WO2015123901A1

WO2015123901A1 - Optical system for stereoprojection and projection method thereof

Info

Publication number: WO2015123901A1
Application number: PCT/CN2014/073558
Authority: WO
Inventors: 刘飞; 龚杰; 苏鹏华
Original assignee: 深圳未来立体科技有限公司
Priority date: 2014-02-21
Filing date: 2014-03-17
Publication date: 2015-08-27
Also published as: CN103792781A; CN103792781B

Abstract

An optical system for stereoprojection comprises an object image (101) and a projection object lens (102). The optical system is provided with a transmission light path and a reflection light path. A polarization beam splitter and a first liquid crystal variable phase retarder (107) are provided in the transmission light path, and the polarization beam splitter, a first lens or lens group (108), a second lens or lens group (109), a plane mirror (110) with an image inversion function and a second liquid crystal variable phase retarder (111) are provided in the reflection light path, wherein the polarization beam splitter comprises a first triangular prism (103), a second triangular prism (104), first flat glass (105) and second flat glass (106). A method for carrying out the stereoprojection is also provided.

Description

Optical system for stereoscopic projection and projection method thereof

Technical field

The present invention relates to the field of 3D stereoscopic projection display, and more particularly to an optical system for stereoscopic projection and a method for stereoscopic projection, which can polarize energy of more than 97% of natural light into linearly polarized light, thereby greatly improving the picture. Brightness and stereoscopic display fidelity.

Background technique

With the premiere of the 2009 Avatar 3D movie, the 3D boom has been heard in most of the world. Most of the theaters currently support 3D playback, including the display chip for Texas Instruments DMD (Digital). Micro mirror device, digital micromirror component) DLP (Digital Light Procession, digital light processing) projectors are used in most theaters. Since the light source used is a xenon lamp, the emitted light is natural light, that is, the polarization state is randomly generated, and the stereoscopic display needs to be polarized to linearly polarized light, and then the liquid crystal variable phase retarder (Liquid) Crystal Variable Retarder (LCVR for short) modulates it, and then the left and right eye images are time-divided into the left and right eyes to achieve the effect of stereoscopic display. Since the conventional method of generating linearly polarized light is to directly add a dichroic polarizer in front of the projection objective, the dichroic polarizer absorbs the electric vector rays parallel to the absorption axis, and more than 55% of the light energy is The polarizer absorbs, which will greatly reduce the display brightness of the screen.

Since the projector continues to play the picture, more than 55% of the emitted light energy will continue to be absorbed by the polarizing plate, which will cause the polarizing plate to heat up, and its polarization degree and the like may be degraded or even cause damage. Moreover, the general polarizer will be attached to the surface of the liquid crystal variable phase retarder, which will cause the liquid crystal molecules in the liquid crystal cell to absorb most of the heat, and the liquid crystal molecules are very sensitive to temperature, which will affect the birefringence coefficient. As a result of its polarization o, the optical path difference of the e-light will also change or even fail, thereby affecting the stereoscopic effect of the screen display.

Due to the energy loss of more than 55%, in order to improve the display brightness, the theater will use a higher power xenon lamp, which greatly increases the cost, and the higher xenon lamp power will cause more energy to be absorbed by the polarizer, making the polarizer and liquid crystal The box is more susceptible to damage. The parameters such as the degree of polarization of the polarizing plate are drastically reduced, which will increase the crosstalk between the left and right eyes, and the 3D stereoscopic display effect is greatly reduced, which will fall into a vicious circle.

technical problem

The technical problem to be solved by the present invention is to provide an optical system for stereoscopic beam splitting and zooming and a method for performing stereoscopic projection, which converts light emitted from a projection objective into as much as possible into polarized light. The brightness of the system is increased by more than 100% compared to the system using only the dichroic polarizer and the liquid crystal variable phase retarder (LCVR).

