JP2006033881A - Image display device, image processing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of attaining an appropriate color reproduction while saving memory capacity, and to provide an image processing method and a program. <P>SOLUTION: According to this image display device for displaying an image by applying a desired image processing to the inputted image data, a first color correction unit 110 refers to a three-dimensional color correction table for making color characteristics of the image display device suitable for reference color characteristics based on characteristic values of the image display device and performs desired color correction on the inputted image data. A second color correction means 120 then refers to a one-dimensional color correction table for performing color correction corresponding to external environments and performs desired color correction on the inputted image data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display device, an image processing method, and a program for performing desired color correction on an output image.

  In the case of an image display device such as a projector, the color reproduction region varies depending on the type of the device, so the color of the display image may change. In order to prevent this, it is common to perform a process called color matching that matches the color characteristics of the image processing apparatus with the color characteristics of a general CRT monitor.

  Further, when using an image display device such as a projector, it is important that an image intended by the manufacturer can be reproduced even if the external environment changes. In particular, it is difficult to reproduce an appropriate color without considering the case where the brightness or color of external illumination or the color of the projection surface changes as a change in the external environment.

  A color correction table is generally used for the color matching and correction for the external environment.

  However, in the case of an image display device such as a projector, it is difficult to hold a large amount of color correction table data due to memory capacity limitations. That is, in the case of a projector, since the individual difference of each unit is large, it is necessary to store a color correction table suitable for each aircraft.

  SUMMARY An advantage of some aspects of the invention is to provide an image display device, an image processing method, and a program that can perform appropriate color reproduction while saving memory capacity.

  In view of the above problems, the invention according to claim 1 is an image display device that displays an image by performing desired image processing on input image data, and based on the characteristic value of the image display device, First color correction means for performing desired color correction on the input image data with reference to a three-dimensional color correction table for adapting color characteristics of the image display device to reference color characteristics, and an external environment Referring to a one-dimensional color correction table for performing color correction according to the second color, a desired color correction is performed on the input image data after the color correction by the first color correction means. Correction means, wherein the first color correction means is provided with rewriting means for rewriting grid point data of the three-dimensional color correction table based on the characteristic value.

  According to the image display device configured as described above and performing desired image processing on the input image data to display an image, the first color correction unit is configured based on the characteristic value of the image display device. Referring to a three-dimensional color correction table for adapting color characteristics of the image display device to reference color characteristics, desired color correction is performed on the input image data. Then, referring to a one-dimensional color correction table for performing color correction according to the external environment by the second color correction means, the desired color correction is performed on the input image data by the first color correction. After color correction by means. In addition, the first color correction means includes rewriting means for rewriting the lattice point data of the three-dimensional color correction table based on the characteristic value.

  According to a second aspect of the present invention, in the image display device according to the first aspect, the one-dimensional color correction table in the second color correction unit is for adjusting a color temperature.

  Furthermore, the invention according to claim 3 is the image display device according to claim 1 or 2, wherein the one-dimensional color correction table in the second color correction means corrects the change in the brightness of the external illumination. It is for doing.

  According to a fourth aspect of the present invention, there is provided the image display device according to any one of the first to third aspects, wherein the one-dimensional color correction table in the second color correction unit is a color of the projection surface. This is for correcting the change.

  Furthermore, the invention according to claim 5 is the image display device according to any one of claims 1 to 4, wherein the one-dimensional color correction table in the second color correction unit is the color of the external illumination. This is for correcting the change.

  The invention according to claim 6 is the image display device according to any one of claims 1 to 5, further comprising means for inputting the characteristic value.

  The invention according to claim 7 is the image display device according to any one of claims 1 to 6, wherein the image display device is a projector.

  According to an eighth aspect of the present invention, there is provided an image processing method for image data input to an image display device, wherein the color characteristic of the image display device is set as a reference color property based on a characteristic value of the image display device. A first color correction step for performing desired color correction on the input image data with reference to a three-dimensional color correction table for adaptation, and a one-dimensional color for performing color correction according to the external environment A second color correction step of referring to a correction table and performing a desired color correction on the input image data after the color correction by the first color correction step, and the first color correction The step is an image processing method including a rewriting step for rewriting the lattice point data of the three-dimensional color correction table based on the characteristic value.

  According to a ninth aspect of the present invention, there is provided a program for causing a computer to execute image processing on image data input to an image display device, wherein the image display device includes: A first color correction process for performing desired color correction on the input image data with reference to a three-dimensional color correction table for adapting color characteristics to reference color characteristics, and color correction according to the external environment A second color correction process in which a desired color correction is performed on the input image data after the color correction by the first color correction process with reference to a one-dimensional color correction table for performing A program for causing a computer to execute the program, wherein the first color correction process includes a rewrite process for rewriting grid point data of the three-dimensional color correction table based on the characteristic value. It is a lamb.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First Embodiment System Configuration FIG. 1 is a functional block diagram of an image processing unit 100 in a projector according to a first embodiment of an image display apparatus of the present invention. The image display apparatus of the present invention includes a projector, a CRT, a liquid crystal display, and the like.

  The image processing unit 100 in the projector according to the first embodiment of the present invention includes a first color correction unit 110 that performs color matching based on the color correction table generated by the first color correction table generation unit 112, and a second color. A second color correction unit 120 that performs desired color correction based on the color correction table generated by the correction table generation unit 150, a third color correction unit 130 for adjusting the output characteristics of the liquid crystal light valve, and a liquid crystal light valve And an L / V (light valve) driving unit 140 for projecting and displaying an image.

  The image processing unit 100 also includes a γ value input unit 116 for inputting a γ value of the projector and data in a color correction table for generating a three-dimensional color correction table (3D-LUT) for color matching. Based on the LUT data storage unit 114 storing (conversion value, LUT data) and grid point data in association with each other, the γ value input by the γ value input unit 116, and the data stored in the LUT data storage unit 114 A first color correction table generating unit 112 for generating a three-dimensional color correction table for color matching.

