CN115903174A - Lens system and projection device - Google Patents

Abstract

A lens system has a first optical axis and a second optical axis, the first optical axis is perpendicular to the second optical axis, and the lens system includes: a modulation device sequentially arranged along the optical axis between the object side and the image side, a first A lens group, a first reflecting mirror, a second lens group, an aperture, a third lens group and a second reflecting mirror arranged in sequence along the second optical axis, wherein the first lens group is a refracting lens group for correcting the system image difference; the first reflector is used to realize the optical path refraction, and the optical axis of the lens is refracted from the first optical axis to the second optical axis; the second lens group is used to further converge the incident light; the third lens group is used for The light passing through the aperture is diffused and fully refracted to the second reflector, and the second reflector includes a reflective surface protruding toward the object side A, and the projected light emitted by the modulation device 431 is reflected by the reflective surface and then emitted. Thus, the volume of the lens system along the second optical axis can be effectively compressed, and the resolution of the lens system can be increased.

Description

Lens system and projection device

Technical Field

The present application relates to the field of display technology, and in particular to a lens system and a projection device.

Background Art

With the improvement of information technology, people have higher and higher requirements for visual appreciation. "Visual impact" has become a standard for people to judge display performance. Visual impact comes not only from clear pictures, but also from super-large pictures. In order to meet this demand, large-screen displays came into being. Taking the living room as an example, the market sales in recent years show that the size of LCD TVs has a trend of gradually increasing. However, the advent of the information age has led to fragmented time. The living room is no longer the only place for video entertainment, and due to the large size and weight of LCD TVs, it cannot be used anytime and anywhere. On the other hand, although the size of mobile phone screens has made great progress, and even larger-sized smart tablets designed for entertainment have appeared, it is difficult to achieve real large-screen display due to its display method. Therefore, to achieve flexible large-screen display, the only technical route is projection.

The projection display system mainly includes the lighting system, the optical-mechanical system, the projection lens and other main parts. The spatial light modulator in the optical-mechanical system, also known as the "light valve", is a crucial device. The light valve is usually a pixelated flat device, each pixel of which can independently regulate the incident illumination light by transmission or reflection, and then regulate the luminous flux of each pixel to form a display image. According to the type of spatial light modulator, the projection display system can be roughly divided into reflective DMD (Digital Micro-Mirror Device) projection, transmissive LCD (Liquid Crystal Display) projection and reflective LCoS (Liquid Crystal on Silicon) projection. According to the number of spatial light modulators, it can be divided into single-chip projection, dual-chip projection and three-chip projection.

As we all know, the core principle of display is to use the red, green and blue primary color display principle, that is, it is necessary to display the image display information of the red, green and blue primary colors through light valves respectively, and then combine the three monochrome images through time integration (generally single-chip projection) or space integration (generally three-chip projection) to make the human eye observe a single color image information. However, the time integration method is easily limited by the "rainbow effect", so this method is not the best solution for realizing large-screen display.

Three-chip projection can fundamentally solve the problem of rainbow effect. However, the three-chip projection solution has problems such as complex optical path system, high hardware cost, and large system volume. Therefore, how to fundamentally solve the shortcomings of the three-chip projection such as complex optical path, high cost and large volume is an urgent problem to be solved by those skilled in the art.

Summary of the invention

In view of the defects of the above-mentioned prior art, the present application provides, on the one hand, a lens system with low cost and small size to be more suitable for a projection system, wherein the lens system has a first optical axis and a second optical axis, wherein the first optical axis is perpendicular to the second optical axis, and the lens system comprises: a modulation device, a first lens group, a first reflector, and a second lens group, an aperture, a third lens group, and a second reflector, which are sequentially arranged along the optical axis between the object side and the image side, wherein the first lens group is a refractive lens group, which is used to correct system aberrations; the first reflector is used to realize light path refraction, and to fold the optical axis of the lens from the first optical axis to the second optical axis; the second lens group is used to further converge the incident light; the third lens group is used to diffuse the light passing through the aperture and fully refract it to the second reflector, and the second reflector comprises a reflective surface convex toward the object side A, and the projection light emitted by the modulation device 431 is emitted after being reflected by the reflective surface.

In some embodiments, the first lens group includes a first lens and a second lens, the object side surface of the first lens is concave, the image side surface of the first lens is convex, the object side surface of the second lens is concave, and the image side surface of the second lens is concave.

In some embodiments, the first lens and the second lens are plastic aspheric lenses.

In some embodiments, the first reflector is a plane reflector, and the first reflector is set at 45° to the first optical axis and the second optical axis.

In some embodiments, the second lens group includes a third lens, a fourth lens, and a fifth lens, the third lens is a plastic aspherical lens, and the fourth lens and the fifth lens are both glass spherical lenses.

In some embodiments, the object side surface of the third lens is convex, and the image side surface of the third lens is concave; the object side surface of the fourth lens is concave, and the image side surface of the fourth lens is convex; the object side surface of the fifth lens is concave, and the image side surface of the fifth lens is convex.

In some embodiments, the fourth lens and the fifth lens are doublet lenses.

In some embodiments, the third lens group includes a sixth lens, a seventh lens, and an eighth lens, and the sixth lens, the seventh lens, and the eighth lens are all plastic aspherical lenses.

In some embodiments, the object-side surface of the sixth lens is convex, and the image-side surface of the sixth lens is convex; the object-side surface of the seventh lens is concave, and the image-side surface of the seventh lens is concave; the object-side surface of the eighth lens is concave, and the image-side surface of the eighth lens is concave.

In some embodiments, the second reflector is an aspheric reflector for eliminating aberrations caused by spherical distortion.

In some embodiments, the lens system satisfies: 0.25＜D/L＜0.4, wherein L represents the distance from the reflection surface of the second reflection mirror to the projection image emission surface along the first optical axis and the second optical axis, and D represents the distance from the reflection surface of the second reflection mirror to the exit surface of the third lens group.

In some embodiments, the lens system satisfies: 1.7≤L1/L2≤2, wherein L1 represents the distance from the reflective surface of the second reflector to the aperture along the second optical axis, and L2 represents the sum of the distances from the aperture to the incident surface of the first lens group along the first optical axis and the second optical axis.

In some embodiments, the projection ratio of the lens system is 0.38:1-0.44:1, when the Nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratio is greater than 70%, and the non-telecentricity is less than 7°.

In some embodiments, the modulation device includes a modulation panel, and the modulation panel is a LTP-LCD panel.

On the other hand, the present application also provides a projection device, comprising the lens system described in any of the above embodiments.

Compared with the prior art, the lens system of the present application includes a modulation device, a first lens group, a first reflector, and a second lens group, an aperture, a third lens group, and a second reflector, which are sequentially arranged along the first optical axis between the object side and the image side. Due to the arrangement of the first reflector and the second reflector, it is possible to achieve optical path folding. At the same time, due to the arrangement of the second lens group and the third lens group, the resolution of the entire lens system is large and there is no risk of thermal defocusing, so that it can be adapted to application scenarios with large panels and strong stray light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a basic optical structure of a projection device;

FIG2 is a schematic structural diagram of a projection device according to a first embodiment of the present application;

FIG3 is a schematic diagram of the structure of the long-side light combining and the short-side light combining of the present application;

FIG4 is a schematic diagram of the structure of a projection device 110 according to a second embodiment of the present application;

FIG5 is a diagram showing the light trajectories when parallel light (telecentric illumination light) illuminates the light combining prism and when non-telecentric illumination light illuminates the light combining prism;

FIG6 is a schematic diagram showing wavelength shift when the reflection spectrum of the projection device 110 of the second embodiment changes with the incident angle;

FIG. 7 is a schematic diagram of the structure of a projection device 120 according to Embodiment 3 of the present application;

FIG8 is a schematic structural diagram of a projection device 130 according to a fourth embodiment of the present application;

FIG9 is a schematic structural diagram of a projection device 140 according to a fifth embodiment of the present application;

FIG10 is a schematic structural diagram of a polarizer 241g of Embodiment 5 of the present application;

FIG. 11 is a schematic structural diagram of a projection device 150 according to a sixth embodiment of the present application;

FIG12 is a schematic structural diagram of a polarizer 251g according to Embodiment 6 of the present application;

FIG. 13 is a schematic structural diagram of a projection device 160 according to a seventh embodiment of the present application;

FIG. 14 is a schematic structural diagram of a projection device 170 according to an eighth embodiment of the present application;

FIG15 is a schematic structural diagram of a lens system 41 according to a ninth embodiment of the present application;

FIG16 is a schematic diagram of a modulation transfer function of the lens system 41;

FIG17 is a graph showing longitudinal spherical aberration values, an astigmatism graph, and a distortion graph of the lens system 41;

FIG18 is a system point diagram of the lens system 41;

FIG19 is a diagram of lateral aberration of the lens system 41;

FIG20 is a relative illumination curve of the lens system 41;

FIG21 is a schematic diagram of chief ray angles of different fields of view of the lens system 41;

FIG22 is a schematic structural diagram of a telecentric lens system 42 according to the tenth embodiment of the present application;

FIG23 is a schematic diagram of a modulation transfer function of a telecentric lens system 42;

FIG. 24 is a graph showing longitudinal spherical aberration values, astigmatism, and distortion of the telecentric lens system 42;

FIG25 is a system point diagram of the telecentric lens system 42;

FIG26 is a diagram of lateral aberration of the telecentric lens system 42;

FIG27 is a relative illumination curve diagram of the telecentric lens system 42;

FIG28 is a schematic diagram of chief ray angles of different fields of view of the telecentric lens system 42;

FIG29 is a schematic structural diagram of a lens system 43 according to the eleventh embodiment of the present application;

FIG30 is a schematic diagram of a modulation transfer function of a lens system 43;

FIG31 is a system point diagram of the lens system 43;

FIG32 is a diagram of lateral aberration of the lens system 43;

FIG33 is a relative illumination curve diagram of the lens system 43;

FIG34 is a schematic diagram of chief ray angles of different fields of view of the lens system 43 .

DETAILED DESCRIPTION

In the display field, since DMD and LCOS have complex manufacturing processes and high costs, and both are reflective devices, their application in three-chip projection will cause the optical path to be more complicated and the volume will be difficult to further reduce. Therefore, the projection architecture of three-chip LCD has always been a more commonly used projection solution among three-chip projection. However, the projection architecture of traditional three-chip LCD still has the problems of high cost and large volume.

At present, LCD panels are divided into HLTP-LCD and LTP-LCD according to the two processes of Low Temperature Poly-Silicon (LTPS) and High Temperature Poly-Silicon (HTPS). Among them, the HTPS process has higher precision. The core HTPS process is mostly in the hands of foreign companies. The liquid crystal pixel size can reach less than 10um, and it can achieve a higher aperture ratio and resolution, which can meet the size requirements of the projector for the light valve. However, HTPS has extremely high requirements for the preparation process, so the cost is relatively high. At the same time, the panel requires the expansion of the light source to be small enough, and generally uses a bulb or laser as the light source, resulting in a larger optical machine size.