Technical solution

The technical solution adopted to solve the technical problem of the present invention is to provide an optical system for stereoscopic projection, which includes an object image and a projection objective lens, the optical system having a transmitted light path and a reflected light path; on the transmitted light path, The optical system includes a polarizing beam splitter and a first liquid crystal variable phase retarder; the optical system comprising the polarizing beam splitter, the first lens or lens group, the second lens or a lens group, a planar mirror having a transfer effect, and a second liquid crystal variable phase retarder; wherein the polarizing beam splitter comprises a first triangular prism, a second triangular prism, a first flat glass, and a second flat glass; The polarizing beam splitter outputs the input natural light to the P light or the S light in the transmitted light path, and simultaneously outputs the P light or the S light in the reflected light path, so that the two optical paths have the same polarization state; the first in the reflected light path The lens or lens group and the second lens or lens group constitute a zoom lens group, and the image of the reflected light path on the screen can be enlarged or reduced to make the vertical axis magnification coincide with the transmitted light path; In the reflected light path, the two screens are completely coincident by adjusting the plane mirror, the first lens or lens group and the second lens or lens group; the first liquid crystal variable phase in the transmitted light path The retarder and the second liquid crystal variable phase retarder in the reflected light path both generate a birefringence effect on the input linearly polarized light, and use the voltage to control the twist angle of the liquid crystal molecules to achieve output o and e light. Phase difference.

In the optical system of the present invention, preferably, the first lens or lens group and the second lens or lens group are placed between the polarization beam splitter of the transmitted light path and the second liquid crystal variable phase retarder to constitute a zoom The lens group makes the two screens coincide.

In the optical system of the present invention, preferably, the inclined surface of the first triangular prism and the inclined surface of the second triangular prism are in contact with each other, and the first flat glass and the light emitting surface of the first triangular prism are attached to each other The second flat glass and the light emitting surface of the second triangular prism are bonded to each other.

In the optical system of the present invention, preferably, the light-passing surfaces of the first triangular prism, the second triangular prism, the first flat glass, and the second flat glass are each plated with a plurality of dielectric films.

In the optical system of the present invention, preferably, the planar mirror substrate employs an optical glass excellent in chemical and physical stability, and a metal dielectric film is plated on the ultra-smooth surface of the optical glass.

Another technical solution adopted to solve the technical problem of the present invention is to provide a method for performing stereoscopic projection, which includes the following steps:

The beam of the random polarization emitted by the object image passes through the objective lens, and the emitted beam continues to propagate forward. After passing through the polarization beam splitter, the beam is polarized by the polarization beam splitter to form a transmitted light path and a reflected light path;

a zoom lens group, a plane mirror, and a first liquid crystal variable phase retarder are sequentially disposed on the reflected light path, and a first liquid crystal variable phase retarder is disposed on the transmitted light path, thereby causing the transmission The final focus of the optical path and the reflected optical path on the screen is the same size;

The first liquid crystal variable phase retarder in the transmitted light path and the second liquid crystal variable phase retarder in the reflected light path both cause a birefringence effect on the input linearly polarized light, using a voltage The twist angle of the liquid crystal molecules is controlled to achieve an arbitrary difference between the output o light and the e light.

In the method of the present invention, preferably, the polarization beam splitter comprises a first triangular prism, a second triangular prism, a first flat glass, and a second flat glass.

In the method of the present invention, preferably, the light-passing surfaces of the first triangular prism, the second triangular prism, the first flat glass, and the second flat glass are each plated with a plurality of dielectric films.

In the method of the present invention, preferably, the inclined surface of the first triangular prism and the inclined surface of the second triangular prism are adhered to each other, and the first flat glass and the light emitting surface of the first triangular prism are mutually And bonding, the second flat glass and the light emitting surface of the second triangular prism are bonded to each other.

In the method of the present invention, preferably, the zoom lens group includes a first lens or lens group and a second lens or lens group placed between a polarization beam splitter of a transmitted optical path and a second liquid crystal variable phase retarder .

