CN115903174A - Lens system and projection device - Google Patents
Lens system and projection device Download PDFInfo
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- CN115903174A CN115903174A CN202110957141.2A CN202110957141A CN115903174A CN 115903174 A CN115903174 A CN 115903174A CN 202110957141 A CN202110957141 A CN 202110957141A CN 115903174 A CN115903174 A CN 115903174A
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Abstract
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: the optical lens system comprises a modulation device, a first lens group, a first reflector, a second lens group, a diaphragm, a third lens group and a second reflector which are sequentially arranged between an object side and an image side along an optical axis, wherein the second lens group, the diaphragm, the third lens group and the second reflector are sequentially arranged along a second optical axis, and 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 turning and turning the optical axis of the lens from the first optical axis to the second optical axis; the second lens group is used for further converging incident light; the third lens group is used for diffusing the light passing through the diaphragm and fully refracting the light to the second reflector, the second reflector comprises a reflecting surface protruding towards the object side A, and the projection light emitted by the modulation device 431 is emitted after being reflected by the reflecting surface. Therefore, the volume of the lens system along the second optical axis can be effectively compressed, and the resolution of the lens system is increased.
Description
Technical Field
The present disclosure relates to display technologies, and particularly to a lens system and a projection apparatus.
Background
With the improvement of information technology, people have higher and higher requirements on visual appreciation. "visual impact" is a criterion for judging display performance. The visual impact comes not only from a clear picture but also from an oversized picture. To meet such a demand, large-screen display has come to be used. Taking the living room as an example, the market sales in recent years show that the size of the liquid crystal television tends to increase gradually. However, the coming of the information age has resulted in time fragmentation, and the living room is no longer the only place for video entertainment, and because of the large size and weight of the lcd tv, it cannot be applied anywhere and anytime. On the other hand, although the mobile phone screen has advanced greatly in size, and even a larger-sized smart tablet dedicated for entertainment appears, it is difficult to realize a real large-screen display due to the limited display mode. Therefore, flexible large-screen display is realized, and only the technical route of projection is available at present.
The projection display system mainly comprises a lighting system, an optical-mechanical system, a projection lens and other main parts. Spatial light modulators, also referred to as "light valves," in opto-mechanical systems are critical devices. Light valves are generally pixelized planar devices, each pixel of which can be independently modulated by transmission or reflection of incident illumination light, thereby modulating the light flux of each pixel to form a display image. Projection Display systems are roughly classified into DMD (Digital Micro-Mirror Device) projection of a reflective type, LCD (Liquid Crystal Display) projection of a transmissive type, and LCoS (Liquid Crystal on Silicon) projection of a reflective type, according to the type of spatial light modulator. The spatial light modulator is classified into a single-chip projection, a two-chip projection, and a three-chip projection.
As is well known, the core principle of display is to adopt the display principle of three primary colors of red, green and blue, i.e. image display information of the three primary colors of red, green and blue needs to be respectively displayed by a light valve, and then three monochromatic images are combined in a time integration (generally, monolithic projection) or space integration (generally, three-piece projection) manner, so that human eyes observe color image information with a single shape. However, the method using time integration is easily limited by the "rainbow effect", and thus, is not an optimal solution for realizing large-screen display.
The three-sheet projection can fundamentally solve the problem of rainbow effect. However, the three-chip projection scheme has the problems of complex optical path system, high hardware cost, large system volume and the like, and therefore, how to fundamentally solve the disadvantages of complex optical path, high cost, large volume and the like of the three-chip projection is a problem to be solved urgently by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present application provides a lens system with low cost and small size to adapt to a projection system, the 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: the optical lens system comprises a modulation device, a first lens group, a first reflector, a second lens group, a diaphragm, a third lens group and a second reflector which are sequentially arranged between an object side and an image side along an optical axis, wherein the second lens group, the diaphragm, the third lens group and the second reflector are sequentially arranged along a second optical axis, and 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 turning and turning 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 substantially refract the light passing through the stop to the second reflecting mirror, and 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 reflected by the reflecting surface and then emitted.
In some embodiments, the first lens group includes a first lens and a second lens, the object-side surface of the first lens is a concave surface, the image-side surface of the first lens is a convex surface, the object-side surface of the second lens is a concave surface, and the image-side surface of the second lens is a concave surface.
In some embodiments, the first lens and the second lens are plastic aspheric lenses.
In some embodiments, the first mirror is a planar mirror disposed at 45 ° to both 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 aspheric lens, and the fourth lens and the fifth lens are both glass spherical lenses.
In some embodiments, the third lens element has a convex object-side surface and a concave image-side surface; 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.
In some embodiments, the fourth lens and the fifth lens are double cemented lenses.
In some embodiments, the third lens group includes a sixth lens, a seventh lens, and an eighth lens, each of which is a plastic aspherical lens.
In some embodiments, 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.
In some embodiments, the second mirror is an aspheric mirror for eliminating aberrations due to spherical distortion.
In some embodiments, 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.
In some embodiments, the lens system satisfies: L1/L2 is more than or equal to 1.7 and less than or equal to 2, wherein L1 represents the distance from the reflecting surface of the second reflector to the diaphragm along the second optical axis, and L2 represents the sum of the distances from the diaphragm to the incident surface of the first lens group along the first optical axis and the second optical axis.
In some embodiments, 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 a nyquist frequency of greater than 22 cycles/mm, and a non-telecentricity of < 7 °.
In some embodiments, the modulation device comprises a modulation panel, which is an LTP-LCD panel.
On the other hand, the present application further provides a projection apparatus, including the lens system according to any of the above embodiments.
Compared with the prior art, the lens system comprises the modulation device, the first lens group, the first reflector, the second lens group, the diaphragm, the third lens group and the second reflector which are sequentially arranged between the object side and the image side along the first optical axis, the first reflector and the second lens group are arranged sequentially along the second optical axis, the light path folding can be realized due to the arrangement of the first reflector and the second reflector, meanwhile, due to the arrangement of the second lens group and the third lens group, the resolving power of the whole lens system is large, and the risk of thermal defocusing does not exist, so that the lens system can be suitable for application scenes with large panels and strong stray light.
Drawings
FIG. 1 is a schematic diagram of a basic optical architecture of a projection apparatus;
fig. 2 is a schematic structural diagram of a first embodiment of a projection apparatus according to the present application;
fig. 3 is a schematic structural diagram of long-side light combination and short-side light combination according to the present application;
fig. 4 is a schematic structural diagram of a projection apparatus 110 according to a second embodiment of the present application;
FIG. 5 is a diagram showing the ray traces of parallel light (telecentric illumination light) irradiating the light-combining prism and non-telecentric illumination light irradiating the light-combining prism;
FIG. 6 is a schematic diagram illustrating wavelength shift of a reflection spectrum of the projection apparatus 110 according to a second embodiment when the reflection spectrum varies with an incident angle;
fig. 7 is a schematic structural diagram of a projection apparatus 120 according to a third embodiment of the present application;
fig. 8 is a schematic structural diagram of a projection apparatus 130 according to a fourth embodiment of the present application;
fig. 9 is a schematic structural diagram of a projection apparatus 140 according to a fifth embodiment of the present application;
FIG. 10 is a schematic structural diagram of a polarizer 241g according to example five of the present application;
fig. 11 is a schematic structural diagram of a projection apparatus 150 according to a sixth embodiment of the present application;
FIG. 12 is a schematic structural diagram of a polarizer 251g according to a sixth embodiment of the present application;
fig. 13 is a schematic structural diagram of a projection apparatus 160 according to a seventh embodiment of the present application;
fig. 14 is a schematic structural diagram of a projection apparatus 170 according to an eighth embodiment of the present application;
fig. 15 is a schematic structural diagram of a lens system 41 according to a ninth embodiment of the present application;
fig. 16 is a diagram illustrating a modulation transfer function of the lens system 41;
fig. 17 is a graph of longitudinal spherical aberration, astigmatism, and distortion of the lens system 41;
fig. 18 is a system diagram of the lens system 41;
fig. 19 is a lateral aberration diagram of the lens system 41;
fig. 20 is a relative illuminance curve of the lens system 41;
FIG. 21 is a schematic view of chief ray angles of different fields of view of the lens system 41;
fig. 22 is a schematic structural diagram of a telecentric lens system 42 according to the tenth embodiment of the present application;
FIG. 23 is a schematic diagram of the modulation transfer function of telecentric lens system 42;
FIG. 24 is a plot of longitudinal spherical aberration, astigmatism, and distortion for telecentric lens system 42;
FIG. 25 is a system diagram of telecentric lens system 42;
FIG. 26 is a transverse aberration diagram of telecentric lens system 42;
FIG. 27 is a contrast plot for telecentric lens system 42;
FIG. 28 is a schematic of chief ray angles for different fields of view of telecentric lens system 42;
fig. 29 is a schematic structural diagram of a lens system 43 according to an eleventh embodiment of the present application;
FIG. 30 is a schematic diagram of the modulation transfer function of the lens system 43;
fig. 31 is a system diagram of the lens system 43;
fig. 32 is a lateral aberration diagram of the lens system 43;
fig. 33 is a comparative chart of the lens system 43;
fig. 34 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 the DMD and the LCOS are respectively manufactured by complicated processes and have high cost, and both are reflective devices, the application thereof to the three-chip type projection causes the problems of more complicated light path and difficult volume reduction, and therefore, the projection architecture of the three-chip type LCD is always a commonly used projection scheme in the three-chip type, however, the conventional projection architecture of the three-chip type LCD still has the problems of high cost and large volume.
At present, an LCD panel is divided into an HLTP-LCD and an LTP-LCD according to two processes of Low Temperature Poly-Silicon (LTPS) and High Temperature Poly-Silicon (HTPS), wherein the HTPS process precision is High, most of the core HTPS processes are mastered in foreign friends, the size of a liquid crystal pixel can reach below 10um, and the aperture ratio and the resolution ratio are High, which can meet the size requirement of a projector on a light valve, but the HTPS has a very High requirement on the preparation process, so the cost is High, and meanwhile, the panel requires a light source with a small enough expansion amount, and generally adopts a bulb or a laser as the light source, which causes the light machine to have a large volume.