The LTP-LCD panel made of LTPS, also known as the color modulation panel, has a high production capacity in China due to its simple process and low cost. However, due to the simple process, its precision is low, the pixel size is usually above 25um, and the panel is large, that is, under a certain resolution, the entire LTP-LCD panel size is large, the subsequent lens size is large, and ultimately the entire projection device size is large. Therefore, LTP-LCD is generally used in single-chip projection, and has never been used in three-chip projection.

It should be noted that the cases actually protected by the claims of this application and the technical solutions to the technical problems specifically solved are mainly recorded in Examples 3 to 8 and 11. The remaining embodiments are premises or extensions for introducing the solutions to be specifically protected by the claims of this application, and are not therefore considered to be prior art. They are only displayed to more clearly state the inventive concept of the technical problems actually solved by this application.

Therefore, the present application proposes a new projection architecture, which uses a non-imaging method to illuminate three LTP-LCDs and a short-side light combination scheme, which reduces the requirement for a small optical extension of the incident light source, solves the technical defects of the three-piece projection architecture caused by the large size of the LTP-LCD panel from a technical level, overcomes the technical prejudice that the LTP-LCD panel is not applied to the three-piece projection architecture because of its large size, solves the problems of high cost, difficulty in mass production, large size, and difficulty in adapting to popular projection application scenarios such as business, education, and home use under the traditional three-piece HLTP-LCD architecture, and truly applies the large-panel LTP-LCD that can be mass-produced to the three-piece projection architecture, accelerating the rapid industrialization of low-end projection products in the projection display industry. It can be understood that the projection device of the present application can be used in projectors such as business machines and educational machines in the traditional projection industry, and can also be better applied to micro projectors, mobile phone integrated projections, etc. due to the simple form and powerful functions of the architecture, and has a very broad application prospect.

Please refer to Figure 1, which is a schematic diagram of the basic optical architecture of the projection device of the present application. The projection device includes a light source module 10, a liquid crystal modulation module 20, a light combining module 30 and a projection lens 40. The light source module 10 includes a plurality of light source modules, which can respectively emit a first light beam, a second light beam and a third light beam, wherein the first light beam, the second light beam and the third light beam are red light, green light or blue light respectively; the liquid crystal modulation module 20 includes a plurality of liquid crystal modulation modules, and is arranged on the light output path of the light source module 10, and is used to modulate the first light beam, the second light beam and the third light beam into a first image light, a second image light and a third image light respectively, wherein the first light beam, the second light beam and the third light beam are incident on the plurality of liquid crystal modulation modules of the liquid crystal modulation module 20 in a non-imaging manner after being emitted from the light source module 10, which greatly reduces the number of components and the distance from the light source module 10 to the display module 20, and can effectively reduce the volume of the lighting system; the light combining module is arranged on the light output path of the plurality of liquid crystal modulation modules, and is used to combine the first image light, the second image light and the third image light modulated by the plurality of liquid crystal modulation modules to generate a colored image light; the projection lens 40 is arranged on the light output path of the light combining module, and is used to image the image light onto a preset projection plane or a screen to display an image. Among them, taking the direction in which the image light is incident on the projection lens as the first direction as an example, the multiple liquid crystal modulation modules and the light combining module of the liquid crystal modulation module 20 combine the lights by short-side light combining (what is short-side light combining will be described in detail later). This method can reduce the volume of the light combining module 30 in the first direction, and also effectively reduce the back focus of the projection lens 40, thereby greatly reducing the volume of the entire projection device.

The embodiments of the present application are described in detail below with reference to the accompanying drawings and implementation methods.

Please refer to FIG. 2, which is a schematic diagram of the structure of the first embodiment of the projection device of the present application. The projection device 100 includes a light source module 10, a liquid crystal modulation module 20, a light combining module 30 and a projection lens 40, wherein the light source module 10 includes a first light source module 10r, a second light source module 10g and a third light source module 10b, which are respectively used to emit a first light beam, a second light beam and a third light beam. In some embodiments, the first light beam is red light, the second light beam is green light, and the third light beam is blue light. The light source module 10 can be a laser or an LED, or a laser fluorescence solution. The present application does not limit the specific type of the light source module 10; the liquid crystal modulation module 20 includes a first liquid crystal modulation module 20r, a second liquid crystal modulation module 20g and a third liquid crystal modulation module 20b, which are respectively used to modulate the first light beam, the second light beam and the third light beam irradiated to the liquid crystal modulation module 20 in a non-imaging manner. In some embodiments, the first liquid crystal modulation module 20r, the second liquid crystal modulation module 20g and the third liquid crystal modulation module 20b are all LTP-LCD modules, so that It is able to provide a larger modulation area, thereby reducing the requirement on the expansion amount of the light beam incident on the liquid crystal modulation module 20; the first light beam, the second light beam and the third light beam modulated by the first liquid crystal modulation module 20r, the second liquid crystal modulation module 20g and the third liquid crystal modulation module 20b are respectively represented as the first image light, the second image light and the third image light, which are respectively incident on the light combining module 30 and then combined into color image light, and imaged onto a preset projection plane through the projection lens 40.

The first light source module 10r, the second light source module 10g and the third light source module 10b are used to emit a first light beam, a second light beam and a third light beam, respectively. Among them, the first light source module 10r is incident on the light combining module 30 along a second direction perpendicular to the first direction, the second light source module 10g is incident on the light combining module 30 along the first direction, and the third light source module 10b is incident on the light combining module 30 along a direction opposite to the second direction. In this embodiment, since the components of the first light source module 10r, the second light source module 10g and the third light source module 10b are the same, only the relative positions with the light combining module 30 are different, therefore, taking the second light source module 10g as an example, the second light source module 10g includes a second light emitting unit 101g, a light collecting unit and a collimating lens 103g arranged in sequence along the first direction. In this embodiment, the second light emitting unit 101g is a green laser, which is used to emit green light.

In this embodiment, the light collecting unit is a conical reflector 102g, and the end with a smaller area of the conical reflector 102g is an incident surface, and the end with a larger area is an exit surface, so that the green light emitted by the second light emitting unit 101g is incident on the conical reflector through the incident surface, and then is reflected by the side wall of the conical reflector and then exits from the exit surface or directly exits, so that the area of the exit light spot is larger than the area of the incident light spot, thereby reducing the divergence angle of the light beam, so that the second light beam is irradiated onto the second liquid crystal modulation module in a non-imaging manner. The conical reflector 102g in this embodiment is a solid conical light guide rod, and the light beam is reflected on the side of the conical reflector 102g by total reflection. In other embodiments of the present application, the conical reflector 102g can also be a hollow conical reflector composed of a reflector plate/reflection surface, which will not be repeated here.

The outgoing light of the conical reflector 102g of this embodiment is irradiated onto the collimating lens 103g, thereby collimating the second light beam so that it can smoothly enter the optical element downstream of the optical path. It can be understood that in other embodiments of the present application, the collimating lens may not be provided, for example, when the second light beam from the upstream optical path meets the small divergence angle.

In some embodiments, a light recycling component (not shown) may be further provided between the conical reflector 102g and the collimating lens 103g, or after the collimating lens 103g. In this case, taking the portion between the conical reflector 102g and the collimating lens 103g as an example, if the second light emitting unit 102g emits non-polarized green light, part of the light is transmitted through the light recycling component and continues to be emitted in a single polarization state, and part of the light is reflected by the light recycling component and returns to the conical reflector 102g, is reflected back and forth in the conical reflector 102g, and is re-emitted through the exit surface of the conical reflector 102g to reach the light recycling component. That is, the light recycling component is used to selectively transmit a single polarization state according to the polarization state of the light emitted by the second light emitting unit, and to recycle the light of another polarization state, thereby improving the utilization rate of the first light beam. It can be understood that if the second light emitting unit 102g adopts LED or laser fluorescence, the above structure can break up the polarized light returned from the light recycling component into natural light again, and then continue to participate in the light cycle. In some embodiments, in order to reduce the number of recycling times of the first light beam after recycling, a structure such as a 1/4 wave plate (not shown) can also be set in the conical reflector to change the polarization state of the light beam. In the present application, the light recycling component can be a device such as a wire grid polarizer. Similarly, the first light source module 10r includes a first light emitting unit 101r, a conical reflector 102r and a collimating lens 103a arranged in sequence along the second direction, and the first light emitting unit 101a is a red laser; the third light source module 10b includes a third light emitting unit 101a, a conical reflector 102b and a collimating lens 103b arranged in sequence along the second direction in the opposite direction, and the third light emitting unit 101b is a red laser. The specific principle is similar to that of the second light source device 10g, and will not be repeated here.

2 , and taking the second light source module 10g as an example, the first light beam from the second light source module 10g is incident on the second liquid crystal modulation module 20g, and the second liquid crystal modulation module 20g includes a polarizer 201g and a second modulation panel 202g. The polarizer 201g is used to control the polarization state of the second light beam so that the polarization state of the second light beam is parallel to the liquid crystal direction of the second modulation panel 202g, so that the second modulation panel 202g can modulate the second light beam to generate a second illumination light. In this embodiment, the second modulation panel 202g includes an analyzer (not shown) arranged on its rear surface, and the analyzer is used to analyze the second illumination light modulated by the second modulation panel 202g so that it can be recognized by the human eye. It can be understood that in some embodiments, the analyzer can also be separated from the second modulation panel 202g to avoid direct thermal contact between the two, thereby avoiding aging and damage of the analyzer caused by the heat generated by the second modulation panel 202g. The second illumination light generated after modulation by the second modulation panel 202g is irradiated to the light combining module 30 along the first direction. Similarly, the first illumination light generated after modulation by the first modulation panel 202a is irradiated to the light combining module 30 along the second direction. The third illumination light generated after modulation by the third modulation panel 202b is irradiated to the light combining module 30 along the opposite direction of the second direction. The relative positions of the first modulation panel 202a, the second modulation panel 202g, and the third modulation panel 202b and the light combining module 30 are described below.

Please refer to FIG. 3, which is a schematic diagram of the structure of the long-side light combination and the short-side light combination of the present application. It can be understood that in order to achieve a better display effect, the standard aspect ratio of the LTP-LCD panel is generally 16:9, 16:10, 4:3. Therefore, the LTP-LCD panel is not a square, but has a long side and a short side. At the same time, in the three-piece projection, except for the different modulation colors, the specifications of the three panels should be consistent. In the long-side light combination method shown in FIG. 3 (r), the long side direction of the green light panel is parallel to the first direction, and is respectively perpendicular to the long side directions of the red light panel and the blue light panel. At this time, the distance from the green light panel to the projection lens 40, that is, the back intercept of the projection lens 40 is at least equal to the long side length of the red light panel and the blue light panel. In the short-side light-combining scheme shown in FIG3(g), the long side direction of the second modulation panel 202g is perpendicular to the first direction and parallel to the long side directions of the first modulation panel 202a and the third modulation panel 202b, so that the back focus distance from the first modulation panel 202a to the projection lens 40 is at least equal to the short side length of the first modulation panel 202a and the third modulation panel 202b. Since the short side of the LTP-LCD panel must be smaller than the long side, the short-side light-combining scheme of the present application can effectively reduce the back focus distance of the traditional long-side light-combining scheme, thereby reducing the volume of the projection device.