Beneficial effect

Compared with the prior art, the optical system of the present invention has an advantage in that the introduction of the polarizing beam splitter in the present invention will make the optical system have a higher degree of polarization, reaching 99.999% or more, and the crosstalk rate of the left and right eyes is lower, 3D. The stereo display is better, and the user experience of the theater audience is greatly improved. In addition, since the introduction of the polarizing beam splitter of the present invention greatly reduces the heat absorbed by the liquid crystal cell in the LCVR module (the conventional mode liquid crystal cell will absorb more than 50% of heat, and the present invention can reduce the heat absorbed by the liquid crystal cell to less than 2%), The liquid crystal molecules work stably at normal temperature, and the LCVR polarized linearly polarized light is left or right circularly polarized light, and the stereoscopic effect of the screen display can be stably maintained, so that the system can operate reliably.

DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a light path diagram of an optical system for stereoscopic projection of the present invention.

Fig. 2 is a graph showing a comparison of the optical characteristic data of the transmitted optical path of the polarizing beam splitter (curve a) obtained by a visible light-spectrophotometer with the data obtained by the prior art (curve b).

Fig. 3 is a graph comparing the optical characteristic data (curve c) of the polarization beam splitter reflected optical path measured by a visible light-spectrophotometer with the data obtained by the prior art (curve d).

4 is a view showing that a liquid crystal variable phase retarder (LCVR) is separately placed in a sample chamber of a visible light-spectrophotometer optical path, and the polarization of the liquid crystal variable phase retarder (LCVR) is circularly polarized after being measured by natural light incidence. A comparison of the transmission curve (curve e) with the curve obtained by the prior art (curve f).

Figure 5 is a graph showing the polarization degree curve (curve h) of an optical system obtained by linearly polarized light (P light or S light) before being incident on a liquid crystal variable phase retarder (LCVR) using a visible light-spectrophotometer. There is a comparison of the technically obtained curves (curve i).

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The optical system of the polarization beam splitting zooming of the present invention firstly converts the natural light (random polarization state) emitted from the object image on the focal plane of the projection objective object through the polarizing beam splitter and simultaneously converts it into P light or simultaneously into S light. That is, the transmitted light path and the reflected light path have the same polarization state, and the liquid crystal variable phase retarder (LCVR) in the transmitted light path and the reflected light path will synchronously polarize the polarized light, and output the left and right circularly polarized light in a time-sharing manner, the transmitted light path and the reflection. The image formed by the optical path will substantially coincide on the screen, and the brightness is greatly improved. The prior art only utilizes the light energy of the transmitted light path and absorbs the energy in the reflected light path. The present invention fully utilizes the light energy to make the brightness of the picture display relatively The prior art method has been improved by more than 100%. The viewer can view the stereoscopic projection effect of the picture by wearing glasses with a 1/4 phase retardation film and a polarizing plate.

1 is a light path diagram corresponding to an optical system for polarized beam splitting zooming for stereoscopic projection disclosed in the present invention. In general, the optical system of polarized beam splitting zoom can include an object image 101 (such as from a DMD chip or other object that can emit image information light), a polarizing beam splitter (including a first triangular prism 103, a second) Triangle prism 104, first plate glass 105 and second plate glass 106), first liquid crystal variable phase retarder 107, first lens or lens group 108, second lens or lens group 109, plane mirror 110, second Liquid crystal variable phase retarder 111.

