CN101931822A - Automatic white balance system and method thereof - Google Patents

Abstract

The invention relates to an automatic white balance (AWB) system suitable for a projection device. The system comprises a light source, a light sensing unit, an analog-digital converter, a control unit and a driving circuit, wherein the light sensing unit comprises a light sensor and a light sensing circuit; and the light sensor is coupled to the light sensing circuit. No matter the light source emits what color light, the light sensor can sense the brightness of the color light emitted by the light source. Compared with the conventional device which uses three color sensors, the AWB system fulfills the aim of balance white by using the light sensor, so that the manufacturing cost of the projection device is lower.

Description

Auto white balance system and method thereof

Technical field

The present invention relates to a kind of coloured light balance sysmte, and particularly about a kind of Automatic white balance (automatic white balance, AWB) system and method thereof of utilizing optical sensor.

Background technology

Along with the progress of projection display technique, the existing rapid development of optical projection system and equipment in recent years breaks through with significant.Projector type mainly can be divided into three kinds at present: cathode ray tube (CRT), display panels (general reference liquid crystal projector) and digital light processor.Wherein liquid crystal projector is with its portable use widely with the characteristics of being convenient to adjust.

Liquid crystal projector possesses the advantage that volume is little, high image quality shows and high brightness is arranged by light-emitting diode (LED).Generally speaking, liquid crystal projector sends white light to a LCD assembly, and this white light is to be formed by ruddiness, green glow and blue light balance that LED sends.Then, image projection to a screen that again LCD assembly shown of liquid crystal projector.Therefore, for liquid crystal projector, can reach white balance be a considerable problem.

Generally speaking, the LED self character is relevant with manufacture process, so the color that LED sends often has some colour casts.Moreover because white light is to be formed by ruddiness, green glow and blue light balance, and these three kinds of coloured light respectively have its colour cast, so the image projection that shows of LCD assembly may have evident difference with the image of reality during to screen.Therefore, can keep suitable white balance in order to make liquid crystal projector, the colour cast degree of understanding the coloured light that LED sent has its necessity, so that compensate and control LED and realize white balance by feeding back.

In prior art, traditional liquid crystal projector need possess three color sensors usually and realize white balance.These three color sensors are used for detecting the colour cast of corresponding coloured light respectively, make liquid crystal projector be able to adjust according to testing result the electric current of LED, and realize white balance.Yet, in liquid crystal projector, use three color sensors to realize the more cost of white balance cost.Expensive color sensor is unfavorable for reducing cost, therefore needs a kind of suitable white balance system.

Summary of the invention

Embodiments of the invention provide a kind of Automatic white balance (automatic white balance, AWB) system and method thereof.The AWB system that embodiments of the invention provided uses a light sensing unit to reach the white balance effect of light source, to reduce cost.

One embodiment of the invention provide a kind of AWB system, and it comprises a light source, a light sensing unit, an analog digital (analog-to-digital, A/D) transducer, a control unit and one drive circuit.Above-mentioned light source provides a plurality of coloured light in regular turn, and wherein above-mentioned coloured light comprises one first coloured light and one second coloured light.The brightness of the coloured light that light sensing unit sensing light source is sent, and export respectively corresponding to one first analog signal of first coloured light and corresponding to one second analog signal of second coloured light.A/D converter couples light sensing unit, and first analog signal and second analog signal are converted to one first digital signal and one second digital signal respectively.Control unit couples A/D converter, and the ratio of foundation one first default value and one second default value, calculate one first correction of first coloured light and one second correction of second coloured light, wherein first default value and second default value corresponding first coloured light of difference and second coloured light.Drive circuit couples control unit, and according to first correction and second correction comes driving light source so that a plurality of coloured light reaches white balance automatically.