  The image processing unit 100 further includes a device characteristic storage memory 160 for storing color characteristic information of the projector when output to the reference projection plane in the dark room, and the reflected light from the projector and external illumination screens. An optical sensor 170 for measuring luminance, and a one-dimensional color correction table (1D-LUT) that takes into account the influence of external illumination based on the colorimetric values of the optical sensor 170 and information stored in the device characteristic storage memory And a second color correction table generating unit 150 that generates

  In the projector according to the first embodiment of the present invention, first, with reference to the color correction table generated by the first color correction table generation unit 112, the first color is applied to the image input signal supplied from a personal computer or the like. Color correction is performed by the correction unit 110. The color-matched image signal is subjected to a desired color correction in consideration of the influence of external illumination by the second color correction unit 120 with reference to the color correction table generated by the second color correction table generation unit 150. Made. The color-corrected image signal is adjusted by the third color correction unit 130 in consideration of the output characteristics of the liquid crystal light valve. Based on the adjusted analog signal, the L / V drive unit 140 drives the liquid crystal light valve to perform image projection display.

Operation of the Image Processing Unit 100 The processing by the image processing unit 100 such as color correction table generation processing and image processing described below executes an image processing program recorded in a program storage unit (not shown) of the projector. Is done by. The program storage unit constitutes a medium on which an image processing program is recorded. Further, the image processing program itself is also included within the scope of the present invention.

(1) Color Correction in First Color Correction Unit 110 The first color correction unit 110 performs color matching by the first color correction table generation unit 112 based on the three-dimensional color correction table generated as follows. 1-1) Processing by First Color Correction Table Generation Unit 112 Next, color correction table generation processing by the first color correction table generation unit 112 will be described with reference to FIG.

  First, when a projector γ value (projector characteristic value) is input from the γ value input unit 116 (S10, Yes), data in the table stored in the LUT data storage unit 114 in the projector ROM (conversion) Value: LUT data) and grid point data are read into the RAM (S12).

Then, the first color correction table generation unit 112 rewrites the lattice point data based on the input γ value (S14). Since the data in the table stored in the LUT data storage unit 114 is created for a projector having a γ value of 2.2 (characteristic reference value), it is necessary to rewrite grid point data based on the γ value of the projector. is there. Specifically, based on the inputted γ value, the value (R, G, B) of the grid point is set as R ′ = R ^{2.2 / γ}
G ′ = G ^{2.2 / γ}
B ′ = B ^{2.2 / γ}
To (R ′, G ′, B ′).

  Then, the first color correction table generation unit 112 associates the converted grid point values (R ′, G ′, B ′) with the conversion values in the table stored in the LUT data storage unit 114. A new three-dimensional color correction table is generated (S16), the generated three-dimensional color correction table is set in the first color correction unit 110 (S18), and the process is terminated.

  As described above, one three-dimensional color correction table is stored and the lattice point data is rewritten based on the γ value of the projector. This is because a large memory capacity is required as compared with the correction table, and this is saved.

(1-2) Generation processing of LUT data stored in the LUT data storage unit 114 Next, generation processing of LUT data stored in the LUT data storage unit 114 will be described with reference to FIG. In the present embodiment, a case will be described in which the color characteristics of the projector are adapted to the color characteristics (reference color characteristics) of the CRT.

First, the input values (R _c G _c B _c ) and output color coordinates (X _c Y _c Z _c ,
L _c * a _c * b _c * etc.) is obtained (S20). The correspondence relationship for typical colors is obtained by actually outputting colors from the CRT and measuring the output light, and the correspondence relationship for the remaining colors is obtained by interpolation calculation or the like. Then, the input value (R _p G _p B _p ) and the output color coordinates (X _p Y _p Z _p ,
L _p * a _p * b _p * etc.) is obtained (S22). Similarly, the correspondence relationship for representative colors is obtained by actually outputting colors from the projector and measuring the output light, and the correspondence relationship for the remaining colors is obtained by interpolation calculation or the like.

Next, the output color (L _p * a _p * b _p *) of the liquid crystal projector for the CRT output color (L _c * a _c * b _c *) is determined (S24). Usually, the same colors ((L _c * = L _p *, a _c * = a _p *, b _c * = b _p *) are associated. However, the CRT output color (L _c * a _c * b _c * ) Is a color that cannot be output by the projector, as shown in FIG. 6, a color that is relatively close to the color that can be output by the projector (for example, a color having the same hue and the smallest distance on the color coordinates). Associate.

Then, as shown in FIG. 5, based on the correspondence obtained from S20 to S26, the value of R _p G _p B _p for each R _c G _c B _c value is obtained, and LUT data is generated (S28).

  In this embodiment, it is assumed that the LUT data and grid point data generated as described above are stored in advance in the LUT data storage unit 114.

(2) Color correction in the second color correction unit 120 (color correction considering changes in the external environment)
(2-1) Color Correction Considering Changes in External Illumination and Projection Surface Next, the operation of the second color correction unit 120 in the projector according to the first embodiment of the present invention will be described with reference to FIG. .

  First, when the use of the projector according to the present invention is started, the second color correction table generation unit 150 performs color correction table generation / rewrite processing (step 204). The generation / rewriting process of the color correction table will be described in detail below with reference to FIG.