In general, the optical system for polarized beam splitting zooming for stereoscopic projection works as follows: a random polarization state emitted by an object image (such as from a DMD chip or other object that can emit image information light) 101 After passing through the objective lens 102, the emitted natural light continues to propagate forward. After the beam of the parallel light passes through the polarization beam splitter, it is polarized into two different directions of linearly polarized light, and the two paths of light have the same The polarization state, that is, a P-ray (or S-light) that continues to propagate forward, and the other beam is an upward-reflected P-light (or S-light). Since the upward-reflected light needs to be transmitted to the screen, it is necessary to The plane mirror 110 is added for beam turning. Assuming that the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) is not added to the optical path, the images of the transmitted light path and the reflected light path that are finally focused and imaged on the screen are inconsistent in size, that is, the reflected light path projection The overall size of the screen to the screen is too large, so it is necessary to add a zoom lens group to reduce the optical vertical axis magnification of the reflected light path, so that the two screen projection images on the screen are the same size, and the naked eye feels like only one light is projected. By moving the relative positions of the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) up and down, the overall size of the screen can be changed to finally match the transmitted light path image. After the P light (or S light) in the reflected light path passes through the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109), it is passed through the second liquid crystal variable phase retarder 111, at which time its polarization The state has the same polarization state as the light beam in the transmitted optical path of the first liquid crystal variable phase retarder 107 (i.e., both P light or S light). The functions of the first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 are completely identical, and the first liquid crystal variable phase retarder 107 and the second can be controlled by generating pulse voltages of different amplitudes by circuit timing. The liquid crystal molecules in the liquid crystal variable phase retarder 111 have deflection angles of liquid crystal molecules, and different deflection angles correspond to different birefringence levels to generate different phase delay values for the o and e lights. The incident linearly polarized light (P light or S light) can be passed through the first liquid crystal variable phase retarder 107 or the second liquid crystal variable phase retarder 111 by setting an appropriate voltage value, and then the left circularly polarized light or Right circularly polarized light, according to the circuit timing (general 3D stereoscopic movie frame rate is 144 Hz, that is, 72 frames of the left eye picture are output in one cycle according to the timing, and then 72 frames of the right eye picture are output) time-division output left circularly polarized light and right circular polarization The voltage amplitude corresponding to the light, the left circularly polarized light and the right circularly polarized light are respectively modulated to produce a left eye image and a right eye image. The left circularly polarized light or the right circularly polarized light is outputted from the optical system of the polarization splitting and combining zoom, and the left circularly polarized light or the right circularly polarized light will continue to propagate forward to the screen 112 (the screen generally has a polarization maintaining effect) Metal screen, gain 1.8~2.4 or more) imaging, left circularly polarized light or right circularly polarized light will be reflected back to the left and right eyes of the person, resulting in realistic stereoscopic viewing.

The projection objective 102 is an optical system inside the projector (or projector), which is also called a projection lens. The projection ratio of the cinema general objective lens is 1.0 to 4.0:1, and the optical system of the present invention can adapt to this range.

The polarization beam splitter includes a first triangular prism 103, a second triangular prism 104, a first flat glass 105, and a second flat glass 106, wherein the first triangular prism 103, the second triangular prism 104, and the first flat glass 105 And each of the light-passing surfaces on the second flat glass 106 is plated with a plurality of dielectric films. The materials, thicknesses and coating sequences of the film layers are solved by Maxwell's equations and interference diffraction theory, and are determined by coating software optimization and trial plating repeated verification. Optimal solution. The first triangular prism 103, the second triangular prism 104, the first flat glass 105 and the second flat glass 106 are glued one by one as shown in the optical path structure of FIG. 1 (ie, the inclined surface of the first triangular prism 103 and the second triangle) The inclined surfaces of the prisms 104 are bonded to each other, and the first flat glass 105 and the light-emitting surface of the first triangular prism 103 are bonded to each other, and the second flat glass 106 and the light-emitting surface of the second triangular prism 104 are bonded to each other. Moreover, the polarization beam splitter can simultaneously transmit and reflect P light or S light by controlling the materials of the first plate glass 105 and the second plate glass 106 and the coated film system. The material of the first flat glass 105 and the second flat glass 106 may be quartz, fisheye and mica, and the anti-reflection system and the phase film system are plated on the surface.