One embodiment of the invention provide the AWB method of a kind of AWB of being used for system, and its step is as follows.(1) provides a plurality of coloured light by a light source.Wherein, above-mentioned coloured light comprises one first coloured light and one second coloured light.(2) by a light sensing unit sensing coloured light, to obtain corresponding to one first analog signal of first coloured light and corresponding to one second analog signal of second coloured light.(3) convert first analog signal and second analog signal to one first digital signal and one second digital signal respectively by an A/D converter.(4) by the ratio of a control unit, calculate one first correction of first coloured light and one second correction of second coloured light according to one first default value and one second default value.Wherein, first default value and second default value corresponding first coloured light of difference and second coloured light.(5) come driving light source by one drive circuit according to first correction and second correction, so that the coloured light that light source provides can reach white balance automatically.In view of the above, the AWB of first coloured light and second coloured light is achieved.In addition, the order of above-mentioned steps is not in order to limit the present invention.

In one embodiment of the invention, light sensing unit more comprises an optical sensor and a light sensing circuit.The brightness of the coloured light that the above-mentioned light source of photosensor senses is sent.Light sensing circuit couples optical sensor and A/D converter, and exports respectively corresponding to one first analog signal of first coloured light and one second analog signal corresponding to second coloured light.

In the AWB of embodiments of the invention system, utilize the method for its AWB, the coloured light that can make light source provide reaches white balance automatically.The AWB system of embodiments of the invention has the optical sensor that is coupled to light sensing circuit, and it is different from the white balance system that uses color sensor.Use the projection arrangement of the AWB system of embodiments of the invention, realize the white balance of a plurality of coloured light, but not use color sensor by optical sensor.Therefore, use the projection arrangement of the AWB system of embodiments of the invention can reduce its cost of manufacture.

For above-mentioned feature and advantage of the present invention can be become apparent, embodiment cited below particularly, and cooperate appended graphic being described in detail below.

Description of drawings

Fig. 1 is the calcspar of the AWB system of one embodiment of the invention.

Fig. 2 illustrates a liquid crystal projector (LCP), and it uses the AWB system of Fig. 1.

Fig. 3 is the flow chart of the AWB method of one embodiment of the invention.

Fig. 4 is a flow chart of obtaining first default value, second default value and the 3rd default value method in the foregoing description.

Fig. 5 illustrates another liquid crystal projector (LCP), and it uses the AWB system of Fig. 1.

[primary clustering symbol description]

The 100:AWB system

200,500: liquid crystal projector (LCP)

102: light source

104: light sensing unit

The 106:A/D transducer

108: control unit

110: drive circuit

112: optical sensor

114: light sensing circuit

210,510: little display floater

The 220:TIR prism

230: projection lens

L1: illuminating bundle

L2: image beam

Embodiment

Expensive color sensor can increase the cost of manufacture of projection arrangement.Therefore, need a kind of suitable auto white balance system and method thereof to reduce its cost of manufacture.At this, embodiments of the invention provide a kind of AWB system and method thereof to reduce the cost of manufacture of projection arrangement.

Fig. 1 is the calcspar of the AWB system of one embodiment of the invention.Please refer to Fig. 1, in the present embodiment, AWB system 100 comprises a light source 102, a light sensing unit 104, an analog digital (A/D) transducer 106, a control unit 108 and one drive circuit 110.Light source 102 for example is a light-emitting diode (LED) light source.In addition, light sensing unit 104 more comprises an optical sensor 112 and a light sensing circuit 114.In the present embodiment, the brightness of the coloured light that optical sensor 112 sensing led light sources 102 are sent, and light sensing circuit 114 is exported an analog signal according to the coloured light brightness that senses.

Fig. 2 illustrates a liquid crystal projector (LCP), and it uses the AWB system of Fig. 1.Please refer to Fig. 2, LCP 200 comprises AWB system 100, one little display floater 210, a total internal reflection prism 220 (TIR prism) and a projection lens 230.LCP 200 that it should be noted that present embodiment for example is a monocrystalline silicon opaque projector, only in order to illustrate, is not in order to limit the present invention at this.

Please refer to Fig. 2, for instance, LCP 200 uses look preface method image projection to a screen (not illustrating) that one user is required.Led light source 102 is suitable for providing an illuminating bundle L1, and wherein illuminating bundle L1 for example is red, green or blue.Little display floater 210 places on the bang path of illuminating bundle L1.Little display floater 210 is suitable for converting illuminating bundle L1 to image beam L2.Then, image beam L2 sees through TIR prism 220 and reflexes to projection lens 230.Afterwards, projection lens 230 projects to image beam L2 on the screen and (does not illustrate).Have in this area and to know that usually the knowledgeable when the basic running that know LCP 200, is just no longer given unnecessary details at this.