  Then, after the color correction table generation / rewriting process, an image is displayed based on the image signal color-corrected by the second color correction unit 120 with reference to the rewritten color correction table (step 206). If the display of the image is not ended (No at Step 208) and a predetermined time has not elapsed since the end of the previous generation / rewrite processing of the color correction table (No at Step 210), the display of the image at Step 206 is performed. The state continues. On the other hand, if the display of the image is not finished (No at Step 208) and a certain time has passed since the end of the previous generation / rewrite processing of the color correction table (Step 210, Yes), the brightness of the external illumination over time Alternatively, in consideration of the case where the color or the color of the projection surface changes, the color correction table is generated and rewritten again (step 204), and the image is displayed (step 206). According to the present invention, since the color correction table is rewritten in consideration of changes in the brightness or color of the external illumination or the color of the projection surface at regular intervals, the brightness or color of the external illumination or the color of the projection surface is determined. Appropriate color reproduction is possible even if it changes.

  Then, when the image display is terminated by turning off the power of the projector (step 208, Yes), the process is terminated.

Color Correction Table Generation / Rewrite Processing Next, with reference to FIG. 8, the color correction table generation / rewrite processing (FIG. 7) by the second color correction table generation unit 150 in the projector according to the first embodiment of the present invention. Will be described.

  In the generation / rewriting process of the color correction table, first, the color correction curve calculation process 1 (correction for a change in the brightness of the external illumination) (step 222), the color correction curve calculation process 2 (correction for a change in the color of the projection surface). ) (Step 223) and color correction curve calculation processing 3 (correction for change in color of external illumination) (step 224) are performed. Next, rounding processes 1, 2 and 3 of the three-stage correction curve are performed (steps 225, 226 and 227). Each correction curve calculation process and correction curve rounding process will be described in detail later.

  Then, based on the calculated correction curve, a new one-dimensional color correction table is generated, and the one-dimensional color correction table referred to by the second color correction unit 120 is determined by the newly generated one-dimensional color correction table. The data is rewritten (step 228), and the process returns to step 206.

Correction curve calculation process 1 (Correction to changes in brightness of external lighting)
Next, the correction curve calculation process 1 will be described with reference to FIG.

  As a premise of the correction curve calculation process 1, white (R = G = B = 255 gradations) is output to the projector (image display device) 20 in the dark room, and the luminance of the reflected light from the screen 10 is measured by the optical sensor 170. Measure in advance.

  In the correction curve calculation process 1, first, the brightness of the reflected light from the screen 10 of the external illumination is measured in a state where there is no output from the projector (step 229).

Next, the γ curve is normalized under each environment (step 230). Since all of the correction curves for W (white), R (red), G (green), and B (blue) are the same curve, the correction curve for W is calculated as an example in this embodiment. The γ curve under each environment (in the dark room and in the presence of external illumination) is assumed as follows. Here, γ is the gradation characteristic of the target projector. It is appropriate to determine gamma by actually measuring the gradation characteristics of the target projector and using the average value. In this embodiment, as an example, γ = 2.2.
In the dark room:
Fd (Din) ＝ Yw ・ Din ^γ … (1)
If external lighting is present:
Fi (Din) = Yw · Din ^γ + Yi (2)
FIG. 10 shows the γ curve under each environment.

Where F is the total luminance of the reflected light from the screen, Din is the RGB digital input value (0 to 255 gradations) normalized to 0 to 1, Yw is the projector white luminance, and Yi is the illumination It is brightness. Then, these expressions (1) and (2) are adapted to the brightness when the projector outputs white in each environment (in the dark room: Yw, in the case of outside of the external lighting: Yw + Yi). Standardize under the assumption that In other words, Equation (1) and Equation (2) are standardized so that the brightness (Yw in the dark room: Yw when there is outside lighting: Yw + Yi) when the projector outputs white under each environment is 1. To do. In particular,
In the dark room:
F'd (Din) = Fd (Din) / Yw = Din ^γ (3)
If external lighting is present:
F'i (Din) = Fi (Din ) / (Yw + Yi) = (Yw · Din γ + Yi) / (Yw + Yi) ... (4)
It becomes.

  FIG. 11 shows the standardized γ curve under each environment.

Next, the γ curve is overlaid at the reference point Do (step 232). As shown in FIG. 12, at the reference point Do, F′d (Din) is set to {F′i (Din) in the F′-axis direction so that F′d (Din) takes the same value as F′i (Din). Translate by (Do) -F'd (Do)}. In particular,
F ″ d (Din) = F′d (Din) + {F′i (Do) −F′d (Do)}
= F'd (Din)-F'd (Do) + F'i (Do)
And Here, using Equation (3) and Equation (4),
F ”d (Din) = Din ^γ− Do ^γ + (Yw · Do ^γ + Yi) / (Yw + Yi) (5)
It becomes.

  Then, the first correction curve is calculated using equation (5) (step 234).

  As described above, in the present embodiment, as shown in FIG. 12, the output value of the correction curve in the presence of the external illumination and the output value of the correction curve in the dark room coincide with each other near the reference point Do. A first correction curve is formed.

  Then, by correcting the input gradation data so that the relative contrast near the reference point Do (the slope of the γ curve) does not change with or without external illumination, the color of the output image changes with or without external illumination. Make it smaller.

  The above is expressed as follows.

F'i (Dout1) ＝ F ”d (Din)… (6)
Here, Dout1 is input gradation data corrected by the first correction curve.
Substituting Equation (4) and Equation (5) into Equation (6),
(Yw · Dout1 ^γ + Yi) / (Yw + Yi) = Din ^γ- Do ^γ + (Yw · Do ^γ + Yi) / (Yw + Yi)
Than this,
Dout1 = [(1 + Yi / Yw) Din ^γ− (Yi / Yw) Do ^γ ] ^{1 / γ} (7)
The first correction curve changes variously by changing the gradation Do as the center when correcting the contrast decrease due to illumination. In general, when the value of Do is small, the first correction curve as shown in FIG. 13 is obtained, and the projection screen looks white and has a light color tone. On the other hand, when the value of Do is increased, the first correction curve as shown in FIG. 14 is obtained, the projection screen looks black, and the gradation change at a low gradation is further reduced (so-called gradation collapse is remarkable). become). By setting Do to an appropriate value, it is possible to perform correction that emphasizes the vividness without changing the overall brightness of the projected image so much as before correction. As a result of evaluation by experiment, it was confirmed that the value of Do is suitable near the middle gradation (about 0.25 ≦ Do ≦ 0.50).