Compared with the polarization beam splitter of the prior art, the polarization beam splitter of the present invention is advantageous in that the transmitted light beam and the reflected light beam have the same polarization state after leaving the polarization beam splitter, and the transmittance and reflectance in the visible wavelength band. Far higher than the ordinary polarizing beam splitter. As shown in FIG. 2 and FIG. 3, the polarized beam splitter of the present invention has an average transmittance of 99%, while the conventional polarizing beam splitter has an average transmittance of less than 70%, and the polarized beam splitter average reflection in the reflected light path. The rate is as high as 96%, and the average reflectance of the conventional polarizing beam splitter is only about 65%, which is far lower than the performance of the polarizing beam splitter of the present invention, that is, the average utilization rate of the polarized light splitter in the present invention reaches 97.5. %, after deducting the reflection loss of the light-passing surface of the polarizing beam splitter and the air contact, the average utilization rate of the light energy of the polarizing beam splitter can also reach 97%. The reason why the reflection energy loss of the light-passing surface is so low is because Each of the optical components of the present invention is solved by physical optical principles to obtain an optimum coating material and thickness, so that the optical energy loss of each optical component is greatly reduced. The material used for the coating may be magnesium fluoride MgF ₂ , silica SiO ₂ , aluminum oxide Al ₂ O ₃ , titanium dioxide TiO ₂ , zirconium dioxide ZrO ₂ , and the thickness is about λ/4, and λ is the wavelength band used in the design of the film system. The central wavelength value, the present invention uses 520nm as the center wavelength, and the optimized design is carried out by software with optical film design and analysis functions, for example, optimized by the optical software ZEMAX of Radiant Zemax, USA. For example, the present invention can use aluminum fluoride AlF ₃ and magnesium fluoride MgF ₂ as the simplest double-layer anti-reflection film, the first layer is air, the second layer is magnesium fluoride MgF ₂ , the thickness is 614.2 nm, the third layer The aluminum fluoride AlF _{3 has a} thickness of 596.5 nm and the fourth layer is a material substrate. The substrate of the present invention can adopt any grade material, and the initial structure can be solved only by optimizing the design according to the corresponding refractive index. The more the number of film layers, the better the optimized effect, that is, the better the anti-reduction performance. According to the basic principle of the above double-layer inversion example, the present invention can also achieve the anti-reflection characteristics by using different coating materials and thicknesses of more than 10 layers. The visible wavelength average reflectance of all the light-passing surfaces (except the mirror surface) of the optical system is less than 0.3%.

The polarizing beam splitter of the present invention has an advantage over the flat-plate polarizing beam splitter in that the flat-plate polarizing beam splitter is placed in the optical path due to the tilting of the two-way optical plane, thereby greatly improving the game-making coefficient and the optical system. The aberrations are increased, and in the reflected light path, both inclined surfaces can reflect light, and ghost images are generated on the image surface (on the screen), which seriously affects the imaging quality of the optical system, so that the viewer clearly feels that the picture is blurred and reduces. User experience. The polarizing beam splitter of the present invention can overcome this shortcoming, so that the optical components are placed in parallel in the optical path, the Sauter's sum coefficient is reduced, the aberration of the optical system becomes large, and no ghost image is introduced onto the screen, and the user experience effect is obtained. Excellent.

The zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) belongs to optical zoom, and the compensation group belongs to optical compensation. Compared with the mechanically compensated zoom optical lens group, the advantage is that only the compensation lens group needs to be opposed to The zoom lens function can be achieved by the fixed lens group for linear motion. The first lens or lens group 108 and the second lens or lens group 109 are combined to form a zoom lens group in order to adapt to different projection distances, because different projection distances may result in different vertical axis magnifications of the transmitted light path and the reflected light path, in order to make two paths The size of the image displayed on the screen is the same, and one of them needs to be zoomed. One of the advantages of the present invention is that the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) is placed in the reflected light path because if the projector is not incorporating the polarization of the polarized beam splitting zoom of the present invention If the front projection image of the system has just filled the entire screen, the optical system of polarization splitting and combining zoom is added, and the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) is placed on the optical system. Between the first plate glass 105 and the first liquid crystal variable phase retarder 107, the vertical axis magnification of the reflected light path is greater than the vertical axis magnification of the transmitted light path, that is, the edge region of the reflected light path will exceed the effective area of the screen. This causes the edge picture to be unobservable. In order to match the vertical axis magnification of the reflected light path, the transmitted light path must adjust the compensation group in the zoom lens group so that the screen of the transmitted light path is gradually increased until it is larger than the screen of the reflected light path. This will cause the edge areas of the two screens to exceed the effective area of the screen, and the optical system must be optically zoomed through the projector's own optical system to reduce the two screens as a whole until it is just full of screens. This will have a fatal effect. The focal length of the 2D source and the 3D source are inconsistent. It is necessary to repeatedly switch the zoom factor of the lens. The cumbersome operation is not user-friendly, which increases the workload of the projection staff. While the present invention can be modified, the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) is directly placed at the position shown in FIG. 1, so that the vertical axis magnification of the transmitted light path will be The 2D source is played consistently, that is, the image projected onto the screen by the transmitted light path is just full of the screen, and the vertical axis of the reflected light path is slightly larger than the transmitted light path (before the lens group is zoomed). In order to reduce the projected image in the reflected light path to just fill the screen, the zoom lens group (the first lens or lens group 108 and the second lens or lens group 109) needs to be zoomed, and the compensation group is slowly adjusted for linear motion until two ways. The screens overlap.

The first lens or lens group 108 and the second lens or lens group 109 in the zoom lens group can be solved by a first-order optical principle and a primary aberration theory to obtain a first lens or lens group 108 and a second lens or lens group. For the initial structure of 109, the first lens or lens group 108 and the second lens or lens group 109 may use any one of the groups as a zoom group and the other group as a compensation group, and further use the theoretical differential equation of the zoom optical system. The group can get the initial solution, and then use optical software to repeatedly optimize the optical zoom system of the present invention to match different projection distances and projection ratios of different theaters.

The planar mirror 110 substrate of the present invention adopts optical glass with excellent chemical and physical stability, and a metal dielectric film is plated on the ultra-smooth surface of the optical glass, and the reflectance in the visible light band is as high as 99%, and the ordinary surface aluminized mirror is used. The average reflectance is only about 85%, in other words, the light energy will be further lost by 15%, and the mirror used in the present invention has only 1% energy loss, which greatly improves the brightness of the screen displayed on the final screen.

The first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 of the present invention have excellent uniformity, low light loss and low wavefront distortion, fast response time, and wide operating temperature range. And a wide range of operating wavelengths. The first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 are each composed of a transparent case filled with a liquid crystal (LC) molecular solution, and can be used as a variable wave plate. The two parallel faces of the transparent case are plated with a transparent conductive film to apply a voltage to the case. In the case where no voltage is applied, the orientation of the liquid crystal molecules is determined by the alignment film. When the AC voltage is applied, the liquid crystal molecules change the default orientation according to the rms value of the applied voltage. Therefore, the phase delay value of the linearly polarized beam can be actively controlled by changing the applied voltage. The liquid crystal variable phase retarder has a very short response time of the order of microseconds, in other words, the liquid crystal variable phase retarder (LCVR) converts from a low birefringence to a high birefringence very quickly under normal conditions. The extremely fast response speed makes the switching speed of the liquid crystal variable phase retarder modulate the left and right eye images faster, the black field time is shorter, the crosstalk is smaller, and the brightness of the screen displayed on the screen is higher. The invention has the advantages that the first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 are placed on the outermost side of the optical path, so that the illuminance received per unit area of the surface of the liquid crystal layer is lower and more uniform, that is, the unit area of the liquid crystal molecules. The absorption of part of the light energy produces a smaller temperature rise, while the liquid crystal molecules are very sensitive to temperature. As the temperature increases, the material density decreases and the retardation decreases. Moreover, the viscosity of the liquid crystal material becomes lower at a high temperature, so that the liquid crystal variable phase retarder (LCVR) can easily switch from one state to another in the case of a decrease in viscosity, resulting in delay of the left and right eye phase delays, that is, Causes crosstalk between left and right eye images. Therefore, placing the first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 on the outermost side of the optical path can optimize the uniformity, contrast and phase delay of the liquid crystal variable phase retarder (LCVR). Performance.

