JP2012039274A - Color space conversion device, image processing device, image display device, and color space conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color space conversion device etc. capable of accurately adjusting the hue etc. of an image.SOLUTION: A second color space conversion circuit 140 for converting an HLS signal to a YUV signal comprises a saturation adjustment circuit 80, a first color difference output device 75, and a second color difference output device 76. A saturation adjustment circuit 80 adjusts a saturation signal included in the HLS signal according to a hue signal included in the HLS signal. The first color difference output device 75 and the second color difference output device 76 generate a color difference signal included in the YUV signal on the basis of the hue signal and the saturation signal adjusted by the saturation adjustment circuit 80.

Description

  The present invention relates to a color space conversion device, an image processing device, an image display device, a color space conversion method, and the like.

  In an image display device that displays various images including a moving image, an image signal is input, processed and displayed in real time. In order to simplify display and image processing, image display devices such as projectors, CRTs (Cathode Ray Tubes), LCDs (Liquid Crystal Displays), etc. use RGB format image signals (RGB signals) and YUV format images. A signal (YUV signal) is generally used. The RGB format image signal includes an R (red) signal, a G (green) signal, and a B (blue) signal. The YUV format image signal is composed of a Y (luminance) signal, a U (first color difference) signal, and a V (second color difference) signal.

  The hue, brightness, saturation, and the like of an image displayed on such an image display device can be adjusted by an image signal source (for example, a DVD player). Recently, an image display device such as a projector has also been adjusted. It has a mechanism. However, when the user tries to adjust the color, brightness, vividness, etc. of the image, the RGB signal, YUV signal, etc., which are handled by these image display devices as standard, are directly adjusted. Therefore, in these signals, if one signal is strengthened or weakened, the change affects other colors, and adjustment for obtaining a desired image is difficult.

  Therefore, conventionally, in a color scanner or the like, for example, the RGB signal of the standard image is once converted into an HLS signal, and the deviation from the standard color is calculated, and this is used to adjust the color of the read image ( For example, see Patent Document 1 below). The HLS signal is a signal conforming to the Munsell color system represented by H (hue), L (lightness), and S (saturation) as the standard of the object color. A technique for performing color correction using an HLS signal is also disclosed in Patent Document 2.

JP-A-9-18724 JP-A-11-69186

  However, both of these techniques correct the deviation and balance deviation inherent in the image processing system. For this reason, in an image display apparatus such as a projector that sometimes handles moving images, it has been impossible to adjust and display an image signal processed in real time in a desired state. From the user's point of view, the user wants to adjust the color, brightness, vividness, etc. of the displayed image according to his / her preference, not the RGB signal or YUV signal. Therefore, the conventional image display apparatus has a problem that it cannot meet such user's demand, and it is desirable that the user can adjust the color, brightness, vividness, etc. of the image as accurately as possible.

  The present invention has been made in view of the above technical problems. According to some aspects of the present invention, for example, a color space conversion device, an image processing device, an image display device, a color space conversion method, and the like that can adjust the color and the like of an image with high accuracy according to user preferences are provided. be able to.

  (1) According to one aspect of the present invention, a color space conversion device that converts an HLS signal into a YUV signal adjusts a saturation signal included in the HLS signal according to a hue signal included in the HLS signal. A color adjustment signal generation unit configured to generate a color difference signal included in the YUV signal based on the signal adjustment unit, the hue signal, and the saturation signal adjusted by the saturation signal adjustment unit;

  In this aspect, the HLS signal is a signal represented by three elements of hue, lightness, and saturation, and the YUV signal is a signal represented by three elements of luminance and two color differences. According to this aspect, when the HLS signal is converted into the YUV signal, the color difference signal constituting the YUV signal can be generated without changing the hue before and after the conversion. Therefore, even if the adjusted HLS signal cannot be accurately mapped to the YUV signal, the color of the image is adjusted with high accuracy according to the user's preference, for example, without the color appearing before and after the conversion. become able to.

(2) In the color space conversion device according to another aspect of the present invention, the saturation signal adjustment unit includes a saturation maximum value generation unit that generates a saturation maximum value corresponding to the hue signal, and the saturation signal. A comparison unit that outputs a smaller one of the saturation value corresponding to the saturation value or the maximum saturation value, and the color difference signal generation unit is configured to output the color difference based on the hue signal and the output signal from the comparison unit. Generate a signal.
According to this aspect, in addition to the above-described effects, it is possible to generate a color difference signal constituting a YUV signal without changing the hue before and after conversion with a simple configuration.

