WO2010099709A1 - 微型投影机用光学引擎 - Google Patents

微型投影机用光学引擎 Download PDF

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WO2010099709A1
WO2010099709A1 PCT/CN2010/070168 CN2010070168W WO2010099709A1 WO 2010099709 A1 WO2010099709 A1 WO 2010099709A1 CN 2010070168 W CN2010070168 W CN 2010070168W WO 2010099709 A1 WO2010099709 A1 WO 2010099709A1
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light
light source
optical
optical engine
projector according
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PCT/CN2010/070168
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English (en)
French (fr)
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李东珍
权赫烈
金城守
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上海三鑫科技发展有限公司
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Priority to JP2011600071U priority Critical patent/JP3174812U/ja
Publication of WO2010099709A1 publication Critical patent/WO2010099709A1/zh

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2073—Polarisers in the lamp house

Definitions

  • Portable pico projectors should be battery-powered if they are to be used in mobile phones. For this purpose, high-efficiency light sources with low power consumption should be used.
  • the most suitable source for such low-power micro-projectors is a laser source or a light-emitting diode (Low). Emitting Diode, referred to as "LED") light source.
  • the laser light source is an efficient light source that has been widely considered to be low in power consumption and high in measurement.
  • a pico projector converts light emitted from a light source into an image frame using a light modulator.
  • a light modulator is usually a projection type/reflective liquid crystal display using liquid crystal (Liquid Crystal) Display, referred to as "LCD”) and liquid crystal on silicon (Liquid Crystal On Silicon, referred to as "LCOS".
  • LCD liquid crystal
  • LCOS liquid crystal on silicon
  • the above-mentioned light modulator uses polarized light to convert the image picture, so before the light emitted from the light source is incident on the light modulator, only one of the P-polarized light and the S-polarized light is usually selected by a polarizer, and the like. Will be discarded.
  • the vibration direction of the light vector (electric field intensity vector) of the S-polarized light is perpendicular to the incident surface, and the vibration direction of the light vector of the P-polarized light is parallel to the incident surface.
  • the incident surface is a plane composed of the interface normal and the wave vector direction of the incident ray.
  • the laser light source is the same phase and linearly polarized light from the root, so it is suitable for the above light modulator.
  • Multiplier refers to converting an existing long-wavelength laser into a short-wavelength.
  • the speed of light is constant, so the frequency of light is increased by 2 times and the wavelength is reduced by 1/2.
  • the RGB light having a wavelength of 532 nm can be obtained by multiplying the 1064 nm IR light.
  • the linear polarization ratio of the laser will be reduced to 70% to 80% during the frequency doubling process. As the linear polarization ratio decreases, the discarded light also increases, and the green light is the primary color light that affects the white light measurement, so it has a great influence on the light efficiency.
  • the light efficiency of an LED source is worse than that of a laser source. Because the LED light source is a mixed light that is not linearly polarized, the green, blue/red primary colors are all polarized by using a polarizing plate at the front end of the light modulator to filter about half of the light to achieve linear polarization.
  • the existing optical engine structure filters a considerable amount of light in order to achieve linear polarization, and the filtered light is gradually converted into heat energy, which causes heat generation of the optical engine, and there is also a rise in power consumption due to low light efficiency.
  • the problem is also a rise in power consumption due to low light efficiency.
  • an optical engine for a pico projector including:
  • At least one light source is provided.
  • a polarized light separating element for separating light emitted from a light source into two optical paths, wherein the two optical paths have different polarization modes
  • Two light modulators for converting light on two optical paths into an image frame
  • At least two polarization beam splitters are used to adjust the two optical paths after passing through the optical modulator to the same optical path.
  • the light is modulated and combined into one way, which can fully utilize the originally filtered polarized light, improve the efficiency of the light source, and reduce the power consumption of the optical engine. Quantity and calorific value.
  • the three primary color laser light source only the different polarized lights of the green laser light are shunted, so that the phase difference caused by the optical path difference of the different optical paths can be completely eliminated by setting the thickness of the polarized light separating element, which is particularly suitable for the current green color.
  • the laser can only be obtained by multiplying the frequency.
  • the effect of laser speckle can be greatly reduced.
  • the light emitted by the three light sources is combined and split by a polarizing element, and the various lights can be uniformly processed with fewer components, which is particularly suitable for the mixed light emitted by the LED light source. happening.
  • the thickness T of the polarized light separating element is adjusted to be 2n ⁇ times the wavelength of the green light 532 nm (n is an integer ) is the most appropriate.