As shown in FIG. 4, the first liquid crystal variable phase retarder 107 and the second liquid crystal variable phase retarder 111 are separately placed in the visible light-spectrophotometer sample chamber, and the first liquid crystal variable phase retarder 107 is measured. The first liquid crystal variable phase retarder 111 polarizes the natural light into a transmittance curve of circularly polarized light. Compared with the transmittance curve obtained in the prior art, it is apparent that the transmittance is delayed from the liquid crystal variable phase of the present invention. The device is low, and the transmittance in the blue and red bands is more greatly reduced, which causes the screen chromaticity value to shift, and the liquid crystal variable phase retarder of the present invention hardly exhibits color cast.

In the optical path of the polarization beam splitting and combining zoom optical system, the polarization degree of the linearly polarized light incident in front of the liquid crystal cell of the liquid crystal variable phase retarder of FIG. 5 is compared with the polarization degree curve obtained by the prior art. The degree of polarization in the invention can be as high as 99.999%, which is much higher than the polarization degree value of the prior art, and the higher degree of polarization means that purer linearly polarized light enters the liquid crystal variable phase retarder and is modulated to be more pure. The eye image makes the crosstalk of the left and right eye images smaller, and the stereoscopic effect is more realistic.

In the embodiment of the present invention, the polarized beam splitter can output the P or S light in the transmitted light path while outputting the P or S light in the reflected light path, so that the two optical paths have the same polarization state. The first lens or lens group and the second lens or lens group in the reflected light path constitute a zoom lens group, so that the image of the reflected light path on the screen can be enlarged or reduced, so that the vertical axis magnification is consistent with the transmitted light path, that is, the two light paths. The size of the image is the same. The planar mirror in the reflected light path has the function of rotating the image, and the two screens can be completely coincident by adjusting the plane mirror, the first lens or lens group and the second lens or lens group. The first liquid crystal variable phase retarder in the transmitted light path and the second liquid crystal variable phase retarder in the reflected light path have the same function, that is, the input linearly polarized light can produce a birefringence effect, and the voltage is used to control the twist of the liquid crystal molecules. The angle is to achieve the difference between the output o-light and the e-light any position. In the present invention, only the o and e light time-division outputs ±1/4λ optical path difference can realize the stereoscopic display effect, and the circuit timing of controlling the liquid crystal variable phase retarder needs to be synchronized with the 3D signal outputted by the projector, that is, linear polarization. The light passes through the liquid crystal variable phase retarder to produce left and right circularly polarized light in a time-sharing manner.

In some implementations, the first lens or lens group 108 and the second lens or lens group 109 of the present invention can be placed between the polarizing beam splitter of the transmitted optical path and the second liquid crystal variable phase retarder 111. The zoom lens group makes the two screens and the like overlap.

In addition, the polarizing beam splitter of the present invention has an advantage over a conventional polarizing beam splitter in that it can polarize both transmitted and reflected light to the same polarization state, whereas a conventional polarizing beam splitter can only transmit light. The light is converted into P light, and the reflected light is polarized into S light. The invention can be simultaneously polarized into P light or simultaneously polarized into S light, so that the structure of the optical system is more compact and reasonable.

In general, the present invention relates to a design and method for stereoscopic projection of a polarization splitting beam combining optical system comprising receiving image light of a random polarization state at a polarizing beam splitter. The above method includes propagating light of a P or S polarization state to a transmitted optical path at a polarizing beam splitter. Also included is the propagation of light in the P or S polarization state by the polarizing beam splitter toward the reflected light path. Moreover, the light beams transmitted by the two optical paths have the same polarization state, that is, both P light and S light at the same time.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

