the polarization characteristics; the light combining surface emits the first sub-beam and the second sub-beam emitted by the first spatial light modulator according to the polarization characteristics The second sub-beam is combined into the outgoing beam.

Wherein, the incident angle of any sub-beam of the illumination beam on the beam splitting surface is smaller than the total reflection angle of the beam splitting surface.

The beneficial effect of the embodiments of the present application is that the projection optical system of the present application includes: a light source, a light splitting and combining device, a first spatial light modulator, and a second spatial light modulator. In the projection optical system, the light source emits an illuminating beam, which is divided into multiple sub-beams, and the multiple sub-beams have different incident angles to the light splitting surface. The light splitting surface divides each sub-beam into a first sub-beam and a second sub-beam. The first sub-beam and the second sub-beam enter the light combining surface after being modulated by the first spatial light modulator or the second spatial light modulator. The incident angle of any sub-beam on the light splitting surface is equal to or substantially the same as the incident angle of the first sub-beam and the second sub-beam corresponding to the sub-beam on the light combining surface. In this way, the transmittance curve of the illuminating beam is approximately the same during light combining and light splitting, which can reduce light loss, and further increase the output brightness of the projection optical system.

Description of the drawings

Fig. 1 is a schematic structural diagram of a first embodiment of a projection optical system according to the present application;

Figure 2 is a color gamut coordinate diagram of the projection optical system of the present application;

3 is a schematic structural diagram of a second embodiment of the projection optical system of the present application;

FIG. 4 is a graph of coating curves of an embodiment of the light splitting surface and the light combining surface in the projection optical system of the present application.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

Example one

Please refer to FIG. 1. FIG. 1 is a schematic structural diagram of the first embodiment of the projection optical system of the present application. The projection optical system includes: a light source 1, a light splitting and combining device 2, a first spatial light modulator 31, and a second spatial light modulator器32.

The light source 1 is used to emit an illuminating light beam, which contains at least two primary colors of light. Wherein, the light source 1 may include solid-state light sources such as laser diodes and light emitting diodes. The illumination beam includes a plurality of sub-beams. When the illuminating beam is incident on the light splitting and combining device 2, there are multiple incident angles. In the embodiment of the present invention, a small beam of light with the same incident angle is used as a sub-beam.

The light splitting and combining device 2 is used to compensate the optical path difference of the illumination beam, total reflection of the illumination beam, color separation, and synthesis of image light. The light splitting and combining device 2 includes a light splitting surface S1 and a light combining surface S2. The multiple sub-beams have different incident angles to the beam splitting surface S1. The dichroic surface S1 is used to divide each sub-beam incident on the dichroic surface S1 into a corresponding first sub-beam and a second sub-beam. The beam splitting surface S1 transmits the first sub-beam and reflects the second sub-beam. The first sub-beam enters the first spatial light modulator 31, and the second sub-beam enters the second spatial light modulator 32. The light combining surface S2 is used for combining the first sub-beam emitted by the first spatial light modulator 31 and the second sub-beam emitted by the second spatial light modulator 32 into an outgoing beam and then emitted. The first spatial light modulator 31 and the second spatial light modulator 32 are mirror-symmetrical about the light combining surface S2.

Since the light splitting surface S1 and the light combining surface S2 are usually coated devices, their light transmittance characteristics are closely related to the angle of light incident on the light splitting surface S1 and the light combining surface S2. The difference in the angle of incidence easily leads to inconsistent light transmittance characteristics, resulting in a lot of light loss. In order to reduce the light loss, in this embodiment, the incident angle of any one of the sub-beams of the illumination beam to the light splitting surface S1 and the difference between the incident angles of the first and second sub-beams corresponding to the sub-beam to the light combining surface S2 The value is less than the preset threshold. The preset threshold can be 1 degree, 3 degrees, 5 degrees, etc., which can be specifically set according to actual needs. It can also be understood that the incident angle of each sub-beam on the light-splitting surface S1 is equal to or substantially the same as the incident angle of the sub-beam to the light-combining surface S2 after light splitting, reflection, and modulation.

It can be understood that, in this embodiment, the multiple sub-beams include a first edge beam and a second edge beam, and the incident angle of the first edge beam on the beam splitting surface S1 is smaller than the incident angle of the second edge beam on the beam splitting surface S1. That is, the first edge beam corresponds to a small incident angle on the beam splitting surface S1, and the second edge beam corresponds to a large incident angle on the beam splitting surface S1. After the first edge beam is split, reflected, and modulated, the incident angle of the first edge beam to the light combining surface S2 still corresponds to a small incident angle. After the second edge beam is split, reflected, and modulated, the incident angle of the second edge beam to the light combining surface S2 still corresponds to a large incident angle.

