TWI511114B - Brightness control method of projector - Google Patents

Description

Projector light source control method

The present invention relates to a light source control method, and more particularly to a light source control method for a projector.

The projection device can project images onto a larger screen to allow more people to simultaneously view the content displayed on the screen. Therefore, it is often used in public places such as companies and schools. Furthermore, as household display products are moving toward larger sizes, projection devices are becoming more and more popular in general households, and become an everyday electronic product in modern life.

With the advancement of technology, all kinds of electronic products are moving toward high speed, high efficiency, light and thin. Under this trend, pico projectors (or mini projectors) have gradually become the mainstream of the personal digital market in the future. In general, the light source of a pico projector uses a light emitting diode or other solid state light source to increase the lumen required by the pico projector, thereby increasing the brightness of the image projected by the pico projector. After the pico projector is finished, the size of the micro projector's battery is about the same as that of a general mobile phone on the market. Even the pico projector can be integrated into a mobile phone. Therefore, the pico projector has the advantage of being portable and without field restrictions.

However, since the projector requires a continuous light source to be projected, the light-emitting diode as a light source must continuously emit light. Further, in the state in which the light-emitting diode is continuously illuminated, the power of the battery is continuously consumed. One In general, when the pico projector is in operation, the power consumed by the light source accounts for 70% to 90% of the entire pico projector system. That is, the light source of the micro projector is the most power-consuming part of the entire pico projector system. And the power consumption of the light source determines the usage time of the pico projector when the battery is used as power.

The invention provides a light source control method for a projector, which can turn off all colors or partial colors provided by the light source module when the gray scale distribution is lower than a gray scale, thereby saving power consumption.

The invention provides a light source control method for a projector, which comprises the steps of: receiving picture data during a picture; performing data analysis according to the picture data to obtain a gray scale distribution of a plurality of colors in the picture data; The order distribution determines whether to turn off all or part of the plurality of color light sources of the projector during the picture period.

The invention also provides a light source control method for a projector, which comprises the steps of: receiving picture data during a picture; performing data analysis according to the picture data to obtain gray scale distribution of multiple colors in the picture data; The gray scale distribution determines whether to turn off the projector's color light source during the picture period.

Based on the above, the light source control method of the projector of the present invention determines whether to turn off the light source provided by the light source module according to the gray scale distribution of the plurality of color light sources. Moreover, the data gain of the picture data and the working period of the color light source are adjusted according to the average brightness of the picture data. Thereby, under the premise of maintaining the display effect, the occurrence of light leakage can be avoided to improve the purity of the picture, and It can save power consumption.

The above described features and advantages of the present invention will be more apparent from the following description.

1 is a system diagram of a projector in accordance with an embodiment of the present invention. Referring to FIG. 1 , the projector 100 includes a driving module 110 , a light source module 120 , and a liquid crystal panel 130 . The liquid crystal panel 130 can be a liquid crystal on silicon (LCOS) panel, and the projector 100 can be a miniature. Projector. The driving module 110 receives the video signal VS, generates a driving voltage VDR to the liquid crystal panel according to the picture data transmitted by the video signal VS, and generates a driving signal SDR to the light source module 120. The liquid crystal panel 130 arranges the liquid crystals according to the driving voltage VDR, and the light source module 120 supplies the light source to the liquid crystal panel 130 according to the driving signal SDR. The liquid crystal panel 130 projects light to a target (such as a curtain or a wall) by the light source provided by the reflective/transmissive light source module 120 to display an image.

In terms of current technology, germanium-based liquid crystal panels can be roughly classified into CF-LCOS and CS-LCOS. The CF-LCOS forms a color filter (CF) on the liquid crystal panel 130, and displays different colors through the color filter, that is, provides spatial mixing to display a color image, and the light source module 120 Correspondingly, only white light is provided as the light source. In addition, the CS-LCOS does not form a color filter on the liquid crystal panel 130, and realizes temporal mixing by using a color sequential (CS) method to display a color image, and the light source module 120 can be Correspondingly provided at different times Light sources of the same color (such as red, blue, and green). Among them, white light, red light, blue light, and green light can be provided by light-emitting diode light of a corresponding color.