Please continue to refer to Figure 3. The light combining module 30 is used to combine the first illumination light, the second illumination light and the third illumination light. It can be understood that when the above-mentioned short-side light combining scheme is adopted, the light combining module 30 can adopt an X-cube light combining prism, wherein the light combining prism includes a first coating surface (not shown) and a second coating surface perpendicular thereto. The first coating surface and the second coating surface are respectively divided into a first coating section 311, a second coating section 312, a third coating section 313 and a fourth coating section 314 in a clockwise direction. The first coating section 311 is a green-transmitting and red-reflecting film, the second coating section 312 is a red-green-transmitting and blue-reflecting film, the third coating section 313 is a blue-green-transmitting and red-reflecting film, and the fourth film section 314 is a green-transmitting and blue-reflecting film.

At the same time, the long side direction of the light-combining prism is parallel to the long side direction of the second modulation panel 202g, and the long side length of the light-combining prism is greater than or equal to the long side direction of the second modulation panel 202g, the short side direction of the light-combining prism is parallel to the short side direction of the second modulation panel 202g, and the short side length of the light-combining prism is greater than or equal to the short side direction of the second modulation panel 202g, when projected along a direction perpendicular to both the first direction and the second direction, the light-combining module 30 is in an "X" shape, wherein the "X" shape is the projection line of the first coating surface and the second coating surface. Through such an arrangement, the first illumination light and the third illumination light can be respectively reflected to the first direction and combined with the second illumination light to generate colored illumination light.

The projection lens 40 is arranged on the outgoing light path of the light combining module 30, and is used to project the color image to a predetermined position to form an image that can be viewed by the audience. In this embodiment, the projection lens 40 is composed of a plurality of lenses. It can be understood that those skilled in the art can design the product lens according to the projection scene requirements, and the projection lens can also include optical structures such as reflective curved surfaces, which will not be described here.

In some embodiments, a pixel expansion module 50 may be provided between the light combining module 30 and the projection lens 40. The pixel expansion module 50 is used to translate the light beam of the color image in a direction perpendicular to the optical axis, so that the color images at different translation positions are superimposed in time sequence to improve the display resolution of the final projection. The pixel expansion module 50 may be a transparent flat optical device (XPR: Expanded Pixel Resolution) whose rotation angle is controlled by current or voltage. When the transparent flat plate of the pixel expansion module 50 rotates a certain angle, the light passing through the transparent flat plate is refracted twice and then translated as a whole. The transparent flat plate stays at the rotation position for a predetermined time and then rotates to other positions. In one image frame cycle, the pixel expansion module 50 may include 2 steady states or 4 steady states, and the image is correspondingly split into 2 subframes or 4 subframes. The human eye superimposes the captured 2 or 4 images through the time integration function to form a high-resolution image in the brain, thereby realizing a high-resolution projection display of 4K or 1080P. It can be understood that the pixel offset device can also include more steady states to achieve higher resolution, and the present application does not limit the number of pixel multiplications.

In other embodiments, the pixel shift device may also be a liquid crystal birefringence device, which controls the deflection angle of the liquid crystal molecules by voltage, thereby shifting the light passing through the liquid crystal birefringence (E-shift) device, thereby achieving the effect of overall pixel shift. The effect is similar to the above-mentioned mechanically rotating pixel shift device, which will not be described in detail here.

其中，L为面板有效照明区 域长度，W为面板有效照明区域宽度，这会使得镜头尺寸依然不够小、成本高，从而限制了整个投影装置的进一步小型化。为此，本申请还提出了体积被进一步 减小的更优方案。It can be understood that in the above scheme, since the light source module 10 uses a non-imaging method to illuminate the liquid crystal modulation module 20, the distance between the light source module 10 and the liquid crystal modulation module 20 is small, which effectively reduces the size of the lighting system. At the same time, since the short-side light-combining scheme is adopted, the light-combining structure of the light-combining module 30 itself can be fully utilized, and the back intercept distance from the first modulation panel 202a to the projection lens 40 is greatly reduced, thereby reducing the volume of the entire projection device. However, since the colored illumination light emitted by the light-combining module 30 is still telecentric illumination light to illuminate the lens, and since the lens usually has an offset of more than 100%, for the telecentric illumination system, the lens diameter d needs to meet

Wherein, L is the length of the effective illumination area of the panel, and W is the width of the effective illumination area of the panel, which will make the lens size still not small enough and the cost high, thus limiting the further miniaturization of the entire projection device. To this end, the present application also proposes a better solution in which the volume is further reduced.

Specifically, please refer to the structural schematic diagram of the projection device 110 of the second embodiment of the present application shown in FIG4. FIG4 is actually a modified embodiment of the first embodiment shown in FIG2. Therefore, for the same components and numbers as those in FIG2, please refer to the description in the first embodiment. The difference between this embodiment and the first embodiment is that, in this embodiment, a beam converging component is added to the projection device. The beam converging component can be set at any position between the collimating lens of the light source module and the light combining module, and is used to converge or partially converge the illumination beam. In this embodiment, the beam converging component is set between the polarizer and the modulation panel of the liquid crystal modulation module. Please continue to refer to Figure 4. Taking the optical path setting between the second light source module 11g and the light combining module 30 as an example, the second light beam converging component 213g is arranged between the polarizer 211g and the second modulation panel 212g of the second liquid crystal modulation module 21g, so that the collimated green parallel light emitted by the second light source module 11g is shaped into a light beam that converges or partially converges along the main optical axis in the first direction and irradiates the light combining module, that is, non-telecentric illumination is achieved to illuminate the panel and the light combining module. Preferably, the second light beam converging component 213g can be attached to the polarizer 211g and the second modulation panel 212g. Similarly, the first light source module 10a and the third light source module 10b are also arranged in the same manner, that is, the first light beam converging component 213r and the third light beam converging component 213b are respectively arranged at corresponding positions, so as to realize the non-telecentric illumination light combining module 30, thereby further reducing the distance from the light source module to the light combining module along the first direction, the second direction and the direction opposite to the second direction, thereby reducing the volume of the entire lighting system.

In some embodiments, the light beam converging component may be a field lens, a Fresnel lens, or a free-form surface lens. Of course, it is not limited thereto, and any optical element that can converge or partially converge the first light beam may be used.

In this embodiment, since a beam converging component is added in front of the light combining module, the illumination light is shaped into a non-telecentric beam that is converged or partially converged along the main optical axis when it enters the light combining module 30, so that the effective illumination area when the illumination light reaches the lens is greatly reduced, thereby reducing the lens diameter and greatly reducing the volume of the entire lighting system.

However, when further technical problems need to be solved, the non-telecentric illumination method used in Example 2 needs to further consider the coating properties of the light combining module. Please refer to the light trajectory diagram when the parallel light (telecentric illumination light) illuminates the light combining prism and the non-telecentric illumination light illuminates the light combining prism shown in Figure 5. For the light combining prism used in this application, as the incident angle of the light increases, the effective optical thickness of the coating layer of the light combining prism will decrease with the angle of the light obliquely incident on the film layer, causing the reflection spectrum or transmission spectrum of the film layer to move toward the short-wave direction. That is to say, as shown in FIG5(a), taking the first light beam and the first illumination light as parallel light beams as an example, when the parallel first illumination light is combined by the light combining prism, the incident angle of the light relative to the reflection surface of the first section coating 311 and the third section coating 313 of the light combining prism is 45°, at this time, the reflection spectrum of the first section coating 311 and the third section coating 313 remains basically unchanged; while for the non-telecentric illumination light, as shown in FIG5b, the incident angle of the first illumination light when it is irradiated on the reflection surface of the first section coating 311 and the third section coating 313 will change, and when the non-telecentric angle is θ, the incident angle of the light will vary between 45°±θ, therefore, the reflection spectrum of the first section coating 311 and the third section coating 313 will also change accordingly.

In order to solve the above technical problems, please refer to the schematic diagram of wavelength shift when the reflection spectrum changes with the incident angle shown in FIG6 , in this embodiment, the first coating 311, the second coating 312, the third coating 313 and the fourth coating 314 of the light-combining prism are designed for coating. For the non-telecentric illumination light shown in FIG5(b), it is assumed that the film layers of the first coating 311, the second coating 312, the third coating 313 and the fourth coating 314 are designed according to the standard incident angle α, if α=45°, wherein, taking the first coating 311 as a green-transmitting and red-reflecting film and the third coating 313 as a blue-green-transmitting and red-reflecting film as an example, it is assumed that the wavelength range of the reflection coating is the light between the first wavelength λ ₁ and the second wavelength λ ₂ , and the spectrum range of the first illumination light is the light between the third wavelength λ ₃ and the fourth wavelength λ ₄ . When the incident angle of the first illumination light increases to 45°+θ, the reflection spectrum of the coating is moved toward the blue light wavelength, that is, blue shift. At this time, the wavelength range of reflection becomes that the first wavelength and the second wavelength are both moved toward the blue light wavelength direction by preset distances Δλ ₁ and Δλ ₂ , as shown in FIG6 , which is moved to the left end of the spectral coordinate axis relative to the telecentric illumination standard spectral curve shown in FIG6 , and is expressed as λ ₁ -Δλ ₁ ～λ ₂ -Δλ ₂ ; when the incident angle of the first illumination light decreases to 45°-θ, the reflection spectrum of the coating is moved toward the red light wavelength direction, that is, red shift. At this time, the wavelength range of reflection becomes that the first wavelength and the second wavelength are respectively moved toward the red light wavelength direction by preset distances Δλ ₁ and Δλ ₂ , as shown in FIG6 , which is moved to the right end of the spectral coordinate axis relative to the telecentric illumination standard spectral curve shown in FIG6 , and is expressed as λ ₁ + Δλ ₁ ～λ ₂ +Δλ ₂ . The values of Δλ ₁ and Δλ ₂ depend on the wavelength range of the first illumination light, the non-telecentric angle θ of the first illumination light, and the coating process and thickness of the first coating 311 and the third coating 313. Since the beam converging component is a symmetrical component, the non-telecentric angle θ of the first illumination light is generally symmetrically offset, that is, Δλ ₁ = Δλ ₂ .

In order to ensure that the wavelength of the illumination light emitted after the first illumination light is combined by the light-combining prism is not changed, that is, to ensure that the color of the illumination light is uniform, the above-mentioned coating also needs to satisfy the conditions of λ ₃ >λ ₁ +Δλ ₁ , and λ ₄ <λ ₂ -Δλ ₂ , that is, the narrowest range of the reflection spectrum λ ₁ +Δλ ₁ ～λ ₂ -Δλ ₂ after the deviation with the incident angle is greater than and includes the spectral range λ ₃ ～λ ₄ of the first illumination light, wherein the narrowest range is recorded as the first range.

