CN201589896U - Polarized light reusing device capable of raising brightness of projector - Google Patents

Abstract

The utility model provides a polarized light reusing device, which comprises a polarized light separating element, wherein the polarized light separating element comprises a light splitting surface, and the light splitting surface can transmit P polarized light and reflect S polarized light; and the two modulated polarized light phase-change elements are respectively positioned in the two light outgoing directions of the polarized light separation element, the modulated polarized light phase-change elements can reflect the polarized light coming out of the polarized light separation element to the light splitting surface of the polarized light separation element according to the requirement, and the vibration direction of the obtained reflected polarized light is vertical to the polarization direction of the incident polarized light. The utility model also provides a projecting apparatus that uses this polarized light to reuse device. The polarized light reusing device can effectively improve the projection brightness of the silicon-based liquid crystal micro projector and has the following advantages: (1) the conversion efficiency is high; (2) the structure is simple; (3) the manufacturing process is simple.

Description

Polarized Light Reuse Device Can Improve Projector Brightness

technical field

The utility model belongs to the technical field of silicon-based liquid crystal LCoS (liquid-crystal on silicon) micro-projection display, in particular to a polarized light reuse device for improving the brightness of a silicon-based liquid crystal projector

Background technique

In recent years, projection technology, especially liquid crystal on silicon (LCoS) projection display technology has developed extremely rapidly due to its advantages of high resolution, high definition, large screen, and portability, and has become a very popular projection display method. It is widely used in multimedia teaching, home theater, conference presentation, and even in military command. Because liquid crystal projection must be illuminated by polarized light to achieve normal projection functions. To generate polarized light, the common method is to add a polarizer in the optical path of the display, so that the polarized light in a certain vibration direction in natural light can pass through, and the polarized light in the other direction is absorbed by the polarizer. Thus, for a light source, only half of the light energy is utilized. In order to improve the utilization rate of light, the concept of reuse after polarized light conversion is proposed. The optical components used are called Polarization conversion system PCS (Polarization conversion system). Its working principle is to convert the polarization direction of the part of the polarized light that cannot be applied to its vertical direction through some devices, and then this part of the light can be used in projection display, which will undoubtedly greatly improve the efficiency of the optical machine. Thereby improving the brightness of the projection display. In the LCoS micro-projection display system, the polarization conversion system (PCS) is one of the very important components, and its performance has a great influence on the light energy utilization rate of the projection system and the display brightness.

The existing polarized light conversion system, as shown in Figure 1, consists of a collimation system, a polarized light separation system and a wave plate. Because the traditional polarized light separation system (PBS) often directs the polarized light perpendicular to each other to different directions when separating polarized light, and then adds a half-wave plate to the linearly polarized light that needs to convert the polarization direction. Then use the reflector to guide this part of the polarized light whose polarization direction has been converted to the same propagation direction as the other part of the linearly polarized light, which inevitably doubles the spot area of the light after polarization conversion, so that the optical The expansion is doubled. Since the transmission of light energy in the optical system is determined by the component with the smallest optical expansion in the optical components of the system, the beam larger than the optical expansion of the component cannot be effectively transmitted by the optical components. Therefore, such When the system is used in a large projector, due to the large etendue value of the entire optical system, the allowable spot area of the system is large, and satisfactory results can be obtained. However, when reducing the volume of the projector so that it can become a handheld device, due to the use of a smaller liquid crystal microdisplay and a lens with a smaller aperture, the etendue of the system is limited by the small display and optical components. When the traditional polarized light conversion system is used, the effective utilization area of the light beam is reduced, the efficiency of the entire optical system cannot be effectively improved, and the volume of the system is correspondingly increased. Therefore, in order to improve the light efficiency in the liquid crystal on silicon micro-projector, the polarized light conversion device added in the optical system must meet the requirements of keeping the etendue of the beam basically unchanged during the conversion of polarized light, and the volume of the system as small as possible. Therefore, it is necessary to realize a novel method for improving the miniature liquid crystal projector without increasing the etendue of the light beam.