2 is a schematic diagram of a system of the driving module of FIG. 1. Referring to FIG. 1 and FIG. 2 , the driving module 110 includes a frame rate control unit 210 , a data analyzing unit 220 , a gain controller 230 , a gamma correction unit 240 , a data controller 250 , and a light source controller 260 . . The frame rate control unit 210 receives the picture data transmitted by the video signal VS, and generates the display data DS to the data controller 250 according to the frame rate control method. The data analysis unit 220 receives the picture data transmitted by the video signal VS and analyzes the picture data, and transmits the analysis result RA to the gain controller 230.

The gain controller 230 outputs the data gain G1 to the gamma correction unit 240 according to the analysis result RA, and outputs the light source gain G2 to the light source controller 260 according to the analysis result RA. The gamma correction unit 240 provides a plurality of gamma voltages VG to the data controller 250 according to the data gain G1, wherein the gamma voltages VG respectively correspond to a gray scale value. The data controller 250 selectively outputs a gamma voltage VG as the driving voltage VDR according to the display data DS. The light source controller 260 generates the driving signal SDR according to the light source gain G2, and the light source controller 260 provides a corresponding number of driving signals SDR according to the number of color light sources provided by the light source module. In other words, if the liquid crystal panel 130 is CF-LCOS, the light source module 120 provides white light. Therefore, the light source controller 260 correspondingly generates a driving signal SDR to drive the white light emitting diode to emit light. In addition, if the LCD panel 130 is a CS-LCOS, and the light source module 120 can provide red light, blue light, and green light at different times. Therefore, the light source controller 260 correspondingly generates three driving signals SDR to respectively control the red light emitting diode and the blue light. The color light emitting diode and the green light emitting diode emit light at different times.

Further, when the data analysis unit 220 receives the screen data during one screen, the data analysis unit 220 analyzes the screen data to obtain the gray scale distribution of the three primary colors (ie, red, blue, and green) as the analysis result RA. Next, the gain controller 230 determines whether to turn off the light source provided by the light source module 120 according to the gray scale distribution of the three primary colors. Taking the CS-LCOS liquid crystal panel as an example, when the grayscale average value of the grayscale distribution of one of the three primary colors (for example, red) is less than or equal to a critical value, it means that the screen has almost no such color component, so the display is The color light source of this color can be turned off (for example, red light); otherwise, when the grayscale average of the grayscale distribution of the color is greater than the critical value, the corresponding color light source of the color is turned on. The threshold value is generally a lower gray scale value (for example, a gray scale value of 15). However, the threshold value may be different according to actual circuit design and no use habit, and is not limited thereto. Therefore, the power consumption of the light source can be saved.

In addition, in addition to determining whether to turn off the corresponding color light source according to the grayscale average value of each color, the gain controller 230 may determine whether to turn off the corresponding color light source according to whether the grayscale distribution of each color is lower than or equal to the critical range. In other words, when the gray scale distribution of a certain color is lower than or equal to a critical range, the color light source corresponding to the color is turned off; otherwise, when the gray scale distribution of the color crosses the critical range (that is, the gray scale distribution of the color is not only When the value is below the critical range and exceeds the critical range, the corresponding response is turned on. The color source of this color. The opening or closing of the color light source can be completed by setting the light source gain G2.

FIG. 3 is a schematic diagram of driving waveforms of a red picture according to an embodiment of the invention. Referring to FIG. 2 and FIG. 3, the data analysis unit 220 receives a plurality of picture data of a red picture during the picture period P _F and transmits the gray scale distribution of the three primary colors to the gain controller 230. Moreover, in the red screen, the blue and green grayscale averages are less than the critical value, or the blue and green grayscales are lower, respectively, because there are fewer or no impurities in the blue and green. At or equal to the critical range. Therefore, the gain controller 230 turns off the blue light and the green light provided during the blue sub-picture period P _B and the green sub-picture period P _G , while retaining only the red light supplied by the red sub-picture period P _R . According to the above, if the data analysis unit 220 receives a solid color picture (for example, pure red, pure green, pure blue, pure yellow, pure purple, pure blue or pure black) or a picture close to a solid color, the data analysis unit 220 transmits the gain control. The unit 230 turns off some or all of the red light, the green light, and the blue light.

As shown in FIG. 3, since the liquid crystal alignment requires reaction time (such as R1 and R2), it is assumed that when P _G provides green light during the green sub-picture, the liquid crystal has not returned to the normal state (that is, the liquid crystal still has light transmittance), and slightly The green light is transmitted through the liquid crystal, which causes light leakage, which reduces the purity of the red picture. According to the above, when the blue light and the green light are turned off, the screen can still be displayed normally, and the light leakage phenomenon can be prevented and the purity of the picture can be improved. Furthermore, the power required to illuminate the green light-emitting diode and the blue light-emitting diode can be saved.