Further, as shown in FIG. 15, the correction amount ΔF can be adjusted by multiplying the correction amount ΔF by α1 (0 ≦ α1 ≦ 1). This is to prevent unnatural image reproduction due to excessive correction. Equation (7) for Dout1 when adjusting the correction amount is
Dout1 = [(1 + α1 • Yi / Yw) Din ^γ− (α1 • Yi / Yw) Do ^γ ] ^{1 / γ} (8)
It becomes. Therefore, the expression of the first correction curve for each color of RGB is
_{D R out1 = [(1 +} α1 · Yi / Yw) D R in γ - (α1 · Yi / Yw) Do γ] 1 / γ ... (9)
D _G out1 = [(1 + α1 · Yi / Yw) D _G in ^γ− (α1 · Yi / Yw) Do ^γ ] ^{1 / γ} (10)
D _B out1 = [(1 + α1 · Yi / Yw) D _B in ^γ− (α1 · Yi / Yw) Do ^γ ] ^{1 / γ} (11)
It becomes.

  Multiplying the correction amount by α1 corresponds to multiplying the illumination brightness Yi by α1 as a result. The value of α1 is preferably in the range of 0.8 ≦ α1 ≦ 1.

  The first correction curve is calculated as in equations (9) to (11) (step 234), and the process returns to step 223 in FIG. 8 to perform the correction curve calculation process 2.

Correction curve calculation process 2 (Correction to change in color of projection surface)
Next, the correction curve calculation process 2 will be described with reference to FIG.

  As a premise of the correction curve calculation process 2, the R (red), G (green), B (blue), and bk (black) colors are output to the reference projection plane from the projector (image display device) 20 in the dark room. The luminance value of the reflected light from the reference projection plane for each color output is measured in advance by the optical sensor 170 and stored in the device characteristic storage memory 160. Here, as the reference projection plane, for example, a standard diffusing plate or the like having a reflectance in the visible light region close to 1 can be selected.

  Further, each color of R (red), G (green), B (blue), and bk (black) is output from the projector (image display device) 20 to the correction target projection plane in the dark room, and the correction target projection plane of each color output is output. The brightness value of the reflected light by the optical sensor 170 is also measured in advance.

In the correction curve calculation process 2, first, the measurement values (R (red), G (green), B (blue), bk (black)), the luminance values of reflected light from the reference projection plane, and R ( The luminance ratio of the RGB colors of the projector on each projection plane is calculated based on the (red), G (green), B (blue), and bk (black) reflected light brightness values from the correction target projection plane (step 242). . The calculation formula is as follows.
_{y R = (Y R -Ybk)} / (Y G -Ybk) ... (12)
y _G = (Y _G −Ybk) / (Y _G −Ybk) = 1 (13)
y _B = (Y _B −Ybk) / (Y _G −Ybk) (14)
Here, Y _R , Y _G , Y _B , and Ybk are the luminances of the R, G, B, and bk colors of the projector, and y _R , y _G , and y _B are the luminance ratios of RGB. Here, since the ratio of G to luminance is taken, y _G is always 1. The RGB luminance ratios y _R0 , y _G0 and y _{B0 on the} reference projection plane are calculated in the same manner.

Next, a second correction curve is calculated (step 246). The primary color (RGB) of the projector is less susceptible to changes in chromaticity due to the difference in projection plane than the secondary and tertiary colors, so the luminance ratio y _R , y _G , y _B of the target projection plane is If correction is made so as to match the luminance ratios y _R0 , y _G0 , and y _B0 of the reference projection plane, changes in chromaticity due to differences in projection planes are corrected for all colors. D _R in2, D _G in2, and D _B in2 are normalized RGB digital input values in the range of 0 to 1 before correction, and RGB digital input values after correction are in the range of 0 to 1 If the standardized ones are D _R out2, D _G out2, and D _B out2, the equation of the correction curve is
_{D R out2 = [y R '} / max (y R', y G ', y B')] 1 / γ × D R in2, y R '= y R0 / y R ... (15)
_{D G out2 = [y G '} / max (y R', y G ', y B')] 1 / γ × D G in2, y G '= y G0 / y G = 1 ... (16)
_{D B out2 = [y B '} / max (y R', y G ', y B')] 1 / γ × D B in2, y B '= y B0 / y B ... (17)
It becomes. Here, max (y _R ′, y _G ′, y _B ′) indicates the maximum value of y _R ′, y _G ′, y _B ′. By correcting in this way, a change in chromaticity due to the projection surface can be corrected colorimetrically.

In this way, changes in chromaticity due to the projection plane can be corrected colorimetrically, but the correction amount α3 (0 <α3 <1) is taken into account by taking into account the effects of human eye adaptation and contrast. When adjusting, the correction curve is
D _R out2 = [1−α 3 {1−y _R ′ / max (y _R ′, y _G ′, y _B ′)}] ^{1 / γ} × D _R in2 (18)
_{D G out2 = [1-α3} {1-y G '/ max (y R', y G ', y B')}] 1 / γ × D G in2 ... (19)
D _B out2 = [1−α 3 {1−y _B ′ / max (y _R ′, y _G ′, y _B ′)}] ^{1 / γ} × D _B in2 (20)
It becomes.

here,
ΔRgain = y _R '/ max (y _R ', y _G ', y _B ')
ΔGgain = y _G '/ max (y _R ', y _G ', y _B ')
ΔBgain = y _B '/ max (y _R ', y _G ', y _B ')
Then (18)-(20)
D _R out2 = {1−α 3 (1−ΔR gain)} ^{1 / γ} × D _R in2 (21)
D _G out2 = {1-α3 (1-ΔGgain)} ^{1 / γ} × D _G in2 (22)
D _B out2 = {1-α3 (1-ΔBgain)} ^{1 / γ} × D _B in2 (23)
It becomes.