  • FIG. 1 is a schematic diagram showing an example of an optical engine constituting a pico projector using only one optical path;
  • FIG. 2 is a schematic diagram showing an example of a laser light source as an optical engine in the first embodiment of the present invention
  • FIG. 3 is a schematic diagram showing an example of an LED light source as an optical engine in a second embodiment of the present invention
  • FIG. 4 is a schematic diagram showing another example of an optical engine using an LED as a light source in the second embodiment of the present invention.
  • Figure 5 is a schematic illustration of a configuration diagram of a polarized light separating element designed in accordance with the present invention
  • Fig. 6 is a schematic diagram showing an example of an optical engine using only one light source in the third embodiment.
  • An important innovation of the present invention is to separate the light emitted by the light source into two optical paths of different polarization modes, and respectively optically modulate the two optical paths into one path.
  • a technical solution that does not use this innovation is described here first. The technical solution is shown in Figure 1.
  • This reflective optical engine includes:
  • the R/G/B light source sequentially illuminates the R/G/B light. Specifically, the time for irradiating one frame is set to T, the time of T/3 is irradiated to the R light source, and the time of the next T/3 is irradiated with the G light source, and then The next T/3 time illuminates the B source. It can be understood that the light source can also be sequentially irradiated in other orders, such as B/G/R.
  • the three light sources (10R, 10G, 10B) are reflected by the respective dichroic mirrors 50R, 50G, 50B or transmitted to the diffuser (20).
  • the dichroic mirror 50G functions to reflect the G light source (green laser light emitted from 10G) and transmit the remaining light.
  • the dichroic mirror 50G can also use a general mirror that can reflect all of the ordinary visible light.
  • the dichroic mirror 50R functions to reflect the R light source (red laser light emitted from 10R) and pass the light of the remaining wavelength range
  • the dichroic mirror 50B functions to reflect the R light source (the blue laser light emitted from 10B) through the remaining wavelength. The effect of the range of light.
  • the diffuser vibrates vertically to the optical axis, so the randomness of the light increases as it passes through the diffuser.
  • This diffuser is a device designed to eliminate laser-specific laser speckles (Speckle) to reduce the coherence of laser light to reduce laser speckle.
  • Beam Shaper Beam Shaper
  • the reason for changing the shape of the beam is to shape the shape of its beam to adapt to the shape of the incident surface of the light modulator (60), thereby improving the light efficiency.
  • a typical example of a beam shaper (30) is a fly-eye lens (Fly Eye Lens), Light Tube (Light Pipe) and so on. Shown in Fig. 1 is a fly-eye lens composed of a plurality of spherical or aspherical small lens combinations on a substrate as a typical example of a beam shaper (30).
  • the compound eye lens (30) is composed of a plurality of small lenses on a transparent substrate, and these small lens bodies can be embodied in various shapes such as a quadrangular convex lens, a hexagonal convex lens, a circular shape, etc., but preferably with a light modulator.
  • the shape (more precisely, the effective picture shape of the light modulator) is consistent.
  • the shape of the small lens body is also preferably a quadrangular shape, thereby minimizing light loss.
  • a double-sided type fly-eye lens having a small lens body on both sides is used, and a single-face type fly-eye lens can also be used.
  • the objective lens (40) is a lens that bundles the light shaped by the beam shaper, and is generally composed of two pieces, and more precise focusing can be achieved by adjusting the distance between the two lenses.
  • the light modulator (60) refers to an element that selectively passes incident light, blocks or changes the optical path to form an image.
  • a typical example of a light modulator (60) is a digital micromirror device (Digital Micromirror Device (“DMD”), Liquid Crystal Display (“LCD”) components, liquid crystal on silicon (Liquid) Crystal On Silicon, referred to as "LCOS” and so on.
  • DMD Digital Micromirror Device
  • LCD Liquid Crystal Display
  • LCOS liquid crystal on silicon
  • DMD is used in digital light processing (Digital Light Processing, referred to as "DLP"), which uses the field timing (field) Sequential), using a digital mirror arranged in the same number of pixels as the number of pixels (DIGITAL MIRROR).
  • DLP refers to a projector that uses light from a light source to adjust the optical path with a digital mirror and reflects it with a spacer to achieve Gradation or image formation.
  • a liquid crystal display element refers to an element that selectively turns on/off a liquid crystal to form an image.