Please refer to Figure 2 again, taking CF-LCOS LCD panel as an example, when the three primary colors When the grayscale average of the grayscale distribution is less than or equal to the critical value (that is, the picture is pure black or nearly pure black), the white light is turned off. Conversely, when the grayscale average of the grayscale distribution of the three primary colors is greater than the critical value, white light is turned on. Alternatively, when the gray scale distribution of the three primary colors is lower than or equal to the critical range, the white light is turned off. Conversely, when the gray scale distribution of one of the three primary colors crosses the critical range, white light is turned on.

In addition, the driving module 110 of the present invention can turn off the color light source provided by the light source module 120, and can adjust the working period of the color light source according to the picture data. Referring to FIG. 2, when the data analysis unit 220 receives the screen data during the screen, the data analysis unit 220 analyzes the screen data to obtain the average brightness of the screen data as the analysis result RA. Moreover, the gain controller 230 adjusts the magnitude of the driving voltage corresponding to the display data and the working period of the light source during the screen period according to the average brightness. In the case of a CS-LCOS liquid crystal panel, the gain controller 230 adjusts the duty cycle of the three primary colors of light. In the case of a CF-LCOS liquid crystal panel, the gain controller 230 adjusts the duty cycle of the white light.

Further, when the average brightness of the picture data is greater than the brightness reference value, the difference between the average brightness and the brightness reference value is reduced according to the driving voltage corresponding to the display data. When the average brightness is less than the brightness reference value, the difference between the average brightness and the brightness reference value increases the magnitude of the driving voltage corresponding to the display data, and correspondingly reduces the working period of the light source. The brightness reference value may be an intermediate brightness value, but is not limited to.

For example, when the average brightness value is half of the brightness reference value (ie, 1/2), the gain controller 230 adjusts the gamma repair through the data gain G1. The gamma voltage VG output by the positive unit 240. Taking the 255 gray scale as an example, the endpoint corresponding to the grayscale value of 1 outputs a gamma voltage with a grayscale value of 2, and the endpoint corresponding to the grayscale value of 2 outputs a gamma voltage having a grayscale value of 4, and the rest And so on. Moreover, since the gamma correction unit 240 outputs the gamma voltage VG having a grayscale value of 255 at the highest, the gamma voltage VG of the grayscale value of 255 is output only for the endpoints of the grayscale value of 128 and higher. .

On the other hand, when the average luminance value is twice the luminance reference value, the gain controller 230 adjusts the gamma voltage VG output from the gamma correction unit 240 through the data gain G1. Taking the 255 gray scale as an example, the endpoint corresponding to the grayscale value of 1 will output a gamma voltage with a grayscale value of 0.5, and the endpoint corresponding to the grayscale value of 2 will output a gamma voltage with a grayscale value of 1. The rest is like this.

According to the above, the relationship between the data gain G1, the display data DS, and the driving voltage VDR can be aggregated into a graph. 4 is a graph of input grayscale values and output grayscale values in accordance with an embodiment of the present invention. Referring to FIG. 4, a curve 410 is a relationship between an input grayscale value of a data gain G1 of 1 and an output grayscale value, and a curve 420 is a relationship between an input grayscale value of the data gain G1 of 2 and an output grayscale value, and a curve 430 is a relationship between the input grayscale value of the data gain G1 of 0.5 and the output grayscale value. The input gray scale value is a gray scale value of the display data DS, and the output gray scale value is a gray scale value corresponding to the driving voltage VDR.

Moreover, when the data gain is greater than 1 (that is, the average brightness of the picture data is greater than the brightness reference value), the duty cycle of the light source can be correspondingly reduced. Taking the CS-LCOS liquid crystal panel as an example, the gain controller 230 can synchronously adjust the duty cycle of the three primary colors of light through the light source gain G2. Referring to FIG. 3 , the working pulse wave 310 corresponding to the red light is taken as an example. The rising edge 311 of the working pulse wave 310 is moved according to the magnitude of the light source gain G2 , that is, the triggering time of the rising edge 311 can be determined according to the light source. Gain G2 is adjusted. Also, the falling edge 312 of the working pulse 310 is fixed to the end time of the red sprite period P _R .