Due to the small size, high efficiency, long life and low heat generation of the LED light source compared to the ultra-high pressure mercury lamp (UHP) currently used, it is used in portable micro-projectors powered by batteries. Combined with the design indicators of the projector and the use characteristics of the micro-projector, when designing the LED lighting system for the micro-projector, there must be the following requirements for the luminous flux projected on the projection screen, that is, in the personal application of the projector, the projection to the projection The brightness on the screen should reach more than 10 lumens. However, since the LED light source is a surface-emitting light source, its Etendue efficiency, that is, the lumen value per unit of Etendue, is not very high, and the miniature projector has extremely strict requirements on the size and power consumption. Requirements, only by designing a reasonable lighting and projection system structure can the lumen brightness requirements of the light output of the portable micro-projector be met.

The current general efficiency of a single white LED with an area of 1x1 mm can reach tens to one hundred lumens per watt. When the power of the LED is 2 watts, it can only provide less than 200 lumens of brightness. Since the LCoS display uses polarized light as the working light, plus the absorption of optical components in the projection light system and the reflection of the surface, the general projector The optical efficiency of the LED is only 3-4%, so it is necessary to increase the working power of the LED, increase the number of LEDs or improve the optical efficiency of the optical mechanical system. Increasing the working power of the LED will increase the working current of the LED, which will greatly shorten the service life of the LED.

Increasing the number of LEDs can increase the projected luminous flux, but it also increases the etendue of the light source. In the current projection system, the etendue of the system is determined by the smallest etendue of the system components. In micro-projectors, this component is generally a light modulator (LCoS microdisplay). If the etendue of the light source is greater than The minimum etendue of the system components. At this time, the increased luminous flux will not be used by the system and will be lost, and the light output cannot be effectively improved.

In order to increase the output brightness of the projector without increasing the working power of the LED, the most used method is to use the polarized light conversion technology to partially utilize half of the wasted polarized light in the system. The existing polarized light conversion technology (as shown in the figure) 1), the natural light emitted by the light source, after passing through the collimation system, becomes approximately parallel light and irradiates on the polarizing beam splitter prism PBS (Polarization Beam Splitter) array behind, and is decomposed by the PBS into linearly polarized light s whose vibration directions are perpendicular to each other light and p-light. Among them, the p light component passes through the PBS film, and the s light component is reflected by the PBS film and enters the adjacent area to exit the prism; a half-wave plate is attached to the corresponding transmission area to rotate the S light polarization direction by 90°, so that it is different from the P light The vibration direction is the same, so as to obtain P-line polarized light. When the conversion device obtains the polarized light with the same polarization direction, the area of the transmitted light is doubled. As a result, the etendue of the entire optical system will be doubled. When a liquid crystal display device smaller than the beam area is used as a projected light modulator, the beam outside the effective area of the device cannot be used, seriously affecting The optical efficiency of the projection system. In addition, a half-wave plate is pasted on the transmission area of the corresponding S light, so that a uniform light component is added at the position of the light beam to make the entire beam uniform, which will undoubtedly partially weaken the light intensity.

Contents of the invention

In order to solve the above problems, the purpose of this utility model is to provide a new polarized light reuse device, which has the advantages of simple process, high polarized light conversion rate, keeping the system etendue constant, etc. The projection brightness of the projector. Another purpose of the utility model is to provide a new type of projector, which has a simple structure, high projection brightness, is easy to carry, and can realize three-dimensional display with a suitable signal source.

In order to achieve the purpose, the polarized light reuse device of the present utility model includes:

A polarized light separation element, the polarized light separation element includes a splitting surface, the splitting surface can transmit P-polarized light, and can reflect S-polarized light; and

Two modulatable polarized light phase transformation elements are respectively located in the two light exit directions of the polarized light separation element, and the modulated polarized light phase transformation element can convert the polarized light emitted from the polarized light separation element The opposite direction is reflected back to the splitting surface of the polarized light splitting element, and the vibration direction of the obtained reflected polarized light is perpendicular to the polarization direction of the incident polarized light.

When the incident light enters the polarized light separation element, the reflection of the P polarized light on the splitting surface disappears completely, no reflection occurs, and it is transmitted from one light output direction of the polarized light separating element. The S polarized light is polarized by the reflection of the splitting surface The other light output direction of the light separation element is reflected and emitted, so as to achieve the purpose of polarized light separation.

