Projection system and control method therefor

A projection system and a control method therefor. The projection system includes: a light source assembly generating three primary color lights capable of being adjusted separately, and a light modulation assembly for modulating the three primary color lights. The method includes: based on the maximum greyscale value of each primary color image in each frame of source images, determining a greyscale adjustment ratio of at least one primary color image; based on the greyscale adjustment ratio, correspondingly adjusting the greyscale value of the primary color image; and based on the adjusted greyscale value of each primary color image and the output power of a primary color light corresponding to the primary color image, controlling the power-on duration of the light modulation assembly, so that the greyscale brightness of each primary color image of display images formed by the light modulation assembly is improved in the same proportion.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to projection display technologies, and in particular, it relates to a projection system and related control method.

Description of Related Art

Conventional technology provides a projection system, as shown inFIG. 1, which includes a light source100, a collection lens101, a phosphor wheel102, a light rod103, an optical relay system104, a spatial light modulator system105and a projection lens106. The light source100emits an excitation light, which is focused by the collection lens101onto the phosphor wheel102. The phosphor wheel102generates red (R), green (G) and blue (B) primary color lights. The three primary color lights are homogenized by the light rod103and transmitted by the optical relay system104, and inputted to the spatial light modulator system105. The lights are modulated by the spatial light modulator system105and combined to form an image, which is projected by the projection lens106onto a predetermined plane. The light source100is a semiconductor laser. The spatial light modulator system105includes a single spatial light modulator component or multiple spatial light modulator components, which may be LCD (Liquid Crystal Display), LCOS (Liquid Crystal On Silicon), or DMD (Digital Micromirror Device), etc.

When the spatial light modulator system105includes a single spatial light modulator component, the grayscale values of the R, G and B primary color signals in a frame of image have maximum values of AR, AG, AB(0≤AR, AG, AB≤255) respectively, the brightness values of the three primary colors are LR, LGand LBrespectively, and the maximum durations are TR, TGand TBrespectively, then these parameters satisfy the following relationships: the ratio of the three primary colors for achieving white balance is x:y:z=LR·TR:LG·TG:LB·TB, the duration of a frame of image is F=TR+TG+TB, the grayscale brightness values of the three primary colors are LR·AR·TR/255, LG·AG·TG/255, LB·AB·TB/255 respectively, and the light utilization efficiency is (LR·AR·TR/255+LG·AG·TG/255+LB·AB·TB/255)/(LR·TR+LG·TG+LB·TB).

When the spatial light modulator system105includes three spatial light modulator components, the grayscale values of the R, G and B primary color signals in a frame of image have maximum values of AR, AG, AB(0≤AR, AG, AB≤255) respectively, the brightness values of the three primary colors are LR, LGand LBrespectively, and the maximum durations are all F, i.e. the duration of a frame, then these parameters satisfy the following relationships: the ratio of the three primary colors for achieving white balance is x:y:z=LR:LG:LB, the grayscale brightness values of the three primary colors are LR·AR·F/255, LG·AG·F/255, LB·AB·F/255 respectively, and the light utilization efficiency is (LR·AR/255, LG·TG/255, LB·AB/255)/(LR+LG+LB).

Because the conventional light modulation process achieves the grayscale values of the different primary color lights by reflecting away parts of the input primary color lights by the spatial light modulation components, when the grayscale values of the R, G, B primary colors of a frame of image are relatively low, i.e., when AR, AG, and ABvalues are relatively low, most of the primary color lights are reflected. This cause low light utilization efficiency of the spatial light modulator system, and low efficiency of the projection system.

SUMMARY

Accordingly, the present invention provides a projection system and related control methods to solve the problems of the conventional projection system, namely, the low light utilization efficiency of the spatial light modulator components and low efficiency of the projection system.

To achieve the above objects, the present invention provides the following technical solutions:

A control method for controlling a projection system, the projection system including a light source system for generating three primary color lights and a spatial light modulator system for modulating the three primary color lights, the method including:

based on maximum grayscale values of three primary color images of a frame of source image, determining a grayscale value adjustment ratio of at least one of the three primary color images;

based on the grayscale value adjustment ratio of the at least one primary color image, adjusting grayscale values of the primary color images;

based on the adjusted grayscale values of the primary color images and light output powers of the primary color lights generated by the light source system that correspond to the primary color images, controlling an ON time of the spatial light modulator system, wherein in the projected image formed by the spatial light modulator system, grayscale brightness values of all of the primary color images are increased by a same ratio relative to grayscale brightness values of the corresponding primary color images of the source image.

Preferably, the step of based on the maximum grayscale value of the primary color images of the frame of source image, determining the grayscale value adjustment ratio of the at least one primary color image includes:

obtaining a maximum grayscale value Ai of a primary color image of the source image; and

setting the grayscale value adjustment ratio for that primary color to Mi;

wherein 1≤Mi≤(K/Ai), wherein i is an index of the primary color image, and K is a maximum grayscale value that the spatial light modulator system is capable of displaying.