In this embodiment, when the vapor deposition process is used and the thickness is 500nm, at this time, for reflecting the first illumination light, that is, red light, λ ₃ =622nm, λ ₄ =700nm, λ ₁ +Δλ ₁ <622nm, λ ₂ -Δλ ₂ >700nm, then Δλ ₁ /θ=Δλ ₂ /θ≈20nm/5°, wherein 0<θ<45°, if the non-telecentric angle is 15°, then the coating range of the first section coating 311 and the third section coating 313 is preferably 562nm-760nm; for reflecting the third illumination light, that is, blue light, λ ₃ =455nm, λ ₄ =488nm, λ ₁ +Δλ ₁ <455nm, λ ₂ -Δλ ₂ >488nm, Δλ ₁ /θ=Δλ ₂ /θ≈10nm/5°, wherein, 0＜θ＜45°, if the non-telecentric angle is 15°, then the coating range of the first coating 311 and the third coating 313 is preferably 425nm～513nm.

Similarly, for the film segment of the transmission coating, it is also necessary to satisfy that the wavelength range of its transmission spectrum after being shifted by the incident angle of the illumination light is greater than and includes the spectrum range of the illumination light itself, so as to ensure the color uniformity of the illumination light. The coating principle is consistent with the range setting of the reflective coating and will not be repeated here.

In the present embodiment, since the coating for the light-combining prism satisfies the relationship that the spectral range λ ₁ +Δλ ₁ ~λ ₂ -Δλ ₂ of the coating reflection spectrum after being offset with the incident angle of the illumination light is greater than and includes the spectral range λ ₃ ~λ ₄ of the illumination light, the light deviation caused by the non-telecentric illumination light beam irradiating the ordinary light-combining prism can be avoided, so that the wavelength of the light irradiating the lens under non-telecentric illumination will not change, thereby ensuring the color uniformity of the illumination light.

It can be understood that in some embodiments, in order to avoid the complex correction method of the above-mentioned coating process, it is also possible to not set a beam converging component in the space between the first light source module 11r, the second light source module 11g, the third light source module 11b and the light combining module, but to set a beam converging component between the light combining module 30 and the projection lens 40, so as to irradiate uniform illumination light into the lens. In this way, complex coating processes can be avoided, and illumination light can be irradiated to the projection lens in a non-telecentric illumination manner, thereby reducing the volume of the entire lighting system.

In the solution of the second embodiment, the first light source module 11r, the second light source module 11g, and the third light source module 11b respectively emit the first light beam, the second light beam, and the third light beam, and then pass through the convergence of the first light beam converging component 213r, the first light beam converging component 213g, and the third light beam converging component 213b, and then pass through the light combining module and project through the lens. However, in the device, when LED is used as the light emitting component, due to the problem of low conversion efficiency of the second light emitting component 111g, under the same conditions, the second light beam emitted by the second light source module will be significantly weaker than the first light source module and the third light source module. For this reason, the present application further improves the light path setting of the second light source module in view of this problem.

Specifically, please refer to the structural schematic diagram of the projection device 120 of Example 3 of the present application shown in Figure 7. This embodiment is similar to the embodiment shown in Figure 4, with the difference that: the light source module in this embodiment also includes a supplementary second light source module 12b1, the supplementary second light source module 12b1 is arranged along the second direction, and its structure is basically consistent with the second light source module 12g (the second light-emitting unit 121g, the light collecting unit 122g and the collimating lens 123g arranged in sequence along the first direction), including a supplementary second light-emitting unit (not marked in the figure), a light collecting unit (not marked in the figure) and a collimating lens (not marked in the figure), the only difference is that the supplementary second light-emitting unit of the supplementary second light source module emits a blue laser, and the outer side surface of the second light-emitting unit 121g is a reflective surface and is coated with a green light-emitting material, such as green phosphor. In addition, a supplementary light combining unit 320g is arranged on the common emission path of the second light source component 12g and the supplementary second light source component 12b1. The supplementary light combining unit 320g is provided with a film layer for reflecting blue laser and transmitting red and green fluorescence. It is used to reflect the blue laser emitted by the supplementary second light source component 12b1 to the green phosphor of the second light-emitting component 121g, to excite green fluorescence, so as to cooperate with the second light-emitting component to emit green light with higher brightness. That is, through the additionally arranged supplementary second light source component 12b1, the green phosphor on the second light-emitting unit 121g can be excited on both sides, which helps to improve the excitation efficiency of the stimulated light, and then improve the light efficiency.

Optionally, the supplementary light combining unit 320g can also be configured as a regional membrane (not shown), including a middle region and an edge region, wherein the middle region is used to reflect the blue laser light with a small optical extension emitted by the supplementary second light source assembly to the second light emitting assembly, and the edge region is used to transmit the green light emitted by the second light emitting assembly and the green fluorescence generated by the green phosphor on the second light emitting assembly excited by the blue laser. In this way, the conversion and utilization efficiency of the double-sided excited green light can be further improved.

Furthermore, in order to further reduce the optical path structure diagram of the second embodiment, the present application also proposes a fourth embodiment. Please refer to the structural diagram of the projection device 130 of the fourth embodiment of the present application shown in Figure 8. This embodiment is similar to the embodiment shown in Figure 4, except that: the first light source module and the third light source module of this embodiment are both arranged along the first direction, but the first liquid crystal modulation module 23r (including the polarizer 231r and the first modulation panel 232r) and the first light beam converging component 233r are still arranged along the second direction, and the third liquid crystal modulation module 23b (including the polarizer 231b and the third modulation panel 232b) and the third light beam converging component 233b are still arranged in the opposite direction of the second direction. A first folding component is also arranged between the first light source module and the first liquid crystal modulation module 23r. The first folding component includes a first light recycling component 631r, a first light transmission device 632r and a first folding element 633r, which is used to adjust the transmission direction of the first light beam from the first direction to In the second direction, by such an arrangement, since the transmission direction of the first light beam is changed, the length of the device along the second direction can be compressed.

Specifically, the first light recycling component 631 is used to transmit the light of the first polarization state of the first light beam emitted by the first light source module and reflect the light of the second polarization state perpendicular to the first polarization state, so as to further realize light recycling. Optionally, the first light recycling component 631 can adopt a reflective polarization anti-reflection film (DBEF, dual brightness enhancement film); a first light transmission device 632r is arranged in the output direction of the first light recycling component 631, which is used to transmit the first light beam to the first folding element 633r without loss. In some embodiments, the first light transmission device can adopt a hollow light guide device, a square rod or a conical rod, etc.; the first folding element 633r can adopt a solid right-angle prism, which is used to fold the transmission direction of the first light beam transmitted along the first direction to transmission along the second direction, thereby compressing the volume along the second direction of the projection device.

Furthermore, when the first deflection element 633r adopts a hollow structure, it includes an incident surface, a reflective surface and an output surface. The incident surface and the output surface can be made of coated glass, quartz or plastic. The shape can be a straight plane, a curved surface or a serrated surface composed of multiple straight planes. The two can be placed perpendicular to each other to meet the transmission and reflection requirements of different light rays.

The angle between the reflection surface of the first deflection element 633r and the first direction can be any angle between -90° and 0°, so as to realize the deflection of the light to any direction. Preferably, when the angle between the reflection surface and the first direction is -45°, the light is deflected by 90°, so that the direction of the first light beam is deflected to the second direction. By such an arrangement, the function of a right-angle prism can be realized.

Similarly, between the third light source module and the third liquid crystal modulation module 23b, a third folding assembly is also provided, which includes a third light recycling assembly 631b, a third light transmission device 632b and a third folding element 633b, which is used to adjust the transmission direction of the third light beam from the first direction to the opposite direction of the second direction. Through such a setting, since the transmission direction of the first light beam is changed, the length of the device in the opposite direction of the second direction can be compressed. At the same time, the angle between the reflection surface of the third folding element 633b and the first direction can be any angle between 0°-90°. The remaining settings are basically the same as the settings between the first light source module and the light combining module, and will not be repeated here.

By bending the transmission direction of the first light beam transmitted along the first direction to transmission along the second direction and adjusting the transmission direction of the third light beam from the first direction to the opposite direction of the second direction, the space along the first direction from the second light source module to the light combining device can be fully utilized, thereby reducing the problem of excessive volume along the second direction caused by the arrangement of the first light source module and the third light source module. At the same time, since the folding component includes the light recycling component, the light transmission device and the folding element, the first light beam can be efficiently and losslessly transmitted to the liquid crystal modulation module, thereby effectively improving the light utilization efficiency while reducing the volume of the device.

Please refer to the structural schematic diagram of the projection device 140 of the fifth embodiment of the present application shown in FIG9. This embodiment is similar to the embodiment shown in FIG4, except that: the light collection unit of this embodiment adopts a second lens 142g, which is a collection lens for collecting the light emitted by the second light-emitting component and emitting a collimated first light beam under the collimation of the collimating lens. Since the surface distribution of the first light beam emitted by the second lens 142g and the collimating lens is circular, and the part to be illuminated by the modulation panel is rectangular, it is necessary to cut a rectangle from the circular light spot, and the present application realizes light spot shaping and light recycling by setting a polarizer 241g of a special shape. As shown in FIG10, the polarizer 241g includes a circular light spot surface distribution 2411g, a first area 2412g and a second area 2413g. Preferably, the circular spot surface distribution 2411g is the spot shape of the first light beam when it is transmitted to the modulation panel, the first area 2412g is a rectangular area that is adapted to the shape of the modulation panel and inscribed in the circular spot, and 2412g is set as a light recycling film layer, which is used to perform polarized light recycling on the rectangular area spot of the first light beam, for example, by using the DBEF mentioned above, so as to maximize the system efficiency, and the second area 2413g is set at the edge part of the circular spot surface distribution 2412g of the polarizer 241g except the first area, and the second area 2413g can use a mirror reflection film layer, so that the edge spot part of the circular spot that does not participate in the illumination will be reflected back to the second lens 142g for reuse, thereby further improving the light utilization efficiency.

Through such a setting, the first light beam can be divided into a rectangular light spot for irradiating the modulation panel and an edge light spot for being reflected and recovered, so that light with different polarization characteristics in different regions can be recovered and reused in space and polarization dimension, thereby maximizing the light utilization efficiency of the light emitted by the light source module.

Please refer to the structural diagram of the projection device 150 of the sixth embodiment of the present application shown in FIG11. This embodiment is similar to the embodiment shown in FIG9, except that: in this embodiment, the second lens is a free-form surface lens, preferably an XY polynomial lens, and the collimating lens 153g adopts a Fresnel lens. The use of a free-form surface lens as the second lens can make the surface distribution of the emitted light a rectangle slightly larger than the illumination area of the modulation panel, thereby matching the illumination part required by the panel. Therefore, the polarizer 251g is set to a structure as shown in FIG12, including a circular rectangular spot surface distribution 2511g, a first area 2512g, and a second area 2513g. Preferably, the circular rectangular spot surface distribution 2511g is the spot shape when the first light beam is transmitted to the modulation panel, the first area 2512g is a rectangular area adapted to the shape of the modulation panel and inscribed in the circular rectangular spot, and 2512g is set as a light recycling film layer, which is used to perform polarized light recycling on the rectangular area spot of the first light beam, for example, using the DBEF mentioned above, so as to maximize the system efficiency, and the second area 2513g is set at the edge part of the circular rectangular spot surface distribution 2512g of the polarizer 251g except the first area, and the second area 2513g can use a mirror reflection film layer, so that the edge spot part of the circular spot that does not participate in the illumination will be reflected back to the second lens for reuse, further improving the light utilization efficiency. Due to the combination of the free-form surface lens and the Fresnel lens, the circular spot can be shaped into a circular rectangular spot first, thereby reducing the area of the edge area. Compared with the fifth embodiment, the light loss efficiency of the reflected light at the edge area is reduced, thereby achieving a higher light utilization efficiency.