By making the incident angle of each sub-beam in the illumination beam equal or substantially the same on the beam splitting surface S1 and the light combining surface S2, the transmittance characteristics of any sub beam at the beam splitting surface S1 and the light combining surface S2 can be kept consistent, thereby reducing light The loss of energy can in turn achieve higher output brightness of the system.

Specifically, the light-splitting and light-combining device 2 includes a first optical part and a second optical part that are adjacently arranged. One part of the surfaces adjacent to the first optical part and the second optical part is provided with a light-splitting surface S1, and the other part is provided with a light-combining surface. S2. The first optical part is used to guide the illumination beam emitted by the light source 1 to the light splitting surface S1 and guide the second sub-beam to the second spatial light modulator 32. The second optical part is used to guide the first sub-beam to the first spatial light modulator 31.

Wherein, the incident angle of the illuminating light beam on the light splitting surface S1 is related to the relative position of the light source 1 and the light splitting and combining device 2. By setting the positional relationship between the light source 1 and the light splitting and combining device 2, the size of the incident angle of any sub-beam in the illumination beam to the light splitting surface S1 can be controlled. The incident angle of any sub-beam in the illumination beam to the beam splitting surface S1 is smaller than the total reflection angle of the beam splitting surface S1.

In this embodiment, the light splitting surface S1 and the light combining surface S2 are on the same plane. In order to make the incident angle of any sub-beam of the illumination beam on the beam splitting surface S1 equal or substantially the same as the incident angle of the sub-beam exiting the light combining surface S2 after splitting, reflection, and modulation, the first sub-beam and the second sub-beam When the sub-beams are reflected to the light-combining surface S2, they have to undergo an odd number of reflections. Specifically, the first optical part needs to guide the second sub-beam to the second spatial light modulator 32 after M reflections, where M is an even number greater than or equal to 2, for example, M is 2, 4, etc., the second spatial light modulator The device 32 modulates the second sub-beam and then reflects the modulated second sub-beam carrying image information to the light combining surface S2. The second optical part needs to guide the first sub-beam to the first spatial light modulator 31 after N reflections, where N is an even number greater than or equal to 2, for example, N is 2, 4, etc., the first spatial light modulator 31 After the first sub-beam is modulated, the modulated first sub-beam carrying image information is reflected to the light combining surface S2.

In a specific embodiment, the first optical part includes a first prism 21 and a second prism 22 that are adjacently arranged, and the surface adjacent to the first prism 21 and the second prism 22 is the first total reflection surface 211, The first total reflection surface 211 totally reflects the light whose incident angle is greater than the first threshold. The surface of the first prism 21 opposite to the first total reflection surface 211 is the second total reflection surface 212, and the second total reflection surface 212 totally reflects light whose incident angle is greater than the second threshold. Optionally, a reflective film may be plated on the first total reflection surface 211 and the second total reflection surface 212 to achieve the reflection function. It is also possible to provide an air gap between the adjacent surfaces of the first prism 21 and the second prism 22 to enable the first total reflection surface 211 to achieve a reflection function.

The second optical part includes a third prism 23 and a fourth prism 24 adjacently arranged. The surface adjacent to the third prism 23 and the fourth prism 24 is a third total reflection surface 231. The third total reflection surface has an incident angle greater than that of the first Three-threshold light total reflection. The surface of the third prism 23 opposite to the third total reflection surface 231 is the fourth total reflection surface 232, and the fourth total reflection surface 232 totally reflects the light whose incident angle is greater than the fourth threshold. Optionally, a reflective film may be plated on the third total reflection surface 231 and the fourth total reflection surface 232 to realize the reflection function. It is also possible to provide an air gap between the adjacent surfaces of the third prism 23 and the fourth prism 24 to enable the third total reflection surface 231 to achieve a reflection function.

The first prism 21 guides the illumination beam to the beam splitting surface S1. The beam splitting surface S1 divides each sub-beam into a first sub-beam that is transmitted and a second sub-beam that is reflected. The second sub-beams sequentially pass through the second total reflection surface 212. After being reflected by the first total reflection surface 211, it enters the second spatial light modulator 32, and the first prism 21 and the second prism 22 reflect the second sub-beam emitted from the second spatial light modulator 32 to the light combining surface S2. The first sub-beam enters the first spatial light modulator 31 after being sequentially reflected by the fourth total reflection surface 232 and the third total reflection surface 231 in the third prism 23. The third prism 23 and the fourth prism 24 then guide the first sub-beam emitted by the first spatial light modulator 31 to the light combining surface S2. The light combining surface S2 combines the first sub-beam and the second sub-beam into an outgoing light beam and then emits it.