  When correction of 100% (α3 = 1) is applied to the color of the projection plane obtained by measurement, correct correction is performed in terms of colorimetry. However, when there is external illumination, the color of the projection surface exists around the projection image, so the correction is stronger than actual due to the contrast between the color of the projection image and the projection surface and the effect of eye adaptation to external illumination. Looks like it's hanging. In order to eliminate this phenomenon, the correction amount is adjusted. The correction amount α3 needs to be adjusted while actually evaluating the image under each environment. The value of α3 is preferably 0.5 to 1.0.

  The second correction curve is calculated as shown in equations (21) to (23) (step 246), and the process returns to step 224 in FIG.

  Here, both the correction curve calculation process 1 and the correction curve calculation process 2 are processes for relatively correcting input values. That is, in the first correction curve equations (9) to (11) and the second correction curve equations (21) to (23), the input value is multiplied by the correction parameter to obtain the output value. Therefore, the correction curve calculation process 1 and the correction curve calculation process 2 can be performed in the reverse order, that is, step 222 and step 223 in FIG. 8 can be interchanged.

Correction curve calculation process 3 (correction for color change of external lighting)
Next, the correction curve calculation process 3 will be described with reference to FIG.

  As a premise of the correction curve calculation process 3, each color of R (red), G (green), B (blue), and bk (black) is output from the projector (image display device) 20 in the dark room, and the reflected light from the screen of each color output. The XYZ values are measured in advance by the optical sensor 170 and stored in the device characteristic storage memory 160. In addition, the XYZ values of the reflected light from the screen 10 of the external illumination are measured in advance in a state where there is no output from the projector.

  In the correction curve calculation process 3, first, the values measured in advance as described above (XYZ values of each color of the projector) are converted into RGB values (step 250). In this embodiment, in order to express the illumination color by the RGB value of the projector, a matrix M for performing conversion between the RGB value of the projector and the XYZ value is calculated for each color of the projector measured as described above. Obtained from XYZ values. The matrix M and the conversion formula are

となる。ここで、Ｘc、Ｙc、Ｚc（c＝R,G,B,bk）はプロジェクタの各R,G,B,bk色のＸＹＺ値、D_R,D_G,D_BはＲＧＢのデジタルの入力値（０〜２５５）を０から１の範囲に規格化したもの、γはプロジェクタの階調特性である。ガンマは、補正カーブの計算処理１と同様に、対象となるプロジェクタの階調特性を実際に測定して求め、当該実施の形態では、一例として、γ＝2.2とする。

It becomes. Here, Xc, Yc, Zc (c = R, G, B, bk) are R, G, B, bk XYZ values of the projector, and D _R , D _G , D _B are RGB digital input values. A value obtained by standardizing (0 to 255) in a range from 0 to 1, γ is a gradation characteristic of the projector. Similar to the correction curve calculation process 1, gamma is obtained by actually measuring the gradation characteristics of the target projector. In this embodiment, for example, γ = 2.2.

If the XYZ values of the illumination are XiYiZi, the RGB values r _i , g _i , b _i when the illumination color is expressed as a mixed color of the projector are

となる。

It becomes.

Next, a third correction curve is calculated using r _i , g _i and b _i (step 254). Complete color reproduction is realized by subtracting r _i , g _i , and b _i obtained by Equation (27) as they are from the RGB output of the projector as they are. However, this method is not practical because the gradation of the projector is greatly crushed.

Therefore, in this embodiment, as shown in FIG. 18, a method of subtracting the differences ΔRoffset, ΔGoffset, and ΔBoffset from the average values of r _i , g _i , b _i as an offset is employed. As a result, the color obtained by superimposing the illumination color and the offset color has the same chromaticity as the gray of the projector.

  In this way, the influence of the color of the illumination can be corrected in colorimetry, but when adjusting the correction amount in consideration of the adaptability of human eyes and the effect of contrast, ΔRoffset, ΔGoffset, ΔBoffset Is multiplied by (α2) (0 <α2 <1). If 100% (α2 = 1) correction is applied to the illumination color obtained by measurement, correct correction is performed in terms of colorimetry, but if the correction is applied too much, an unnatural image will be reproduced. There is. In order to eliminate this phenomenon, the correction amount is adjusted. The correction amount α2 needs to be adjusted while actually evaluating the image under each environment. The value of α2 is preferably 0.2 to 0.5.

By the way, when the RGB output of the projector is r, g, b and the output of the projector after correction is r ′, g ′, b ′, the correction process is expressed by an expression as follows. However, in order to simplify the description, only the formula of R is shown. That is, from equation (26)
R output of projector r (D _R ) (= D _R ^γ ) (28)
Is adjusted using the correction amount α2, the output r ′ (D _R ) after correcting R of the projector is
r ′ (D _R ) = D _R ^γ− α ₂ ΔR offset (29)
ΔRoffset = r _i − (r _i + g _i + b _i ) / 3
It becomes. From the above, if the input value before correction is D _R in3 and the input value after correction is D _R out, the third correction curve is
r (D _R out) = r ′ (D _R in3) (30)
It becomes. From Equation (29) and Equation (30),
D _R out = (D _R in3 ^γ− α2ΔRoffset) ^{1 / γ} (31)
It becomes. Similarly, D _G out and D _B out are
D _G out = (D _G in3 ^γ− α2ΔGoffset) ^{1 / γ} (32)
D _B out = (D _B in3 ^γ− α2ΔBoffset) ^{1 / γ} (33)
It becomes.