Preferably, the step of based on the grayscale value adjustment ratio of the at least one primary color image, adjusting grayscale values of the primary color images includes:

adjusting the grayscale value of the primary color image to Ai′, wherein Ai′=Ai*Mi, wherein Ai is the grayscale value of the primary color before the adjustment, and Ai′ is a grayscale value of the primary color after the adjustment.

Preferably, in the step of based on the adjusted grayscale values of the primary color images and light output powers of the primary color lights that correspond to the primary color images, controlling the ON time of the spatial light modulator system, wherein in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image, the adjusted grayscale values of the primary color images satisfy:
AR:AG:AB=AR′:AG′:AB′, whereinAR′=AR×MR, AG′=AG×MG, andAB′=AB×MB;

wherein ARis a maximum grayscale value of a red primary color image before adjustment, AGis a maximum grayscale value of a green primary color image before adjustment, ABis a maximum grayscale value of a blue primary color image before adjustment;

wherein AR′ is a maximum grayscale value of the red primary color image after adjustment, AG′ is a maximum grayscale value of the green primary color image after adjustment, AB′ is a maximum grayscale value of the blue primary color image after adjustment; and

wherein MRis a grayscale value adjustment ratio of the red primary color image, MGis a grayscale value adjustment ratio of the green primary color image, and MBis a grayscale value adjustment ratio of the blue primary color image.

Preferably, the three primary color lights generated by the light source system are independently adjustable.

Preferably, the method further includes, before the step of based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights, controlling the ON time of the spatial light modulator system:

based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the light output powers of the primary color lights that correspond to the primary color images of the source image, wherein in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image;

wherein the step of based on the adjusted grayscale values of the primary color images and light output powers of the primary color lights, controlling the ON time of the spatial light modulator system includes:

based on the adjusted light output powers of the primary color lights that correspond to the primary color images and the adjusted grayscale values of the corresponding primary color images, adjusting the ON time of the spatial light modulator system.

Preferably, the step of based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the light output powers of the primary color lights that correspond to the primary color images of the source image includes:

based on the grayscale value adjustment ratio of the at least one primary color image, adjusting sustained durations or brightness values of the primary color lights that correspond to the primary color images of the source image.

Preferably, the step of based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the sustained duration of the primary color lights that correspond to the primary color images of the source image includes:

adjusting the sustained durations of the primary color lights to TR′, TG′ and TB′, which satisfy:

wherein AR′=AR×MR; AG′=AG×MG; AB′=AB×MB; T is a display duration of a frame of image, K is a maximum grayscale value that the spatial light modulator system is capable of displaying;

wherein ARis a maximum grayscale value of a red primary color image before adjustment, AGis a maximum grayscale value of a green primary color image before adjustment, ABis a maximum grayscale value of a blue primary color image before adjustment;

wherein AR′ is a maximum grayscale value of the red primary color image after adjustment, AG′ is a maximum grayscale value of the green primary color image after adjustment, AB′ is a maximum grayscale value of the blue primary color image after adjustment;

wherein MRis a grayscale value adjustment ratio of the red primary color image, MGis a grayscale value adjustment ratio of the green primary color image, MBis a grayscale value adjustment ratio of the blue primary color image;

wherein LRis a brightness value of the red primary color light, LGis a brightness value of the green primary color light, LBis a brightness value of the blue primary color light; and

wherein TRis a sustained duration of the red primary color light before adjustment, TGis a sustained duration of the green primary color light before adjustment, and TBis a sustained duration of the blue primary color light before adjustment.

Preferably, the step of based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the brightness values of the primary color lights that correspond to the primary color images of the source image includes:

adjusting the brightness values of the primary color lights to LR′, LG′ and LB′, which satisfy:

wherein AR′=AR×MR; AG′=AG×MG; AB′=AB×MB; T is a display duration of a frame of image, L is a total brightness value of the three primary color lights, K is a maximum grayscale value that the spatial light modulator system is capable of displaying;

wherein ARis a maximum grayscale value of a red primary color image before adjustment, AGis a maximum grayscale value of a green primary color image before adjustment, ABis a maximum grayscale value of a blue primary color image before adjustment;

wherein AR′ is a maximum grayscale value of the red primary color image after adjustment, AG′ is a maximum grayscale value of the green primary color image after adjustment, AB′ is a maximum grayscale value of the blue primary color image after adjustment;

wherein MRis a grayscale value adjustment ratio of the red primary color image, MGis a grayscale value adjustment ratio of the green primary color image, MBis a grayscale value adjustment ratio of the blue primary color image; and

wherein LRis a brightness of the red primary color light, LGis a brightness of the green primary color light, and LBis a brightness of the blue primary color light.