An optical system for stereoscopic projection, comprising an object image and a projection objective, wherein: the optical system has a transmitted optical path and a reflected optical path; and the optical system includes a polarizing beam splitter on the transmitted optical path And a first liquid crystal variable phase retarder; on the reflected light path, the optical system includes the polarizing beam splitter, a first lens or lens group, a second lens or lens group, and a planar reflection having a rotating image a mirror and a second liquid crystal variable phase retarder; wherein the polarizing beam splitter comprises a first triangular prism, a second triangular prism, a first flat glass, and a second flat glass;

The polarizing beam splitter outputs the input natural light to the P light or the S light in the transmitted light path, and simultaneously outputs the P light or the S light in the reflected light path, so that the two optical paths have the same polarization state; the first in the reflected light path The lens or lens group and the second lens or lens group constitute a zoom lens group, and the image of the reflected light path on the screen can be enlarged or reduced to make the vertical axis magnification coincide with the transmitted light path; in the reflected light path, Adjusting the planar mirror, the first lens or lens group and the second lens or lens group to completely coincide the two screens; the first liquid crystal variable phase retarder in the transmitted light path and the reflected light path The second liquid crystal variable phase retarder in the second liquid crystal causes the input linearly polarized light to produce a birefringence effect, and the voltage is used to control the twist angle of the liquid crystal molecules to achieve an arbitrary difference between the output o light and the e light.
The optical system for stereoscopic projection according to claim 1, wherein the first lens or lens group and the second lens or lens group are disposed in a polarization beam splitter of the transmitted light path and the second liquid crystal variable phase Between the retarders, the two sets of screens and the like are largely overlapped to form a zoom lens group.
The optical system for stereoscopic projection according to claim 1, wherein a slope of the first triangular prism and a slope of the second triangular prism are in contact with each other, the first flat glass and the first The light-emitting surfaces of the triangular prisms are in contact with each other, and the second flat glass and the light-emitting surface of the second triangular prism are in contact with each other.
The optical system for stereoscopic projection according to claim 3, wherein the light-passing surfaces of the first triangular prism, the second triangular prism, the first flat glass, and the second flat glass are each coated with a multilayer dielectric film .
The optical system for stereoscopic projection according to claim 1, wherein the planar mirror substrate is made of an optical glass having good chemical and physical stability, and a metal dielectric film is plated on the ultra-smooth surface of the optical glass. .
A method for performing stereoscopic projection, which comprises the following steps:

The beam of the random polarization emitted by the object image passes through the objective lens, and the emitted beam continues to propagate forward. After passing through the polarization beam splitter, the beam is polarized by the polarization beam splitter to form a transmitted light path and a reflected light path;

a zoom lens group, a plane mirror, and a first liquid crystal variable phase retarder are sequentially disposed on the reflected light path, and a first liquid crystal variable phase retarder is disposed on the transmitted light path, thereby causing the transmission The final focus of the optical path and the reflected optical path on the screen is the same size;

The first liquid crystal variable phase retarder in the transmitted light path and the second liquid crystal variable phase retarder in the reflected light path both cause a birefringence effect on the input linearly polarized light, using a voltage The twist angle of the liquid crystal molecules is controlled to achieve an arbitrary difference between the output o light and the e light.
The method of performing stereoscopic projection according to claim 6, wherein the polarization beam splitter comprises a first triangular prism, a second triangular prism, a first flat glass, and a second flat glass.
The method of performing stereoscopic projection according to claim 7, wherein the light-passing surfaces of the first triangular prism, the second triangular prism, the first flat glass, and the second flat glass are each plated with a plurality of dielectric films.
The method of performing stereoscopic projection according to claim 7, wherein the inclined surface of the first triangular prism and the inclined surface of the second triangular prism are bonded to each other, and the first flat glass and the first The light-emitting surfaces of the triangular prisms are bonded to each other, and the second flat glass and the light-emitting surface of the second triangular prism are bonded to each other.
The method of performing stereoscopic projection according to claim 6, wherein the zoom lens group comprises a first lens or lens group disposed between a polarization beam splitter of a transmitted optical path and a second liquid crystal variable phase retarder And a second lens or lens group.