Please refer to the structural diagram of the projection device 160 of the seventh embodiment of the present application shown in FIG13. This embodiment is similar to the embodiment shown in FIG4, except that: this embodiment is further provided with an ultra-short focus lens on the basis of the second embodiment shown in FIG4, including a reflector 462 and a reflector cup 461, for deflecting the illumination beam, thereby avoiding the lens being too long and making the system size larger. This projection device can increase the space utilization rate and reduce the size of the projection device after folding the light, effectively solving the problems of large size and high cost of the illumination system using a direct projection lens. At the same time, the use of an ultra-short focus lens can make the distance from the projection device to the projection surface smaller than that of an optical machine using a direct projection lens under the same transmittance, thereby reducing the space occupied by the projection device when used by the user and improving the user experience.

Please refer to the structural schematic diagram of the projection device 170 of the eighth embodiment of the present application shown in Figure 14. This embodiment is similar to the embodiments shown in Figures 8 and 13, except that: this embodiment is further provided with an ultra-short focus lens on the basis of the fourth embodiment shown in Figure 8. Compared with the seventh embodiment, the structural layout of this embodiment can further utilize the space from the second light source module along the first direction to the lens, thereby further reducing the volume of the projection device.

More preferably, in order to better adapt to the direct projection device of Example 1 shown in Figure 2 of the present application, the non-telecentric direct projection device of Example 2 shown in Figure 4, and the non-telecentric ultra-short focus projection device shown in Figure 14, the present application proposes a lens system that can be adapted to the above-mentioned projection devices.

For the direct projection device of the first embodiment, since LTP-LCD is used, a certain aperture ratio needs to be maintained while achieving a higher resolution (such as 1080P), which will cause the size of the modulation panel to be larger than that of HTPS-LCD with the same resolution (generally more than 1 inch, or even 2 inches), resulting in a large lens volume and high cost. Therefore, the present application proposes a non-telecentric lens system, and the image circle size corresponding to the modulation panel is 68mm. According to the parameters of Tables 1 to 7, it can be concluded that the non-telecentric lens system uses non-telecentric illumination light with a non-telecentricity of less than 10°, the lens length is less than 65mm, the F number is 4.0, and the projection ratio is 1.3:1.

It is understandable that those skilled in the art will know that the F number represents the inverse of the relative aperture of the lens, that is, the aperture number, which can characterize the resolution of the lens. The smaller the F number, the smaller the distance between two points that can be distinguished, that is, the higher the resolution. The projection ratio is equal to the distance from the projection device lens to the projection screen divided by the width of the projection screen, so that users can install the projection device according to the projection ratio value and the size of the projection screen.

Specifically, please refer to the structural schematic diagram of the lens system 41 of the ninth embodiment of the present application shown in FIG. 15 . The lens system 41 adopts an asymmetric structure, has an optical axis, and includes a modulation device 411, a first lens group 412, a second lens group 413, and an aperture 414, which are sequentially arranged between the object side A and the image side B along the optical axis O1. The first lens group 412 has a positive optical focal length and is used to converge the light. The first lens group 412 includes at least a first lens 4121. The effective light passing diameter of the first lens 4121 is smaller than the size of the image circle. It can be understood that in this embodiment, the optical axis of the lens 41 coincides with the center of the modulation device 411, that is, the lens is not set with an offset. Therefore, the image circle diameter is equal to the diagonal length of the modulation panel. The second lens group 413 has a positive optical focal length and is used to further converge the light. No lens is set on the image side of the aperture 414, so that the lens structure of this embodiment is an asymmetric arrangement. The projection light emitted by the modulation device 411 is incident on the first lens group 412, the second lens group 413 and the aperture 414 in sequence and then projected out.

Among them, the first lens group 412, the second lens group 413 and the aperture 414 are arranged on the same optical axis, and the optical axis of the first lens group 412, the second lens group 413 and the aperture 414 is the optical axis O1. The projection light emitted by the projection device through the modulation device 411 passes through the first lens group 412, the second lens group 413 and the aperture 414 and is projected onto the screen to form a projection image.

In the lens system 41 provided in this embodiment, the first lens group 412 has a positive focal length and is used to converge light. The first lens group 412 includes at least a first lens 4121, which is an aspherical lens and has an effective light-clearance diameter smaller than the size of the image circle. The second lens group 413 has a positive focal length and is used to further converge light. No lens is provided on the image side of the aperture 414. The lens system is asymmetrically provided, which can make the light of each field of view at the position relatively dispersed, so as to maximize the effect of the glass aspherical lens in correcting aberrations (especially distortion) and improve the imaging effect of the lens system 41. At the same time, since the first lens 4121 is an aspherical lens with positive focal length, it can effectively adapt to the application scenario of the larger panel of the LTP-LCD, reducing the incompatibility of the traditional lens to the system.

In this embodiment, the first lens group 412 and the second lens group 413 form a refractive lens group of the projection device 41. The first lens group 412 is located at the incident end of the refractive lens group, that is, the first lens group 412 is the lens group closest to the modulation device 411, and there is no other lens between the first lens group 412 and the modulation device 411. The second lens group 413 is located at the exit end of the refractive lens group, that is, the second lens group 413 is the lens group closest to the aperture 414, and there is no other lens between the second lens group 413 and the aperture 414. Those skilled in the art can add or reduce lenses in the refractive lens group according to actual conditions, as long as the first lens group 412 and the second lens group 413 can be respectively located at the two ends of the refractive lens group.

In this embodiment, the modulation device 411 may include a modulation panel equivalent surface 4110 and a prism 4111. The prism 4111 is located between the modulation panel equivalent surface 4110 and the first lens group 412. The modulation panel adopts the LTP-LCD panel described in the present application. The projection light emitted by the projection device is the image source light emitted after modulation by the modulation panel.

In some embodiments, the first lens group 412 further includes a second lens 4122 and a third lens 4123 arranged in sequence from the object side A to the image side B. The second lens 4122 and the third lens 4123 are both aspherical lenses, and the first lens 4121, the second lens 4122 and the third lens 4123 are all made of plastic materials, so that the aberration correction effect of the plastic aspherical lens can be maximized, and since the cost of the plastic aspherical lens is relatively low, the cost of the first lens group 412 can be effectively reduced. At the same time, the apertures of the first lens 4121, the second lens 4122 and the third lens 4123 are reduced in sequence, so that the effective light diameters of the first lens 4121, the second lens 4122 and the third lens 4123 are all smaller than the size of the image circle, so that the projection light emitted by the projection device under non-telecentric illumination can be collected by the first lens group 412, and in this way, the difficulty of lens design under non-telecentric illumination is reduced.

Furthermore, in order to ensure that the optical power of the first lens group 412 is positive, the first lens 4121 is an aspheric lens with positive optical power, the second lens 4122 is an aspheric lens with positive optical power, and the third lens 4123 is an aspheric lens with negative optical power. Through such an arrangement, the aberration of the entire asymmetric lens structure can be balanced.

It can be understood that the aspheric surface shapes of the first lens 4121, the second lens 4122 and the third lens 4123 can satisfy the equation:

In the above equation, parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the unit of lens length; k is the coefficient of the conic quadratic curve; when the k coefficient is less than -1, the surface curve of the lens is a hyperbola; when the k coefficient is equal to -1, the surface curve of the lens is a parabola; when the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse; when the k coefficient is equal to 0, the surface curve of the lens is a circle; when the k coefficient is greater than 0, the surface curve of the lens is an oblate circle; a_1 to a_8 respectively represent the coefficients corresponding to their respective radial coordinates.

In this embodiment, on the optical axis O1, the first lens 4121 may be the lens in the first lens group 412 that is closest to the modulation device 411, and the third lens 4123 may be the lens in the first lens group 412 that is second closest to the spherical reflector 120.

In some embodiments, the first lens 4121, the second lens 4122 and the third lens 4123 are all plastic aspheric lenses. Through such an arrangement, the aberration correction effect of the plastic aspheric lenses can be maximized. Among them, the object side surface of the first lens 4121 can be convex, and the image side surface of the first lens 4121 is concave; the object side surface of the second lens 4122 is convex, and the image side surface of the second lens 4122 is convex; the object side surface of the third lens 4123 is concave, and the image side surface of the third lens 4123 is convex.

In some embodiments, the second lens group 413 includes a fourth lens 4132 and a fifth lens 4131 which are sequentially arranged from the object side A to the image side B. The fourth lens 4132 and the fifth lens 4131 are both glass spherical lenses. This can maximize the effect of the glass spherical lenses in correcting aberrations and improve resolution. In addition, glass spherical lenses are easier to manufacture than glass aspherical lenses, which can effectively reduce the cost of the second lens group 413. At the same time, since the F number of the projection device in the embodiment is large and the power is high, the use of a glass spherical lens can effectively reduce the risk of thermal defocusing.

In this embodiment, on the optical axis O1, the fourth lens 4132 may be the lens closest to the aperture 414 in the second lens group 413, and the fifth lens 4131 may be the lens second closest to the aperture 414 in the second lens group 413. The object side surface of the fourth lens 4132 may be a convex surface, and the image side surface of the fourth lens 4132 may be a plane; the object side surface of the fifth lens 4131 may be a plane, and the image side surface of the fifth lens 4131 may be a concave surface.

In some embodiments, the fourth lens 4132 and the fifth lens 4131 can be glued together. By using the lens gluing method, chromatic aberration can be corrected and imaging effect can be improved. Exemplarily, the fourth lens 4132 and the fifth lens 4131 can be bonded together by optical glue. Of course, in other embodiments, the fourth lens 4132 and the fifth lens 4131 may not be glued together.

Taking the first lens 4121 as a plastic aspheric lens, the second lens 4122 as a plastic aspheric lens, the third lens 4123 as a plastic aspheric lens, the fourth lens 4132 as a glass spherical lens, and the fifth lens 4131 as a glass spherical lens as an example, the lens system 41 can achieve a projection ratio of 1.3:1, the resolution meets the resolution requirements of 1080P, and the distortion can be controlled within -0.1%-0.5%. Specifically, in this embodiment, the lens design parameters of the lens system 41 are shown in Table 1 below, the aspheric parameters of the object side of the first lens 4121 are shown in Table 2 below, the aspheric parameters of the image side of the first lens 4121 are shown in Table 3 below, the aspheric parameters of the object side of the second lens 4122 are shown in Table 4 below, the aspheric parameters of the image side of the second lens 4122 are shown in Table 5 below, the aspheric parameters of the object side of the third lens 4123 are shown in Table 6 below, and the aspheric parameters of the image side of the third lens 4123 are shown in Table 7 below.