(3) In the color space conversion device according to another aspect of the present invention, the saturation maximum value generation unit outputs a saturation component in a boundary value of a color gamut corresponding to the YUV signal as the saturation maximum value. .
According to this aspect, when the HLS signal is converted into the YUV signal, the entire color gamut corresponding to the YUV signal can be used, so that more accurate color space conversion can be performed in addition to the above effect. It becomes.

  (4) According to one aspect of the present invention, a color space conversion device that converts an HLS signal into a YUV signal has a first color difference signal included in the YUV signal based on a hue signal and a saturation signal included in the HLS signal. And a color difference signal generation unit that generates a second color difference signal, and a signal value of the first color difference signal or the first color difference signal while maintaining a ratio between the signal value of the first color difference signal and the signal value of the second color difference signal. A color difference signal adjusting unit that outputs the first color difference signal and the second color difference signal obtained by clipping the signal value of the two color difference signals to the boundary value of the color gamut corresponding to the YUV signal.

  In this aspect, when the HLS signal is converted into the YUV signal, the color difference signal constituting the YUV signal can be generated without changing the hue before and after the conversion. Therefore, even when the adjusted HLS signal cannot be accurately mapped to the YUV signal, the color of the image can be adjusted with high accuracy without the color appearing before and after the conversion.

  (5) According to one aspect of the present invention, the image processing apparatus includes a first color space conversion unit that converts a YUV signal into an HLS signal, and a hue signal that constitutes the HLS signal converted by the first color space conversion unit. The color adjustment unit that adjusts at least one of a lightness signal and a saturation signal and outputs an adjusted HLS signal, and converts the HLS signal adjusted by the color adjustment unit into a YUV signal A color space conversion device.

  In this aspect, the YUV signal is once converted into an HLS signal, color adjustment is performed in the state of the HLS signal, and then the HLS signal after color adjustment is returned to the YUV signal. As a result, it is possible to provide an image processing apparatus that can intuitively adjust image color adjustment for each element of hue, brightness, and saturation, and that can adjust the color of an image with high accuracy.

  (6) One aspect of the present invention includes the color space conversion device according to any one of the above, wherein an image display device that displays an image based on an image signal converts an HLS signal corresponding to the image signal into a YUV signal. The image is displayed using the YUV signal converted by the color space conversion device.

  According to this aspect, it is possible to provide an image display device that can adjust the color and the like of an image with high accuracy.

  (7) According to one aspect of the present invention, a color space conversion method for converting an HLS signal into a YUV signal adjusts a saturation signal included in the HLS signal according to a hue signal included in the HLS signal. And a color difference signal generation step of generating a color difference signal included in the YUV signal based on the signal adjustment step, the hue signal, and the saturation signal adjusted in the saturation signal adjustment step.

  (8) In one aspect of the present invention, a color space conversion method for converting an HLS signal to a YUV signal is based on a hue signal and a saturation signal included in the HLS signal, and the first color difference signal included in the YUV signal. And a color difference signal generating step for generating a second color difference signal, and a signal value of the first color difference signal or the first color difference signal while maintaining a ratio between the signal value of the first color difference signal and the signal value of the second color difference signal. And a color difference signal adjustment step of outputting the first color difference signal and the second color difference signal obtained by clipping the signal value of the two color difference signals to the boundary value of the color gamut corresponding to the YUV signal.

  In any one of the above aspects, when the HLS signal is converted into the YUV signal, the color difference signal constituting the YUV signal can be generated without changing the hue before and after the conversion. Therefore, even when the adjusted HLS signal cannot be accurately mapped to the YUV signal, the color of the image is adjusted with high accuracy according to the user's preference, for example, without the color appearing before and after the conversion. become able to.