  • the direct-view projection is a method in which the background light behind the liquid crystal display element forms an image through the LCD panel and can be directly observed;
  • the projection type projection is to enlarge an image formed by the liquid crystal display element by using a projection lens and project it onto the screen, and observe the slave screen.
  • the way of reflecting the image; the reflective type is basically the same as the projected type, except that the reflective type is provided with a reflective film on the substrate under the LCD, and the reflected light is amplified and projected onto the screen.
  • LCOS is a reflective liquid crystal display, which converts the lower substrate of the two-sided substrate of the conventional liquid crystal display end from a transparent glass to a silicon substrate, thereby operating in a reflective manner.
  • the projection lens (70) is composed of a plurality of lenses, and an image formed by the light modulator (60) is enlarged and projected onto a screen (not shown).
  • PBS polarization beam splitter
  • an incident polarizing plate (110) between the PBS and the objective lens, which serves to linearly polarize the light incident on the light modulator.
  • the green laser light source reduces light by 20% to 30%, and in the case of an LED, it reduces light by about half.
  • a first embodiment of the present invention relates to an optical engine for a pico projector, the structure of which is substantially as shown in FIG.
  • a green light source (10G) is separated into P-polarized light and S-polarized light by a polarized light separation film (90).
  • the same result can be obtained by reflecting the P-polarized light through the S-polarized light or the P-polarized light and the S-polarized light.
  • the reflected P-polarized light is taken as an example.
  • the P-polarized light reflected by the polarized light separation film (90) passes through the dichroic mirror (50R, 50B), the diffuser (20), the beam shaper (30), and the objective lens (40) are incident on the PBS (200).
  • the dichroic mirror (50R) has the characteristic of reflecting the red light and the rest of the light is given.
  • the dichroic mirror (50B) has the characteristic of reflecting the blue light and the rest of the light is given to pass, and all of the three primary colors of green/red/blue are unified to the same optical axis. The role.
  • the polarized light separation film (201) of the PBS (200) is opposite to the polarized light separation film (90) positioned before the green light source (10G), and P-polarized light is passed to and reflects the S-polarized light. Subsequently, the above P-polarized light passing through the objective lens is incident on the light modulator (601) through the PBS (200). The light reflected from the reflective optical modulator (601) is converted into S-polarized light by phase conversion. The converted light is reflected by the polarized light separation film of the PBS (200) and incident on the projection lens.
  • Light from the red light source (10R) passes through the dichroic mirror (50R, 50B) and is incident on the projection lens through the same path as the P-polarized light of the green light.
  • Light from the blue light source (10B) passes through the dichroic mirror (50B) and is incident on the projection lens through the same path as the above-described red light.
  • the red light source (10R) and the blue light source (10B) described above are adjusted to be the same P-polarized light as the P-polarized light of the green light.
  • the light from the green light source (10G) is reflected by the reflective film (80) through the polarized light separation film (90), passes through the diffuser (20), the beam shaper (30), and the objective lens (40) is incident on the PBS (100). .
  • the polarized light separation film (101) of the PBS (100) reflects the S-polarized light to pass P-polarized light like the polarized light separation film (201).
  • the light incident on the PBS (100) is then incident on the light modulator (602) through the polarized light separation film (101).
  • the light reflected by the light modulator (602) is then converted into P-polarized light and incident on the projection lens through the polarized light separation film (101).
  • the light separated by the polarized light has only green light, so the light modulator (602) converts only the image picture of the corresponding green light. Therefore, it suffices to perform light modulation according to the time point of the green light.
  • Fig. 5 is a view for explaining in more detail the polarization separating element. As shown in FIG. 5, the light reflected by the polarized light separation film (90) travels longer than the directly passing light, and the length of the optical path difference is equal to the length (300) passing through the reflecting surface (80).
  • the length (300) is the thickness T of the polarized light separating element. This optical path difference should not affect the phase of the separated light.
  • the light separated by polarized light is green light, so the thickness T should be 2n ⁇ times the wavelength of the green laser light of 532 nm. (n is an integer).
  • the optical path difference of the two optical paths is 2n ⁇ times the wavelength of the light.
  • the different polarized lights of the green laser light are shunted, so that the phase difference caused by the optical path difference of the different optical paths can be completely eliminated by setting the thickness of the polarization separating element, which is particularly suitable for the current green laser only. It can be obtained by frequency doubling and the linear polarization ratio is low.
  • a second embodiment of the present invention relates to an optical engine for a pico projector.