The LTP-LCD panel prepared by the LTPS is also called a color modulation panel, and has high productivity in China due to simple process and low cost. However, since the process is simple and the precision is low, the pixel size is usually above 25um, and the panel is large, that is, in the case of a certain resolution, the size of the whole LTP-LCD panel is large, and the size of the subsequent lens is large, which finally results in a large size of the whole projection apparatus, the LTP-LCD is generally applied to the monolithic projection, and never applied to the three-piece projection.
It should be noted that the actual protection cases and technical solutions of the technical problems specifically solved by the claims of the present application are mainly described in the third to eighth embodiments and eleventh embodiments, and the remaining embodiments are the premise or extension for leading out the solutions specifically claimed by the claims of the present application, and are not considered as the prior art, but are shown only for more clearly stating the inventive concepts of the technical problems actually solved by the present application.
Therefore, the application provides a new projection architecture, a scheme of illuminating three-piece LTP-LCDs in a non-imaging mode and combining short sides is adopted, the requirement on small optical expansion of an incident light source is reduced, the technical defect of the three-piece projection architecture caused by large panel size of the LTP-LCD is solved from the technical aspect, the technical bias that the panel size of the LTP-LCD is large and the LTP-LCD cannot be applied to the three-piece projection architecture is overcome, the problems that the traditional three-piece HLTP-LCD architecture is high in cost, difficult to produce in volume, large in size, difficult to adapt to civilized projection application scenes such as commercial teaching and household use and the like are solved, the large-panel LTP-LCD capable of producing in volume is really applied to the three-piece projection architecture, and the rapid industrialization of middle and low-end projection products in the projection display industry is accelerated. It can be understood that the projection device of the application can be used for projectors such as business machines and education machines in the traditional projection industry, can be better applied to micro projectors, mobile phone integrated projection and the like due to the simple structure and the powerful functions, and has a very wide application prospect.
Referring to fig. 1, a basic optical architecture of a projection apparatus according to the present application is shown, the projection apparatus 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, and can emit a first light beam, a second light beam, and a third light beam, where 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 comprises a plurality of liquid crystal modulation modules, is arranged on an emergent light path of the light source module 10, and is used for respectively modulating light beams such as a first light beam, a second light beam, a third light beam and the like into a first image light, a second image light and a third image light, wherein the first light beam, the second light beam and the third light beam are respectively emitted from the light source module 10 and then enter the plurality of liquid crystal modulation modules of the liquid crystal modulation module 20 in a non-imaging mode, so that the number and the distance of elements from the light source module 10 to the display module 20 are greatly reduced, and the volume of the illumination system can be effectively reduced; the light combining module is arranged on the emergent light path of the liquid crystal modulation modules and is used for combining the first image light, the second image light and the third image light modulated by the liquid crystal modulation modules to generate colorful image light; the projection lens 40 is disposed on an exit light path of the light combining module, and is configured to image the image light onto a preset projection plane or a screen to display an image. Taking the direction of the image light entering the projection lens as the first direction as an example, the plurality of liquid crystal modulation modules and the light combining module of the liquid crystal modulation module 20 combine light by adopting a short-edge light combining (which is detailed later as short-edge light combining), which can reduce the volume of the light combining module 30 in the first direction, and also effectively reduce the back intercept of the projection lens 40, thereby greatly reducing the volume of the whole projection apparatus.
The embodiments of the present application will be described in detail below with reference to the drawings and embodiments.
Fig. 2 is a schematic structural diagram of a projection apparatus according to a first embodiment of the present application. The projection apparatus 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 for emitting a first light beam, a second light beam and a third light beam, in some embodiments, the first light beam is a red light beam, the second light beam is a green light beam, the third light beam is a blue light beam, the light source module 10 may be a laser or an LED, or may also adopt a scheme of laser fluorescence, and the 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 for modulating a first light beam, a second light beam and a third light beam which are provided with non-imaging modes and irradiate the liquid crystal modulation module 20, wherein 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 all adopt LTP-LCD modules, so that a larger modulation area can be provided, and the requirement for the expansion amount of the light beam incident on the liquid crystal modulation module 20 is reduced; 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 a first image light, a second image light and a third image light, and the first image light, the second image light and the third image light are respectively incident to the light combination module 30 and then combined into a color image light, and are imaged on 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 respectively used for emitting a first light beam, a second light beam and a third light beam. The first light source module 10r enters the light combining module 30 along a second direction perpendicular to the first direction, the second light source module 10g enters the light combining module 30 along the first direction, and the third light source module 10b enters the light combining module 30 along a direction opposite to the second direction. In the present embodiment, since the first light source module 10r, the second light source module 10g and the third light source module 10b have the same components and are only different from the light combining module 30 in relative positions, 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 sequentially arranged along the first direction. In the present embodiment, the second light emitting unit 101g is a green laser for emitting green light.
In this embodiment, the light collection unit is a conical reflector 102g, the end of the conical reflector 102g with the smaller area is an incident surface, and the end with the larger area is an emergent surface, so that the green light emitted by the second light emitting unit 101g is incident into the conical reflector through the incident surface, and then is emitted by the emergent surface or directly emitted after being reflected by the side wall of the conical reflector, so that the area of the emergent light spot is larger than that of the incident light spot, thereby reducing the divergence angle of the light beam, and irradiating the second light beam 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 light beams are reflected on the side surface of the conical reflector 102g in a total reflection manner. In other embodiments of the present application, the conical reflector 102g may also be a hollow conical reflector composed of a reflective plate/surface, which is not described herein again.
The outgoing light from the conical reflector 102g of the present embodiment is irradiated onto the collimator lens 103g, so that the second light beam is collimated and smoothly enters the optical element downstream of the optical path. It will be appreciated that in other embodiments of the present application, the collimating lens may not be provided, for example, where the second light beam from the upstream optical path satisfies a small divergence angle.
In some embodiments, a light recycling assembly (not shown) may be further disposed between the conical reflector 102g and the collimating lens 103g, or after the collimating lens 103g, in this case, taking the conical reflector 102g and the collimating lens 103g as an example, if the light emitted by the second light-emitting unit 102g is unpolarized green light, part of the light is transmitted through the light recycling assembly and then continuously emitted in a single polarization state, and part of the light is reflected by the light recycling assembly and then returns to the conical reflector 102g, is reflected back and forth in the conical reflector 102g, and is emitted again through the emitting surface of the conical reflector 102g to reach the light recycling assembly, that is, the light recycling assembly is configured to selectively transmit a single polarization state according to the polarization state of the light emitted by the second light-emitting unit, and recycle light in another polarization state, so as to improve the utilization rate of the first light beam. It can be understood that if the second light emitting unit 102g employs LED or laser fluorescence, the above structure can re-disperse the polarized light returned from the light recycling assembly into natural light, and then continue to participate in light circulation. In some embodiments, in order to reduce the recycling times of the recycled first light beam, a structure such as a 1/4 wave plate (not shown) may be disposed in the conical reflector to change the polarization state of the light beam. In the present application, the light recovery component may 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, which are sequentially arranged 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, which are sequentially disposed along the second direction in an opposite direction, the third light emitting unit 101b is a red laser, and the specific principle is similar to that of the second light source device 10g and is not repeated herein.
Continuing to refer to fig. 2, 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, where the polarizer 201g is configured 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 the second illumination light, in this embodiment, the second modulation panel 202g includes an analyzer (not shown) disposed on the rear surface thereof, and the analyzer is configured to analyze the second illumination light modulated by the second modulation panel 202g, so as to be recognized by human eyes. The second illumination light generated after being modulated by the second modulation panel 202g is irradiated to the light combining module 30 along the first direction, and similarly, the first illumination light generated after being modulated by the first modulation panel 202a is irradiated to the light combining module 30 along the second direction, and the third illumination light generated after being modulated by the third modulation panel 202b is irradiated to the light combining module 30 along the opposite direction of the second direction. Next, 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 will be described.
Please refer to fig. 3, which is a schematic structural diagram of long-side light combination and short-side light combination according to the present application. It is understood that the standard aspect ratio of LTP-LCD panels is typically 16: 9, 16: 10,4: 3 for better display performance, and thus, the LTP-LCD panels are not square, but have long and short sides. Meanwhile, in the three-panel projection, the specifications of the three panels should be consistent except for the modulation colors. In the long-edge light combination mode shown in fig. 3 (r), the long-edge direction of the green light panel is parallel to the first direction and perpendicular to the long-edge directions of the red light panel and the blue light panel, respectively, and 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 length of the long edges of the red light panel and the blue light panel. In the short-side light combination scheme shown in fig. 3 (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 intercept from the first modulation panel 202a to the projection lens 40 is at least equal to the short side lengths of the first modulation panel 202a and the third modulation panel 202 b.
With reference to fig. 3, the light combining module 30 is configured to combine the first illumination light, the second illumination light, and the third illumination light, and it can be understood that, when the scheme of combining the short sides is adopted, the light combining module 30 may adopt an X-cube light combining prism, where the light combining prism includes a first film coating surface (not shown) and a second film coating surface perpendicular to the first film coating surface, the first film coating surface and the second film coating surface are sequentially divided into a first section film coating 311, a second section film coating 312, a third section film coating 313, and a fourth section film coating 314 along a clockwise direction, the first section film coating 311 is a green-transparent red-reflective film, the second section film coating 312 is a red-green-transparent blue-reflective film, the third section film coating 313 is a blue-green-transparent red-reflective film, and the fourth section film coating 314 is a green-transparent blue-reflective film.
Meanwhile, the long side direction of the light combining prism is parallel to the long side direction of the second modulation panel 202g, 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 the light combining module 30 is projected along the 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 a projection line of the first coated surface and the second coated surface. With this arrangement, the first illumination light and the third illumination light are reflected in the first direction, respectively, and combined with the second illumination light to generate colored illumination light.