In this embodiment, both the first sub-beam and the second sub-beam are incident on the light combining surface S2 after being reflected three times. Wherein, the incident angle of any one of the sub-beams of the illumination beam on the light-splitting surface S1 is equal to or substantially the same as the incident angle of the sub-beam entering the light-combining surface S2 after light splitting and reflection. In this way, the coating characteristics of the light splitting surface S1 and the light combining surface S2 can be consistent during coating, so that the transmittance curves of the illuminating beam during light splitting and light combining are basically the same, so that no loss of light energy can be achieved.

In this embodiment, the propagation paths of any sub-beams are on the same plane. Therefore, the light splitting and combining device 2 of this embodiment adopts a plane light routing method, that is to say, in this embodiment, the light splitting and light splitting of any sub-beam in the illumination beam The reflection and combination of light are in the same plane.

Further, the light splitting surface S1 is disposed on the adjacent surface of the first prism 21 and the third prism 23, and is used to divide the illumination beam into a first sub-beam and a second sub-beam according to wavelength characteristics. The beam splitting surface S1 can be a wavelength beam splitter or other optical elements that can split any sub-beam into a first sub-beam and a second sub-beam, such as a light-splitting coating layer. In this embodiment, the illuminating light beam includes the first color light, the second color light and the third color light, and the light splitting feature of the light splitting surface S1 may be to transmit the first color light and reflect the second color light and the third color light. In a specific embodiment, the first color light is red light, the second color light is blue light, and the third color light is green light. In other alternative embodiments, the first color light may also be blue light, the second color light may be red light, and the third color light may be green light or the like. It can be understood that the above are only examples of the first color light, the second color light, and the third color light, and the first color light, the second color light, and the third color light are not limited to the above examples.

The light combining surface S2 is arranged on the adjacent surface of the second prism 22 and the fourth prism 24, and is used to transmit the first sub-beam emitted by the first spatial light modulator 31 and the second sub-beam emitted by the second spatial light modulator 32. The beams are combined to exit the beams and then exit. The light combining surface S2 may be a wavelength combining sheet or other optical element that can combine the first sub-beam emitted by the first spatial light modulator 31 and the second sub-beam emitted by the second spatial light modulator 32 to emit the emitted light beam. , Such as Heguang coating layer. The light combining surface S2 may be configured to transmit the first color light and reflect the second color light and the third color light. In this embodiment, the first color light may be red light, the second color light may be blue light, and the third color light may be green light. In other embodiments, the characteristics of the light combining surface S2 can also be set to transmit the second color light, reflect the first color light and the third color light, and so on. It can be understood that the above are only examples of the first color light, the second color light, and the third color light, and the first color light, the second color light, and the third color light are not limited to the above examples.

The first prism 21 may be a prism of any shape including the first total reflection surface 211, the second total reflection surface 212, and the dichroic surface S1, such as a prism in the shape of a quadrangular prism. When the shape of the first prism 21 is a quadrangular prism, the first total reflection surface 211 and the second total reflection surface 212 are opposed to each other, and the light splitting surface S1 connects the first total reflection surface 211 and the second total reflection surface 212.

The second prism 22 may be a prism of any shape including the first total reflection surface 211 and the light combining surface S2, such as a prism in a triangular prism shape, a prism in a quadrangular prism shape, and the like. When the second prism 22 is a prism in the shape of a quadrangular prism, the light combining surface S2 is connected to the first total reflection surface 211.

The third prism 23 may be a prism of any shape including the third total reflection surface 231, the fourth total reflection surface 232, and the dichroic surface S1, such as a prism in the shape of a quadrangular prism. When the third prism 23 is a quadrangular prism-shaped prism, the third total reflection surface 231 and the fourth total reflection surface 232 are opposed to each other, and the light splitting surface S1 connects the third total reflection surface 231 and the fourth total reflection surface 232.

The fourth prism 24 may be a prism of any shape including the third total reflection surface 231 and the light combining surface S2, such as a prism in the shape of a triangular prism.

Optionally, the first spatial light modulator 31 and the second spatial light modulator 32 may be reflective display elements, for example, digital micromirror devices (DMD). In other alternative embodiments, the first spatial light modulator 31 and the second spatial light modulator 32 may also be reflective liquid crystal panels.