The final correction curve is obtained by connecting the first correction curve, the second correction curve and the third correction curve obtained as described above (step 256). That is, in formulas (9) to (11) and formulas (21) to (23),
D _R in2 ＝ D _R out1
D _G in2 ＝ D _G out1
D _B in2 ＝ D _B out1
And in formulas (21) to (23) and formulas (31) to (33),
D _R in3 ＝ D _R out2
D _G in3 ＝ D _G out2
D _B in3 ＝ D _B out2
Then, the final correction curve is
D _R out = [{1-α3 (1-ΔRgain)}
× {(1 + α1 · Yi / Yw) D _R in ^γ− (α1 · Yi / Yw) Do ^γ } −α2ΔRoffset)] ^{1 / γ}
… (34)
D _G out = [{1-α3 (1-ΔGgain)}
× {(1 + α1 · Yi / Yw) D _G in ^γ− (α1 · Yi / Yw) Do ^γ } −α2ΔGoffset)] ^{1 / γ}
… (35)
D _R out = [{1-α3 (1-ΔBgain)}
× {(1 + α1 · Yi / Yw) D _B in ^γ− (α1 · Yi / Yw) Do ^γ } −α2ΔBoffset)] ^{1 / γ}
… (36)
It becomes.

In the case where the results D _R out, D _G out, and D _B out calculated by the equations (34) to (36) are negative, D _R out = D _G out = D _B out = 0. Similarly, when the results D _R out, D _G out, and D _B out calculated by the expressions (34) to (36) are larger than 1, D _R out = D _G out = D _B out = 1. .

  An example of the final correction curve is shown in FIG.

  A final correction curve is obtained as in the equations (34) to (36) (step 256), and the correction curve rounding process 1 in step 225 of FIG. 8 is performed.

Correction curve rounding 1
Next, a correction curve rounding process 1 is performed (step 225).

As shown in FIG. 19, in the correction curve obtained by Expression (34), there are gradations in which Dout remains 0 and remains unchanged in the low gradation and high gradation areas. Therefore, the correction curve is rounded by the following procedure. First, the following expression Dout4 = [Dout− | (Dout−Din) | ^β ] (Dout> Din) (37)
Dout4 = [Dout + | (Dout−Din) | ^β ] (Dout <Din) (38)
Is used to calculate Dout4 from Dout. Here, β is a parameter for adjusting the degree of rounding. According to the evaluation results obtained while actually viewing the image, it was confirmed that β = 1.5 was appropriate. According to the equations (37) and (38), there is no gradation in which Dout remains 0. In this way, after the correction curve rounding process 1 is completed, the correction curve rounding process 2 is performed.

Correction curve rounding 2
Next, a correction curve rounding process 2 is performed (step 226).

  In the correction curve rounding process 2, for each value of the equation (37) or the equation (38), an average value of values at a total of five points including the two points before and after the value is calculated.

Taking Din × 255 = 128 as an example,
Dout5 (128) = [Dout4 (112) + Dout4 (120) + Dout4 (128) + Dout4 (136)
+ Dout4 (144)] / 5… (39)
It becomes. By performing the correction curve rounding process 2, the correction curve becomes smooth.

However, for the following 4 points of Din × 255 = 0, 8, 248, 255, Dout5 (0) = Dout4 (0)
… (40)
Dout5 (8) = [Dout4 (0) + Dout4 (8) + Dout4 (16)] / 3 (41)
Dout5 (248) = [Dout4 (240) + Dout4 (248) + Dout4 (255)] / 3 (42)
Dout5 (255) = Dout4 (255)
… (43)

And In this way, after the correction curve rounding process 2 is completed, the correction curve rounding process 3 is performed.

Correction curve rounding 3
Next, a correction curve rounding process 3 is performed (step 227).

In the correction curve rounding process 3, the following expression Dout6 = Din + (Dout5−Din) [1 − {(0.25−Din) /0.25} ^θ ] (Din × 255 <64)
… (44)
Dout6 = Din + (Dout5−Din) [1 − {(Din−0.75) /0.25} ^θ ] (Din × 255> 192)
… (45)
Is used to calculate Dout6. This Dout6 is the final correction result.

  The result is shown in FIG. As shown in FIG. 20, no correction is applied in the vicinity of Din × 255 = 0, 255, and the maximum brightness and contrast of the projector are maintained. Θ in Equation (44) and Equation (45) is a parameter for adjusting the degree of attenuation of the correction amount in the vicinity of Din × 255 = 0, 255, and depends on the evaluation result obtained while actually viewing the image. In this case, it was confirmed that θ = 5.0 is appropriate.

If Dout5 (0) and Dout5 (255) are already 0, the correction curve rounding process 3 (step 227) is not performed.
Dout6 = Dout5
And

  Then, after the correction curve rounding process 3 is completed, the process returns to step 228.

  In the present embodiment, the second color correction unit 120 sequentially generates a one-dimensional color correction table and performs color correction using the newly generated one-dimensional color correction table. It is also possible to store a one-dimensional color correction table and perform color correction using a predetermined one-dimensional color correction table according to the external environment. The reason is that, in the case of a one-dimensional color correction table, a large amount of memory capacity is not required as compared with the three-dimensional color correction table, so even if a plurality of one-dimensional color correction tables are stored in advance, there is no problem. Because.

(2-2) Color Temperature Adjustment Next, a color correction table generation process capable of adjusting the color temperature will be described with reference to FIG. In (2-1), in consideration of the case where the brightness or color of the external illumination or the color of the projection surface changes, the second color correction table generation unit 150 performs the color correction table generation / rewrite processing again, An example in which the projector displays an image with reference to the rewritten color correction table has been described. (2-2) describes a case where the second color correction table generation unit 150 generates a color correction table that can be adjusted in color temperature.