The projection lens 40 is disposed on the light emitting path of the light combining module 30, and is used for projecting the color image to a predetermined position to form an image that can be viewed by a viewer. In the present embodiment, the projection lens 40 is composed of a plurality of lenses. It can be understood that a person skilled in the art can design a product lens according to a projection scene requirement, and the projection lens may further include optical structures such as a reflective curved surface, which will not be described herein again.
In some embodiments, a pixel expansion module 50 may be further disposed between the light combining module 30 and the projection lens 40, and the pixel expansion module 50 is configured to translate the light beams of the color images along a direction perpendicular to the optical axis, so that the color images at different translation positions are temporally overlapped, so as to improve the display resolution of the final projection. The Pixel expansion module 50 may be a transparent flat plate optical device (XPR) whose rotation angle is controlled by current or voltage, and 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 integrally, and the transparent flat plate stays at the rotation position for a predetermined time and then rotates to other positions. In one image frame period, the pixel expansion module 50 may include 2 or 4 stable states, the image is divided into 2 or 4 sub-frames in response, and the human eye superimposes the captured 2 or 4 images through a time integration function to form a high-resolution image in the brain, thereby implementing a 4K or 1080P high-resolution projection display. It will be appreciated that the pixel shifting arrangement may also include more stable states to achieve higher resolution, and the number of pixel multiplications is not limited by the present application.
In other embodiments, the pixel shifting device may also be a liquid crystal birefringence device, and the deflection angle of liquid crystal molecules is controlled by voltage, so that light passing through the liquid crystal birefringence (E-shift) device is translated, thereby implementing the effect of shifting the whole pixel, the effect is similar to that of the above mechanically rotated pixel shifting device, and details are not repeated here.
It can be understood that, in the above solution, since the light source module 10 adopts the non-imaging mode to irradiate the liquid crystal modulation module 20, the distance from the light source module 10 to the liquid crystal modulation module 20 is relatively small, and the size of the illumination system is effectively reduced, and meanwhile, since the light combining solution of combining light with a short side is adopted, the light combining structure of the light combining module 30 itself can be fully utilized, the back intercept from the first modulation panel 202a to the projection lens 40 is greatly reduced, and the volume of the whole projection apparatus is reduced. However, since the color illumination light emitted from the light combining module 30 is still telecentric illumination light to illuminate the lens, the lens usually has an offset (offset) of 100% or more, and therefore, for the telecentric illumination system, the lens diameter d needs to satisfy
Wherein, L is the panel effective illumination area length, and W is the panel effective illumination area width, which makes the lens size still not small enough, with high costs, thereby limiting the further miniaturization of the whole projection device. For this reason, the present application also proposes a more preferable solution in which the volume is further reduced.
Specifically, please refer to fig. 4 illustrating a schematic structural diagram of a projection apparatus 110 according to a second embodiment of the present application, and fig. 4 illustrates a modified embodiment of the first embodiment illustrated in fig. 2, so that components and numbers identical to those of fig. 2 are referred to for description in the first embodiment. The difference between this embodiment and the first embodiment is that in this embodiment, a light beam converging component is added in the projection apparatus. The light beam converging component can be arranged at any position between the collimating lens of the light source module and the light combining module and is used for converging or partially converging the illumination light beam. With reference to fig. 4, taking an example of a light path from the second light source module 11g to the light combining module 30, the second light beam converging component 213g is disposed between the polarizer 211g of the second liquid crystal modulation module 21g and the second modulation panel 212g, so as to shape the collimated green parallel light emitted from the second light source module 11g into a light beam converged or partially converged along the main optical axis of the first direction and irradiate the light combining module, that is, the panel and the light combining module are irradiated in a non-telecentric illumination manner, preferably, the second light beam converging component 213g may be attached to the polarizer 211g and the second modulation panel 212 g. 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 assembly 213r and the third light beam converging assembly 213b are respectively arranged at corresponding positions, so as to realize the non-telecentric illumination light combining module 30, further reduce 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, and reduce the volume of the whole illumination system.
In some embodiments, the light beam converging component may be a field lens, a fresnel lens, or a free-form lens, although not limited thereto, as long as the optical element is capable of converging or partially converging the first light beam.
In this embodiment, because the beam converging assembly is added in front of the light combining module, when the illumination light enters the light combining module 30, the illumination light is shaped into a non-telecentric beam converging along the main optical axis or partially converging, so that the area of an effective illumination region when the illumination light reaches the lens is greatly reduced, thereby reducing the diameter of the lens and greatly reducing the volume of the whole illumination system.
However, when the technical problem needs to be further solved, the non-telecentric illumination mode adopted in the second embodiment needs to further consider the film coating property of the light combining module. Please refer to fig. 5, which shows the ray traces of the parallel light (telecentric illumination light) and the non-telecentric illumination light when they are irradiated to the light-combining prism. To the x-ray prism that this application adopted, along with the increase of light incident angle, the effective optical thickness of x-ray prism's coating film rete can reduce along with the angle of light oblique incidence rete, leads to the reflectance spectrum or the transmission spectrum of rete to short wave direction removal. That is, as shown in fig. 5 (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 beam with respect to the reflection surfaces of the first-stage plated film 311 and the third-stage plated film 313 of the light combining prism is 45 °, at this time, the reflection spectra of the first-stage plated film 311 and the third-stage plated film 313 are basically unchanged; for the non-telecentric illumination light, as shown in fig. 5b, the incident angle of the first illumination light on the reflective surfaces of the first segment plating film 311 and the third segment plating film 313 changes, and when the non-telecentric angle is θ, the incident angle of the light changes between 45 ° ± θ, and therefore, the reflection spectra of the first segment plating film 311 and the third segment plating film 313 also change accordingly.
In order to solve the above technical problem, please refer to the schematic diagram of the wavelength shift of the reflection spectrum varying with the incident angle shown in fig. 6, in this embodiment, the first, second, third and fourth sections of the coating films 311, 312, 313 and 314 of the light combining prism are subjected to coating design. For the non-telecentric illumination shown in fig. 5 (b), it is assumed that the film layers of the first section of coating film 311, the second section of coating film 312, the third section of coating film 313 and the fourth section of coating film 314 are all designed according to the standard incident angle α, and if α =45 °, taking the first section of coating film 311 as the green-transparent and red-reflective film and the third section of coating film 313 as the blue-green-reflective film as the example, the wavelength range of the reflective coating film is set as the first wavelength λ 1 To a second wavelength lambda 2 And the spectral range of the first illumination light is a third wavelength lambda 3 To a fourth wavelength λ 4 In between. When the incident angle of the first illumination light is increased to 45 degrees plus theta, the reflection spectrum of the coating film is moved to the blue light wavelength, namely blue shift, and at the moment, the reflected wavelength range is changed into that the first wavelength and the second wavelength are both moved to the blue light wavelength direction by a preset distance delta lambda 1 、Δλ 2 A blue-shifted spectral curve, as shown in FIG. 6, shifted to the left of the spectral coordinate axis relative to the standard spectral curve for telecentric illumination as shown in FIG. 6 and denoted as λ 1 -Δλ 1 ～λ 2 -Δλ 2 (ii) a When the incident angle of the first illumination light is reduced to 45-theta, the reflection spectrum of the coating film is shifted to the red wavelength direction, namely red shift,at this time, the reflected wavelength range is changed to a first wavelength and a second wavelength which are respectively moved to the red wavelength direction by a preset distance delta lambda 1 、Δλ 2 The red-shifted spectral curve shown in FIG. 6, shifted to the right of the spectral coordinate axis relative to the standard spectral curve of telecentric illumination shown in FIG. 6, is denoted by λ 1 + Δλ 1 ～λ 2 +Δλ 2 . Wherein, the above-mentioned delta lambda 1 、Δλ 2 The size of the first section of the coating film 311 is determined by the wavelength range of the first illumination light, the non-telecentric angle theta of the first illumination light, the coating processes of the first section of the coating film 311 and the third section of the coating film 313, the thickness and the like. Since the beam converging element is a symmetric element, the non-telecentric angle θ of the first illumination light is generally symmetrically offset, i.e., Δ λ 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, the color of the illumination light is uniform, the coating film needs to satisfy λ 3 ＞λ 1 +Δλ 1 And λ 4 ＜λ 2 -Δλ 2 Condition (b), i.e. the narrowest lambda of the reflection spectrum after a shift with angle of incidence 1 +Δλ 1 ～λ 2 -Δλ 2 Is larger than and includes the spectral range lambda of the first illumination light 3 ～λ 4 Wherein the narrowest range is referred to as the first range.
In this embodiment, when the thickness is 500nm in the case of vapor deposition, λ is the value for reflecting the first illumination light, i.e., red light 3 ＝622nm，λ 4 ＝700nm，λ 1 +Δλ 1 ＜ 622nm、λ 2 -Δλ 2 > 700nm, then. DELTA.lambda 1 /θ＝Δλ 2 The theta is approximately equal to 20nm/5 degrees, wherein the theta is more than 0 and less than 45 degrees, and if the non-center angle is 15 degrees, the plating ranges of the first section of plating film 311 and the third section of plating film 313 are preferably 562nm to 760nm; for the case of reflecting the third illumination light, i.e. blue light, lambda 3 ＝455nm，λ 4 ＝ 488nm，λ 1 +Δλ 1 ＜455nm、λ 2 -Δλ 2 ＞488nm，Δλ 1 /θ＝Δλ 2 Theta is 10nm/5 degrees, whereinAnd theta is more than 0 and less than 45 degrees, and if the non-telecentric angle is 15 degrees, the coating ranges of the first section of coating 311 and the third section of coating 313 are preferably 425 nm-513 nm.