  • the second embodiment is basically the same as the first embodiment, and the difference mainly lies in:
  • the light source is a laser light source of three primary colors of red, green, and blue, and the polarization separating element divides only the green laser into two optical paths, and the red and blue lasers exist only in one optical path.
  • the light source is an LED light source of three primary colors of red, green, and blue, and the light of the three light sources is first combined into one optical path and then separated by the polarization separating element into two optical paths of different polarization modes. Because the three LED light sources emit mixed light, the light of different polarization modes is separately modulated and combined into one way, which can nearly double the efficiency of the light source.
  • the polarized light separation film (90) is set to reflect P-polarized light and to pass S-polarized light.
  • the S-polarized light passing through the polarized light separation film (90) is incident on the PBS (200) through the beam shaper (30) and the objective lens (40).
  • the polarized light separation film (201) of the PBS (200) passes through the S-polarized light to reflect the P-polarized light.
  • the S-polarized light incident on the PBS (200) is then incident on the light modulator.
  • the light reflected by the light modulator (601) is then converted into P-polarized light and incident on the projection lens (70) through the polarized light separation film (201).
  • P-polarized light reflected by the polarization separation film (90) enters the beam shaper (30), the objective lens (40), and the PBS (100) through the reflection film (80).
  • the polarized light separation film (101) of the PBS (100) is the same as the polarized light separation film (201), and the P-polarized light is reflected by the S-polarized light.
  • the incident P-polarized light is then reflected by the polarized light separation film (101) and then incident on the light modulator (602), and then converted into S-polarized light by the light modulator (602) and passed through the PBS (100) and the PBS ( 200) incident on the projection lens (70).
  • the thickness T of the polarized light separating element is adjusted to 2n ⁇ times (n is an integer) of the green light wavelength 532 nm.
  • the polarization separating element may not be exactly 2n ⁇ times exactly 532 nm, and a certain advantageous effect can be obtained as long as it is 2n ⁇ times a wavelength near the central wavelength of visible light.
  • FIG. 3 can also have other variations.
  • a variation is shown in FIG. 4.
  • the variation of FIG. 4 has a mirror 50G with respect to FIG. 3, and 50G can reflect only green light. It can be all light reflected.
  • a third embodiment of the present invention relates to an optical engine for a pico projector.
  • the third embodiment is basically the same as the second embodiment, the difference is mainly that the second embodiment uses three light sources, and the third embodiment uses only one light source.
  • the structure of the optical engine in the third embodiment is as shown in FIG. .
  • a typical application of the third embodiment is a pico projector that displays black and white images using a white light source 10 and a mirror 50.
  • a single-color laser can be used as a light source.
  • the image is a monochrome "grayscale image" that can be applied to some occasions where color images are not required.
  • a fourth embodiment of the present invention relates to an optical engine for a pico projector.
  • the fourth embodiment is basically the same as the first embodiment, and the difference mainly lies in:
  • the first embodiment uses three source light sources, while the fourth embodiment uses a hybrid light source, ie the light source comprises at least one laser source and at least one LED source.
  • the light source comprises at least one laser source and at least one LED source.
  • a light source with a lower linear polarization ratio such as an LED light source and a laser source obtained by frequency doubling
  • a light source with a higher linear polarization ratio such as a laser source that is not multiplied, may appear in only one optical path or simultaneously in two optical paths.