  As shown in FIG. 21, the second color correction table generation unit 150 uses the optical sensor 150 to maximize the output of W (white), R (red), G (green), and B (blue) of the projector. XYZ value is measured (S30).

XYZ values when the R output is maximum are X _R , Y _R , Z _R , XYZ values when the G output is maximum X _G , Y _G , Z _G , and XYZ values when the B output is maximum Are X _B , Y _B and Z _B. Assuming that the projector has an ideal output characteristic expressed by a predetermined gradation characteristic parameter γ, there is a gap between the input RGB value and the output XYZ value.

の関係が成立する。

The relationship is established.

Next, the target white point chromaticity coordinate x ₀ ,
y ₀ is set (S32).

Then, the XYZ value of the target white point is calculated (S34). That is, from the values of Y _R , Y _G , Y _B obtained in S30 and the values of x ₀ , y ₀ set in S32
Y ₀ = Y _R + Y _G + Y _B
X ₀ = Y ₀ × x ₀ / y ₀
Z ₀ = Y ₀ × (1−x ₀ −y ₀ ) / y ₀
From these, the values of X ₀ , Y ₀ , Z ₀ are obtained.

Next, RGB values (R ₀ , G ₀ , B ₀ ) necessary for producing the color of the white point are obtained (S36).

The values of R ₀ , G ₀ and B ₀ are

R₀ ＝ 255×[ r₀／max( r₀,
g₀, b₀ ) ]^1／γ
G₀ ＝ 255×[ g₀／max( r₀,
g₀, b₀ ) ]^1／γ
B₀ ＝ 255×[ b₀／max( r₀,
g₀, b₀ ) ]^1／γ
によって求められる。ここで、max( r₀,
g₀, b₀ )はr₀, g₀, b₀の最大値、行列の指数−1はこの行列が逆行列であることを示す。

R ₀ = 255 × [r ₀ / max (r ₀ ,
g ₀ , b ₀ )] ^{1 / γ}
G ₀ = 255 × [g ₀ / max (r ₀ ,
g ₀ , b ₀ )] ^{1 / γ}
B ₀ = 255 × [b ₀ / max (r ₀ ,
g ₀ , b ₀ )] ^{1 / γ}
Sought by. Where max (r ₀ ,
g ₀ , b ₀ ) is the maximum value of r ₀ , g ₀ , b ₀ , and the matrix index −1 indicates that this matrix is an inverse matrix.

From the above, input values R ', G',
B 'is the following formula
_{R '= (R 0/255} ) × R ... (46)
_{G '= (G 0/255} ) × G ... (47)
_{B '= (B 0/255} ) × B ... (48)
(S38).

  In this way, the second color correction table generation unit 150 generates a color correction table capable of adjusting the color temperature based on the equations (46) to (48). Then, the second color correction unit 120 performs color temperature adjustment based on the color correction table generated in this way.

  In the present embodiment, the second color correction unit 120 sequentially generates a one-dimensional color correction table and performs color correction using the newly generated one-dimensional color correction table. It is also possible to store a one-dimensional color correction table and perform color correction using a predetermined one-dimensional color correction table according to a predetermined color temperature. The reason is that in the case of the one-dimensional color correction table, a large amount of memory capacity is not required as compared with the three-dimensional color correction table, so that it is not a problem if a plurality of one-dimensional color correction tables are stored in advance. Because.

  (2-3) In this embodiment, as an example of “color correction considering changes in external environment”, (2-1) “color correction considering changes in ambient light and projection plane” and (2-2 ) “Color correction for color temperature adjustment” has been described independently, but after performing color correction using a one-dimensional color correction table that takes into account changes in ambient light and projection plane, It is also possible to perform color correction using the one-dimensional color correction table.

(3) Color Correction in Third Color Correction Unit 130 Next, color correction processing by the third color correction unit 130 will be described with reference to FIG.

  First, as shown in FIG. 22A, the output characteristics of the projector are set, and as shown in FIG. 22B, the input / output characteristics of the liquid crystal panel are measured. Based on FIGS. 22A and 22B, as shown in FIG. 22C, the correspondence between the input signal and the input value to the liquid crystal panel is obtained.

  The third color correction unit 130 adjusts the input value of the liquid crystal panel with reference to a color correction table expressing the correspondence between the input signal and the input value to the liquid crystal panel shown in FIG. The color correction table is stored in advance for each projector.

Second Embodiment FIG. 2 shows a functional block diagram of an image processing unit 100 in a projector according to a second embodiment of the image display apparatus of the present invention. The image display apparatus of the present invention includes a projector, a CRT, a liquid crystal display, and the like.

  The image processing unit 100 in the projector according to the first embodiment of the present invention refers to the one-dimensional color correction table generated by the first color correction table generating unit 112 and based on the input γ value, A γ correction unit 102 that rewrites data, a first color correction unit 110 that performs desired color correction with reference to a three-dimensional color correction table (3D-LUT) for performing color matching for γ = 2.2, A second color correction unit 120 that performs desired color correction based on the color correction table generated by the second color correction table generation unit 150, a third color correction unit 130 for adjusting the output characteristics of the liquid crystal light valve, And an L / V (light valve) driving unit 140 for driving the liquid crystal light valve to perform projection display of an image.

  The image processing unit 100 also includes a γ value input unit 116 for inputting the γ value of the projector, an LUT data storage unit 114 that stores lattice point data, and a γ value input by the γ value input unit 116. And a first color correction table generation unit 112 for generating a one-dimensional color correction table for rewriting the grid point data stored in the LUT data storage unit 114 based on the value.

  Furthermore, as in the first embodiment, the image processing unit 100 includes a device characteristic storage memory 160 for storing projector color characteristic information when output to the reference projection plane in a dark room, a projector, One-dimensional in consideration of the influence of the external illumination based on the optical sensor 170 for measuring the brightness of the reflected light from the screen of the external illumination, the colorimetric value of the optical sensor 170 and the information stored in the device characteristic storage memory And a second color correction table generation unit 150 that generates a color correction table (1D-LUT).