Similarly, for the film segment of the transmission coating film, the wavelength range of the transmission spectrum after the shift along with the incident angle of the illumination light is also required to be larger than and include the spectrum range of the illumination light, so as to ensure the color uniformity of the illumination light, and the coating principle is consistent with the range setting of the reflection coating film, which is not described herein again.
In this embodiment, the coating film for the light-combining prism satisfies the spectrum range λ of the reflection spectrum of the coating film after being shifted with the incident angle of the illumination light 1 +Δλ 1 ～λ 2 -Δλ 2 Range greater than and including the spectral range lambda of the illumination light 3 ～λ 4 The relationship of (1) can avoid light deviation caused when the non-telecentric illumination light beam irradiates the common light-combining prism, so that the wavelength of light irradiating the lens under the non-telecentric illumination cannot be changed, and the color uniformity of the illumination light is further ensured.
It can be understood that, in some embodiments, in order to avoid the above-mentioned complicated modification manner of the coating process, a light beam converging component may not be disposed 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 a light beam converging component may be disposed between the light combining module 30 and the projection lens 40, so as to irradiate uniform illumination light into the lens.
In the second embodiment, after the first light source module 11r, the second light source module 11g, and the third light source module 11b emit the first light beam, the second light beam, and the third light beam respectively, the light beams are converged by the first light beam converging assembly 213r, the first light beam converging assembly 213g, and the third light beam converging assembly 213b, and then are converged by the light converging module and projected through the lens. However, in this device, when the LED is used as the light emitting element, the second light emitting element 111g has a problem of low conversion efficiency, and therefore, under the same condition, the second light beam emitted from the second light source module is significantly weaker than the first light source module and the third light source module. Therefore, the application further improves the light path setting of the second light source module aiming at the problem.
Specifically, please refer to a schematic structural diagram of a projection apparatus 120 according to a third embodiment of the present application shown in fig. 7, which is similar to the embodiment shown in fig. 4, except that: in this embodiment, the light source module further includes a supplementary second light source module 12b1, the supplementary second light source module 12b1 is disposed along the second direction, and the structure of the supplementary second light source module 12g (the second light emitting unit 121g, the light collecting unit 122g and the collimating lens 123g sequentially disposed along the first direction) is substantially the same, and the supplementary second light emitting unit (not identified in the figure), the light collecting unit (not identified in the figure) and the collimating lens (not identified in the figure) are included, and the difference is only that the supplementary second light emitting unit of the supplementary second light source module emits blue laser, and the outer side surface of the second light emitting unit 121g is a reflection surface and is coated with a green emitting material, such as green phosphor. And a supplementary light combination unit 320g is arranged on a common emergent path of the second light source assembly 12g and the supplementary second light source assembly 12b1, a film layer for reflecting blue laser and transmitting red and green fluorescence is arranged on the supplementary light combination unit 320g, and the blue laser emitted by the supplementary second light source assembly 12b1 is reflected to green phosphor of the second light emitting assembly 121g to excite green fluorescence, so that the second light emitting assembly is matched to emit green light with higher brightness together, that is, the supplementary second light source assembly 12b1 is additionally arranged, so that the green phosphor on the second light emitting assembly 121g can be excited in a double-sided mode, the excitation efficiency of the excited laser can be improved, and the light efficiency can be further improved.
Optionally, the supplementary light combining unit 320g may also be configured as an area film (not shown) including a middle area and an edge area, the middle area is configured to reflect blue laser light that supplements the second light source assembly and has a smaller etendue onto the second light emitting assembly, and the edge area is configured to transmit green light emitted by the second light emitting assembly and green fluorescence generated by the blue laser light exciting the green phosphor on the second light emitting assembly. In this way, the conversion and utilization efficiency of the green light of the double-sided excitation can be further improved.
Further, in order to further reduce the schematic optical path structure of the second embodiment, a fourth embodiment is also proposed in the present application, please refer to a schematic structural diagram of a projection apparatus 130 of the fourth embodiment shown in fig. 8, which is similar to the embodiment shown in fig. 4, except that: the first light source module and the third light source module of this embodiment are both disposed along the first direction, but the first liquid crystal modulation module 23r (including the polarizer 231r and the first modulation panel 232 r) and the first light beam converging component 233r are still disposed along the second direction, and the third liquid crystal modulation module 23b (including the polarizer 231b and the third modulation panel 232 b) and the third light beam converging component 233b are still disposed along the opposite direction of the second direction, and a first folding component is further disposed between the first light source module and the first liquid crystal modulation module 23r, and the first folding component includes a first light recycling component 631r, a first light transmitting device 632r, and a first folding component 633r for adjusting the transmission direction of the first light beam from the first direction to the second direction.
Specifically, the first light recycling assembly 631 is configured to transmit light of a first polarization state of the first light beam emitted by the first light source module and reflect light of a second polarization state perpendicular to the first polarization state, so as to further achieve light recycling, and optionally, the first light recycling assembly 631 may adopt a reflective polarization antireflection film (DBEF); a first light transmission device 632r is disposed in the emergent direction of the first light recycling assembly 631, and is used for transmitting the first light beam to the first turning element 633r without loss, in some embodiments, the first light transmission device may adopt a hollow light guide device, a square rod, a conical rod, or the like; the first turning element 633r may be a solid right-angle prism for turning the transmission direction of the first light beam transmitted in the first direction to be transmitted in the second direction, thereby compressing the volume along the projection apparatus in the second direction.
Furthermore, when the first refractive element 633r is of a hollow structure, the first refractive element includes an incident surface, a reflecting surface and an emergent surface, the incident surface and the emergent surface may be made of coated glass, quartz or plastic, and may be in the shape of a straight plane, a curved surface or a sawtooth surface formed by a plurality of straight planes, and the two may be placed at mutually perpendicular positions to satisfy the requirements of transmission and reflection of different light rays.
The included angle between the reflecting surface of the first turning element 633r and the first direction can be any angle between-90 degrees and 0 degrees, so that the light can be turned to any direction. Preferably, when the angle between the reflecting surface and the first direction is-45 °, the light is folded by 90 °, so that the direction of the first light beam is folded into the second direction.
Similarly, a third turning component is further disposed between the third light source module and the third liquid crystal modulation module 23b, and includes a third light recovery component 631b, a third light transmission device 632b, and a third turning element 633b, for adjusting the transmission direction of the third light beam from the first direction to the opposite direction of the second direction. Meanwhile, the angle between the reflecting surface of the third turning element 633b and the first direction may be any angle between 0 ° and 90 °. The rest of the settings are substantially the same as the settings from the first light source module to the light combining module, and are not described herein again.
The transmission direction of the first light beam transmitted along the first direction is converted into the transmission direction of the first light beam transmitted along the second direction and the transmission direction of the third light beam is adjusted to be the opposite direction of the second direction from the first direction, the space along the first direction from the second light source module to the light combining device can be fully utilized, the problem that the size of the first light source module and the third light source module is too large along the second direction when the first light source module and the third light source module are arranged is reduced, meanwhile, the light transmission device and the converting component are included in the converting component, the first light beam can be efficiently and nondestructively transmitted to the liquid crystal modulation module, and the light utilization efficiency is effectively improved on the premise that the size of the device is reduced.
Referring to fig. 9, a schematic structural diagram of a projection apparatus 140 according to a fifth embodiment of the present application is shown, and the present embodiment is similar to the embodiment shown in fig. 4, except that: the light collection unit of the embodiment adopts the second lens 142g, the second lens 142g is a collection lens, and is used for collecting light emitted by the second light emitting component and emitting collimated first light beams under the collimation effect of the collimating lens, and because the surface distribution of the first light beams emitted by the second lens 142g and the collimating lens is circular, and the illumination part required by the modulation panel is rectangular, the rectangular light spots need to be cut out from the circular light spots, and the light spot shaping and the light ray recovery are realized by the polarizer 241g with a special shape. As shown in fig. 10, the polarizer 241g includes a circular speckle pattern 2411g, a first region 2412g and a second region 2413g. Preferably, the circular spot surface distribution 2411g is a spot shape when the first light beam is transmitted to the modulation panel, the first region 2412g is a rectangular region adapted to the modulation panel and inscribed in the circular spot, and 2412g is configured as a light circulation film layer for performing polarized light circulation on the rectangular region spot of the first light beam, for example, the above-mentioned DBEF is used, so as to maximize the system efficiency, the second region 2413g is disposed at an edge portion of the circular spot surface distribution 2412g of the polarizer 241g except the first region, and the second region 2413g may be a mirror reflection film layer, so that an edge spot portion of the circular spot not participating in illumination may be reflected back to the second lens 142g for reuse, thereby further improving the light utilization efficiency.
Through the arrangement, the first light beam can be divided into the rectangular light spot used for irradiating the modulation panel and the edge light spot which is reflected and recycled, so that the light with different areas and different polarization characteristics can be recycled and reused from space and polarization dimension, and the light utilization efficiency of the light emitted by the light source module is ensured to the maximum extent.
Referring to fig. 11, a schematic structural diagram of a projection apparatus 150 according to a sixth embodiment of the present application is shown, which is similar to the embodiment shown in fig. 9 except that: in this embodiment, the second lens is a free-form surface lens, preferably an XY polynomial lens, the collimating lens 153g is a fresnel lens, and the free-form surface lens is used as the second lens to make the surface distribution of the outgoing light a rectangle slightly larger than the illumination area of the modulation panel, so as to match with the illumination portion required by the panel. Accordingly, the polarizer 251g is provided in a structure as shown in fig. 12, including a circular rectangular spot profile 2511g, a first region 2512g, and a second region 2513g. Preferably, the circular rectangular spot surface distribution 2511g is a spot shape when the first light beam is transmitted to the modulation panel, the first region 2512g is a rectangular region adapted to the modulation panel and inscribed in the circular rectangular spot, and 2512g is set to be a light circulation film layer for performing polarized light circulation on the rectangular region spot of the first light beam, for example, the above-mentioned DBEF is adopted, so that the system efficiency is maximally improved, the second region 2513g is arranged at the edge part of the circular rectangular spot surface distribution 2512g of the polarizer 251g except the first region, and the second region 2513g can be a mirror reflection film layer, so that the edge spot part of the circular spot not participating in illumination can be reflected back to the second lens for reuse, thereby further improving the light utilization efficiency. Due to the combination of the free-form surface lens and the Fresnel lens, the circular light spot can be shaped into the circular rectangular light spot, the area of the edge area is reduced, and compared with the fifth embodiment, the light loss efficiency of reflected light at the edge area is reduced, so that higher light utilization efficiency is realized.