It is a block diagram which shows the whole structure of the liquid crystal projector in 1st Embodiment. It is a block diagram which shows the structure of the color space conversion circuit in 1st Embodiment. It is explanatory drawing which showed the relationship between a YUV signal and a HLS signal. It is explanatory drawing which looked at YUV space and HLS space from the Y-axis and L-axis corresponding to the element of a brightness | luminance and a brightness. It is explanatory drawing which showed an example of the floating point calculation in a floating point converter. It is explanatory drawing explaining the calculation method in which a selector adder outputs a hue value. It is explanatory drawing which illustrates notionally the calculation method of the hue value which a selector adder performs. It is a block diagram which shows the structure of a color adjustment circuit. It is explanatory drawing which showed the image for hue adjustment. It is explanatory drawing which showed the image for saturation adjustment. It is explanatory drawing which showed the concept of the process which a saturation adjustment circuit performs. It is the figure which looked at the YUV color space and the HLS color space from the Y-axis and the L-axis. It is a block diagram which shows the structure of the 2nd color space conversion circuit in 1st Embodiment. It is explanatory drawing which showed the calculation method in which Ph output device calculates a hue angle and a quadrant value. It is explanatory drawing of the saturation maximum value which a saturation maximum value generation circuit outputs according to a hue value. It is operation | movement explanatory drawing of the 2nd color space conversion circuit in 1st Embodiment. It is explanatory drawing which showed the computing equation of the calculation which a 1st color difference output device performs. It is explanatory drawing which showed the computing equation of the calculation which a 2nd color difference output device performs. It is a block diagram of the structural example of the 2nd color space conversion circuit in 2nd Embodiment. It is a block diagram of the structural example of the 2nd color space conversion circuit in 3rd Embodiment. It is operation | movement explanatory drawing of the 2nd color space conversion circuit in 3rd Embodiment. It is operation | movement explanatory drawing of a color difference adjustment circuit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, all of the configurations described below are not necessarily indispensable configuration requirements for solving the problems of the present invention.
In the following, an example is described in which the color space conversion device according to the present invention is applied to a liquid crystal projector that is an image display device, but the image display device according to the present invention is not limited to a liquid crystal projector.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration example of a liquid crystal projector according to the first embodiment of the present invention. The liquid crystal projector 100 is a projector that employs a liquid crystal light valve as light modulation means. The liquid crystal projector 100 includes a first color space conversion circuit 110, a color adjustment circuit 120, a CPU 130, and a second color space conversion circuit 140. Furthermore, the liquid crystal projector 100 includes a liquid crystal light valve driving circuit 150, a liquid crystal light valve 160, a light source unit 170, a projection lens 180, an operation control unit 190, and operation buttons 192. The liquid crystal projector 100 displays an image (moving image) on the screen 200 based on the image signal input to the first color space conversion circuit 110. The color adjustment circuit 120, the CPU 130, and the operation control unit 190 are connected by the internal bus 102. The image signal is input to the first color space conversion circuit 110 in real time by an input device such as a video camera, a scanner, or a personal computer (not shown). Alternatively, the image signal may be read to the first color space conversion circuit 110 from a computer-readable storage medium (not shown). Here, the computer-readable storage medium may be any of ROM, RAM, CD-ROM, DVD, FD, MD, memory card, and the like.

  The first color space conversion circuit 110 is an electric circuit that performs YUV-HLS conversion on a digital image signal input as a YUV signal and outputs the image signal as an HLS signal. The color adjustment circuit 120 includes hue, brightness, and saturation signals corresponding to the HLS signal input from the first color space conversion circuit 110 (hereinafter, these signals are also referred to as a hue signal, a brightness signal, and a saturation signal). ) For performing color adjustment processing. Specifically, the color adjustment circuit 120 can change the hue corresponding to the HLS signal. The color adjustment circuit 120 can correct the output gain value of each signal (hereinafter also referred to as gain correction) for the brightness and saturation corresponding to the HLS signal. The color adjustment circuit 120 performs hue change and gain correction in accordance with commands from the CPU 130.

  The CPU 130 can implement various functions by reading a specific program stored in advance in a ROM (not shown) and executing processing corresponding to the program. For example, the CPU 130 can realize the function of the color adjustment instruction unit 132 by reading a specific program stored in the ROM and executing processing corresponding to the program. The color adjustment instruction unit 132 controls the processing content performed by the color adjustment circuit 120 described above.

  The second color space conversion circuit 140 is a circuit that converts the HLS signal input from the color adjustment circuit 120 into a YUV signal (hereinafter also referred to as HLS-YUV conversion) and outputs the YUV signal. The HLS signal input to the second color space conversion circuit 140 is a signal whose hue has been changed and gain correction has been performed by the above-described color adjustment by the user.