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Description

微型投影机用光学引擎 技术领域
便携式微型投影机
背景技术
为了把比手掌还小的便携微型投影机或可装入笔记本的投影机商用化，需要开发体积小、耗电低的投影机。要实现投影机的微型化需要使用体积小且量度高的光源。
便携微型投影机如果要适用于手机的话，应当可以用电池驱动，为此就要使用相对耗电低的高效光源。最适合于此类低耗电微型投影机的光源为激光光源或是发光二级管（Low Emitting Diode，简称“LED”）光源。激光光源是已被广泛认为低耗电、量度高的高效光源。
微型投影机利用光调制器把从光源射出的光转换为影象画面。目前此种光调制器通常是利用液晶的投射型/反射型液晶显示器（Liquid Crystal Display，简称“LCD”）和硅基液晶（Liquid Crystal On Silicon，简称“LCOS”）。但是上述光调制器利用了偏振光来转换影象画面，所以在把光源射出的光入射到光调制器之前，通常利用偏振光板（Polarizer）在P偏振光和S偏振光中只选择一个，其它的会被丢弃。其中，S偏振光的光矢量（电场强度矢量）的振动方向垂直于入射面，P偏振光的光矢量的振动方向平行于入射面， 入射面是界面法线和入射光线的波矢方向组成的平面。
激光光源从根源上是同一相位且线偏振的光，所以很适合上述光调制器。
为了表现影象画面，需要绿/蓝/红三种原色的激光。目前蓝色和红色的半导体激光已经存在，但不过固态（Solid state）的绿色激光还没有被开发出来。为了克服这个问题可以使用倍频（Frequency Doubling）技术。倍频是指把现有的长波段的激光转换为短波段。
波长λ、速度v和频率f之间的关系为：v=λ*f。
光的速度是一定的，所以把光的频率提高2倍，波长会减少1/2。为了得到532nm的绿色光，把1064nm的IR光进行倍频以后就可以得到其减半的532nm波长光。不过在倍频过程中激光的线偏振比例会减少到原来的70%~80%。随着线偏振比例的减少，废弃光也会增加，而绿色光是影响白光量度的原色光，所以对光效率有很大的影响。
LED光源的光效率比激光光源还要差。因为LED光源是不会线偏振的混合光，所以绿/蓝/红三种原色都是利用光调制器前端入射偏振光板来把大约一半的光过滤掉来达到线偏振。
 技术问题
现有的光学引擎构造为了达到线偏振要把相当多的光过滤掉，过滤后的光会逐渐转换成热能，从而引起光学引擎的发热问题，并还会存在因为光效率的低下导致电力消耗上升的问题。
技术解决方案
为解决上述技术问题，本发明的实施方式提供了一种微型投影机用光学引擎，包括：
至少一个光源，
偏振光分离元件，用于将光源射出的光分离为2个光路，这两个光路的偏振方式不同；
两个光调制器，分别用于将2个光路上的光转换成影象画面；
至少两个偏振分光镜，用于将经过光调制器后的2个光路调整为相同的光路。
 有益效果
本发明实施方式与现有技术相比，主要区别及其效果在于：
通过将从光源射出的光分为两个不同偏振方式的光路，分别进行光调制后合为一路，可以充分利用原先被过滤掉的偏振光，提高了光源的效率，减少了光学引擎的耗电量和发热量。
进一步地，对于三原色激光光源，只对绿色激光的不同偏振光进行分路处理，从而可以通过设置偏振光分离元件的厚度而完全消除不同光路的光程差所导致的相位差，特别适合目前绿色激光只能通过倍频得到的情况。
进一步地，通过在激光光源和光调制器之间引入漫射体，可以大大减少激光散斑的影响。
进一步地，对于LED光源，将三个光源发出的光合成一路后以一个偏振光元件进行分路处理，可以用较少的元件对各种光进行统一处理，特别适合LED光源所发出是混合光的情况。
进一步地，LED的情况下全波长的光全部被偏振光分离，且在亮度上绿色光的影响是最大的，所以偏振光分离元件的厚度T调整为绿色光波长532nm的2nπ倍（n是整数）最为妥当。
 附图说明
图1是只用一个光路的构成微型投影机的光学引擎的简略图实例；
图2是本发明第一实施方式中以激光光源为光学引擎的简略图实例；
图3是本发明第二实施方式中以LED光源为光学引擎的简略图实例；
图4是本发明第二实施方式中另一种以LED为光源的光学引擎的简略图实例；
图5是根据本发明设计的偏振光分离元件构造图的简略图实例；
图6是第三实施方式中只用一个光源的光学引擎的简略图实例。
 本发明的最佳实施方式
在以下的叙述中，为了使读者更好地理解本申请而提出了许多技术细节。但是，本领域的普通技术人员可以理解，即使没有这些技术细节和基于以下各实施方式的种种变化和修改，也可以实现本申请各权利要求所要求保护的技术方案。