Referring to fig. 13, a schematic structural diagram of a projection apparatus 160 according to a seventh embodiment of the present application is shown, and this embodiment is similar to the embodiment shown in fig. 4, except that: in this embodiment, an ultra-short-focus lens is further disposed on the basis of the second embodiment shown in fig. 4, and includes a reflector 462 and a reflective cup 461, so as to deflect the illumination light beam, thereby avoiding that the lens is too long and the size of the system becomes large. The projection device can increase the space utilization rate after folding light, reduce the volume of the projection device, effectively solve the problems of large volume, high cost and the like of an illumination system adopting the direct projection lens, and simultaneously adopt the ultra-short focal lens to ensure that the distance from the projection device to a projection surface under the condition of the same transmittance is less than that of an optical machine using the direct projection lens, thereby reducing the space occupied by the projection device when a user uses the projection device and improving the user experience.
Referring to fig. 14, a schematic structural diagram of a projection apparatus 170 according to an eighth embodiment of the present application is shown, which is similar to the embodiment shown in fig. 8 and 13, except that: in this embodiment, an ultra-short-focus lens is further disposed on the basis of the fourth embodiment shown in fig. 8, and compared with the seventh embodiment, the structural layout of this embodiment can further utilize the space from the second light source module to the lens along the first direction, thereby further reducing the volume of the projection apparatus.
Preferably, in order to further adapt to the direct projection type projection apparatus of the first embodiment shown in fig. 2 of the present application, the non-telecentric direct projection apparatus of the second embodiment shown in fig. 4, and the non-telecentric ultra-short focus projection apparatus shown in fig. 14, the present application proposes a lens system capable of realizing adaptation to the projection apparatus.
For the direct projection apparatus according to the first embodiment, since the LTP-LCD is adopted, a higher resolution (e.g. 1080P) needs to be achieved while a certain aperture ratio needs to be maintained, which may result in a larger size of the modulation panel (generally more than 1 inch, even two inches) compared to the HTPS-LCD with the same resolution, and thus a larger lens size and higher cost are caused. Therefore, the application provides a non-telecentric lens system, the size of an image circle corresponding to a modulation panel is 68mm, according to various parameters of tables 1-7, the non-telecentric lens system can be obtained to adopt non-telecentric illumination light with non-telecentric degree less than 10 degrees, the lens length is less than 65mm, the F number is 4.0, and the projection ratio is 1.3: 1.
It is understood that the F number represents the reciprocal of the relative aperture of the lens, i.e. the F-number, and can characterize the resolution of the lens, and the smaller the F number, the smaller the distance between two points to be resolved, i.e. the higher the resolution. The projection ratio is equal to the distance between the lens of the projection device and the projection screen divided by the width of the projection screen, so that a user can conveniently install the projection device according to the projection ratio value and the size of the projection screen.
Specifically, please refer to the schematic diagram of the lens system 41 in fig. 15 in the ninth embodiment of the present application, wherein the lens system 41 has an asymmetric structure, and includes a modulation device 411, a first lens group 412, a second lens group 413, and an aperture 414, which are sequentially disposed between an object side a and an image side B along an optical axis O1, wherein a focal power of the first lens group 412 is positive for converging light, the first lens group 412 at least includes a first lens 4121, and an effective clear diameter of the first lens 4121 is smaller than a size of an image circle, it can be understood that in this embodiment, the optical axis of the lens 41 coincides with a center of the modulation device 411, that is, the lens is not provided with offset (offset), and therefore, the image circle diameter is equal to a diagonal length of the modulation panel; the optical power of the second lens group 413 is positive for further converging light rays, and no lens is disposed on the image side of the stop 414, so that the lens structure of the present embodiment is asymmetrically disposed. The projection light emitted from the modulation device 411 is incident on the first lens group 412, the second lens group 413, and the stop 414 in sequence and then projected.
The first lens group 412, the second lens group 413 and the diaphragm 414 are disposed on the same optical axis, the optical axes of the first lens group 412, the second lens group 413 and the diaphragm 414 are the optical axis O1, and the projection light emitted by the projection device via the modulation device 411 passes through the first lens group 412, the second lens group 413 and the diaphragm 414 and is projected onto the screen to form a projection image.
In the lens system 41 provided in this embodiment, the focal power of the first lens group 412 is positive for converging light, the first lens group 412 at least includes the first lens 4121, the first lens 4121 is an aspheric lens and has an effective light-passing diameter smaller than the size of an image circle, the focal power of the second lens group 413 is positive for further converging light, no lens is disposed on the image side of the stop 414, and the lens system is disposed asymmetrically at this time, so that light rays of each field at the position are relatively dispersed, thereby the function of correcting aberration (particularly distortion) of the aspheric lens can be exerted to the greatest extent, and the imaging effect of the lens system 41 is improved. Meanwhile, the first lens 4121 is an aspheric lens with positive focal power, so that the large application scene of the panel of the LTP-LCD can be effectively adapted, and the non-adaption degree of the traditional lens to the system is reduced.
In this embodiment, the first lens group 412 and the second lens group 413 form a refractive lens group of the projection apparatus 41, the first lens group 412 is located at an incident end of the refractive lens group, that is, the first lens group 412 is the lens group closest to the modulation apparatus 411, no other lens is located between the first lens group 412 and the modulation apparatus 411, the second lens group 413 is located at an exit end of the refractive lens group, that is, the second lens group 413 is the lens group closest to the diaphragm 414, and no other lens is located between the second lens group 413 and the diaphragm 414; a person skilled in the art may add or subtract lenses in the refractive lens group according to actual circumstances, as long as it is ensured that the first lens group 412 and the second lens group 413 can be located at both ends of the refractive lens group, respectively.
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 is an LTP-LCD panel as described herein, and the projection light emitted by the projection device is the image source light emitted by the modulation panel after modulation.
In some embodiments, the first lens group 412 further includes a second lens 4122 and a third lens 4123 disposed in order from the object side a to the image side B, the second lens 4122 and the third lens 4123 are both aspheric lenses, and the first lens 4121, the second lens 4122 and the third lens 4123 are all made of plastic materials, so that the effect of the plastic aspheric lens on aberration correction can be exerted to the maximum extent, and the cost of the first lens group 412 can be effectively reduced due to the low cost of the plastic aspheric lens. Meanwhile, the calibers of the first lens 4121, the second lens 4122 and the third lens 4123 are sequentially reduced, so that the effective light passing diameters of the first lens 4121, the second lens 4122 and the third lens 4123 are all smaller than the size of an image circle, and therefore projection light emitted by the projection device under non-telecentricity illumination can be collected by the first lens group 412.
Further, in order to ensure that the refractive power of the first lens group 412 is positive, the first lens 4121 is an aspherical lens having positive refractive power, the second lens 4122 is an aspherical lens having positive refractive power, and the third lens 4123 is an aspherical lens having negative refractive power, and by such arrangement, it is possible to balance the aberrations of the entire asymmetric lens structure.
It is understood that the aspherical surface shapes of the first lens 4121, the second lens 4122, and the third lens 4123 may satisfy the equation:
in the above equation, the parameter c is the curvature corresponding to the radius, and y is the radial coordinate, and the unit of the radial coordinate is the same as the unit of the lens length; k is a conic section coefficient; when the k coefficient is less than-1, the surface-shaped curve of the lens is a hyperbola; when the k coefficient is equal to-1, the surface-shaped curve of the lens is a parabola; when the k coefficient is between-1 and 0, the surface-shaped curve of the lens is an ellipse; when the k coefficient is equal to 0, the surface-shaped curve of the lens is circular; when the k coefficient is larger than 0, the surface-shaped curve of the lens is oblate; a _1 to a _8 respectively represent coefficients corresponding to respective radial coordinates.
In this embodiment, on the optical axis O1, the first lens 4121 may be the lens closest to the modulating device 411 in the first lens group 412, and the third lens 4123 is the lens second closest to the spherical mirror 120 in the first lens group 412.
In some embodiments, the first lens 4121, the second lens 4122, and the third lens 4123 are all plastic aspheric lenses, and this configuration can maximize the effect of the plastic aspheric lenses in correcting aberrations. The object-side surface of the first lens element 4121 can be convex, and the image-side surface of the first lens element 4121 can be concave; the object-side surface of the second lens element 4122 is convex, and the image-side surface of the second lens element 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 disposed in order from the object side a to the image side B, and the fourth lens 4132 and the fifth lens 4131 both use glass spherical lenses, so that the effect of the glass spherical lenses in correcting aberrations can be exerted to the greatest extent, the resolution can be improved, and the glass spherical lenses are easier to manufacture than glass aspherical lenses, and the cost of the second lens group 413 can be effectively reduced.
In this embodiment, on the optical axis O1, the fourth lens 4132 may be the lens closest to the stop 414 in the second lens group 413, and the fifth lens 4131 may be the lens second closest to the stop 414 in the second lens group 413. The object-side surface of the fourth lens element 4132 may be a convex surface, and the image-side surface of the fourth lens element 4132 may be a flat surface; the object-side surface of the fifth lens 4131 is flat, and the image-side surface of the fifth lens 4131 is concave.
In some embodiments, the fourth lens 4132 and the fifth lens 4131 may be glued together, and chromatic aberration may be corrected by using a lens gluing method, so as to improve imaging effect. Illustratively, the fourth lens 4132 and the fifth lens 4131 may be adhesively connected by optical glue. Of course, in other embodiments, fourth lens 4132 and fifth lens 4131 may not be cemented.