In another aspect, the present invention provides projection system, including a light source system, a spatial light modulator system, and an image processing system;

wherein the light source system generates three primary color lights;

wherein the spatial light modulator system includes at least one spatial light modulator component for modulating the three primary color lights,

wherein the image processing system is configured to: based on maximum grayscale values of the primary color images of a frame of source image, determine a grayscale value adjustment ratio of at least one of the primary color images; based on the grayscale value adjustment ratio, adjust grayscale values of the primary color images; based on the grayscale value adjustment ratio of the at least one primary color image, adjust light output powers of the primary color lights generated by the light source system that correspond to the primary color images of the source image; and based on the adjusted output powers of the primary color lights and the adjusted grayscale values of the primary color images, adjust an ON time of the spatial light modulator system; wherein in a projected image formed by the spatial light modulator system, grayscale brightness values of the primary color images are increased by a same ratio relative to grayscale brightness values of the corresponding primary color images of the source image.

Preferably, the light source system includes a light source, a switching system, and a color wheel system;

wherein the switching system switches a light emitted by the light source into at least three light beams using time division or light intensity division; and

wherein the color wheel system is disposed on the transmission path of each of the at least three light beams, for generating three primary color lights of predetermined ratios when illuminated by the at least three light beams.

Preferably, the switching system switches the light emitted by the light source into at least three light beams using time division, the switching system includes a first light switch, a second light switch and a first controller;

wherein the first light switch switches the light emitted by the light source into a first light beam within first time intervals, and switches the light emitted by the light source into a second light beam within second time intervals, where the first light beam and the second light beam have different polarization states;

wherein the second light switch switches the second light beam into a third light beam within first sub-intervals of the second time intervals, and switches the second light beam into a fourth light beam within a second sub-intervals of the second time intervals, where the third light beam and the fourth light beam have different polarization states;

wherein the first controller, based on the grayscale value adjustment ratio of the at least one primary color image, controls durations of the first light beam and the second light beam output by the first light switch and durations of the third light beam and the fourth light beam output by the second light switch, to control the light output powers of the primary color lights generated by the light source system that correspond to the primary color images of the source image.

Preferably, the switching system switches the light emitted by the light source into at least three light beams using light intensity division, the switching system includes a first light switch, a second light switch and a first controller;

wherein the first light switch switches the light emitted by the light source into a first light beam and a second light beam simultaneously, where the first light beam and the second light beam have different polarization states;

wherein the second light switch switches the second light beam into a third light beam and a fourth light beam simultaneously, where the third light beam and the fourth light beam have different polarization states;

wherein the first controller, based on the grayscale value adjustment ratio of the at least one primary color image, controls rotation angles of the first light switch and the second light switch, to control the light output powers of the primary color lights generated by the light source system that correspond to the primary color images of the source image.

Preferably, the color wheel system includes a first color wheel, a second color wheel, and a third color wheel;

wherein the first color wheel is located on a first light path of the first light beam, for generating the first primary color light when illuminated by the first light beam; wherein the second color wheel is located on a second light path of the third light beam, for generating the second primary color light when illuminated by the third light beam; and wherein the third color wheel is located on a third light path of the fourth light beam, for generating the third primary color light when illuminated by the fourth light beam.

Preferably, the first color wheel is a color wheel containing a red phosphor, wherein the first primary color light is a red light; wherein the second color wheel is a color wheel containing a green phosphor, wherein the second primary color light is a green light; and wherein the third color wheel is a color wheel containing a blue phosphor, wherein the third primary color light is a blue light.

Preferably, the switching system further includes a first dichroic prism, a second dichroic prism, and a reflector;

wherein the first dichroic prism is located between the first light switch and the first color wheel, for reflecting the first light beam to the first light path and transmitting the second light beam;

wherein the second dichroic prism is located between the second light switch and the second color wheel, for reflecting the third light beam to the second light path and transmitting the fourth light beam; and

wherein the reflector is located between the second dichroic prism and the third color wheel, for reflecting the fourth light beam to the third light path.

Preferably, the projection system further includes a light combination system located between the light source system and the spatial light modulator system;

wherein the light combination system includes at least one reflector and at least two dichroic mirrors, wherein the reflector and the dichroic mirrors are respectively located on output paths of different primary color lights, for reflecting the primary color lights to the spatial light modulator system.

Preferably, the switching system switches the light emitted by the light source into the at least three light beams using time division, the spatial light modulator system includes a light splitting and combining prism, a spatial light modulator component and a second controller;

wherein the light splitting and combining prism sequentially transmits the first primary color light, the second primary color light and the third primary color light to the spatial light modulator component; and

wherein the spatial light modulator component sequentially modulates the first primary color light, the second primary color light and the third primary color light, wherein the modulated first primary color light, second primary color light and third primary color light combine to form an image; and

wherein the second controller, based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights that correspond to the primary color images, controls the ON time of the spatial light modulator component.