为使本发明的目的、技术方案和优点更加清楚，下面将结合附图对本发明的实施方式作进一步地详细描述。
本发明的一个重要创新是将光源射出的光分离为2个不同偏振方式的光路，对两个光路分别进行光调制后再合为一路。为了进行比较，这里先说明未使用这一创新的一种技术方案。该技术方案如图1所示。
这个反射型的光学引擎包括：
R光源（10R），G光源（10G），B光源（10B），分色镜50R、40G、50B，漫射体（20），光束整形器（30），物镜（40），光调制器（60），投射透镜（70），偏振分光镜（80），其中R代表红色，G代表绿色，B代表蓝色。
R/G/B光源依次照射R/G/B光，具体地说，把照射一个帧的时间设为T，T/3的时间照射R光源，接着的T/3的时间照射G光源，再接着的T/3时间照射B光源。可以理解，光源也可以按照其它顺序依次照射，如B/G/R等。
三个光源（10R，10G，10B）被各自的分色镜50R，50G，50B反射或是透射到漫射体（20）。
分色镜50G起到反射G光源（从10G照射出的绿色激光）并让剩余光线透过的作用，分色镜50G也可以使用能够将普通可视光线全部予以反射的一般镜子。分色镜50R起到反射R光源（从10R照射出的红色激光）、通过剩余波长范围的光线的作用，分色镜50B起到反射R光源（从10B照射出的蓝色激光）通过剩余波长范围光线的作用。
漫射体垂直振动于光轴，因此通过漫射体的时候，光的随机性（Randomness）会得到增加。这种漫射体，是为了消除激光特有的激光散斑（Speckle）而设置的装置，用以减少激光光线的连贯性（Coherence）特征来达到减少激光散斑的目的。
通过漫射体的光会通过光束整形器（Beam Shaper）以转变光束形状。转变光束形状的原因是要将其光束的模样进行整形，以适应于光调制器（60）的入射面形状，从而提高光效率。光束整形器（30）的典型事例为复眼透镜（Fly Eye Lens）、灯管（Light Pipe）等。在图1中标示的是作为光束整形器（30）的典型例子的，在基板上面用多块球面或非球面的小型透镜组合构成的复眼透镜。
复眼透镜（30）由透明基板上多个小型透镜所组成，这些小型透镜体们可以体现为各种形状，如四角形凸透镜、六角形凸透镜以及圆形等等，但最好是与光调制器的形状（更加准确地说，是光调制器的有效画面形状）相一致。例如：光调制器的有效画面大致为四角形状，那么小型透镜体的形状也最好也为四角形状，从而使光损失最小化。
在图1的实例中使用了双面都有小透镜体的双面型复眼透镜，也可以使用单面型复眼透镜。
物镜（40）是将经过光束整形器整形的光线进行集束的透镜，一般由两片组成，通过调节两片透镜之间的距离可以达到更加准确的聚焦。
光调制器（60）是指将入射的光线进行选择性通过、阻断或改变光径来形成影像图片的元件。光调制器（60）的典型实例有数字微镜器件（Digital Micromirror Device，简称“DMD”）、液晶显示（Liquid Crystal Display，简称“LCD”）元件、硅基液晶（Liquid Crystal On Silicon，简称“LCOS”）等等。
DMD是用在数字光处理（Digital Light Processing，简称“DLP”）投影机的元件，它利用场时序（field sequential）的驱动方式，使用与像素数量一样多的矩阵形态排列的数码镜（DIGITAL MIRROR）。DLP是指从光源照射出的光用数码镜来调节光径，并用隔板反射来达到渐变（Gradation）或形成图象的投影仪。
液晶显示元件（LCD）是指选择性地开/关液晶来形成图象的元件。使用LCD元件的投影机中，有直视型（direct-view）、投射型以及反射型。直视型投影是液晶显示元件后面的背景光通过LCD面板形成图象并可以直接观察的方式；投射型投影是将通过液晶显示元件形成的图象利用投射透镜放大后投射到屏幕，观察从屏幕反射的图象的方式；反射型与投射型的结构基本相同，区别之处在于，反射型在LCD下面基板上设有反射膜，反射的光线被放大投射到屏幕上。
LCOS属于反射型液晶显示，它将以往液晶显示端的两面基板中的下方基板由透明的玻璃改为硅基板，从而用反射型方式运作。
投射透镜（70）由多个透镜构成，将由光调制器（60）形成的图象向屏幕（图中未标识）上放大投射。
因为是反射型光调制器，在光调制器和投射透镜之间还有偏振分束器（Polarizing Beam Splitter，简称“PBS”）（80）。