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 requirement of 1080P, and the distortion can be controlled within-0.1% -0.5%. Specifically, in the present embodiment, the lens design parameters of the lens system 41 are as shown in table 1 below, the aspheric parameters of the object-side surface of the first lens 4121 are as shown in table 2 below, the aspheric parameters of the image-side surface of the first lens 4121 are as shown in table 3 below, the aspheric parameters of the object-side surface of the second lens 4122 are as shown in table 4 below, the aspheric parameters of the image-side surface of the second lens 4122 are as shown in table 5 below, the aspheric parameters of the object-side surface of the third lens 4123 are as shown in table 6 below, and the aspheric parameters of the image-side surface of the third lens 4123 are as shown in table 7 below.
Table 1: lens design parameter table of lens system 41
Table 2: aspheric parameters of object-side surface of first lens 4121
| Parameter(s) | Value of |
| Radius of | 20.767213v |
| Conic constant (K) | -1.835847v |
| Coefficient of order 4 (A) | -0.000015v |
| Coefficient of order 6 (B) | 7.163594e-009v |
| Coefficient of order 8 (C) | 2.344202e-012v |
| Coefficient of order 10 (D) | -1.726715e-015v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 3: aspheric parameters of the image-side surface of the first lens 4121
| Parameter(s) | Value of |
| Radius of the pipe | 28.077366v |
| Conic constant (K) | -1.068099v |
| Coefficient of 4 th order (A) | -0.000024v |
| Coefficient of order 6 (B) | 1.575782e-008v |
| Coefficient of order 8 (C) | -5.957790e-012v |
| Coefficient of order 10 (D) | 1.003217e-015v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 4: aspheric parameters of object-side surface of second lens 4122
| Parameter(s) | Value of |
| Radius of | 3431.678774v |
| Conic constant (K) | 32.633406v |
| Coefficient of 4 th order (A) | -0.000027v |
| Coefficient of order 6 (B) | -7.157527e-008v |
| Coefficient of order 8 (C) | 9.416280e-011v |
| Coefficient of order 10 (D) | -5.549242e-014v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 5: aspheric parameters of the image-side surface of the second lens 4122
| Parameter(s) | Value of |
| Radius of | -32.342190v |
| Conic constant (K) | -1.265841v |
| Coefficient of 4 th order (A) | -0.000041v |
| Coefficient of order 6 (B) | -8.887856e-008v |
| Coefficient of order 8 (C) | 1.033228e-010v |
| Coefficient of order 10 (D) | -4.591008e-014v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 6: aspheric parameters of object-side surface of third lens 4123
| Parameter(s) | Value of |
| Radius of the pipe | -8.769225v |
| Conic constant (K) | -1.001430v |
| Coefficient of 4 th order (A) | -0.000090v |
| Coefficient of order 6 (B) | 9.808048e-008v |
| Coefficient of order 8 (C) | -9.60961 1e-010v |
| Coefficient of order 10 (D) | 1.0845450e-012v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 7: aspheric parameter of image side surface of third lens 4123
| Parameter(s) | Value of |
| Radius of | -15.397627v |
| Conic constant (K) | -1.224714v |
| Coefficient of order 4 (A) | -0.000021v |
| Coefficient of order 6 (B) | 13411379e-007v |
| Coefficient of order 8 (C) | -4.930595e-010v |
| Coefficient of order 10 (D) | 4.304075e-013v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
The optical performance of the lens system 41 is verified by specific experiments.
The Modulation Transfer Function (MTF) of the lens system 41 is represented in fig. 16, in which the abscissa represents the spatial frequency and the ordinate represents the Modulation Transfer Function ratio. As can be seen from fig. 16, when the nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratio can still be greater than 60%, and there is no significant degradation in the modulation transfer function ratio, which means that each pixel can be clearly analyzed, and good image quality can be obtained.
The graph of the longitudinal spherical aberration of the lens system 41 is shown in FIG. 17 (a), and FIG. 17 (a) shows the graph of the longitudinal spherical aberration with light having wavelengths of 455nm, 545nm and 615nm, which reflects the optical distortion level of the lens system 41 to a certain degree.
The astigmatism graph of the lens system 41 is shown in fig. 17 (b), and fig. 17 (b) shows the astigmatism field curves of the light beams with the wavelengths of 455nm, 545nm and 615nm, and it can be seen from fig. 17 (b) that the degree of astigmatism is relatively light, which reflects the relatively low optical distortion level of the lens system 41 to some extent.
The distortion curve of the lens system 41 is shown in fig. 17 (c), and fig. 17 (c) shows the distortion curve of the lens system 41 by using the light rays with the wavelengths of 455nm, 545nm and 615nm, and it can be seen from fig. 17 (c) that the lens system 41 has a relatively low maximum distortion rate and good optical performance.
The system dot sequence of the lens system 41 is shown in fig. 18, and it can be seen from the figure that the average diffuse spot radius of the dot sequence under each field of view is small, the image quality is good, and the resolution requirement of 1080P can be met.
The lateral aberration diagram of the lens system 41 is shown in fig. 19, 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. As shown in fig. 20, the contrast curve of the lens system 41 is shown in fig. 19 and 20, and the lens system 41 has good imaging quality in terms of lateral chromatic aberration and relative illuminance.
Fig. 21 shows a schematic diagram of chief ray angles of different fields of view of the lens system 41, and it can be seen from the diagram that the average value of image space angles, i.e. non-telecentricity, is less than 10 °, which meets the illumination requirement of the projection apparatus.
The lens system 41 provided in this embodiment includes a modulation device 411, a first lens group 412, a second lens group 413, and a stop 414, which are sequentially disposed between an object side a and an image side B along an optical axis O1, where a focal power of the first lens group 412 is positive for converging light rays, the first lens group 412 at least includes a first lens 4121, an effective clear diameter of the first lens 4121 is smaller than a size of an image circle, and no lens is disposed on the image side of the stop 414, and the lens system is disposed asymmetrically at this time, so that light rays of each field at the present position are relatively dispersed, thereby a function of a glass aspheric lens for correcting aberrations (especially distortion) can be exerted to the maximum extent, and an imaging effect of the lens system 41 is improved; meanwhile, the first lens 4121 is an aspheric lens with positive focal power, so that the large application scene of the LTP-LCD panel can be effectively adapted, and the incompatibility degree of the traditional lens to the system is reduced.
However, although the lens system 41 can effectively reduce the volume and cost of the lens, the lens system can dilute the etendue of the illumination light, thereby affecting the efficiency and uniformity of the final projection device, and in addition, the lens system has the problems of high requirements on the adaptability of the non-telecentric projection device and the coupling precision of the illumination light and the lens coupling. Therefore, the tenth embodiment of the present application provides another asymmetric telecentric ultra-short focus lens system 42 on the basis of the lens system 41, which can control the lens length below 120mm, the F-number below 3.8, the projection ratio below 1.3: 1 and the resolution 1080P in cooperation with the telecentric illumination projection apparatus of the first embodiment.
Specifically, referring to the structural diagram of the telecentric lens system 42 of the tenth embodiment of the present application shown in fig. 22, the telecentric lens system 42 also adopts an asymmetric structure, and includes a modulation device 421, a first lens group 422, a second lens group 423, an aperture 424, and a third lens group 425 sequentially disposed between an object side a and an image side B along an optical axis O2, wherein the focal power of the first lens group 422 is positive for converging light, the first lens group 422 at least includes a first lens 4221, and the effective clear diameter of the first lens 4221 is smaller than the size of an image circle, it can be understood that in the present embodiment, the optical axis of the lens 42 coincides with the center of the modulation device 421, that is, the lens does not have an offset (offset), and therefore, the diameter of the image circle is equal to the diagonal length of the modulation panel; the focal power of the second lens group 423 is positive for further converging light, only the third lens group 425 is disposed on the image side of the stop 424, and the number of lenses of the third lens group 425 is less than the sum of the lenses of the first lens group and the second lens group, so that the lens structure of the present embodiment is asymmetrically disposed. Projection light emitted from the modulation device 421 enters the first lens group 422, the second lens group 423, the stop 424, and the third lens group 425 in sequence, and is projected.
The first lens group 422, the second lens group 423 and the stop 424 are disposed on the same optical axis, the optical axes of the first lens group 422, the second lens group 423, the stop 424 and the third lens group are the optical axis O2, and the projection light emitted by the projection device via the modulation device 421 passes through the first lens group 422, the second lens group 423, the stop 424 and the third lens group 425 and is projected onto a screen to form a projection image.
In the telecentric lens system 42 provided by this embodiment, the focal power of the first lens group 422 is positive for converging light, the first lens group 422 at least includes the first lens 4221, the first lens 4221 is an aspheric lens and the effective clear diameter thereof is smaller than the size of an image circle, the focal power of the second lens group 423 is positive for further converging light, only one third lens group is disposed on the image side of the stop 424, and the telecentric lens system is disposed asymmetrically at this time, so that light of each field at the position can be relatively dispersed, thereby exerting the function of the glass aspheric lens for correcting aberration (especially distortion) to the maximum extent, and improving the imaging effect of the telecentric lens system 42. Meanwhile, the first lens 4221 is an aspheric lens with positive focal power, so that the large application scene of the panel of the LTP-LCD can be effectively adapted, and the non-adaption degree of the traditional lens to the system is reduced. Furthermore, the third lens group is arranged, so that the etendue of the illumination light can be effectively adapted to be diluted, and the problem of poor efficiency and uniformity caused by asymmetric arrangement is avoided, and meanwhile, the third lens group can also be arranged so that the lens 42 of this embodiment can be adapted to not only an imaging illumination mode, such as a direct projection apparatus adopting an illumination mode of a square rod, an imaging lens or a compound eye and an imaging lens as shown in the fifth embodiment shown in fig. 9, but also a non-imaging illumination mode, such as a non-telecentric direct projection apparatus adopting a cone rod and free-form surface lens system as shown in the sixth embodiment shown in fig. 10.