In a specific embodiment, after the illumination beam emitted by the light source 1 is split and combined to achieve spectrum losslessness, the colors of the separated red phosphor (RP) and green phosphor (GP) will be relatively poor. As shown in Figure 2, x and y are chromaticity coordinates in the figure. In order to meet the DCI-P3 color gamut standard of film projectors, it is necessary to add more red lasers (RL) and green lasers (GL) to meet the requirements, and lasers, especially green lasers, have a greater contribution to lumens. . Therefore, the projection optical system of this embodiment can achieve higher output brightness when implementing the same standard color gamut.

Optionally, in order to allow the main optical axis of the illumination beam to be perpendicularly incident to the light splitting and combining device 2, the light splitting and combining device 2 further includes a fifth prism 25, and the fifth prism 25 is located between the light source 1 and the first prism 21. Specifically, the fifth prism 25 includes a first surface adjacent to the second total reflection surface 212 of the first prism 21, and a second surface perpendicular to the main optical axis of the illuminating light beam. The second surface is used to guide the illuminating light beam. Incident. The fifth prism 25 may be a prism of any shape including the first surface and the second surface, such as a prism in the shape of a triangular prism. In another embodiment of the present application, the first prism 21 and the fifth prism 25 can also be made into an integral prism.

Further, the projection optical system further includes an optical relay system 5, which is located between the light source 1 and the light splitting and combining device 2, which can condense the illuminating light beam to a predetermined range. The optical relay system 5 is used to collect the light emitted from the light source 1 to obtain an illumination beam for entering the light splitting and combining device 2.

Optionally, the projection optical system further includes a projection objective lens 4, and the projection objective lens 4 is arranged opposite to the light combining surface S2. The light combining surface S2 combines the first sub-beam emitted by the first spatial light modulator 31 and the second sub-beam emitted by the second spatial light modulator 32 into an outgoing beam, which is then emitted to the projection objective lens 4.

Different from the prior art, the projection optical system of this embodiment includes: a light source 1, a light splitting and combining device 2, a first spatial light modulator 31, and a second spatial light modulator 32. In this projection optical system, the light source 1 emits an illuminating beam, which is divided into multiple sub-beams. The multiple sub-beams have different incident angles to the beam splitting surface S1. The beam splitting surface S1 divides the sub beams into a first sub-beam and a second sub-beam. . The first sub-beam and the second sub-beam enter the light combining surface S2 after being split and reflected by the light splitting and combining device 2 and the first spatial light modulator 31 and the second spatial light modulator 32. The incident angle of any sub-beam on the beam splitting surface S1 is equal to or substantially the same as the incident angle of the first sub-beam and the second sub-beam corresponding to the sub-beam on the light combining surface S2. In this way, the transmittance curve of the illuminating beam is approximately the same during light combining and light splitting, which can reduce light loss, and further increase the output brightness of the projection optical system.

Example two

Please refer to FIG. 3. FIG. 3 is a schematic structural diagram of a second embodiment of a projection optical system according to the present application. Based on the first embodiment, the light source 1 in this embodiment can be set as a polarized illumination light source. The projection optical system of this embodiment can also achieve non-destructive light effects when splitting and combining polarized illumination light.

In the dielectric material, because the transmittance of the two polarization states of S light and P light is different, the transmittance curve of the dielectric film for S light and P light is different. Even if the incident angle remains the same, the transmittance The curves are also separated from each other. For example, as shown in Figure 4, P25 is the transmittance curve when the P light incident angle is 25 degrees, S25 is the transmittance curve when the S light incident angle is 25 degrees; P13 is the transmittance curve when the P light incident angle is 13 degrees. Transmittance curve, S13 is the transmittance curve when the incident angle of S light is 13 degrees; P1 is the transmittance curve when the incident angle of P light is 1 degree, and S1 is the transmittance when the incident angle of S light is 1 degree. curve. It can be seen from the figure that when the incident angle is the same, the transmittance curves of P light and S light are still separated, but as the incident angle decreases, the degree of separation of the transmittance curves of P light and S light decreases.

In this embodiment, under the condition that the light source 1 adopts a polarized illumination light source, the illuminating light beam emitted by it is transmitted, split, totally reflected and combined in the same plane (vertical or parallel to the electric field direction) in the light splitting and combining device. Its polarization state does not change. When the light splitting and combining device is used for light splitting and light combining, the polarization state and incident angle can be kept consistent, so that the lossless light splitting and combining of polarized illumination light can be realized.

Different from the first embodiment, the beam splitting surface S1 in this embodiment divides any sub-beam in the illumination beam into a first sub-beam and a second sub-beam according to polarization characteristics. Specifically, the first sub-beam is P-polarized light, and the second sub-beam is S-polarized light. The beam splitting surface S1 transmits P-polarized light and reflects S-polarized light.