Preferably, the switching system switches the light emitted by the light source into at least three light beams using light intensity division, the switching system includes a light splitting and combining prism, a first spatial light modulator component, a second spatial light modulator component, a third spatial light modulator component and a second controller;

wherein the light splitting and combining prism transmits the first primary color light to the first spatial light modulator component, transmits the second primary color light to the second spatial light modulator component, transmits the third primary color light to the third spatial light modulator component;

wherein the first spatial light modulator component modulates the first primary color light;

wherein the second spatial light modulator component modulates the second primary color light;

wherein the third spatial light modulator component modulates the third primary color light; and

wherein the second controller, based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights that correspond to the primary color images, controlling an ON time of each of the first spatial light modulator component, the second spatial light modulator component and the third spatial light modulator component.

Compared to conventional technologies, embodiments of the present invention have the following advantages:

In the projection system an the control method according to embodiments of the present invention, based on the maximum grayscale values of the primary color images of the source image, the grayscale value adjustment ratio of at least one primary color image is determined; based on the grayscale value adjustment ratio of at least one primary color image, the grayscale values of the corresponding primary color images are adjusted; and based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights, the ON time of the spatial light modulator system is adjusted. This way, in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image. I.e., by increasing the grayscale value of at least one primary color image, the utilization efficiency of the spatial light modulator system and the efficiency of the projection system are increased.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are described in detail below with reference to the drawings. These embodiments are only some embodiments, and not all embodiments of the present invention. Based on the embodiments described below, those skilled in the art may derive other embodiments without creative work, all of which are within the scope of the present invention.

First Embodiment

This embodiment provides a control process for a projection system. The projection system includes a light source system and a spatial light modulator system. The light source system generates three primary color lights that can be independently adjusted. The spatial light modulator system is used to modulate the three primary color lights. The control process flow, as shown inFIG. 2, includes:

Step S201: Based on the maximum grayscale value of each primary color image of a frame of source image, determining a grayscale value adjustment ratio of at least one primary color image.

From the input video or image data, the projection system obtains source image data to be projected. The source image data includes individual frames of source images, and each frame of source image includes three primary color image data that together form the color image. Thus, from each frame of source image data, the maximum grayscale values of the primary color images of the frame of source image are obtained. Then, based on the maximum grayscale values of the primary color images of the frame of source image, the grayscale value adjustment ratio of at least one primary color image is determined.

More specifically, this step includes: Obtaining the maximum grayscale value Ai of a primary color image of the source image, and setting the grayscale value adjustment ratio for that primary color to Mi, where 1≤Mi≤(K/Ai), where i is an index of the primary color image. For example: when i is R, ARis the maximum grayscale value of the red primary color image, and MRis the grayscale value adjustment ratio for the red primary color image; when i is G, AGis the maximum grayscale value of the green primary color image, and MGis the grayscale value adjustment ratio for the green primary color image; and when i is B, ABis the maximum grayscale value of the blue primary color image, and MBis the grayscale value adjustment ratio for the blue primary color image. K is the maximum grayscale value that can be displayed by the spatial light modulator system, which is typically 255.

Step S202: Based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the grayscale values of the corresponding primary color images.

More specifically, this step includes: Adjusting the grayscale value of the primary color image to Ai′, where Ai′=Ai*Mi, where Ai is the grayscale value of the primary color before the adjustment, and Ai′ is the grayscale value of the primary color after the adjustment. Here, the grayscale value of the primary color image refers to the grayscale value of each pixel, i.e., the R, G, B pixels of the image, thus, the above equation refers to multiplying the grayscale value of each pixel before the adjustment by the grayscale value adjustment ratio, to achieve the grayscale value adjustment of the primary color image.

Because 1≤Mi≤(K/Ai), and Ai′=Ai*Mi, therefore Ai≤Ai′≤K. Further, in actual implementation, to maximally increase the brightness of the projected image, the maximum grayscale values of all three primary color images can be adjusted to K (e.g. 255), i.e., AR′=K, AG′=K, and AB′=K. Of course, the invention is not limited to this; in other embodiments, the grayscale value adjustment ratios of the primary color images may be set to other values.

Step S203: Based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights that correspond to the primary color images, controlling the ON time of the spatial light modulator system, so that in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image.

In this embodiment, when adjusting the grayscale values of the primary color images, the adjusted grayscale values of the primary color images satisfy the following condition:
AR:AG:AB=AR′:AG′:AB′, whereAR′=AR×MR, AG′=AG×MG, andAB′=AB×MB;

where ARis the maximum grayscale value of the red primary color image before adjustment; AGis the maximum grayscale value of the green primary color image before adjustment; ABis the maximum grayscale value of the blue primary color image before adjustment; AR′ is the maximum grayscale value of the red primary color image after adjustment; AG′ is the maximum grayscale value of the green primary color image after adjustment; AB′ is the maximum grayscale value of the blue primary color image after adjustment; MRis the grayscale value adjustment ratio of the red primary color image; MGis the grayscale value adjustment ratio of the green primary color image; and MBis the grayscale value adjustment ratio of the blue primary color image. This way, the projected image after the adjustment and the projected image before the adjustment can maintain consistent white balance, which prevents adverse impact on the projected image quality due to white balance drift.