  The liquid crystal light valve driving circuit 150 is a circuit that drives the liquid crystal light valve 160. The liquid crystal light valve 160 is a light modulation element that visualizes the signal generated by the liquid crystal light valve driving circuit 150. Specifically, the liquid crystal light valve 160 modulates the light emitted from the light source unit 170 based on the signal generated by the liquid crystal light valve driving circuit 150 and directs the light necessary for projection toward the screen 200 side. Eject.

  The light source unit 170 is a light source for projecting an image, and mainly includes a lamp 171 that emits light and a lens 172 that collimates light emitted from the lamp 171. The parallel light is modulated by the liquid crystal light valve 160 and then enters the projection lens 180. The projection lens 180 enlarges and displays the light emitted from the light source unit 170 and modulated by the liquid crystal light valve 160 on the screen. The screen 200 has a projection surface that displays a projection image projected from the liquid crystal projector 100.

  The operation control unit 190 receives a color adjustment instruction for the image projected by the liquid crystal projector 100 from the user via the operation button 192 and transmits the instruction to the CPU 130 via the internal bus 102. The operation button 192 includes a cross key button and a determination button. When performing color adjustment described later, the user performs image color adjustment using these buttons. In the first embodiment, the liquid crystal projector 100 receives an instruction from the user via the operation control unit 190 and the operation button 192. However, the present invention is not limited to this. For example, an instruction from the user may be received via an operation panel provided in the liquid crystal projector 100 or an external operation device such as a mouse or a keyboard provided in a computer connected to the liquid crystal projector 100.

  FIG. 2 shows a block diagram of a configuration example of the first color space conversion circuit 110 of FIG. The first color space conversion circuit 110 includes a lightness calculation unit 10, a saturation calculation unit 20, and a hue calculation unit 30. The first color space conversion circuit 110 converts a luminance signal (Y), a first color difference signal (U), and a second color difference signal (V) included in an input image signal into a lightness signal (L) and a saturation signal ( S), converted into a hue signal (H) and output. Note that a synchronous clock (not shown) is input to each arithmetic unit and synchronizes the operation between the circuits, but the synchronous clock signal is not shown. Therefore, the YUV signal input to the first color space conversion circuit 110 is converted as an HLS signal corresponding to the set of signals using this synchronous clock, and is output in synchronization.

Here, the relationship between the YUV signal and the HLS signal will be described.
FIG. 3 is an explanatory diagram of the relationship between the YUV signal and the HLS signal. As shown in FIG. 3, the YUV signal represents the image signal in a three-dimensional orthogonal coordinate space (hereinafter also referred to as a YUV color space) composed of three elements of luminance, first color difference, and second color difference. Signal. On the other hand, the HLS signal is a signal representing an image signal in a three-dimensional polar coordinate space (hereinafter also referred to as an HLS color space) composed of three elements of hue, brightness, and saturation. As shown in FIG. 3, the brightness in the YUV color space and the brightness in the HLS color space have the same axial direction in both coordinate spaces and have a one-to-one correspondence. Therefore, the luminance signal and the brightness signal can be handled as the same signal. As a result, converting an image signal input as a YUV signal into an HLS signal substantially converts the first color difference signal and the second color difference signal included in the image signal into a hue signal and a saturation signal. It corresponds to that.

FIG. 4 shows a view of both coordinate spaces shown in FIG. 3 as seen from the Y-axis and L-axis corresponding to the luminance and brightness elements.
The saturation signal corresponds to a signal obtained by projecting the YUV signal onto the UV plane in the YUV space. The hue signal is a signal corresponding to an angle formed by the saturation signal in the YUV space and the first color signal. Based on the relationship between the YUV space and the HLS space shown in FIGS. 3 and 4, the first color space conversion circuit 110 shown in FIG. 2 performs YUV-HLS conversion.

  In FIG. 2, the lightness calculation unit 10 uses a value (hereinafter also referred to as a luminance value) corresponding to the luminance signal (Y) input to the color space conversion circuit 110 as a value (hereinafter referred to as the luminance signal (L)). , Also referred to as a lightness value) and output as a lightness signal (L). This is because, as shown in FIG. 3, the luminance in the YUV color space and the brightness in the HLS color space have a one-to-one correspondence in both coordinate spaces. In other words, the input luminance signal (Y) is output as it is as the brightness signal (L). In the first embodiment, the luminance signal (Y) and the lightness signal (L) are both 10-bit gradation data.