PBS和物镜之间还有入射偏振光板（110），起到把往光调制器入射的光进行线偏振过滤的作用。通过这样的过滤，在激光光源的情况下，绿色激光光源减少20%至30%的光，LED的情况下大约减少一半的光。
本发明第一实施方式涉及一种微型投影机用光学引擎，其结构大致如图2所示。
从绿色光源（10G）射出的光，通过偏振光分离膜（90）分离成P偏振光和S偏振光。反射P偏振光通行S偏振光或是通行P偏振光反射S偏振光都可以得到相同结果，在此以反射P偏振光为例说明。
通过偏振光分离膜（90）反射的P偏振光经过分色镜（50R，50B），漫射体（20），光束整形器（30），物镜（40）入射到PBS（200）。分色镜（50R）有反射红色光其余光给予通行的特性，分色镜（50B）有反射蓝色光其余光给予通行的特性，都起着把绿/红/蓝三原色光统一到同一光轴的作用。
PBS（200）的偏振光分离膜（201）和位置在绿色光源（10G）前的偏振光分离膜（90）相反，通行P偏振光给并反射S偏振光。随后，经过物镜的上述P偏振光通过PBS（200）入射到光调制器（601）。从反射型光调制器（601）反射的光因相位变换而转换为S偏振光。转换后的光通过PBS（200）的偏振光分离膜反射，入射到投射透镜。
从红色光源（10R）出发的光经过分色镜（50R，50B），通过和上述绿色光的P偏振光同一路径入射到投射透镜。
从蓝色光源（10B）出发的光经过分色镜（50B），通过和上述红色光同一路径入射到投射透镜。上述的红色光原（10R）和蓝色光源（10B）要调整成和上述绿色光的P偏振光相同的P偏振光。
绿色光源（10G）出发的光经过偏振光分离膜（90）由反射膜（80）反射，再经过漫射体（20），光束整形器（30），物镜（40）入射到PBS（100）。
PBS（100）的偏振光分离膜（101）和偏振光分离膜（201）一样反射S偏振光通行P偏振光。随之入射到PBS（100）的光经过偏振光分离膜（101）反射入射到光调制器（602）。接着经过光调制器（602）反射的光转换为P偏振光通过偏振光分离膜（101）入射到投射透镜。
被偏振光分离的光只有绿色光，所以光调制器（602）只转换相应绿色光的影象画面。所以只要根据绿色光的发光时间点进行光调制就可以了。
图5是对偏振光分离元件更为详细说明的图。如图5所示，经过偏振光分离膜（90）反射的光比直接通行的光行进更长的光路，光路差的长度等于经过反射面（80）的长度（300）。
长度（300）是偏振光分离元件的厚度T。这个光路差不应该影响到分离光的相位。在使用激光光源的情况下偏振光分离的光是绿色光，所以厚度T应该为绿色激光波长532nm的2nπ倍 （n是整数）。
可以理解，关键是两个光路的光程差为光波长的2nπ倍。除了偏振光分离元件的厚度为532纳米的2nπ倍这种方法以外，也可以有其它的方法，例如在其中一个光路中增加一个调整光程差的部件，这个部件可以是独立的，也可以只是附在该光路上某个光学元件表面上的一层透明薄膜。
对于三色激光光源，只对绿色激光的不同偏振光进行分路处理，从而可以通过设置偏振光分离元件的厚度而完全消除不同光路的光程差所导致的相位差，特别适合目前绿色激光只能通过倍频得到、线偏振比例较低的情况。
本发明第二实施方式涉及一种微型投影机用光学引擎。第二实施方式与第一实施方式基本相同，区别主要在于：
在第一实施方式中，光源是红、绿、蓝三原色的激光光源，偏振光分离元件仅将绿色激光分为2个光路，红、蓝两色激光只存在于一个光路。
然而在第二实施方式中，光源是红、绿、蓝三原色的LED光源，这三个光源的光先合成一个光路再由偏振光分离元件分离为2个不同偏振方式的光路。因为三个LED光源发出的是混合光，所以将不同偏振方式的光分别调制后再合为一路，可以使光源效率提高一近一倍。
第二实施方式中一个使用LED光源的光学引擎实例如图3所示。为了说明上的简便，设定为偏振光分离膜（90）反射P偏振光通行S偏振光。通过偏振光分离膜（90）的S偏振光经过光束整形器（30）和物镜（40）入射到PBS（200）。PBS（200）的偏振光分离膜（201）通行S偏振光反射P偏振光。随之入射到PBS（200）的S偏振光入射到光调制器。然后经过光调制器（601）反射的光转换为P偏振光通过偏振光分离膜（201）入射到投射透镜（70）。
此外，经过偏振光分离膜（90）反射的P偏振光通过反射膜（80）进入光束整形器（30）、物镜（40）和PBS（100）。
PBS（100）的偏振光分离膜（101）和偏振光分离膜（201）一样，反射P偏振光通行S偏振光。随之入射的P偏振光经偏振光分离膜（101）反射后入射到光调制器（602），然后通过光调制器（602）转换成S偏振光的反射光经过PBS（100）和PBS（200）入射到投射透镜（70）。