After adjusting the grayscale values of the primary color images using the above adjustment ratios, based on the adjusted grayscale values of the primary color images and the light output powers of the corresponding primary color lights generated by the light source of the projection system, the ON time of the spatial light modulator system is controlled. This way, the utilization efficiency of the spatial light modulator system is increased, and the brightness of the projected image of the projection system is increased.

In another embodiment, after adjusting the grayscale values of corresponding primary color images based on the grayscale value adjustment ratio of at least one primary color image, the process further includes:

Based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the light output powers of the primary color lights generated by the light source that correspond to the primary color images of the source image.

After adjusting the light output powers, based on the adjusted output powers of the primary color lights and the adjusted grayscale values, the ON time of the spatial light modulator system is adjusted. This way, not only is the ON time of the spatial light modulator system is adjusted, the output powers of the light source are also adjusted; therefore, in addition to increasing the utilization efficiency of the spatial light modulator system, the brightness of the projected image of the projection system is further increased, and the light utilization efficiency of the projection system is increased.

In the above steps, the adjustment of the output powers of the primary color lights generated by the light source includes: Based on the grayscale value adjustment ratio of at least one primary color image, adjusting the sustained durations or brightness values of the primary color lights.

More specifically, the adjustment of the sustained durations of the primary color lights includes: Adjusting the sustained durations of the primary color lights to TR′, TG′ and TB′, which satisfy the following two conditions:

where AR′=AR×MR; AG′=AG×MG; AB′=AB×MB; T is the display duration of a frame of image; K is the maximum grayscale value that can be achieved by the spatial light modulator system; ARis the maximum grayscale value of the red primary color image before adjustment; AGis the maximum grayscale value of the green primary color image before adjustment; ABis the maximum grayscale value of the blue primary color image before adjustment; AR′ is the maximum grayscale value of the red primary color image after adjustment; AG′ is the maximum grayscale value of the green primary color image after adjustment; AB′ is the maximum grayscale value of the blue primary color image after adjustment; MRis the grayscale value adjustment ratio of the red primary color image; MGis the grayscale value adjustment ratio of the green primary color image; MBis the grayscale value adjustment ratio of the blue primary color image; LRis the brightness value of the red primary color light; LGis the brightness value of the green primary color light; LBis the brightness value of the blue primary color light; TRis the sustained duration of the red primary color light before adjustment; TGis the sustained duration of the green primary color light before adjustment; and TBis the sustained duration of the blue primary color light before adjustment.

Similarly, the adjustment of the brightness values of the primary color lights includes: Adjusting the brightness values of the primary color lights to LR′, LG′ and LB′, which satisfy the following two conditions:

where AR′=AR×MR; AG′=AG×MG; AB′=AB×MB; T is the display duration of a frame of image; L is the total brightness value of the three primary color lights; K is the maximum grayscale value that can be achieved by the spatial light modulator system, ARis the maximum grayscale value of the red primary color image before adjustment; AGis the maximum grayscale value of the green primary color image before adjustment; ABis the maximum grayscale value of the blue primary color image before adjustment; AR′ is the maximum grayscale value of the red primary color image after adjustment; AG′ is the maximum grayscale value of the green primary color image after adjustment; AB′ is the maximum grayscale value of the blue primary color image after adjustment; MRis the grayscale value adjustment ratio of the red primary color image; MGis the grayscale value adjustment ratio of the green primary color image; MBis the grayscale value adjustment ratio of the blue primary color image; LRis the brightness of the red primary color light; LGis the brightness of the green primary color light; and LBis the brightness of the blue primary color light. In the projection system control method of this embodiment, based on the maximum grayscale values of the primary color images of the source image, the grayscale value adjustment ratio of at least one primary color image is determined; based on the grayscale value adjustment ratio of at least one primary color image, the grayscale values of the corresponding primary color images are adjusted; based on the adjusted grayscale values of the primary color images and the light output powers of the primary color lights, the ON time of the spatial light modulator system is adjusted. This way, in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image. I.e., by increasing the grayscale value of at least one primary color image, the utilization efficiency of the spatial light modulator system and the efficiency of the projection system are increased.