  The saturation calculation unit 20 outputs a saturation signal (S) based on the first color difference signal (U) and the second color difference signal (V) input to the first color space conversion circuit 110. The saturation calculator 20 includes a first multiplier 21, a second multiplier 22, an adder 23, a floating point converter 24, a lookup table 25, a saturation index calculator 26, and a bit shift calculator 27. Hereinafter, the lookup table is also referred to as an LUT. For example, the lookup table 25 is also referred to as an LUT 25.

  Hereinafter, the process until the saturation calculation unit 20 converts the first color difference signal (U) and the second color difference signal (V) into the saturation signal (S) will be described along the order in which the signals flow. The first color difference signal (U) and the second color difference signal (V) are each 10-bit gradation data. For this reason, both signals take a signal value of (0 to 1023), but when the signal value is (512), they are treated as indicating that they are colorless. The value is expressed as (−512 to 511).

The first multiplier 21 converts the input first color difference signal into (−512 to 511) gradation data, and then converts the signal value to a gradation value having symmetry centered on 0 (zero). In order to express, gradation processing of (−512 to 511) is rounded to gradation data of (−511 to 511). After the rounding process, the first multiplier 21 calculates a first multiplication value Uv ² that is a power of the value of the first color difference signal (hereinafter also referred to as the first color difference value Uv). The second multiplier 22 performs the same process as the first multiplier 21 on the input second color difference signal, and powers the value of the second color difference signal (hereinafter also referred to as the second color difference value Vv). calculating a second multiplication value Vv ^2. The adder 23 calculates an addition value obtained by adding the first multiplication value Uv ² and the second multiplication value Vv ² output from the first multiplier 21 and the second multiplier 22 to each other, that is, a value of Uv ² + Vv ^2. .

  A value obtained by calculating a square root value with respect to the added value output from the adder 23 and normalized to the scale of the HLS signal is the saturation value Sv. The normalization is performed by multiplying the square root result value R by √2, where the square root value of the added value is the square root result value R. At this time, the saturation value Sv and the square root extraction result value R are expressed by Expression (1).

When the floating point converter 24 receives the addition value Uv ² + Vv ² , that is, a signal corresponding to the value of R ² , the floating point converter 24 performs a floating point operation on the value of R ² , and satisfies the expression (2) The real value Ks and the first index value Ls are calculated. At this time, the value of the first index value Ls is calculated as an even value. An example of the floating point calculation in the floating point converter 24 is shown in FIG.

Sv = √2 * R (1)
R ² = Ks / 2 ^Ls (2)

  Next, when the saturation value Sv is expressed by the second real value Sr and the second exponent value Si satisfying the equation (3), the second real value Sr and the second value are expressed by the equations (1) to (3). The index value Si can be expressed as Expression (4) and Expression (5). Note that n in the equations (4) and (5) is a positive integer. This n avoids a decrease in the accuracy of the subsequent calculation due to the small value of the output signal due to the nature of the calculation performed by each arithmetic unit described later. In order to ensure the accuracy of the operation, a positive integer is appropriately substituted for n, and a bit shift is performed on the value of the signal output by the operation.

Sv = Sr / 2 ^Si (3)
Sr = 2 ⁿ * √2 * √Ks (4)
Si = Ls / 2 + n (5)

  The LUT 25 illustrated in FIG. 2 is an LUT that reads the second real value Sr that satisfies Expression (4) with respect to the value of the first real value Ks output from the floating point converter 24. In the first embodiment, the value of the second real value Sr corresponding to the first real value Ks taking a value of (0 to 2047) is stored in the LUT 25.

  The saturation index calculator 26 is a calculator that calculates the second index value Si by performing the arithmetic processing shown in Expression (5) on the value of the first index value Ls output from the floating point converter 24. is there. As described above, the floating point converter 24 outputs the first exponent value Ls as an even value. Therefore, when the saturation index calculator 26 performs the arithmetic processing shown in Expression (5), it is not necessary to perform arithmetic including the concept of decimal numbers. The saturation index calculator 26 outputs the second index value Si as an integer value.

  The bit shift calculator 27 calculates a saturation value Sv satisfying the expression (3) from the second real value Sr output from the LUT 25 and the second exponent value Si output from the saturation index calculator 26. It is. The second exponent value Si is output from the saturation index calculator 26 as an integer value. Therefore, the bit shift calculator 27 outputs a saturation value Sv by performing a bit shift of Si digits on the value of the second real value Sr when performing the calculation process of the expression (3). Here, the floating point converter 24, the LUT 25, the saturation index calculator 26, and the bit shift calculator 27 correspond to a square root extractor.