LED的情况下全波长的光全部被偏振光分离，且在亮度上绿色光的影响是最大的，所以偏振光分离元件的厚度T调整为绿色光波长532nm的2nπ倍（n是整数）最为妥当。对于光源为多个LED的情况，偏振光分离元件也可以不是正好为532纳米的2nπ倍，只要是在可见光中央波长附近的一个波长的2nπ倍也可以取得一定的有益效果。
图3所示的实例也可以有其它的变化形态，一种变化形态如图4所示，图4的变化形态相对于图3多了一个反射镜50G，50G可以是只反射绿光的，也可以是反射所有光的。
本发明第三实施方式涉及一种微型投影机用光学引擎。第三实施方式与第二实施方式基本相同，区别主要在于第二实施方式使用了三个光源，而第三实施方式只使用了一个光源，第三实施方式中光学引擎的结构如图6所示。第三实施方式的一种典型的应用是显示黑白图像的微型投影机，该微型投影机使用一个发白光的光源10和一个反射镜50。当然也可以不用白光光源，而是用单色的激光作为光源，此时图像是一种单色的“灰度图像”，可以应用在某些不需要彩色图像的场合。
本发明第四实施方式涉及一种微型投影机用光学引擎。第四实施方式与第一实施方式基本相同，区别主要在于：
第一实施方式使用了三个源光光源，而第四实施方式使用了混合光源，即光源包括至少一个激光光源和至少一个LED光源。在光路的设置上可以参考第一和第二实施方式，即将线偏振比例较低的光源（如LED光源和经倍频得到的激光光源）分为两个不同偏振方式的光路，分别调制后合为一路。线偏振比例较高的光源，如未经倍频的激光光源，可以只出现在一个光路中，也可以同时出现在两个光路中。
虽然通过参照本发明的某些优选实施方式，已经对本发明进行了图示和描述，但本领域的普通技术人员应该明白，可以在形式上和细节上对其作各种改变，而不偏离本发明的精神和范围。
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Claims (10)

1．一种微型投影机用光学引擎，其特征在于，包括：
至少一个光源；
偏振光分离元件，用于将所述光源射出的光分离为2个光路，这两个光路的偏振方式不同；
两个光调制器，分别用于将所述2个光路上的光转换成影象画面；
至少两个偏振分光镜，用于将经过所述光调制器后的所述2个光路调整为相同的光路。
2．根据权利要求1所述的微型投影机用光学引擎，其特征在于，所述光源有多个。
3．根据权利要求2所述的微型投影机用光学引擎，其特征在于，所述光源是红、绿、蓝三色的激光光源，所述偏振光分离元件仅将绿色激光分为2个光路，红、蓝两色激光只存在于一个光路。
4．根据权利要求3所述的微型投影机用光学引擎，其特征在于，所述光源和光调制器之间，存在用于减少散斑的漫射体。
5．根据权利要求3所述的微型投影机用光学引擎，其特征在于，所述光调制器将一帧的时间分为3个时间片，在每个时间片调制与一个所述光源相对应的图像信号；
其中，位于仅有绿色激光的光路上的光调制器仅在与绿色激光光源相对应的时间片进行图象调制。
6．根据权利要求2所述的微型投影机用光学引擎，其特征在于，所述光源是红、绿、蓝三色的发光二级管光源，这三个光源的光先合成一个光路再由述偏振光分离元件分离为2个光路。
7．根据权利要求2所述的微型投影机用光学引擎，其特征在于，所述光源包括至少一个激光光源和至少一个发光二级管光源。
8．根据权利要求1至9中任一项所述的微型投影机用光学引擎，其特征在于，所述偏振光分离元件的厚度为532纳米的2nπ倍，其中n是整数。
9．根据权利要求1至9中任一项所述的微型投影机用光学引擎，其特征在于，各所述偏振分光镜的偏振光轴相同。
10．根据权利要求1至9中任一项所述的微型投影机用光学引擎，其特征在于，所述光调制器是以下之一：
液晶显示元件、数字微镜器件、硅基液晶。
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CN109270778A (zh) * 2018-11-02 2019-01-25 深圳彩翼光电科技有限公司 一种光源光路系统
CN109270778B (zh) * 2018-11-02 2023-12-22 深圳彩翼光电科技有限公司 一种光源光路系统
CN110456603A (zh) * 2019-08-05 2019-11-15 深圳光维科技有限公司 投影显示光学系统

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