The polarized light separation element includes a light-incoming direction for receiving light input to the polarized light separation element from the outside; the other three directions are light-outgoing directions.

Preferably, the polarized light splitting element is a traditional polarized light beam splitting prism. More preferably, the polarizing beam splitting prism is selected from the following group: MacNeille (S. MacNeille) prism, line grating prism, reflective polarizer.

Preferably, the modulatorable polarized light phase transformation element is an LCoS panel. The LCoS panel is placed in the two light-emitting directions of the polarized light separation element. On the one hand, it acts as a micro-display for the entire projection system. On the other hand, according to the working principle of LCoS, the polarization direction of the incident polarized light is reflected by the LCoS panel. After that, it will become polarized light perpendicular to the original polarization direction.

Preferably, the phase conversion element for modulating polarized light is arranged at an angle of 45° to the beam splitting surface.

According to another aspect of the present utility model, the present application also provides a projector, including a light source, the polarized light reuse device as described above, and a projection lens, wherein the light emitted by the light source is separated, converted and adjusted by the polarized light reuse device, and then Mixed before entering the projection lens for imaging. Preferably, the projector further includes a collimation system, so that the light from the light source is collimated by the collimation system and then enters the polarized light reuse device. More preferably, the light enters the polarized light separating element of the polarized light reuse device at a direction of 45° to the beam splitting plane.

Preferably, the light source is an LED light source. More preferably, the LED light source is a white light source or an LED light source in three primary colors of red, blue and green.

Preferably, the LED light source is a red, blue, and green three-color LED light source, and the projector also includes a harmony light system, which is located before the incident surface of the polarized light separation element, and is used to combine the red, blue, and green three-color light into white Light. The sum optical system is, for example, an x-prism.

The projectors of the present application may also include other optical and/or mechanical components for adjusting the shape and position of the light beam. These optical components and/or mechanical components for adjusting the shape and position of the light beam are well known to those skilled in the art, and those skilled in the art can select suitable components from the prior art as required for this application in the projector. The other optical components and/or mechanical components for adjusting the shape and position of the light beam are, for example, mechanical guide rails, piezoelectric ceramics, and the like.

The polarized light reuse device of the utility model not only completes the reuse of the polarized light, but also keeps the light expansion flux of the projection system unchanged, and greatly improves the projection brightness of the projector. Therefore, the brightness of the projector provided by the utility model is improved.

When two LCoS panels are used as the modulating polarized light phase conversion element, the LCoS panel can also be used as a microdisplay, that is, the projected image is displayed on the panel.

Compared with the prior art, the utility model omits the process of accurately aligning and sticking the wave plate, greatly reducing the difficulty of the process and the manufacturing cost.

Compared with the projector in the prior art, the projector of the utility model has simple structure, low manufacturing cost, smaller system volume, and is more portable.

Description of drawings

FIG. 1 is a schematic diagram of the prior art polarized light conversion technology;

FIG. 2 is a schematic diagram of a projector according to an embodiment of the present invention.

Detailed ways

The preferred embodiments of the present utility model are described below, and it should be understood that the preferred embodiments described here are only used to illustrate and explain the present utility model, and are not intended to limit the present utility model.

As shown in FIG. 2 , there is a beam splitting surface 6 in the polarized light separation element 2 , and the polarized light modulating phase transformation elements 3 and 4 are perpendicular to each other and arranged at 45° to the beam splitting surface. The light (P+S) emitted by the light source 1, after entering the polarized light separation element 2, is split into two beams of polarized light (P polarized light and S polarized light) whose polarization directions are vertical on the beam splitting surface 6 of the polarized light separation element 2, in:

(1) The P polarized light is transmitted from the splitting surface 6, and directly enters the modulable polarized light phase conversion element 4, and the modulatable polarized light phase conversion element 4 modulates and reflects the incident P polarized light, so that the modulated polarized light phase conversion element 4 The polarization direction of the polarized light reflected in the polarized light is rotated by 90°, becomes S polarized light, enters the polarized light separation element 2 again, reflects on the light splitting surface 6 of the polarized light separation element 2, and propagates toward the projector lens 5 direction;

(2) The S polarized light is reflected on the splitting surface 6 of the polarized light separation element 2, and enters the modulatorable polarized light phase conversion element 3. Similarly, the modulatorable polarized light phase conversion element 3 modulates and reflects the incident S light, so that from The polarization direction of the polarized light reflected by the modulating polarized light phase conversion element 3 is rotated by 90°, becomes P polarized light, and enters the polarized light separation element 2 again, passes through the light splitting surface 6 of the polarized light separation element 2, and transmits to the projector lens 5 Direction propagation.