In this embodiment, the first lens group 422 and the second lens group 423 constitute a refractive lens group of the projection apparatus 42, the first lens group 422 is located at an incident end of the refractive lens group, that is, the first lens group 422 is a lens group closest to the modulation apparatus 421, no other lens is located between the first lens group 422 and the modulation apparatus 421, the second lens group 423 is located at an exit end of the refractive lens group, that is, the second lens group 423 is a lens group closest to the diaphragm 424, and no other lens is located between the second lens group 423 and the diaphragm 424; a person skilled in the art can add or subtract lenses in the refractive lens group according to the actual situation as long as it is ensured that the first lens group 422 and the second lens group 423 can be respectively located at both ends of the refractive lens group.
In this embodiment, the third lens group 425 constitutes an object side lens group of the telecentric lens system 42, and comprises a sixth lens 4251 and a seventh lens 4252 for improving 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, the prism 4211 is located between the modulation panel equivalent surface 4210 and the first lens group 422, the modulation panel is an LTP-LCD panel described herein, and the projection light emitted by the projection device is the image source light emitted by the modulation panel after modulation.
In some embodiments, the first lens group 422 further includes a second lens 4222 and a third lens 4223 which are arranged in order from the object side a to the image side B, the second lens 4222 and the third lens 4223 are both aspheric lenses, and the first lens 4221, the second lens 4222 and the third lens 4223 are all made of plastic materials, so that the effect of the plastic aspheric lenses on aberration correction can be exerted to the maximum extent, and the cost of the first lens group 422 can be effectively reduced due to the low cost of the plastic aspheric lenses. Meanwhile, the calibers of the first lens 4221, the second lens 4222 and the third lens 4223 are sequentially reduced, so that the effective light passing diameters of the first lens 4221, the second lens 4222 and the third lens 4223 are all smaller than the size of an image circle, and therefore projection light rays emitted by the projection device under non-telecentric illumination can be collected by the first lens group 422.
Further, in order to ensure that the refractive power of the first lens group 422 is positive, the first lens 4221 is an aspheric lens with positive refractive power, the second lens 4222 is an aspheric lens with positive refractive power, and the third lens 4223 is an aspheric lens with negative refractive power, and by such arrangement, the aberrations of the entire asymmetric lens structure can be balanced.
In the present embodiment, on the optical axis O2, the first lens 4221 may be the lens closest to the modulator 421 in the first lens group 422, and the third lens 4223 may be the lens second closest to the spherical mirror 120 in the first lens group 422.
In some embodiments, the first lens 4221, the second lens 4222 and the third lens 4223 are all plastic aspheric lenses, and by means of the arrangement, the effect of the plastic aspheric lenses on aberration correction can be exerted to the maximum extent. The object-side surface of the first lens element 4221 can be convex, and the image-side surface of the first lens element 4221 can be concave; the object-side surface of the second lens element 4222 is convex, and the image-side surface of the second lens element 4222 is convex; the object-side surface of the third lens element 4223 is concave, and the image-side surface of the third lens element 4223 is convex.
In some embodiments, the second lens group 423 includes the fourth lens 4232 and the fifth lens 4231 arranged in order from the object side a to the image side B, and the fourth lens 4232 and the fifth lens 4231 both use glass spherical lenses, so that the aberration correction effect of the glass spherical lenses can be exerted to the greatest extent, the resolution is improved, the glass spherical lenses are easier to manufacture than glass aspheric lenses, the cost of the second lens group 423 can be effectively reduced, and meanwhile, due to the fact that the F number of the projection apparatus in the embodiments is larger and the power is higher, the risk of thermal defocus can be effectively reduced by using glass spherical lenses.
In the present embodiment, on the optical axis O1, the fourth lens 4232 may be the lens closest to the stop 424 in the second lens group 423, and the fifth lens 4231 may be the lens second closest to the stop 424 in the second lens group 423. The object-side surface of the fourth lens element 4232 can be convex, and the image-side surface of the fourth lens element 4232 can be planar; the object-side surface of the fifth lens element 4231 is a flat surface, and the image-side surface of the fifth lens element 4231 is a concave surface.
In some embodiments, the fourth lens 4232 and the fifth lens 4231 can be glued into a whole, and chromatic aberration can be corrected by adopting a lens gluing mode, so that the imaging effect is improved. Illustratively, the fourth lens 4232 and the fifth lens 4231 may be adhesively connected by optical glue. Of course, in other embodiments, fourth lens 4232 and fifth lens 4231 may not be cemented.
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, so that the function of correcting aberration of the glass spherical lenses can be exerted to the greatest extent, the resolving power of the lens is improved, the glass spherical lenses are easier to manufacture than glass aspheric lenses, the cost of the third lens group 425 can be effectively reduced, and meanwhile, due to the fact that the F number of the projection device in the embodiments is larger and the power is higher, the risk of thermal defocus can be further reduced by adopting the glass spherical surfaces.
In the present embodiment, on the optical axis O2, the sixth lens 4251 may be the lens closest to the stop 424 in the third lens group 425, and the seventh lens 4252 may be the lens second closest to the stop 424 in the third lens group 425. The object-side surface of the sixth lens element 4251 may be a convex surface, and the image-side surface of the sixth lens element 4251 is a plane; the object-side surface of the seventh lens element 4252 is concave, and the image-side surface of the seventh lens element 4252 is convex.
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 realize a projection ratio of 1.3: 1, the resolution meets the requirement of image resolution of 1080P, and the distortion can be controlled to be less than 0.5% or even better. Specifically, in the present embodiment, the lens design parameters of the telecentric lens system 42 are as shown in table 8 below, the aspheric parameters of the object-side surface of the first lens 4221 are as shown in table 9 below, the aspheric parameters of the image-side surface of the first lens 4221 are as shown in table 10 below, the aspheric parameters of the object-side surface of the second lens 4222 are as shown in table 11 below, the aspheric parameters of the image-side surface of the second lens 4222 are as shown in table 12 below, the aspheric parameters of the object-side surface of the third lens 4223 are as shown in table 13 below, and the aspheric parameters of the image-side surface of the third lens 4223 are as shown in table 14 below.
Table 8: lens design parameter table for telecentric lens system 42
Table 9: aspheric parameters of object side of first lens 4221
| Parameter(s) | Value of |
| Radius of | 23.378917v |
| Conic constant (K) | -3.408604v |
| Coefficient of 4 th order (A) | -0.000004v |
| Coefficient of order 6 (B) | 2.317770e-009v |
| Coefficient of order 8 (C) | 4.961431e-013v |
| Coefficient of order 10 (D) | -5.096263e-016v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (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(s) | Value of |
| Radius of | 466.015227v |
| Conic constant (K) | 32.633406v |
| Coefficient of order 4 (A) | 0.000018v |
| Coefficient of order 6 (B) | -5.813403e-008v |
| Coefficient of order 8 (C) | 7.652725e-011v |
| Coefficient of order 10 (D) | -4.748475e-014v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 12: aspheric parameters of the image-side surface of the second lens 4222
| Parameter(s) | Value of |
| Radius of the pipe | -42.955815v |
| Conic constant (K) | -0.319589v |
| Coefficient of 4 th order (A) | 0.000036v |
| Coefficient of order 6 (B) | -8.885299e-008v |
| Coefficient of order 8 (C) | 1.021140e-010v |
| Coefficient of order 10 (D) | -5.106487e-014v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
Table 13: aspheric parameters of the image-side surface of the third lens 4323
Table 14: aspheric parameter of image side surface of third lens 4223
| Parameter(s) | Value of |
| Radius of | -14.544204v |
| Conic constant (K) | -0.886741v |
| Coefficient of 4 th order (A) | 0.000009v |
| Coefficient of order 6 (B) | 1.346666e-007v |
| Coefficient of order 8 (C) | -3.746224e-010v |
| Coefficient of order 10 (D) | 3.110053e-013v |
| Coefficient of order 12 (E) | 0.000000 |
| Coefficient of order 14 (F) | 0.000000 |
| Coefficient of order 16 (G) | 0.000000 |
| Coefficient of 18 th order (H) | 0.000000 |
| Coefficient of order 20 (J) | 0.000000 |
The optical performance of telecentric lens system 42 is demonstrated by specific experiments.
A modulation transfer function representation of telecentric lens system 42 is shown in fig. 23, where the abscissa represents spatial frequency and the ordinate represents modulation transfer function ratio. As can be seen from fig. 16, when the nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratios are all greater than 60% and the ratios of the corresponding positions are also all greater than that of the lens system 41, and the modulation transfer function ratios have no significant degradation, which means that each pixel can be more clearly analyzed compared with the lens system 41, and good image quality is obtained.
The graph of longitudinal spherical aberration of telecentric lens system 42 is shown in fig. 24 (a), where fig. 24 (a) shows the graph of longitudinal spherical aberration using 455nm, 545nm and 615nm light, which reflects to some extent that the optical distortion level of telecentric lens system 42 is between 0-1.4%, and the distortion range is smaller than that of lens system 41.
The astigmatism graph of telecentric lens system 42 is shown in fig. 24 (b), where fig. 24 (b) shows the astigmatism field curvature plots of light rays with wavelengths of 455nm, 545nm and 615nm, and it can be seen from fig. 24 (b) that the degree of astigmatism is relatively light, which reflects to some extent that telecentric lens system 42 has a relatively low optical distortion level.
The distortion curve of the telecentric lens system 42 is shown in fig. 24 (c), and fig. 24 (c) shows the distortion curve of the lens system 41 with the light rays having the wavelengths of 455nm, 545nm and 615nm, and it can be seen from fig. 24 (c) that the lens system 41 has a relatively low maximum distortion rate and a good optical performance.
The system dot-sequence diagram of the telecentric lens system 42 is shown in fig. 25, and it can be seen from the diagram that the average diffuse spot radius of the dot-sequence diagram under each field of view is small, the image quality is good, and the resolution requirement of 1080P can be met.