Second Embodiment

This embodiment provides a projection system, including a light source system, a spatial light modulator system, an image processing system and a light combination system. The light source system generates three primary color lights that are independently adjustable. The spatial light modulator system includes at least one spatial light modulator component for modulating the three primary color lights, so that the modulated three primary color lights can be combined to form a projected image. The image processing system performs the following: based on the maximum grayscale values of the primary color images of a frame of source image, determining a grayscale value adjustment ratio of at least one primary color image; based on the grayscale value adjustment ratio, adjusting the grayscale values of the corresponding primary color image; based on the grayscale value adjustment ratio of the at least one primary color image, adjusting the light output powers of the primary color lights generated by the light source system; and based on the adjusted output powers of the primary color lights and the adjusted grayscale values of the primary color images, adjusting the ON time of the spatial light modulator system. This way, in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image. The light combination system is disposed between the light source system and the spatial light modulator system, and includes at least one reflector and at least two dichroic mirrors, where the reflector and the dichroic mirrors are respectively disposed on the output light paths of the different primary color lights, to reflect the three primary lights to the spatial light modulator system.

In this embodiment, as shown inFIG. 3, the light source system includes a light source30, a switching system60and a color wheel system70. The light source30is a laser module emitting a blue light. The laser module may include one or more semiconductor lasers. The switching system60switches the light emitted by the light source30into at least three light beams using time division. The color wheel system70is disposed on the transmission path of each of the at least three light beams, and when illuminated by the at least three light beams, generates three primary color lights of predetermined ratios. For example, the color wheel system70includes at least three color wheels, respectively disposed on the transmission path of different light beams, to generate the three primary color lights.

As shown inFIG. 3, the switching system60includes a first light switch601, a second light switch602, a first controller603, a first dichroic prism604, a second dichroic prism605, and a reflector606. The first light switch601and the second light switch602may be electro-optical devices such as a liquid crystal phase retarder, or magneto-optical devices, or acousto-optic devices. The color wheel system70includes a first color wheel701, a second color wheel702, and a third color wheel703. The first color wheel701is a color wheel containing a red phosphor; the second color wheel702is a color wheel containing a green phosphor; and the third color wheel703is a color wheel containing a scattering powder. The light combination system includes a reflector503, a dichroic mirror505and a dichroic mirror506. The dichroic mirrors505and506are partly transmitting, partly reflecting mirrors. The spatial light modulator system includes a light splitting and combining prism808, spatial light modulator component809and a second controller.

When the image processing system10receives the image or video source data, it decodes the source data to obtain individual frames of source image data. It then determines the grayscale value adjustment ratio of at least one primary color image based on maximum grayscale values of the primary color images of the source image, adjusts the grayscale value of the corresponding primary color image based on the grayscale value adjustment ratio, and transmits the grayscale value adjustment ratio to the first controller603and the second controller. The first controller603adjusts the output powers of the primary color lights generated by the light source system. The second controller, based on the adjusted output powers of the primary color lights and the adjusted grayscale values of the primary color images, adjusts the ON time of the spatial light modulator system.

The process by which the first controller603controls the output powers, i.e. the sustained duration, of the three primary color lights generated by the light source system includes: After the first controller603receives the grayscale value adjustment ratio, based on the grayscale value adjustment ratio, it controls the durations of the first light beam and the second light beam output by the first light switch601, as well as the durations of the third light beam and the fourth light beam output by the second light switch602, so as to control the output powers of the primary color lights generated by the light source system. The first light beam and the second light beam have different polarization states, and the third light beam and the fourth light beam have different polarization states.

The first controller603controls the sustained durations of the three primary color lights to TR′, TG′ and TB′, which satisfy the following conditions:

Under the control of the first controller603, the first light switch601, within first time intervals, switches the S polarized blue light λ0emitted by the light source30into the first light beam λ1, and within second time intervals, switches the light λ0emitted by the light source30into the second light beam λ2, where the switched first light beam λ1remains S polarized blue light, and the switched second light beam λ2becomes P polarized blue light. Similarly, under the control of the first controller603, the second light switch602, within first sub-intervals of the second time intervals, switches the second light beam λ2into the third light beam λ3, i.e., it rotates the polarization of the P polarized blue light λ2by 90 degrees to an S polarized blue light beam λ3, and within the second sub-intervals of the second time intervals, switches the second light beam λ2into the fourth light beam λ4, which remains a P polarized blue light.

The first dichroic prism604transmits the second light beam λ2, i.e. the P polarized blue light, and reflects the first light beam λ1, i.e., the S polarized blue light, to the first color wheel701located on the first light path. The first color wheel701has a red phosphor, and can absorb the blue light to generate a red light R, i.e., it generates the first primary color light i.e. red light. The second dichroic prism605transmits the fourth light beam λ4, i.e. the P polarized blue light, and reflects the third light beam λ3, i.e., the S polarized blue light, to the second color wheel702located on the second light path. The second color wheel702has a green phosphor, and can absorb the blue light to generate a green light R, i.e., it generates the second primary color light i.e. green light G. The reflector606reflects the fourth light beam λ4which has transmitted through the second dichroic prism605, i.e., the P polarized blue light, to the third color wheel703located on the third light path. The third color wheel703has a scattering powder, and can transmit blue light and depolarize the S polarized blue light, and outputs it as the third primary color light i.e. blue light B. The durations of the first primary color light, the second primary color light and the third primary color light are TR′, TG′ and TB′, where the sum of TR′, TG′ and TB′ is the time duration of a frame of image, T.