  Next, the hue calculation unit 30 will be described. As shown in FIG. 2, the hue calculation unit 30 is based on the first color difference signal (U), the second color difference signal (V), the first real value Ks calculated by the saturation calculation unit 20, and the second index value Si. The hue signal (H) is output. The hue calculation unit 30 includes an LUT 31, an Ur multiplier 33, a Vr multiplier 34, a selector 35, an LUT 36, a selector subtractor 37, and a selector adder 38.

  Here, using the first color difference value Uv, the second color difference value Vv, and the square rooted result value R, the cosine value Ur and the sine value Vr shown in the equations (6) and (7) are defined. Also, using the second real value Sr calculated by the saturation calculation unit 20, the reciprocal of the second real value Sr is defined by invSr shown in Expression (8). Moreover, invSr can be represented by Formula (8a) from Formula (4) and Formula (8). As a result, the cosine value Ur and the sine value Vr can be expressed by the equations (9) and (10) from the equations (1) to (8) and (8a). Note that w and m in Expression (8), Expression (8a), Expression (9), and Expression (10) are positive integers. As in the case of n described above, a positive integer is appropriately substituted for w and m in order to ensure the accuracy of the calculation due to the nature of the calculation by each calculation unit described later, and the value of the signal output by the calculation is Bit shift is performed.

Ur = Uv / R (6)
Vr = Vv / R (7)
invSr = w / Sr (8)
invSr = w / 2 ⁿ * √2 * √Ks (8a)
Ur = | Uv | * √2 * invSr * 2 ^(Si-m) (9)
Vr = | Vv | * √2 * invSr * 2 ^(Si-m) (10)

  The LUT 31 illustrated in FIG. 2 is an LUT that reads invSr that satisfies the equation (8a) corresponding to the first real value Ks output from the floating point converter 24. Similarly to the LUT 25 described above, in the first embodiment, the value of invSr corresponding to the first real value Ks having a value of (0 to 2047) is stored in the LUT 31.

  The Ur multiplier 33 performs the arithmetic processing shown in Expression (9) on the first color difference value Uv, the second exponent value Si output from the saturation index calculator 26, and invSr output from the LUT 31, and the cosine The value Ur is calculated. In addition, the Vr multiplier 34 performs the arithmetic processing shown in Expression (10) on the second color difference value Vv, the second exponent value Si output from the saturation index calculator 26, and invSr output from the LUT 31. The sine value Vr is calculated.

  The selector 35 compares the magnitudes of the cosine value Ur and the sine value Vr output from the Ur multiplier 33 and the Vr multiplier 34, and selects and outputs the smaller value (hereinafter also referred to as the selector output value D). . The selector 35 outputs selector information indicating which is smaller as a result of the comparison between the cosine value Ur and the sine value Vr together with the selector output value D.

  The LUT 36 is an LUT that reads the LUT calculation value E that satisfies the expression (11) corresponding to the selector output value D output from the selector 35. W in formula (11) is a positive integer as described above.

E = arcsin (D / w) (11)
The unit of E is “degree”.

  Based on the selector information output from the selector 35, the selector subtracter 37 selects two subtraction processes shown in (12) or (13) and calculates the hue angle Ph for the LUT output value E. .

When Ur ≧ Vr, Ph = E (12)
When Ur <Vr, Ph = 90−E (13)

FIG. 6 is an explanatory diagram of a calculation method in which the selector adder 38 outputs the hue value Hv that is the value of the hue signal H based on the first color difference value Uv, the second color difference value Vv, and the hue angle Ph. The selector adder 38 selects the output method of the hue value Hv according to the combination of the input first color difference value Uv and the second color difference value Vv.
FIG. 7 is an explanatory diagram conceptually illustrating a method for calculating the hue value Hv performed by the selector adder 38. FIG. 7 is a U-V graph in which the horizontal axis represents the first color difference value Uv and the vertical axis represents the second color difference value Vv. Hereinafter, the calculation method of the hue value Hv by the selector adder 38 will be described with reference to FIGS.

  For example, when the first color difference value Uv input to the selector adder 38 is a positive value and the second color difference value Vv is a positive value, as shown in FIG. 7, the hue angle Ph is the second value on the U-V graph. It corresponds to an angle in one quadrant. In this case, it can be understood from FIG. 7 that the hue value Hv and the hue angle Ph are the same. In FIG. 6, the calculation method of H corresponding to the positive value of the first color difference value Uv and the positive value of the second color difference value Vv is Hv = Ph, which has been described with reference to FIG. It turns out that it corresponds to the calculation method of hue value Hv.