Concerning the display quality of LCP, white balance is a considerable problem.In the present embodiment, the AWB system 100 with light sensing unit 104 by its AWB method to guarantee the display quality of LCP 200.

Fig. 3 is the flow chart of the AWB method of one embodiment of the invention.Please be simultaneously referring to figs. 1 through Fig. 3, led light source 102 is suitable for providing an illuminating bundle L1, and wherein illuminating bundle L1 for example is red, green or blue.At first, in step S301, drive circuit 110 driving LED light sources 102 send red beam with high-high brightness.In present embodiment, drive circuit 110 uses the PWM light modulating method to come driving LED light source 102.The PWM light modulating method utilizes a fixed current to come LED in the driving light source 102, and reaches the purpose of regulating brightness by the time scale (duty ratio) that LED opens and closes.At this, when led light source 102 sent the red beam of high-high brightness, drive circuit 110 for example was that the drive signal Drv_R with about 80% time scale comes driving LED light source 102.In other embodiment, drive circuit 110 can come driving LED light source 102 with analog modulation method.Analog modulation method is to regulate brightness by the flow through electric current of the LED in the light source 102 of change.

In this simultaneously, the little display floater 210 with white input pattern (white input pattern) reflexes to projection lens 230 with the red beam of high-high brightness by TIR prism 220.Then, light sensing unit 104 have by optical sensor 112 sensings high-high brightness red beam brightness L ' (R).Afterwards, in step S302, light sensing unit 104 is further given A/D converter 106 by light sensing circuit 114 outputs corresponding to first analog signal of red beam.Continue it, in step S303, the A/D converter 106 that is coupled to light sensing unit 104 becomes first digital signal with first analog signal conversion, and exports to control unit 108.

In the present embodiment, control unit 108 is understood the brightness L ' related data (R) of buffer memory red beam after receiving first digital signal.In step S304, if control unit 108 has only the related data of the brightness of redness, green or blue light beam, then led light source 102 can change the color of the light beam that it sent, and therefore whole flow process can be got back to step S301.For example, in step S304, when control unit 108 had only the related data of brightness of red beam, whole flow process can be got back to step S301.Therefore, in step S301, led light source will change into and send green beam.In the present embodiment, step S301 constantly repeats to the circulation meeting of step S304, the brightness L ' that has a red beam up to control unit 108 (R), the brightness L ' of green beam (G) and the brightness L ' related data (B) of blue light beam.

After loop ends, in step S305, control unit 108 calculate the first correction rL ' (R), the second correction gL ' (G) and the 3rd correction bL ' (B).In the present embodiment, control unit 108 calculates above-mentioned three corrections according to following equation:

$\frac{L\left(R\right)}{L^{\′}\left(R\right)-r{L}^{\′}\left(R\right)}=\frac{L\left(G\right)}{L^{\′}\left(G\right)-g{L}^{\′}\left(G\right)}=\frac{L\left(B\right)}{L^{\′}\left(B\right)-b{L}^{\′}\left(B\right)}---\left(1\right)$

Wherein L (R) is first default value, L (G) is second default value, L (B) is the 3rd default value, L ' is the brightness of red beam (R), L ' is the brightness of green beam (G), and L ' is the brightness of blue light beam (B), and rL ' is first correction (R), gL ' is second correction (G), and bL ' is the 3rd correction (B).In addition, above-mentioned three coloured light brightness L ' (R), L ' (G) and L ' (B) in step S302, measure respectively and get by the optical sensor 112 that couples light sensing circuit 114.By equation (1) as can be known, but one of them of r, the g of control unit 108 set-up and calculated gained, b value is zero and two other is for negative.Therefore, in case one of them that know r, g, b value is zero, get final product two values for negative.

So, control unit 108 by equation (1) can get rL ' (R), gL ' (G) and (B) three corrections of bL '.In step S306, drive circuit 110 is according to result of calculation and come driving LED light source 102 with the PWM light modulating method.Under the control of control unit 108, the PWM light modulating method utilizes adjusted fixed current and adjusted time scale (duty ratio) to come driving LED light source 102.