Table 1: Lens design parameters of lens system 41

Table 2: Aspheric parameters of the object side of the first lens 4121

parameter value radius 20.767213v Quadratic surface constant (K) -1.835847v 4th order coefficient (A) -0.000015v 6th order coefficient (B) 7.163594e-009v 8th order coefficient (C) 2.344202e-012v 10th order coefficient (D) -1.726715e-015v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 3: Aspheric parameters of the image-side surface of the first lens 4121

parameter value radius 28.077366v Quadratic surface constant (K) -1.068099v 4th order coefficient (A) -0.000024v 6th order coefficient (B) 1.575782e-008v 8th order coefficient (C) -5.957790e-012v 10th order coefficient (D) 1.003217e-015v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 4: Aspheric parameters of the object side surface of the second lens 4122

parameter value radius 3431.678774v Quadratic surface constant (K) 32.633406v 4th order coefficient (A) -0.000027v 6th order coefficient (B) -7.157527e-008v 8th order coefficient (C) 9.416280e-011v 10th order coefficient (D) -5.549242e-014v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 5: Aspheric parameters of the image-side surface of the second lens 4122

parameter value radius -32.342190v Quadratic surface constant (K) -1.265841v 4th order coefficient (A) -0.000041v 6th order coefficient (B) -8.887856e-008v 8th order coefficient (C) 1.033228e-010v 10th order coefficient (D) -4.591008e-014v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 6: Aspheric parameters of the object side of the third lens 4123

parameter value radius -8.769225v Quadratic surface constant (K) -1.001430v 4th order coefficient (A) -0.000090v 6th order coefficient (B) 9.808048e-008v 8th order coefficient (C) -9.60961 1e-010v 10th order coefficient (D) 1.0845450e-012v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 7: Aspheric parameters of the image-side surface of the third lens 4123

parameter value radius -15.397627v Quadratic surface constant (K) -1.224714v 4th order coefficient (A) -0.000021v 6th order coefficient (B) 13411379e-007v 8th order coefficient (C) -4.930595e-010v 10th order coefficient (D) 4.304075e-013v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

The optical performance of the lens system 41 is verified and explained below through specific experiments.

The modulation transfer function (MTF) performance diagram of the lens system 41 is shown in FIG16. In the figure, the horizontal axis represents the spatial frequency and the vertical axis represents the modulation transfer function ratio. As can be seen from FIG16, when the Nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratio can still be greater than 60%, and the modulation transfer function ratio has no obvious decay, which means that each pixel can be clearly resolved and good image quality can be obtained.

The longitudinal spherical aberration value curve of the lens system 41 is shown in Figure 17(a). Figure 17(a) shows the longitudinal spherical aberration value curve using light with wavelengths of 455nm, 545nm and 615nm. The graph can reflect the optical distortion level of the lens system 41 to a certain extent.

The astigmatism curve of the lens system 41 is shown in FIG17( b ). FIG17( b ) shows an astigmatism field curvature diagram using light with wavelengths of 455 nm, 545 nm and 615 nm. It can be seen from FIG17( b ) that the astigmatism is relatively light, which can reflect to a certain extent that the lens system 41 has a relatively low optical distortion level.

The distortion curve of the lens system 41 is shown in FIG17( c ). FIG17( c ) shows the distortion curve of light with wavelengths of 455 nm, 545 nm and 615 nm. It can be seen from FIG17( c ) that the lens system 41 has a relatively low maximum distortion rate and has better optical performance.

The system point diagram of the lens system 41 is shown in FIG18 . It can be seen from the figure that the average diffuse spot radius of the point diagram under each field of view is small, the image quality is very good, and it can meet the resolution requirement of 1080P.

The lateral aberration diagram of the lens system 41 is shown in FIG19 , in which S-L (Short-Long) represents the difference between the short wavelength and the long wavelength, and S-R (Short-Ref) represents the difference between the short wavelength and the reference wavelength. The relative illumination curve of the lens system 41 is shown in FIG20 . As shown in FIGS. 19 and 20 , the lens system 41 has good imaging quality in terms of lateral chromatic aberration and relative illumination.

A schematic diagram of the chief ray angles of different fields of view of the lens system 41 is shown in FIG21 . It can be seen from the figure that the average value of the image angle, that is, the non-telecentricity, is less than 10°, which meets the illumination requirements of the projection device.

The lens system 41 provided in this embodiment includes a modulation device 411, a first lens group 412, a second lens group 413 and an aperture 414, which are sequentially arranged between the object side A and the image side B along the optical axis O1. The first lens group 412 has a positive optical focal length and is used to converge light. The first lens group 412 includes at least a first lens 4121. The effective light transmission diameter of the first lens 4121 is smaller than the size of the image circle. No lens is arranged on the image side of the aperture 414. At this time, the lens system is asymmetrically arranged, which can make the light of each field of view at the position relatively dispersed, so that the effect of the glass aspherical lens in correcting aberrations (especially distortion) can be maximized, thereby improving the imaging effect of the lens system 41. At the same time, since the first lens 4121 is an aspherical lens with positive optical focal length, it can effectively adapt to the larger application scenario of the LTP-LCD panel, reducing the incompatibility of the traditional lens with the system.

However, although the lens system 41 can effectively reduce the size and cost of the lens, the lens system will dilute the optical extension of the illumination light, thereby affecting the efficiency and uniformity of the final projection device. In addition, the lens system also has the problem of adaptability to non-telecentric projection devices and high requirements for the coupling accuracy of the illumination light and the lens. Therefore, the embodiment 10 of the present application, based on the lens system 41, also proposes another asymmetric telecentric ultra-short focus lens system 42, which can be used with the telecentric illumination projection device of the embodiment 1 to control the lens length to less than 120 mm, the F number is 3.8, the projection ratio is 1.3:1, and the resolution is 1080P.

Specifically, please refer to the structural schematic diagram of the telecentric lens system 42 of the embodiment 10 of the present application shown in FIG. 22. The telecentric lens system 42 also adopts an asymmetric structure, including a modulation device 421, a first lens group 422, a second lens group 423, an aperture 424, and a third lens group 425, which are sequentially arranged between the object side A and the image side B along the optical axis O2. The first lens group 422 has a positive focal length and is used to converge light. The first lens group 422 at least includes a first lens 4221. The effective light passing diameter of the first lens 4221 is smaller than the size of the image circle. It can be understood that in this embodiment, the optical axis of the lens 42 coincides with the center of the modulation device 421, that is, the lens is not set with an offset. Therefore, the image circle diameter is equal to the diagonal length of the modulation panel. The second lens group 423 has a positive focal length and is used to further converge light. Only the third lens group 425 is arranged on the image side of the aperture 424, and the number of lenses in the third lens group 425 is smaller than that of the first lens group and the second lens group. The projection light emitted by the modulation device 421 is incident on the first lens group 422, the second lens group 423, the aperture 424 and the third lens group 425 in sequence and then projected out.

Among them, the first lens group 422, the second lens group 423 and the aperture 424 are arranged on the same optical axis, and the optical axes of the first lens group 422, the second lens group 423, the aperture 424 and the third lens group are the optical axis O2. The projection light emitted by the projection device through the modulation device 421 passes through the first lens group 422, the second lens group 423, the aperture 424 and the third lens group 425 and is projected onto the screen to form a projection image.

In the telecentric lens system 42 provided in this embodiment, the first lens group 422 has a positive focal power, which is used to converge the light. The first lens group 422 includes at least a first lens 4221, which is an aspherical lens and has an effective light-clearing diameter smaller than the size of the image circle. The second lens group 423 has a positive focal power, which is used to further converge the light. Only one third lens group is provided on the image side of the aperture 424. At this time, the telecentric lens system is asymmetrically arranged, which can make the light of each field of view at the position relatively dispersed, so that the glass aspherical lens can maximize the effect of correcting aberrations (especially distortion) and improve the imaging effect of the telecentric lens system 42. At the same time, since the first lens 4221 is an aspherical lens with positive focal power, it can effectively adapt to the application scenario of a larger panel of LTP-LCD, reducing the incompatibility of the traditional lens to the system. Furthermore, due to the provision of the third lens group, the dilution of the optical extension of the illumination light can be effectively adapted, thereby avoiding the problem of poor efficiency and uniformity caused by the asymmetric arrangement. At the same time, the arrangement of the third lens group can also enable the lens 42 of this embodiment to be adapted not only to the imaging illumination mode, such as the direct projection device using the illumination mode of the square rod, imaging lens or compound eye and imaging lens as shown in the fifth embodiment as shown in FIG9 , but also to be adapted to the non-imaging illumination mode, such as the non-telecentric direct projection device using the cone rod and free-form surface lens system as shown in the sixth embodiment as shown in FIG10 .

In this embodiment, the first lens group 422 and the second lens group 423 form a refractive lens group of the projection device 42. The first lens group 422 is located at the incident end of the refractive lens group, that is, the first lens group 422 is the lens group closest to the modulation device 421, and there is no other lens between the first lens group 422 and the modulation device 421. The second lens group 423 is located at the exit end of the refractive lens group, that is, the second lens group 423 is the lens group closest to the aperture 424, and there is no other lens between the second lens group 423 and the aperture 424. Those skilled in the art can add or reduce lenses in the refractive lens group according to actual conditions, as long as the first lens group 422 and the second lens group 423 can be respectively located at the two ends of the refractive lens group.

In this embodiment, the third lens group 425 constitutes the object side lens group of the telecentric lens system 42, including the sixth lens 4251 and the seventh lens 4252, which are used to improve the resolution of the telecentric lens system 42.

In this embodiment, the modulation device 421 may include a modulation panel equivalent surface 4210 and a prism 4211, and the prism 4211 is located between the modulation panel equivalent surface 4210 and the first lens group 422. The modulation panel adopts the LTP-LCD panel described in the present application, and the projection light emitted by the projection device is the image source light emitted after modulation by the modulation panel.

In some embodiments, the first lens group 422 further includes a second lens 4222 and a third lens 4223 which are sequentially arranged from the object side A to the image side B. The second lens 4222 and the third lens 4223 are both aspherical lenses, and the first lens 4221, the second lens 4222 and the third lens 4223 are all made of plastic materials, so that the aberration correction effect of the plastic aspherical lens can be maximized, and since the cost of the plastic aspherical lens is relatively low, the cost of the first lens group 422 can be effectively reduced. At the same time, the apertures of the first lens 4221, the second lens 4222 and the third lens 4223 are sequentially reduced, so that the effective light diameters of the first lens 4221, the second lens 4222 and the third lens 4223 are all smaller than the size of the image circle, so that the projection light emitted by the projection device under non-telecentric illumination can be collected by the first lens group 422, and in this way, the difficulty of lens design under non-telecentric illumination is reduced.

Furthermore, in order to ensure that the optical power of the first lens group 422 is positive, the first lens 4221 is an aspheric lens with positive optical power, the second lens 4222 is an aspheric lens with positive optical power, and the third lens 4223 is an aspheric lens with negative optical power. Through such an arrangement, the aberration of the entire asymmetric lens structure can be balanced.

In this embodiment, on the optical axis O2, the first lens 4221 may be the lens in the first lens group 422 that is closest to the modulation device 421, and the third lens 4223 may be the lens in the first lens group 422 that is second closest to the spherical reflector 120.