The lateral aberration diagram of telecentric lens system 42 is shown in fig. 26, where 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 contrast curve of the telecentric lens system 42 is shown in fig. 27, and as shown in fig. 26 and 27, the telecentric lens system 42 has good imaging quality in terms of lateral chromatic aberration and relative illumination.
Fig. 28 shows schematic diagrams of chief ray angles of different fields of view of the telecentric lens system 42, and it can be seen from the diagrams that the average value of image space angles, i.e. non-telecentricity, is less than 5 °, which meets the illumination requirement of the projection apparatus.
The telecentric lens system 42 provided by this embodiment includes a modulation device 421, a first lens group 422, a second lens group 423, a diaphragm 414, and a third lens group 424 sequentially disposed between the object side a and the image side B along the optical axis O2, and the third lens group is disposed, so that the etendue of the illumination light can be effectively adapted to be diluted, and the problem of poor efficiency and uniformity caused by asymmetric disposition is avoided, and meanwhile, the disposition of the third lens group can also enable the telecentric lens system 42 of this embodiment to be adapted to not only the illumination mode of imaging, such as the direct projection apparatus of the illumination mode using the square rod, the imaging lens or the fly-eye and the imaging lens shown in the fifth embodiment shown in fig. 9, but also the illumination mode of non-imaging, such as the non-telecentric direct projection apparatus of the sixth embodiment shown in fig. 10, which uses the cone rod and the free-form lens system.
Furthermore, in the projection apparatus 160 shown in the seventh embodiment and the projection apparatus 170 shown in the eighth embodiment, since the light beam converging component, such as the field lens, the fresnel lens or the free-form surface lens, is provided, much stray light is brought to affect the ANSI contrast, so that the application also provides an ultra-short focal length lens system 43, the length is less than 220mm, the f number is 3.2, the projection ratio is 0.4: 1, and the volume of the projection apparatus can be further reduced.
As shown in fig. 29, a lens system 43 according to 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, a second lens group 434, a stop 435, a third lens group 436 and a second reflector 437 which are sequentially disposed along the optical axis O3 between an object side a and an image side B, wherein the first reflector 433 is a plane reflector for realizing optical path folding, and folds the optical axis of the lens from the first optical axis O3 to the second optical axis O4, so that light is reflected from the direction along the first optical axis O3 to the direction along the second optical axis O4, the volume of the lens system 43 along the second optical axis O4 is compressed, the second reflector 437 is a plastic aspheric reflector including a reflective surface protruding toward the object side a, and the projected 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 sequentially disposed along the first optical axis O3, and the projection light emitted from the modulation device 431 sequentially enters the first lens group 432 and the first reflector 433, and is reflected by the first reflector 433 as an incident light along the second optical axis O4.
In this embodiment, the first lens group 432 is a refractive lens group, and mainly functions to correct system aberration. Specifically, the first lens group 432 includes a first lens 4321 and a second lens 4322, wherein an object-side surface of the first lens 4321 is a concave surface, an image-side surface of the first lens 4321 is a convex surface, an object-side surface of the second lens 4322 is a concave surface, an image-side surface of the second lens 4322 is a concave surface, and an overall focal power of the first lens group is negative.
The first mirror 433 is a plane mirror, preferably disposed at 45 ° to both the first optical axis O3 and the second optical axis O4, thereby preventing the light from being blocked or overlapping while ensuring the light to be folded.
In the subsequent optical path of the first reflecting mirror 433, a second lens group 434, a stop 435, a third lens group 436, and a second reflecting mirror 437 are disposed in this order 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 for further converging light, wherein the third lens 4341 is a plastic aspheric lens, and the fourth lens 4242 and the fifth lens are glass spherical lenses, so that the third lens group 434 can further converge the light reflected by the first reflector 433 and can prevent a thermal defocus problem at the position of the stop 434 due to too high converging energy of the light.
In some embodiments, the object-side surface of the third lens element 4341 is convex and the image-side surface of the third lens element 4341 is concave. The object-side surface of the fourth lens element 4242 is concave, and the image-side surface of the fourth lens element 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 power of the second lens group is positive.
In some embodiments, the fourth lens 4342 and the fifth lens 4343 are glued together, and chromatic aberration can be corrected by using lens gluing, so that the imaging effect is improved. Illustratively, the fourth lens 4342 and the fifth lens 4343 may be adhesively connected by optical glue. Of course, in other embodiments, the fourth lens 4342 and the fifth lens 4343 may not be cemented.
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, so that light passing through the stop can be effectively diffused and sufficiently refracted onto the second reflecting mirror 437, and further the influence of stray light on ANSI is reduced.
In some embodiments, an object-side surface of the sixth lens element 4361 is convex and an image-side surface of the sixth lens element 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 entire optical power of the third lens group 436 is negative.
The second reflecting mirror 437 is an aspheric reflecting mirror for eliminating aberration caused by spherical distortion, so that the projection light incident from the third lens group 436 to the second reflecting mirror 437 is shaped, thereby increasing the optical path at the second reflecting mirror 437, reducing the number of lenses, making the whole optical system simpler, reducing the assembly difficulty, and the second reflecting mirror 437 can effectively shape and correct the projection light, thereby improving the system resolution; in addition, based on the reduction of the number of the lenses, the energy loss caused by the fact that the projection light passes through different media for multiple times can be reduced, and the projection quality is improved. On the other hand, the second reflecting mirror 437 can also be made of glass, which has better thermal stability and can avoid thermal defocusing under high illumination.
In this embodiment, the second reflecting mirror 437 is a non-spherical reflecting mirror, and the reflecting surface of the second reflecting mirror is coated with a reflective film, and the reflectivity of the reflecting surface may be greater than 95%. Illustratively, the reflective film may be a silver reflective layer or an aluminum reflective layer to achieve a reflectance of greater than 95%.
In some embodiments, the modulation device 431 has a projection image emitting surface, the distance from the reflecting surface of the second reflector 437 to the projection image emitting surface along the first optical axis O3 and the second optical axis O4 is L (not shown), the distance from the reflecting surface of the second reflector 437 to the exit surface of the third lens group 436 is D (not shown), and the requirements are satisfied
Thereby, aberration can be eliminated, resolution can be improved andand a smaller transmittance is achieved, so that the lens system 43 has a better optical performance. The projection image emitting surface is a surface of the modulation panel facing the prism 4312, and the exit surface of the third lens group 436 is an object side surface of the eighth lens 4363.
In some embodiments, on the second optical axis O4, the distance from the reflecting surface of the second mirror 437 to the stop 435 is L1 (not shown), the sum of the distances from the stop 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. Thereby, it is possible to eliminate aberration, improve resolution, and achieve smaller transmittance, so that the lens system 43 has better optical performance. An incident surface of the first lens group 432 is an image side surface of the first lens 4321.
In this embodiment, the lens system 43 can achieve a projection ratio of 0.38: 1 to 0.44: 1. Illustratively, the lens system 43 can achieve a 0.4: 1 projection ratio with a resolution meeting 1080P resolution requirements.
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 parameter table 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 described below by way of specific experiments.
A modulation transfer function representation of lens system 43 is shown in fig. 30, where the abscissa represents spatial frequency and the ordinate represents modulation transfer function ratio. As can be seen from fig. 30, when the nyquist frequency is greater than 22 cycles/mm, the modulation transfer function ratios are both greater than 70% and the ratios of the corresponding positions are also both greater than those of the lens system 41 and the telecentric lens system 42, and the modulation transfer function ratios have no significant degradation, which means that each pixel can be analyzed more clearly than those of the lens system 41 and the telecentric lens system 42, and good image quality is obtained.
The system dot sequence of the lens system 43 is shown in fig. 31, and it can be seen from the figure that the average dispersed spot radius of the dot sequence under each field of view with the defocus amount from-0.09 mm to +0.09mm is small, the image quality is good, and the resolution requirement of 1080P can be satisfied.
The lateral aberration diagram of the lens system 43 is shown in fig. 32, 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 contrast curve of the lens system 43 is shown in fig. 33, and as shown in fig. 32 and 33, the lens system 43 has good imaging quality in terms of both lateral chromatic aberration and relative illuminance.
Fig. 34 shows schematic diagrams of chief ray angles of different fields of view of the lens system 43, and it can be seen from the diagrams that the average values of image space angles are all less than 7 °, which meets the illumination requirement of the projection apparatus.
The lens system 43 provided in this embodiment includes a modulation device 431, a first lens group 432, a first mirror 433, and a second lens group 434, a diaphragm 435, a third lens group 436, and a second mirror 437 which are sequentially disposed along the optical axis O3 between the object side a and the image side B, wherein the first mirror 433 and the second mirror are disposed to realize optical path folding, so as to effectively compress the volume of the lens system 43 along the second optical axis O4, and meanwhile, the second lens group and the third lens group are disposed to make the resolving power of the entire lens system 43 large and avoid the risk of thermal defocusing, so as to be adapted to the application scenarios with large panels 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 embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The above description is only an embodiment of the present application, and is not intended to limit the scope of the present application, and all equivalent structures or equivalent processes performed by the present application and the contents of the attached drawings, or directly or indirectly applied to other related technical fields are also included in the 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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|---|---|---|---|
| CN202110957141.2A CN115903174A (en) | 2021-08-19 | 2021-08-19 | Lens system and projection device |
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| CN202110957141.2A CN115903174A (en) | 2021-08-19 | 2021-08-19 | Lens system and projection device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116299985A (en) * | 2023-05-17 | 2023-06-23 | 歌尔光学科技有限公司 | Projection lens and projection module |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116299985A (en) * | 2023-05-17 | 2023-06-23 | 歌尔光学科技有限公司 | Projection lens and projection module |
| CN116299985B (en) * | 2023-05-17 | 2023-08-29 | 歌尔光学科技有限公司 | Projection lens and projection module |
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