For example, according to result calculated, control unit 108 can be adjusted into the drive current that drive circuit 110 is exported the fixed current of one correspondence, and the time scale of drive signal Drv_R is 80% at this moment.Therefore, drive circuit 110 comes driving LED light source 102 with corrected drive signal Drv_R ', and its time ratio then is 80%+80% * r.Similarly, drive circuit 110 comes driving LED light source 102 with revised drive signal Drv_G ' and Drv_B ' respectively.The time scale of revised drive signal Drv_G ' and Drv_B ' is respectively 80%+80% * g and 80%+80% * b.Therefore, equation (1) is satisfied in optical sensor 112 brightness that measures red, green and blue light beam.In other embodiments, the time scale of drive signal Drv_R, Drv_G and Drv_B can be approximately 90% and 70% or the like.

Thus, the ratio of redness, green and blue light beam brightness promptly equals the ratio of the first default value L (R), the second default value L (G) and the 3rd default value L (B).Therefore, by the AWB system and the method thereof of present embodiment, the purpose in the white balance of LCP 200 is achieved.Use three color sensors to compare according to the LCP that different coloured light detects corresponding colour cast respectively with tradition, the brightness that the LCP200 of present embodiment utilizes optical sensor 112 to come the light beam that sensing LED sent is no matter and which kind of color the light beam that LED sent is.Therefore, LCP 200 utilizes optical sensor 112 to realize white balance, uses the LCP of three color sensors to have lower cost compared with tradition.Following examples will illustrate how to obtain the first default value L (R), the second default value L (R) and the 3rd default value L (B).

Fig. 4 is a flow chart of obtaining first default value, second default value and the 3rd default value method in the foregoing description.In the present embodiment, use LCP 200 duplicate LCP to obtain the first default value L (R), the second default value L (G) and the 3rd default value L (B) with volume production.Please be simultaneously with reference to Fig. 2 and Fig. 4, on the bang path of the image beam L2 of above-mentioned LCP, place an optical measurement instrument and obtain the first default value L (R), the second default value L (G) and the 3rd default value L (B).At this, the optical measurement instrument for example is a colorimeter (Chroma meter).In step S402, the led light source 102 of LCP sends redness, green and blue light beam simultaneously with high-high brightness.At the same time, little display floater 210 of LCP reflexes to colorimeter with redness, green and blue light beam, and wherein little display floater has a white input pattern.Then, in step S404, Chromaticity metering colour examining degree coordinate (x, y).Afterwards, in step S406, (x, y), the led light source 102 of manual adjustment LCP is to reach white balance for the chromaticity coordinate that measures with reference to step S404 colorimeter.Therefore, in step S408, obtain the first default value L (R), the second default value L (G) and the 3rd default value L (B) by the optical sensor 112 of LCP.Default value L (R), L (G) and L (B) can be recorded among other the LCP (for example LCP 200 of Fig. 2) in advance to carry out the white balance method of Fig. 3.

In the present embodiment, the AWB method of LCP 200 can be carried out when LCP 200 starts shooting at the beginning.In other embodiments, the AWB method of LCP 200 can be carried out when LCP 200 runnings.

Fig. 5 illustrates another liquid crystal projector (LCP), and it uses the AWB system of Fig. 1.Please refer to Fig. 5, the LCP 500 of present embodiment is similar to the LCP 200 of Fig. 2, and only topmost between the two difference is that the optical sensor 112 of present embodiment is placed near led light source 102.Thus, little display floater 510 by TIR prism 520 with beam reflection before the projection lens 530, optical sensor can measure respectively beam brightness L ' (R), L ' (G) and L ' (B).Because optical sensor 112 places near led light source 102, even therefore little display floater 510 tool white input pattern not also can be carried out the AWB method of LCP 500.Thus, the AWB method of LCP 500 can be performed when LCP 500 runnings.In addition, the AWB method of the LCP 500 of present embodiment is similar to the LCP 200 of Fig. 2, just repeats no more at this.