In general, when the light source gain G2 is 1, the distance between the rising edge 311 and the falling edge 312 of the working pulse wave 310 may be a standard light-emitting period of the red light-emitting diode, wherein the standard light-emitting period may be equal to or smaller than the red sub-picture. During the period P _R , the general knowledge in the field can be adjusted according to the actual design requirements. When the light source gain G2 decreases, the triggering time of the rising edge 311 will correspondingly approach the falling edge 312. That is, the light-emitting time of the red light-emitting diode is equal to the standard light-emitting period multiplied by the light source gain G2. Further, since the liquid crystal is arranged to the display position in the reaction time R1, which is a low-luminance section, the usage rate of the red color light source can be improved by adjusting the rising edge 311 of the working pulse wave 310. The adjustment method of the working cycle of the green light and the blue light can be referred to the adjustment method of the duty cycle of the red light, and will not be described here.

Taking the CF-LCOS liquid crystal panel as an example, the gain controller 230 can synchronously adjust the working period of the white light through the light source gain G2. FIG. 5 is a driving waveform diagram of white light according to an embodiment of the present invention. Referring to FIG. 5, in the present embodiment, the duty cycle of the white light is adjusted by adjusting the trigger time of the rising edge of the working pulse wave 510 corresponding to the white light. Also, the falling edge 512 of the working pulse 510 is the end time of the triggering of the picture period P _F . It is worth mentioning that the display effect of the driving voltage corresponding to the average brightness adjustment display data and the working cycle size of the color light source can be expressed by the following function: (1/G)×BL×(G ^{1/ γ} × Data) ^γ

Among them, (1/G) is the light source gain, G is the data gain, and 1/γ is the gamma correction parameter. Further, the display effect represented by the above function is the same as the general display effect (also BL × (Data) ^γ ).

According to the above, the light source control method of a projector can be integrated. FIG. 6 is a flow chart of a method of controlling a light source according to an embodiment of the invention. Referring to FIG. 6 , firstly, a screen data is received in a screen period (step S610 ), and data analysis is performed according to the screen data to obtain gray scale distribution of the three primary colors and average brightness of the screen data in the screen data (step S620). ). Then, according to the gray scale distribution of the three primary colors, whether to turn off the color light source provided by the light source module of the projector is determined during the screen period (step S630). Moreover, according to the average brightness, the data gain is adjusted during the picture period to adjust the size of the driving voltage corresponding to the display data, and to adjust the working period of the color light source. The details of each step can be referred to the above description, and will not be described again here.

In summary, the light source control method of the projector of the present invention can close the use of less color light sources when the acquired picture material is a solid color picture according to the gray scale distribution of the three primary colors. And, according to the average brightness of the picture data, the size of the driving voltage corresponding to the display data and the working period of the color light source are adjusted. Thereby, under the premise of maintaining the display effect, the occurrence of light leakage can be avoided, thereby improving the purity of the screen and reducing the power consumption. And, the work of adjusting the color light source can be adjusted by adjusting the rising edge of the working pulse wave. Cycle to increase the usage of color light sources.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Projector

110‧‧‧Drive Module

120‧‧‧Light source module

130‧‧‧LCD panel

VS‧‧‧ video signal

SDR‧‧‧ drive signal

VDR‧‧‧ drive voltage

210‧‧‧ Frame speed control unit

220‧‧‧Data Analysis Unit

230‧‧‧ Gain Controller

240‧‧‧Gamma Correction Unit

250‧‧‧ data controller

260‧‧‧Light source controller

RA‧‧‧ analysis results

DS‧‧‧Display information

G1‧‧‧ data gain

G2‧‧‧Light source gain

VG‧‧ gamma voltage

P _F ‧‧‧Screen period

P _R , P _G , P _B ‧‧‧Split period

R1, R2‧‧‧ liquid crystal reaction time

310, 510‧‧‧ working pulse

311, 511‧‧‧ rising edge

312, 512‧‧‧ falling edge

410, 420, 430‧‧‧ curves

S610, S620, S630, S640‧‧‧ steps

1 is a system diagram of a projector in accordance with an embodiment of the present invention.

2 is a schematic diagram of a system of the driving module of FIG. 1.

FIG. 3 is a schematic diagram of driving waveforms of a red picture according to an embodiment of the invention.

4 is a graph of input grayscale values and output grayscale values in accordance with an embodiment of the present invention.

FIG. 5 is a driving waveform diagram of white light according to an embodiment of the present invention.