The light combining surface S2 combines the first sub-beam emitted by the first spatial light modulator 31 and the second sub-beam emitted by the second spatial light modulator 32 into the outgoing beam according to the polarization characteristics. Specifically, the light combining surface S2 combines the P-polarized light emitted by the first spatial light modulator 31 and the S-polarized light emitted by the second spatial light modulator to synthesize the outgoing beam and then emit it.

For other specific structures of the light-splitting and light-combining device, please refer to the drawings and text descriptions in the first embodiment, which will not be repeated here.

In this embodiment, a polarized illumination light source is used, which can achieve non-destructive light splitting and light combining and high 3D efficiency.

The above are only implementations of this application, and do not limit the scope of this application. Any equivalent structure or equivalent process transformation made using the content of the description and drawings of this application, or directly or indirectly applied to other related technologies In the same way, all fields are included in the scope of patent protection of this application.

Claims

A projection optical system, characterized in that the projection optical system comprises: a light source, a light splitting and combining device, a first spatial light modulator, and a second spatial light modulator; wherein the light source is used to emit an illumination beam, and The illumination beam includes a plurality of sub-beams;

The light splitting and combining device includes a light splitting surface and a light combining surface. A plurality of the sub-beams have different incident angles to the light splitting surface, and the light splitting surface is used to divide each of the sub-beams into a first sub-beam and a second sub-beam. Two sub-beams, the first sub-beam enters the first spatial light modulator, the second sub-beam enters the second spatial light modulator, and the light combining surface is used to transmit the first spatial light The first sub-beam emitted by the modulator and the second sub-beam emitted by the second spatial light modulator are combined into an emergent beam;

Wherein, the incident angle of any one of the sub-beams in the illumination beam to the beam splitting surface and the incident angles of the first sub-beam and the second sub-beam corresponding to the sub-beams to the light combining surface The difference is less than the preset threshold.
The projection optical system according to claim 1, wherein the light splitting and light combining device comprises a first optical part and a second optical part arranged adjacently, and the first optical part is adjacent to the second optical part One part of the surface is provided with the light splitting surface, and the other part is provided with the light combining surface;

The first optical part is used to guide the illumination beam to the dichroic surface, and guide the second sub-beam to the second spatial light modulator after M reflections, where M is greater than or equal to 2 The even number

The second optical part is used to guide the first sub-beam to the first spatial light modulator after being reflected N times, where N is an even number greater than or equal to 2.
The projection optical system according to claim 2, wherein the first optical part comprises a first prism and a second prism arranged adjacently, and the first prism and the second prism are adjacent to each other. The surface is a first total reflection surface, the surface of the first prism opposite to the first total reflection surface is a second total reflection surface, and the second sub-beam sequentially passes through the second total reflection surface and the The first total reflection surface is reflected to the second spatial light modulator.
The projection optical system according to claim 3, wherein the second optical part comprises a third prism and a fourth prism arranged adjacently, and the surface of the third prism and the fourth prism adjacent to each other is The third total reflection surface, the surface of the third prism opposite to the third total reflection surface is the fourth total reflection surface, and the first sub-beam sequentially passes through the fourth total reflection surface and the third total reflection surface. The total reflection surface is reflected to the first spatial light modulator.
4. The projection optical system according to claim 4, wherein the light splitting and light combining device further comprises a fifth prism, and the fifth prism comprises a first surface adjacent to the second total reflection surface of the first prism , And the second surface perpendicular to the main optical axis of the illumination beam.
The projection optical system according to claim 1, wherein the illuminating light beam includes a first color light, a second color light, and a third color light, and the light splitting surface transmits the first color light according to wavelength characteristics, and The second color light and the third color light are reflected, and the light combining surface transmits the first color light according to the wavelength characteristics, and reflects the second color light and the third color light.
The projection optical system according to claim 1, wherein the projection optical system further comprises an optical relay system, and the optical relay system is located between the light source and the light splitting and combining device for making The illuminating light beam is condensed into a predetermined range.
The projection optical system according to claim 1, wherein the light source is a polarized illumination light source.
8. The projection optical system according to claim 8, wherein the light splitting surface divides each of the sub-beams into the first sub-beam and the second sub-beam according to polarization characteristics; the light combining surface The first sub-beam emitted by the first spatial light modulator and the second sub-beam emitted by the second spatial light modulator are combined into the emergent beam according to the polarization characteristic.
The projection optical system according to claim 1, wherein the incident angle of any one of the sub-beams of the illumination beam on the beam splitting surface is smaller than the total reflection angle of the beam splitting surface.