In sum, according to the AWB system of the use optical sensor of embodiments of the invention, it is different from the AWB system that tradition is used three color sensors.That is to say, use the LCP of the AWB system of embodiments of the invention, the white balance of its color light beam is to use optical sensor to realize, but not uses color sensor.Therefore, by adjusting drive current and time ratio, the beam brightness that optical sensor is measured is consistent with default value, no matter and what color light beam is.Compared to the LCP of three color sensors of tradition use, the AWB system of embodiments of the invention utilizes optical sensor to reach the purpose of white balance, and then makes LCP can have lower cost of manufacture.Therefore, the AWB system of use embodiments of the invention can reduce the cost of manufacture of projection arrangement.

Though the present invention discloses as above with embodiment; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when doing a little change and retouching, so protection scope of the present invention is as the criterion when looking the accompanying Claim book person of defining.

Claims (16)

1. An Automatic white balance (Automatic White Balance, AWB) system comprises:

   One light source provides a plurality of coloured light in regular turn, and wherein these coloured light comprise one first coloured light and one second coloured light;

   One light sensing unit, the brightness of these coloured light that this light source of sensing is sent, and export respectively corresponding to one first analog signal of this first coloured light and corresponding to one second analog signal of this second coloured light;

   (analog-to-digital, A/D) transducer couple this light sensing unit to one analog digital, and this first analog signal and this second analog signal are converted to one first digital signal and one second digital signal respectively;

   One control unit, couple this A/D converter, and the ratio of foundation one first default value and one second default value, calculate one first correction of this first coloured light and one second correction of this second coloured light, wherein this first default value and this second default value are respectively to should first coloured light and this second coloured light; And

   One drive circuit couples this control unit, and according to this first correction and this second correction drives this light source so that these coloured light reach white balance automatically.
2. 2. auto white balance system as claimed in claim 1, wherein this light sensing unit comprises:

   One optical sensor, the brightness of these coloured light that this light source of sensing is sent; And

   One light sensing circuit couples this optical sensor and A/D converter, and exports respectively corresponding to this first analog signal of this first coloured light and this second analog signal corresponding to this second coloured light.
3. 3. auto white balance system as claimed in claim 1, wherein this light source provides the high-high brightness of these coloured light to this light sensing unit.
4. 4. auto white balance system as claimed in claim 1, wherein this control unit calculates these corrections according to an equation, and this equation is:

   $\frac{L\left(1\right)}{L^{\′}\left(1\right)-a_1{L}^{\′}\left(1\right)}=\frac{L\left(2\right)}{L^{\′}\left(2\right)-a_2{L}^{\′}\left(2\right)}$

   Wherein, L (1) is this first default value, and L (2) is this second default value, and L ' (1) is one first sensing value of this first coloured light, and L ' (2) is one second sensing value of this second coloured light, a ₁L ' (1) is this first correction, and a ₂L ' (2) is this second correction.
5. 5. auto white balance system as claimed in claim 4, wherein by revising this first sensing value and this second sensing value, make its ratio equal the ratio of this first default value and this second default value, and this control unit according to this this drive circuit of revised proportional control to drive this light source.
6. 6. auto white balance system as claimed in claim 1, wherein these coloured light more comprise one the 3rd coloured light, this control unit is according to the ratio of this first default value and one the 3rd default value, calculate one the 3rd correction of the 3rd coloured light, and this drive circuit drives this light source according to this first correction, this second correction and the 3rd correction, so that these coloured light reach white balance automatically, wherein the 3rd default value is to should the 3rd coloured light.
7. 7. auto white balance system as claimed in claim 6, wherein this control unit calculates these corrections according to an equation, and this equation is:

   $\frac{L\left(1\right)}{L^{\′}\left(1\right)-a_1{L}^{\′}\left(1\right)}=\frac{L\left(2\right)}{L^{\′}\left(2\right)-a_2{L}^{\′}\left(2\right)}=\frac{L\left(3\right)}{L^{\′}\left(3\right)-a_3{L}^{\′}\left(3\right)}$