Then, the first primary color light is reflected by the reflector503to be incident on the dichroic filter505; after passing through the dichroic filter505, the dichroic filter506and the light splitting and combining prism808, it enters the spatial light modulator component809to be modulated. The second primary color light is reflected by the dichroic filter505; after passing through the dichroic filter506and the light splitting and combining prism808, it enters the spatial light modulator component809to be modulated. The third primary color light is reflected by the dichroic filter506; after passing through the light splitting and combining prism808, it enters the spatial light modulator component809to be modulated.

In this embodiment, to increase the utilization efficiency of the spatial light modulator system, the durations of the R, G, B primary color lights generated by the light source system are respectively adjusted to TR′, TG′ and TB′, where TR′+TG′+TB′=T. The adjusted output powers of the R, G, B primary color lights of the projected image are respectively LR·TR, LG·TG, and LB·TB. After the adjustment, the ratio of the RGB primary color lights is the same as the ratio of the primary color lights of the projection system before the adjustment, so as to maintain the white balance, i.e.: LR·AR′TR′/K:LG·AG′TG′/K:LB·AB′TB′/K=LR·ARTR/K:LG·AGTG/K:LB·ABTB/K. Thus, it can be seen that the grayscale brightness values of the RGB primary color lights after the adjustment, relative to the values before the adjustment, are increased by a ratio of AR′TR′/ARTR=AG′TG′/AGTG=AB′TB′/ABTB.

Further, to maximally increase the brightness of the projected image, the maximum grayscale values of all three primary color images can be increased to K (e.g. 255), i.e., AR′=K, AG′=K, AB′=K. In this case, the brightness of the projected image after the adjustment is increased relative to before the adjustment by a ratio of KTR′/ARTR.

In the projection system of this embodiment, based on the maximum grayscale values of the primary color images of the source image, the grayscale value adjustment ratio of at least one primary color image is determined; based on the grayscale value adjustment ratio, the grayscale values of the corresponding primary color images are adjusted; based on the grayscale value adjustment ratio of at least one primary color image, the sustained durations of the primary color lights generated by the light source system are adjusted; based on the adjusted durations of the primary color lights and the adjusted grayscale values of the primary color images, the ON time of the spatial light modulator system is controlled. This way, in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image. I.e., by increasing the grayscale value of at least one primary color image, the utilization efficiency of the spatial light modulator system and the efficiency of the projection system are increased.

Third Embodiment

This embodiment provides a projection system, which has a structure similar to that of the projection system of the second embodiment; one difference is that in the third embodiment, the switching system uses light intensity division to switch the light generated by the light source into at least three light beams. Further, the spatial light modulator system of this embodiment, as shown inFIG. 4, includes a light splitting and combining prism804, a first spatial light modulator component805, a second spatial light modulator component806, and a third spatial light modulator component807.

In this embodiment, when the image processing system10receives the image or video source data, it decodes the source data to obtain individual frames of source image data. It then determines the grayscale value adjustment ratio of at least one primary color image based on the maximum grayscale values of the primary color images of the source image, adjusts the grayscale value of the corresponding primary color image based on the grayscale value adjustment ratio, and transmits the grayscale value adjustment ratio to the first controller603and the second controller. The first controller603adjusts the output powers of the primary color lights generated by the light source system. The second controller, based on the adjusted output powers of the primary color lights and the adjusted grayscale values of the primary color images, adjusts the ON time of the spatial light modulator system.

The process by which the first controller603controls the output power (i.e. brightness) of the three primary color lights generated by the light source system includes: After the first controller603receives the grayscale value adjustment ratio, based on the grayscale value adjustment ratio of the primary colors, it controls the rotation angles of the first light switch and the second light switch, so as to control the output power (i.e. brightness) of the primary color lights generated by the light source system.

More specifically, the step of controlling the brightness of the primary color lights based on the grayscale value adjustment ratio of the primary color image includes the following:

Adjusting the brightness values of the three primary color lights to LR′, LG′ and LB′, which satisfy the following conditions:

Assuming that the light intensity of the light generated by the light source is I, the rotation angle of the first light switch601is α, which is between 0 degrees and 90 degrees, then the output light of the first light switch601contains both S polarized light and P polarized light, and the light intensities of the S polarized light and the P polarized light are respectively I cos2α and I sin2α; i.e., the light intensities of the first light beam λ1and the second light beam λ2are respectively I cos2α and I sin2α. Assuming the rotation angle of the second light switch602is β, then the light intensities of the S polarized light and the P polarized light output by the second light switch602are respectively I sin2α sin2β and I sin2α cos2β; i.e., the light intensities of the third light beam λ3and the fourth light beam λ4are respectively I sin2α sin2β and I sin2α cos2β.