FIG. 6 is a flow chart of a method of controlling a light source according to an embodiment of the invention.

S610, S620, S630, S640‧‧‧ steps

Claims (14)

A light source control method for a projector, comprising: receiving a picture data during a picture; performing data analysis according to the picture data to obtain a gray scale distribution of the plurality of colors in the picture data; and gray scale according to the colors Distributing, during the picture period, determining whether to turn off all or part of the plurality of color light sources of the projector to determine whether to display a picture corresponding to the picture material or a corresponding part of the plurality of sub-pictures in the picture, wherein During the picture, the closed color sources do not provide corresponding color light. The light source control method of the projector of claim 1, further comprising: performing data analysis according to the screen data to obtain an average brightness of the picture data; and adjusting according to the average brightness during the picture period A data gain of the picture material and a working period of the color light sources. The light source control method of the projector of claim 2, wherein the step of: adjusting the data gain of the picture material and the duty cycle of the color light sources during the picture period according to the average brightness includes: When the average brightness is greater than a brightness reference value, the data gain is decreased according to the difference between the average brightness and the brightness reference value; and when the average brightness is less than the brightness reference value, according to the average brightness and the brightness reference value The gap increases the gain of the data and correspondingly reduces the The size of the duty cycle of these color light sources. The method for controlling a light source of a projector according to the second aspect of the invention, wherein the step of adjusting a working period of the color light sources comprises: adjusting a triggering time of a rising edge of a working pulse corresponding to the color light sources respectively. . The light source control method of the projector of claim 4, wherein a falling edge of the working pulse wave corresponding to each of the color light sources is triggered by each of the color light sources corresponding to the image period An end time during a sub-picture. The light source control method of the projector according to claim 1, wherein "determining whether to turn off all or part of the plurality of color light sources of the projector during the screen period according to the gray scale distribution of the colors" The step of: turning off a first color source corresponding to the first color of the color light sources when a grayscale average value of a first color of the colors is less than or equal to a threshold value; and when the gray scale When the average value is greater than the threshold, the first color light source is turned on. The light source control method of the projector according to claim 1, wherein "determining whether to turn off all or part of the plurality of color light sources of the projector during the screen period according to the gray scale distribution of the colors" The step of: closing a color light source corresponding to the first color when the gray scale distribution of a first color of the colors is lower than or equal to a critical range a color light source; and turning on the first color light source when the gray scale distribution of the first color spans the critical range. A light source control method for a projector, comprising: receiving a picture data during a picture; performing data analysis according to the picture data to obtain a gray scale distribution of the plurality of colors in the picture data; and gray scale according to the colors Distribution, determining whether to turn off a light source of the projector during the screen period to determine whether to display a screen corresponding to the screen material or a corresponding portion of the plurality of sub-screens in the screen, wherein during the screen, the screen is closed The color light sources do not provide corresponding color lights. The light source control method of the projector of claim 8, further comprising: performing data analysis according to the screen data to obtain an average brightness in the picture data; and according to the average brightness, in the picture period Adjusting a data gain of the picture data and a working period of the light source. The light source control method of the projector of claim 9, wherein the step of: adjusting the data gain of the picture material and the duty cycle of the light source during the picture period according to the average brightness includes: When the average brightness is greater than a brightness reference value, the data gain is reduced according to the difference between the average brightness and the brightness reference value; and when the average brightness is less than the brightness reference value, the difference between the average brightness and the brightness reference value is increased. The data gain, and correspondingly reduce the The size of the working cycle of the light source. The light source control method of the projector of claim 9, wherein the step of adjusting the working period of the light source comprises: adjusting a triggering time of a rising edge of a working pulse corresponding to the light source. The light source control method of the projector of claim 11, wherein a falling edge of the working pulse wave corresponding to the light source is an end time triggered during the picture period. The light source control method of the projector of claim 8, wherein the step of: determining whether to turn off the light source of the projector during the screen period according to the gray scale distribution of the colors includes: When the grayscale average of the grayscale distribution of the color is less than or equal to a critical value, the light source is turned off; and when the grayscale average is greater than the critical value, the light source is turned on. The light source control method of the projector of claim 8, wherein the step of: determining whether to turn off the light source of the projector during the screen period according to the gray scale distribution of the colors includes: When the gray scale distribution of the color is lower than or equal to a critical range, the light source is turned off; and when the gray scale distribution of the colors crosses the critical range, the light source is turned on.