   Wherein, L (1) is this first default value, and L (2) is this second default value, L (3) is the 3rd default value, and L ' (1) is one first sensing value of this first coloured light, and L ' (2) is one second sensing value of this second coloured light, L ' (3) is one the 3rd sensing value of the 3rd coloured light, a ₁L ' (1) is this first correction, a ₂L ' (2) is this second correction, and a ₃L ' (3) is the 3rd correction.
8. 8. auto white balance system as claimed in claim 6, wherein by revising this first sensing value, this second sensing value and the 3rd sensing value, make its continued proportion equal the continued proportion of this first default value, this second default value and the 3rd sensing value, and this control unit is controlled this drive circuit to drive this light source according to this revised continued proportion.
9. 9. an Automatic white balance (AWB) method comprises:

   Provide a plurality of coloured light by a light source, wherein these coloured light comprise one first coloured light and one second coloured light;

   By these coloured light of light sensing unit sensing, to obtain corresponding to one first analog signal of this first coloured light and corresponding to one second analog signal of this second coloured light;

   Convert this first analog signal and this second analog signal to one first digital signal and one second digital signal respectively by an analog digital (A/D) transducer;

   By the ratio of a control unit according to one first default value and one second default value, calculate one first correction of this first coloured light and one second correction of this second coloured light, wherein this first default value and this second default value are respectively to should first coloured light and this second coloured light; And

   Drive this light source by one drive circuit according to this first correction and this second correction, so that these coloured light reach white balance automatically.
10. 10. method as claimed in claim 9, wherein in the step of these coloured light was provided, the high-high brightness that these coloured light are provided was to this light sensing unit.
11. 11. method as claimed in claim 9 is wherein being calculated by this control unit in the step of this first correction and this second correction, this control unit calculates this first correction and this second correction according to an equation, and this equation is:

    $\frac{L\left(1\right)}{L^{\′}\left(1\right)-a_1{L}^{\′}\left(1\right)}=\frac{L\left(2\right)}{L^{\′}\left(2\right)-a_2{L}^{\′}\left(2\right)}$

    Wherein, L (1) is this first default value, and L (2) is this second default value, and L ' (1) is one first sensing value of this first coloured light, and L ' (2) is one second sensing value of this second coloured light, a ₁L ' (1) is this first correction, and a ₂L ' (2) is this second correction.
12. 12. method as claimed in claim 11, wherein calculating by this control unit in the step of this first correction and this second correction, revise this first sensing value and this second sensing value, make its ratio equal the ratio of this first default value and this second default value.
13. 13. method as claimed in claim 11 is wherein driving by this drive circuit in the step of this light source, controls this drive circuit by this control unit and drives this light source according to this revised ratio.
14. 14. method as claimed in claim 9, wherein in the step of these coloured light is provided, one the 3rd coloured light is provided, calculating by this control unit in the step of this first correction and this second correction, ratio according to this first default value and one the 3rd default value, calculate one the 3rd correction of the 3rd coloured light, and driving by this drive circuit in the step of this light source, according to this first correction, this second correction and the 3rd correction, drive this light source by this drive circuit, so that these coloured light reach white balance automatically, wherein the 3rd default value is to should the 3rd coloured light.
15. 15. method as claimed in claim 14 is wherein being calculated by this control unit in the step of these corrections, this control unit calculates this first correction, this second correction and the 3rd correction according to an equation, and this equation is:

    $\frac{L\left(1\right)}{L^{\′}\left(1\right)-a_1{L}^{\′}\left(1\right)}=\frac{L\left(2\right)}{L^{\′}\left(2\right)-a_2{L}^{\′}\left(2\right)}=\frac{L\left(3\right)}{L^{\′}\left(3\right)-a_3{L}^{\′}\left(3\right)}$

    Wherein, L (1) is this first default value, and L (2) is this second default value, L (3) is the 3rd default value, and L ' (1) is one first sensing value of this first coloured light, and L ' (2) is one second sensing value of this second coloured light, L ' (3) is one the 3rd sensing value of the 3rd coloured light, a ₁L ' (1) is this first correction, a ₂L ' (2) is this second correction, and a ₃L ' (3) is the 3rd correction.
16. 16. method as claimed in claim 14, wherein calculating by this control unit in the step of this first correction, this second correction and the 3rd correction, revise this first sensing value, this second sensing value and the 3rd sensing value, make its ratio equal the continued proportion of this first default value, this second default value and the 3rd default value.

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