Under the control of the first controller603, the first light switch601switches the light beam λ0emitted by the light source30into a first light beam λ1which is an S polarized blue light and a second light beam λ2which is a P polarized blue light. Similarly, under the control of the first controller603, the second light switch602switches the second light beam λ2into a third light beam λ3which is an S polarized blue light and a fourth light beam λ4which is a P polarized blue light.

The first dichroic prism604transmits the second light beam λ2, i.e. the P polarized blue light, and reflects the first light beam λ1, i.e., the S polarized blue light, to the first color wheel701located on the first light path. The first color wheel701has a red phosphor, and can absorb the blue light to generate a red light R, i.e., it generates the first primary color light i.e. red light. The second dichroic prism605transmits the second light beam λ4, i.e. the P polarized blue light, and reflects the third light beam λ3, i.e., the S polarized blue light, to the second color wheel702located on the second light path. The second color wheel702has a green phosphor, and can absorb the blue light to generate a green light, i.e., it generates the second primary color light i.e. green light. The reflector606reflects the fourth light beam λ4which has transmitted through the second dichroic prism605, i.e., the P polarized blue light, to the third color wheel703located on the third light path. The third color wheel703has a scattering powder, and can transmit blue light and depolarize the S polarized blue light, and outputs it as the third primary color light i.e. blue light. The light intensities of the first primary color light, the second primary color light and the third primary color light are respectively I cos2α, I sin2α sin2β and I sin2α cos2β.

Then, the first primary color light is reflected by the reflector503to be incident on the dichroic filter505; after passing through the dichroic filter505, the dichroic filter506and the light splitting and combining prism804, it enters the first spatial light modulator component805to be modulated. The second primary color light is reflected by the dichroic filter505; after passing through the dichroic filter506and the light splitting and combining prism804, it enters the second spatial light modulator component806to be modulated. The third primary color light is reflected by the dichroic filter506; after passing through the light splitting and combining prism804, it enters the third spatial light modulator component807to be modulated. The second controller, after receiving a second control command, controls the first spatial light modulator component805, the second spatial light modulator component806and the third spatial light modulator component807to modulate the first primary color light, the second primary color light and the third primary color light during the time interval T which is the time of one frame of image.

In this embodiment, to increase the utilization efficiency of the spatial light modulator system, the image processing system10adjusts the intensities of the RGB primary color lights generated by the light source to LR′, LG′ and LB′, respectively, where LR′=I cos2α, LG′=I sin2α sin2β, and LB′=I sin2α cos2β. The time durations in which the first spatial light modulator component805, the second spatial light modulator component806and the third spatial light modulator component807modulate the respective lights are all the time interval T which is the time of one frame of image. Thus, in this embodiment, the brightness values of the projected image are respectively LR′·T, LG′·T, and LB′·T. After the adjustment, the ratio of the RGB primary color lights is the same as the ratio of the primary color lights of the projection system before the adjustment, i.e.: LR′·AR′ T/K:LG′·AG′T/K:LB′·AB′T/K=LR·ART/K:LG·AGT/K:LB·ABT/K. Thus, it can be seen that the grayscale brightness values of the RGB primary color lights after the adjustment, relative to the values before the adjustment, are increased by a ratio of AR′LR′/ARLR, where AR′LR′/ARLR=AG′LG/AGLG=AB′LB′/ABLB.

Further, to maximally increase the brightness of the projected image, the maximum grayscale values of all three primary color images can be increased to K (e.g. 255), i.e., AR′=K, AG′=K, AB′=K. In this case, the brightness of the projected image after the adjustment is increased relative to before the adjustment by a ratio of KTR′/LRTR. In the projection system of this embodiment, based on the maximum grayscale values of the primary color images of the source image, the grayscale value adjustment ratio of at least one primary color image is determined; based on the grayscale value adjustment ratio, the grayscale values of the corresponding primary color images are adjusted; based on the grayscale value adjustment ratio of at least one primary color image, the brightness values of the primary color lights generated by the light source system are adjusted; and based on the adjusted brightness values of the primary color lights and the adjusted grayscale values of the primary color images, the ON time of the spatial light modulator system is adjusted. This way, in the projected image formed by the spatial light modulator system, the grayscale brightness values of the primary color images are increased by the same ratio relative to the grayscale brightness values of the corresponding primary color images of the source image. I.e., by increasing the grayscale value of at least one primary color image, the utilization efficiency of the spatial light modulator system and the efficiency of the projection system are increased.

The embodiments are described in a progressive manner in this disclosure, and each embodiment is described by focusing on its differences from other embodiment; the similar aspects of the embodiments can be understood by referring to each other. It will be apparent to those skilled in the art that various modification and variations can be made in the projection system and control method of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.