  In the image processing unit 100 of the second embodiment, the γ correction unit 102 rewrites the lattice point data based on the input γ value, and the first color correction unit 110 is rewritten, as in S12 and S14 of FIG. The image processing unit according to the first embodiment is configured to perform desired color correction with reference to the three-dimensional color correction table (3D-LUT) for γ = 2.2 (characteristic reference value) based on the lattice point data. Different from 100. Even if the γ correction unit 102 and the first color correction unit 110 are provided as in the second embodiment, the same processing as that of the first color correction unit 110 of the first embodiment can be performed.

  When γ = 2.2 (characteristic reference value) is input from the γ value input unit 116, the image input signal is directly input to the first color correction unit 110 without passing through the γ correction unit 102. It can also be configured to be.

  The configurations and operations of the second color correction unit 120, the third color correction unit 130, the L / V drive unit 140, the second color correction table generation unit 150, the device characteristic storage memory 160, and the optical sensor 170 will be described in detail. Since it is the same as that of the first embodiment, its description is omitted.

It is a functional block diagram of the image processing part in the projector concerning 1st Embodiment of this invention. It is a functional block diagram of the image processing part in the projector concerning 2nd Embodiment of this invention. 6 is a flowchart for explaining color correction table generation processing by a first color correction table generation unit 112; 10 is a flowchart for explaining processing for generating LUT data stored in an LUT data storage unit 114. It is a figure for demonstrating the production | generation process of LUT data. It is a figure for demonstrating matching with the color of a CRT, and the color of a projector. 6 is a flowchart for explaining an operation of a second color correction unit 120 in the projector according to the first embodiment of the present invention. 6 is a flowchart for explaining color correction table generation / rewriting processing by a second color correction table generation unit 150 in the projector according to the first embodiment of the present invention. It is a flowchart for demonstrating the correction curve calculation process 1 (correction | correction with respect to the change of the brightness of external illumination) by this invention. It is a graph which shows the gamma curve in each environment. It is a graph which shows the standardized gamma curve in each environment. It is a graph which shows the state which match | combined the standardized (gamma) curve in each environment with the reference point Do. It is a graph (1) which shows an example of the correction curve at the time of changing Do. It is a graph (2) which shows an example of the correction curve at the time of changing Do. It is a figure for demonstrating adjustment of the correction amount (alpha) 1 of a 1st correction curve. It is a flowchart for demonstrating the correction curve calculation process 2 (correction | amendment with respect to the change of the color of a projection surface) by this invention. It is a flowchart for demonstrating the correction curve calculation process 3 (correction | amendment with respect to the change of the color of external illumination) by this invention. It is a figure for demonstrating the calculation principle of a 3rd correction curve. It is a graph which shows an example of an example (before a rounding process) of a correction curve. It is a graph which shows an example (after a rounding process) of an example of a correction curve. It is a flowchart for demonstrating the color correction table production | generation process which can adjust color temperature. FIG. 6 is a diagram for explaining color correction processing by a third color correction unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image processing part 102 γ correction part 110 First color correction part 112 First color correction table generation part 114 LUT data storage part 116 γ value input part 120 Second color correction part 130 Third color correction part 140 L / V drive part 160 Device characteristic storage memory 150 Second color correction table generation unit 170 Optical sensor

Claims (9)

An image display device that performs desired image processing on input image data and displays an image,
Based on the characteristic value of the image display device, a desired color correction is performed on the input image data with reference to a three-dimensional color correction table for adapting the color characteristic of the image display device to a reference color characteristic. First color correction means to be applied;
Referring to a one-dimensional color correction table for performing color correction according to the external environment, desired color correction is performed on the input image data after color correction by the first color correction means. Two-color correction means;
With
The image display device, wherein the first color correction means includes rewriting means for rewriting grid point data of the three-dimensional color correction table based on the characteristic value. The image display device according to claim 1,
An image display device in which the one-dimensional color correction table in the second color correction means is for adjusting a color temperature. The image display device according to claim 1 or 2,
An image display device in which the one-dimensional color correction table in the second color correction means is for correcting a change in brightness of external illumination. The image display device according to any one of claims 1 to 3,
An image display device in which the one-dimensional color correction table in the second color correction means is for correcting a change in the color of the projection surface. The image display device according to any one of claims 1 to 4,
An image display device in which the one-dimensional color correction table in the second color correction means is for correcting a change in color of external illumination. An image display device according to any one of claims 1 to 5,
An image display device further comprising means for inputting the characteristic value. The image display apparatus according to claim 1, wherein the image display apparatus is a projector. An image processing method for image data input to an image display device,
Based on the characteristic value of the image display device, a desired color correction is performed on the input image data with reference to a three-dimensional color correction table for adapting the color characteristic of the image display device to a reference color characteristic. Applying a first color correction step;
Referring to a one-dimensional color correction table for performing color correction according to the external environment, a desired color correction is performed on the input image data after the color correction in the first color correction step. A two-color correction process;
With
The image processing method, wherein the first color correction step includes a rewriting step for rewriting grid point data of the three-dimensional color correction table based on the characteristic value. A program for causing a computer to execute image processing on image data input to an image display device,
Based on the characteristic value of the image display device, a desired color correction is performed on the input image data with reference to a three-dimensional color correction table for adapting the color characteristic of the image display device to a reference color characteristic. A first color correction process to be performed;
Referring to a one-dimensional color correction table for performing color correction according to an external environment, a desired color correction is performed on the input image data after the color correction by the first color correction process. Two-color correction processing;
Is a program for causing a computer to execute
The program in which the first color correction process includes a rewrite process for rewriting grid point data of the three-dimensional color correction table based on the characteristic value.

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