In some embodiments, the first lens 4221, the second lens 4222 and the third lens 4223 are all plastic aspheric lenses. Through such an arrangement, the aberration correction effect of the plastic aspheric lenses can be maximized. Among them, the object side surface of the first lens 4221 can be convex, and the image side surface of the first lens 4221 is concave; the object side surface of the second lens 4222 is convex, and the image side surface of the second lens 4222 is convex; the object side surface of the third lens 4223 is concave, and the image side surface of the third lens 4223 is convex.

In some embodiments, the second lens group 423 includes a fourth lens 4232 and a fifth lens 4231 which are sequentially arranged from the object side A to the image side B. The fourth lens 4232 and the fifth lens 4231 are both glass spherical lenses. This can maximize the effect of the glass spherical lenses in correcting aberrations and improve resolution. In addition, glass spherical lenses are easier to manufacture than glass aspherical lenses, which can effectively reduce the cost of the second lens group 423. At the same time, since the F number of the projection device in the embodiment is large and the power is high, the use of a glass spherical lens can effectively reduce the risk of thermal defocusing.

In this embodiment, on the optical axis O1, the fourth lens 4232 may be the lens closest to the aperture 424 in the second lens group 423, and the fifth lens 4231 may be the lens second closest to the aperture 424 in the second lens group 423. The object side surface of the fourth lens 4232 may be a convex surface, and the image side surface of the fourth lens 4232 may be a plane surface; the object side surface of the fifth lens 4231 may be a plane surface, and the image side surface of the fifth lens 4231 may be a concave surface.

In some embodiments, the fourth lens 4232 and the fifth lens 4231 can be glued together. By using the lens gluing method, chromatic aberration can be corrected and imaging effect can be improved. Exemplarily, the fourth lens 4232 and the fifth lens 4231 can be bonded together by optical glue. Of course, in other embodiments, the fourth lens 4232 and the fifth lens 4231 may not be glued together.

In some embodiments, the sixth lens 4251 and the seventh lens 4252 are both spherical lenses, and the sixth lens 4251 and the seventh lens 4252 are both made of glass materials. In this way, the aberration correction effect of the glass spherical lens can be maximized to improve the resolution of the lens. In addition, compared with the glass aspherical lens, the glass spherical lens is easier to manufacture, which can effectively reduce the cost of the third lens group 425. At the same time, since the F number of the projection device in the embodiment is large and the power is high, the use of a glass spherical surface can further reduce the risk of thermal defocusing.

In this embodiment, on the optical axis O2, the sixth lens 4251 may be the lens closest to the aperture 424 in the third lens group 425, and the seventh lens 4252 may be the lens second closest to the aperture 424 in the third lens group 425. The object side surface of the sixth lens 4251 may be a convex surface, and the image side surface of the sixth lens 4251 may be a flat surface; the object side surface of the seventh lens 4252 may be a concave surface, and the image side surface of the seventh lens 4252 may be a convex surface.

Taking the first lens 4221 as a plastic aspheric lens, the second lens 4222 as a plastic aspheric lens, the third lens 4223 as a plastic aspheric lens, the fourth lens 4232 as a glass spherical lens, the fifth lens 4231 as a glass spherical lens, the sixth lens 4251 as a glass spherical lens and the seventh lens 4252 as a glass spherical lens as an example, the telecentric lens system 42 can achieve a projection ratio of 1.3:1, the resolution meets the resolution requirement of 1080P, and the distortion can be controlled to be less than 0.5% or even better. Specifically, in this embodiment, the lens design parameters of the telecentric lens system 42 are shown in Table 8 below, the aspheric surface parameters of the object side surface of the first lens 4221 are shown in Table 9 below, the aspheric surface parameters of the image side surface of the first lens 4221 are shown in Table 10 below, the aspheric surface parameters of the object side surface of the second lens 4222 are shown in Table 11 below, the aspheric surface parameters of the image side surface of the second lens 4222 are shown in Table 12 below, the aspheric surface parameters of the object side surface of the third lens 4223 are shown in Table 13 below, and the aspheric surface parameters of the image side surface of the third lens 4223 are shown in Table 14 below.

Table 8: Lens design parameters of telecentric lens system 42

Table 9: Aspheric parameters of the object side surface of the first lens 4221

parameter value radius 23.378917v Quadratic surface constant (K) -3.408604v 4th order coefficient (A) -0.000004v 6th order coefficient (B) 2.317770e-009v 8th order coefficient (C) 4.961431e-013v 10th order coefficient (D) -5.096263e-016v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 10: Aspheric parameters of the image-side surface of the first lens 4321

Table 11: Aspheric parameters of the object side surface of the second lens 4222

parameter value radius 466.015227v Quadratic surface constant (K) 32.633406v 4th order coefficient (A) 0.000018v 6th order coefficient (B) -5.813403e-008v 8th order coefficient (C) 7.652725e-011v 10th order coefficient (D) -4.748475e-014v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 12: Aspheric parameters of the image-side surface of the second lens 4222

parameter value radius -42.955815v Quadratic surface constant (K) -0.319589v 4th order coefficient (A) 0.000036v 6th order coefficient (B) -8.885299e-008v 8th order coefficient (C) 1.021140e-010v 10th order coefficient (D) -5.106487e-014v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

Table 13: Aspheric parameters of the image-side surface of the third lens 4323

Table 14: Aspheric parameters of the image-side surface of the third lens 4223

parameter value radius -14.544204v Quadratic surface constant (K) -0.886741v 4th order coefficient (A) 0.000009v 6th order coefficient (B) 1.346666e-007v 8th order coefficient (C) -3.746224e-010v 10th order coefficient (D) 3.110053e-013v 12th order coefficient (E) 0.000000 14th order coefficient (F) 0.000000 16th order coefficient (G) 0.000000 18th order coefficient (H) 0.000000 20th order coefficient (J) 0.000000

The optical performance of the telecentric lens system 42 is verified and explained below through specific experiments.

The modulation transfer function performance diagram of the telecentric lens system 42 is shown in FIG23 , in which the horizontal axis represents the spatial frequency and the vertical axis represents the modulation transfer function ratio. As can be seen from FIG16 , when the Nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratio is greater than 60% and the ratio at the corresponding position is also greater than that of the lens system 41, and the modulation transfer function ratio has no obvious decay, which means that it can more clearly resolve each pixel compared to the lens system 41, and obtain good image quality.

The longitudinal spherical aberration value curve of the telecentric lens system 42 is shown in Figure 24(a). Figure 24(a) shows the longitudinal spherical aberration value curve using light with wavelengths of 455nm, 545nm and 615nm. This figure can reflect to a certain extent that the optical distortion level of the telecentric lens system 42 is between 0-1.4%, and its distortion range is smaller than that of the lens system 41.

The astigmatism curve of the telecentric lens system 42 is shown in FIG24( b). FIG24( b) shows an astigmatism field curvature diagram using light with wavelengths of 455 nm, 545 nm and 615 nm. It can be seen from FIG24( b) that the astigmatism is relatively light, which can reflect to a certain extent that the telecentric lens system 42 has a lower optical distortion level.

The distortion curve of the telecentric lens system 42 is shown in Figure 24(c). Figure 24(c) shows the distortion curve using light with wavelengths of 455nm, 545nm and 615nm. It can be seen from Figure 24(c) that the lens system 41 has a relatively low maximum distortion rate and its optical performance is better.

The system point diagram of the telecentric lens system 42 is shown in FIG25 . It can be seen from the figure that the average diffuse spot radius of the point diagram under each field of view is small, the image quality is very good, and can meet the resolution requirement of 1080P.

The lateral aberration diagram of the telecentric lens system 42 is shown in FIG26 , in which S-L (Short-Long) represents the difference between the short wavelength and the long wavelength, and S-R (Short-Ref) represents the difference between the short wavelength and the reference wavelength. The relative illumination curve of the telecentric lens system 42 is shown in FIG27 . As shown in FIGS. 26 and 27 , the telecentric lens system 42 has good imaging quality in terms of lateral chromatic aberration and relative illumination.

A schematic diagram of the chief ray angles of different fields of view of the telecentric lens system 42 is shown in FIG28 . It can be seen from the figure that the average value of the image angle, i.e., the non-telecentricity, is less than 5°, which meets the lighting requirements of the projection device.

The telecentric lens system 42 provided in this embodiment includes a modulation device 421, a first lens group 422, a second lens group 423, an aperture 414 and a third lens group 424 which are sequentially arranged between the object side A and the image side B along the optical axis O2. Since the third lens group is arranged, the dilution of the optical etendue of the illumination light can be effectively adapted, and the problems of poor efficiency and uniformity caused by the asymmetric arrangement can be avoided. At the same time, the arrangement of the third lens group can also make the telecentric lens system 42 of this embodiment not only adapt to the imaging illumination mode, such as the direct projection device using the illumination mode of the square rod, imaging lens or compound eye and imaging lens shown in the fifth embodiment as shown in FIG9 , but also adapt to the non-imaging illumination mode, such as the non-telecentric direct projection device using the cone rod and free-form surface lens system shown in the sixth embodiment as shown in FIG10 .

Furthermore, in the projection device 160 shown in the seventh embodiment and the projection device 170 shown in the eighth embodiment, since a beam converging component such as a field lens, a Fresnel lens or a free-form surface lens is provided, more stray light will be introduced to affect the ANSI contrast. For this reason, the present application also proposes an ultra-short focus lens system 43 with a length of less than 220 mm, an F number of 3.2, and a projection ratio of 0.4:1, which can further reduce the volume of the projection device.

Please refer to FIG. 29 . The lens system 43 provided in the eleventh embodiment of the present application has a first optical axis O3 and a second optical axis O4. The first optical axis O3 is perpendicular to the second optical axis O4. The lens system 43 includes a modulation device 431, a first lens group 432, a first reflector 433, and a second lens group 434, an aperture 435, a third lens group 436, and a second reflector 437, which are sequentially arranged along the optical axis O3 between the object side A and the image side B. The first reflector 433 is a plane reflector, which is used to realize the light path refraction, and fold the optical axis of the lens from the first optical axis O3 to the second optical axis O4, so that the light is reflected from the direction along the first optical axis O3 to the direction along the second optical axis O4, and the volume of the lens system 43 along the second optical axis O4 is compressed. The second reflector 437 is a plastic aspherical reflector, which includes a reflective surface convex toward the object side A. The projection light emitted from the modulation device 431 is reflected by the reflective surface and then emitted.

The modulation device 431, the first lens group 432 and the first reflector 433 are arranged along the first optical axis O3 in sequence. The projection light emitted by the modulation device 431 is incident on the first lens group 432 and the first reflector 433 in sequence, and is reflected by the first reflector 433 as incident light along the second optical axis O4.

In this embodiment, the first lens group 432 is a refractive lens group, and its main function is to correct system aberrations. Specifically, the first lens group 432 includes a first lens 4321 and a second lens 4322, wherein the object side surface of the first lens 4321 is a concave surface, the image side surface of the first lens 4321 is a convex surface, the object side surface of the second lens 4322 is a concave surface, the image side surface of the second lens 4322 is a concave surface, and the overall optical power of the first lens group is negative. The two work together to correct system aberrations and improve resolution, so that the lens system 43 has higher resolution, simpler optical structure and smaller volume.