The S-polarized light and P-polarized light transmitted from the polarized light separation element are mixed before entering the projection lens, and a high-brightness, high-definition image is projected on the projection screen through adjustment means such as mechanical alignment or image processing.

Example 1

Adopted the scheme shown in Figure 2 in the present embodiment, wherein:

Light source 1 is an LED light source with a working power of 1W and an area of 1 square millimeter;

The polarization separation element 2 is a polarization beam splitting prism, and its length and width are respectively 10mm and 8mm;

Both the modulating polarized light phase transformation elements 3 and 4 are liquid crystal on silicon (LCoS), and their length and width are 9mm and 8mm;

The projection lens 5 is f2.4

When there is only one modulable polarized light phase conversion element, that is, there is only one liquid crystal on silicon (LCoS) display, the output brightness of the projection lens is 3.8 lumens, and when two adjustable polarized light phase conversion elements are used, the output of the projection lens is 6.2 lumens.

Example 2

Adopted the scheme shown in Figure 2 in the present embodiment, wherein:

Light source 1 is an LED light source with a working power of 1W and an area of 1 square millimeter;

The polarization separation element 2 is a polarization beam splitting prism, and its length and width are 8mm and 6mm respectively;

Both the modulating polarized light phase transformation elements 3 and 4 are liquid crystal on silicon (LCoS), and their length and width are 7 mm and 5.5 mm;

The projection lens 5 is f2.4

When there is only one modulable polarized light phase conversion element, that is, there is only one liquid crystal on silicon (LCoS) display, the output brightness of the projection lens is 3.3 lumens, and when two adjustable polarized light phase conversion elements are used, the output of the projection lens is 5.3 lumens.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still The technical solutions recorded in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A polarized light reuse device, comprising: A polarized light separation element, the polarized light separation element includes a splitting surface, the splitting surface can transmit P-polarized light, and can reflect S-polarized light; and Two modulatable polarized light phase conversion elements are respectively located in the two light exit directions of the polarized light separation element, and the modulated polarized light phase conversion element can modulate the polarized light coming out of the polarized light separation element and use The direction opposite to the direction in which it comes out is reflected back to the splitting surface of the polarized light splitting element, and the vibration direction of the obtained reflected polarized light is perpendicular to the polarization direction of the incident polarized light. 2. The polarized light reuse device according to claim 1, wherein the polarized light splitting element is a polarized light beam splitting prism. 3. The polarized light reuse device according to claim 2, the polarized light beam splitting prism is selected from the group consisting of McNair prisms, line grating prisms, and reflective polarizers. 4. The polarized light reuse device according to claim 1 or 2, wherein the phase transformation element for modulating polarized light is a liquid crystal on silicon panel. 5. The polarized light reuse device according to claim 1 or 2, wherein the modulatorable polarized light phase transformation element is arranged at 45° to the beam splitting plane. 6. A projector, comprising a light source, the polarized light reuse device and a projection lens as claimed in any one of claims 1-5, wherein the light emitted by the light source is separated, converted and adjusted by the polarized light reuse device, before entering the projection lens Mixed for imaging. 7. The projector according to claim 6, wherein the projector further comprises a collimation system, so that the light of the light source is collimated by the collimation system and then enters the polarized light reuse device. 8 . The projector according to claim 7 , wherein the light from the light source enters the polarized light separation element of the polarized light reuse device in a direction 45° from the beam splitting plane after being collimated by a collimating system. 9. The projector according to any one of claims 6-8, wherein the light source is a red, blue, and green primary color LED light source, and the projector also includes a harmony light system, and the harmony light system is arranged on polarized light Before separating the incident surface of the component, it is used to combine red, blue and green light into white light. 10. The projector of claim 9, wherein the summing system is an x-prism.

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