The first reflector 433 is a plane reflector. Preferably, the plane reflector is arranged at 45° to the first optical axis O3 and the second optical axis O4, thereby ensuring the deflection of light while avoiding blocking or overlapping of light.

In the subsequent optical path of the first reflecting mirror 433, the second lens group 434, the aperture 435, the third lens group 436 and the second reflecting mirror 437 are sequentially arranged along the second optical axis O4.

In some embodiments, the second lens group 434 includes a third lens 4314, a fourth lens 4342 and a fifth lens 4343, which are used to further converge the light, wherein the third lens 4341 is a plastic aspherical lens, and the fourth lens 4242 and the fifth lens are both glass spherical lenses. Thus, the third lens group 434 can further converge the light reflected by the first reflector 433 and prevent thermal defocusing caused by excessive light convergence energy at the aperture 434.

In some embodiments, the object side surface of the third lens 4341 is convex, and the image side surface of the third lens 4341 is concave. The object side surface of the fourth lens 4242 is concave, and the image side surface of the fourth lens 4242 is convex. The object side surface of the fifth lens 4343 is concave, and the image side surface of the fifth lens 4343 is convex, so that the optical power of the second lens group is positive.

In some embodiments, the fourth lens 4342 and the fifth lens 4343 are glued together. By using the lens gluing method, chromatic aberration can be corrected and imaging effect can be improved. Exemplarily, the fourth lens 4342 and the fifth lens 4343 can be bonded together by optical glue. Of course, in other embodiments, the fourth lens 4342 and the fifth lens 4343 may not be glued together.

In some embodiments, the third lens group 436 includes a sixth lens 4361, a seventh lens 4362 and an eighth lens 4363, wherein the sixth lens 4361, the seventh lens 4362 and the eighth lens 4363 are all plastic aspheric lenses, thereby effectively diffusing the light passing through the aperture and fully refracting it onto the second reflector 437, thereby reducing the influence of stray light on ANSI. At the same time, since plastic aspheric lenses are used, the cost of the third lens group can be effectively reduced, and the volume of the entire projection device can be further reduced.

In some embodiments, the object side surface of the sixth lens 4361 is convex, and the image side surface of the sixth lens 4361 is convex. The object side surface of the seventh lens 4362 is concave, and the image side surface of the seventh lens 4362 is concave. The object side surface of the eighth lens 4363 is concave, and the image side surface of the eighth lens 4363 is concave, so that the overall optical power of the third lens group 436 is negative.

The second reflector 437 is an aspheric reflector, which is used to eliminate the aberration caused by spherical distortion. Therefore, the projection light incident on the second reflector 437 from the third lens group 436 will be shaped, thereby increasing the optical path at the second reflector 437, thereby reducing the number of lenses, making the entire optical system more concise, reducing the difficulty of assembly, and the second reflector 437 can effectively shape and correct the projection light, thereby improving the system resolution; in addition, based on the reduction in the number of lenses, the energy loss caused by the projection light passing through different media multiple times can be reduced, thereby improving the projection quality. On the other hand, the second reflector 437 can also be made of glass, which has better thermal stability in this case and can avoid thermal defocusing under high light conditions.

In this embodiment, the second reflector 437 is an aspheric reflector whose reflective surface is coated with a reflective film, and the reflectivity of the reflective surface can be greater than 95%. Exemplarily, the reflective film can be a silver reflective layer or an aluminum reflective layer to achieve a reflectivity greater than 95%.

由此，可以消除像差，提高分辨率并且实现较小的透射比，使 得镜头系统43具有较好的光学性能。其中，投影像发射面为调制面板朝向棱镜 4312的表面，第三透镜组436的出射面的出射面为第八透镜4363的物侧面。In some embodiments, the modulation device 431 has a projection image emission surface, the distance from the reflection surface of the second reflection mirror 437 to the projection image emission surface along the first optical axis O3 and the second optical axis O4 is L (not shown), the distance from the reflection surface of the second reflection mirror 437 to the exit surface of the third lens group 436 is D (not shown), and satisfies

Thus, aberrations can be eliminated, resolution can be improved, and a smaller transmittance can be achieved, so that the lens system 43 has better optical performance. The projection image emission surface is the surface of the modulation panel facing the prism 4312, and the emission surface of the third lens group 436 is the object side surface of the eighth lens 4363.

In some embodiments, on the second optical axis O4, the distance from the reflection surface of the second reflector 437 to the aperture 435 is L1 (not shown), and the sum of the distances from the aperture 435 to the incident surface of the first lens group 130 along the first optical axis O3 and the second optical axis O4 is L2 (not shown), and 1.7≤L1/L2≤2 is satisfied. Thus, aberrations can be eliminated, resolution can be improved, and a smaller transmittance can be achieved, so that the lens system 43 has better optical performance. Among them, the incident surface of the first lens group 432 is the image side surface of the first lens 4321.

In this embodiment, the lens system 43 can achieve a projection ratio of 0.38:1-0.44:1. For example, the lens system 43 can achieve a projection ratio of 0.4:1, and the resolution meets the resolution requirement of 1080P.

Specifically, the lens design parameters of the lens system 43 are shown in Table 15, the aspheric parameters of the second reflector 437, the eighth lens 4363, the seventh lens 4362 and the sixth lens 4361 are shown in Table 16, and the aspheric parameters of the third lens 4341, the second lens 4322 and the first lens 4321 are shown in Table 17.

Table 15: Lens design parameters of lens system 43

Table 16: Aspheric parameters of the second reflector, the eighth lens 4363, the seventh lens 4362 and the sixth lens 4361

Table 17: Aspheric parameters of the third lens 4341, the second lens 4322 and the first lens 4321

The optical performance of the lens system 43 is verified and explained below through specific experiments.

The modulation transfer function performance diagram of the lens system 43 is shown in FIG30 , in which the horizontal axis represents the spatial frequency and the vertical axis represents the modulation transfer function ratio. As can be seen from FIG30 , when the Nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratio is greater than 70% and the ratio at the corresponding position is also greater than that of the lens system 41 and the telecentric lens system 42, and the modulation transfer function ratio has no obvious decay, indicating that it can more clearly resolve each pixel and obtain good image quality compared to the lens system 41 and the telecentric lens system 42.

The system point diagram of the lens system 43 is shown in FIG31 . It can be seen from the figure that the average diffuse spot radius of the point diagram under each field of view with a defocus amount ranging from -0.09 mm to +0.09 mm is small, and the image quality is very good, which can meet the resolution requirement of 1080P.

The lateral aberration diagram of the lens system 43 is shown in FIG32 , in which S-L (Short-Long) represents the difference between the short wavelength and the long wavelength, and S-R (Short-Ref) represents the difference between the short wavelength and the reference wavelength. The relative illumination curve of the lens system 43 is shown in FIG33 . As shown in FIGS. 32 and 33 , the lens system 43 has good imaging quality in terms of lateral chromatic aberration and relative illumination.

A schematic diagram of the chief light angles of different fields of view of the lens system 43 is shown in FIG34 . It can be seen from the figure that the average value of the image angle is less than 7°, which meets the lighting requirements of the projection device.

The lens system 43 provided in this embodiment includes a modulation device 431, a first lens group 432, a first reflector 433, which are sequentially arranged along the optical axis O3 between the object side A and the image side B, and a second lens group 434, an aperture 435, a third lens group 436 and a second reflector 437, which are sequentially arranged along the optical axis O4. Due to the provision of the first reflector 433 and the second reflector, the optical path can be folded, and the volume of the lens system 43 along the second optical axis O4 is effectively compressed. At the same time, due to the provision of the second lens group and the third lens group, the resolution of the entire lens system 43 can be large and there is no risk of thermal defocusing, so that it can be adapted to application scenarios with a large panel and strong stray light, such as the projection device 160 shown in the seventh embodiment and the projection device 170 shown in the eighth embodiment.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims (15)

1. A lens system having a first optical axis and a second optical axis, the first optical axis being perpendicular to the second optical axis, the lens system comprising: a modulation device, a first lens group, a first reflector, and a second lens group, a diaphragm, a third lens group, and a second reflector arranged in sequence along a second optical axis between an object side and an image side,

the first lens group is a refraction lens group and is used for correcting system aberration;

the first reflector is used for realizing light path conversion, and converting the optical axis of the lens from a first optical axis to a second optical axis;

the second lens group is used for further converging incident light;

the third lens group is configured to diffuse and fully refract the light passing through the stop to the second reflecting mirror, the second reflecting mirror includes a reflecting surface protruding toward the object side a, and the projection light emitted from the modulation device 431 is emitted after being reflected by the reflecting surface.

2. The lens system of claim 1, wherein the first lens group comprises a first lens and a second lens, the object-side surface of the first lens is concave, the image-side surface of the first lens is convex, the object-side surface of the second lens is concave, and the image-side surface of the second lens is concave.

3. The lens system as claimed in claim 2, wherein the first lens and the second lens are plastic aspherical lenses.

4. A lens system as recited in claim 1, wherein the first mirror is a flat mirror disposed at 45 ° to both the first optical axis and the second optical axis.

5. The lens system according to claim 1, wherein the second lens group includes a third lens, a fourth lens, and a fifth lens, the third lens is a plastic aspherical lens, and the fourth lens and the fifth lens are each a glass spherical lens.

6. The lens system as recited in claim 5, wherein the object-side surface of the third lens element is convex and the image-side surface of the third lens element is concave; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a convex surface.

7. The lens system as claimed in claim 6, wherein the fourth lens and the fifth lens are double cemented lenses.

8. The lens system as claimed in claim 6, wherein the third lens group includes a sixth lens, a seventh lens and an eighth lens, and the sixth lens, the seventh lens and the eighth lens are all plastic aspherical lenses.

9. The lens system as claimed in claim 8, wherein the object-side surface of the sixth lens element is convex, and the image-side surface of the sixth lens element is convex; the object side surface of the seventh lens is a concave surface, and the image side surface of the seventh lens is a concave surface; the object side surface of the eighth lens is a concave surface, and the image side surface of the eighth lens is a concave surface.

10. A lens system as recited in claim 1, wherein the second mirror is an aspheric mirror for removing aberrations due to spherical distortion.

11. A lens system as set forth in claim 1, wherein the lens system satisfies:

0.25＜D/L＜0.4，

wherein, L represents the distance between the reflecting surface of the second reflector and the projection image emitting surface along the first optical axis and the second optical axis, and D represents the distance between the reflecting surface of the second reflector and the emergent surface of the third lens group.

12. A lens system as recited in claim 8, wherein the lens system satisfies:

1.7≤L1/L2≤2，

wherein L1 denotes a distance from the reflection surface of the second reflecting mirror to the stop along the second optical axis, and L2 denotes a sum of distances from the stop to the incident surface of the first lens group along the first optical axis and the second optical axis.

13. A lens system as recited in claim 1, wherein the lens system has a projection ratio of 0.38: 1 to 0.44: 1, a modulation transfer function ratio of greater than 70% at nyquist frequencies greater than 22 cycles/mm, and a non-telecentricity of less than 7 °.

14. A lens system as recited in claim 1, wherein the modulation device includes a modulation panel, the modulation panel being an LTP-LCD panel.

15. A projection device comprising a lens system as claimed in claims 1 to 14.

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