  Next, as a second specific example, when the first color difference value Uv input to the selector adder 38 is a negative value and the second color difference value Vv is a negative value, as shown in FIG. Ph corresponds to an angle in the third quadrant on the U-V graph. In this case, as shown in FIG. 7, it can be understood that the hue value Hv is obtained by adding 180 degrees to the hue angle Ph. In FIG. 6, the calculation method of Hv corresponding to the negative value of the first color difference value Uv and the negative value of the second color difference value Vv is Hv = Ph + 180, which has been described with reference to FIG. It turns out that it corresponds to the calculation method of hue value Hv. As shown in the above two specific examples, the selector adder 38 outputs the hue value Hv based on the first color difference value Uv, the second color difference value Vv, and the hue angle Ph by the calculation method corresponding to FIG. As described above, the first color space conversion circuit 110 performs YUV-HLS conversion on the YUV signal input as the image signal by the above method, and outputs an HLS signal.

Next, details of color adjustment performed by the user and processing performed by the liquid crystal projector 100 at the time of color adjustment will be described. The HLS signal output by the YUV-HLS conversion performed by the first color space conversion circuit 110 is input to the color adjustment circuit 120.
FIG. 8 shows a block diagram of a configuration example of the color adjustment circuit 120. FIG. 8 illustrates the first color space conversion circuit 110 and the CPU 130 that output various signals to the color adjustment circuit 120 in addition to the color adjustment circuit 120. The color adjustment circuit 120 includes a hue adjustment circuit 40, a saturation adjustment circuit 50, and a brightness adjustment circuit 60 as shown in the figure.

  The hue adjustment circuit 40 includes an LUT 41. The LUT 41 is an LUT that stores the value of the hue signal (H) to be output with respect to the value of the input hue signal (H), and is composed of a RAM. Hereinafter, the value of a signal input to the LUT is also referred to as an input signal value, and the value of a signal output from the LUT is also referred to as an output signal value.

  The saturation adjustment circuit 50 includes an LUT 51, an LUT 52, a saturation gain interpolation circuit 53, and a saturation multiplication circuit 54. A hue signal (H) and a saturation signal (S) are input to the saturation adjustment circuit 50. The LUT 51 outputs when the saturation value which is the signal value of the saturation signal is Sv = 0 (minimum value of saturation value) among the hue signal and the saturation signal input to the saturation adjustment circuit 50. This is an LUT in which an output gain value corresponding to a saturation value is stored for each hue value. The LUT 52 outputs the output gain value corresponding to the output saturation value for each hue when the signal value of the saturation signal input to the saturation adjustment circuit 50 is Sv = 1023 (the maximum value of the saturation value). LUT stored for each value. The saturation gain interpolation circuit 53 calculates and outputs a saturation gain value that is an output gain value of the saturation signal in each hue when the input signal value of the saturation signal is between 0 and 1023. The saturation multiplication circuit 54 multiplies the saturation signal (S) and the saturation gain value and outputs the result as a saturation signal (S) after color adjustment.

  The brightness adjustment circuit 60 has substantially the same configuration as the saturation adjustment circuit 50 described above. Compared to the saturation adjustment circuit 50, the difference in configuration and processing is that the signal to be processed is a lightness signal (L). The brightness adjustment circuit 60 includes an LUT 61, an LUT 62, a brightness gain interpolation circuit 63, and a brightness multiplication circuit 64. A hue signal (H) and a brightness signal (L) are input to the brightness adjustment circuit 60. The LUT 61 corresponds to the lightness value to be output when the lightness value which is the signal value of the lightness signal is Lv = 0 (minimum value of the lightness signal value) among the hue signal and the lightness signal input to the lightness adjustment circuit 60. This is an LUT in which the output gain value is stored for each hue value. The LUT 62 stores, for each hue value, an output gain value corresponding to the output brightness value when the signal value of the brightness signal input to the brightness adjustment circuit 60 is Lv = 1023 (maximum value of brightness value). LUT. The lightness gain interpolation circuit 63 calculates and outputs a lightness gain value that is an output gain value of the lightness signal in each hue when the input signal value of the lightness signal is between 0 and 1023. The lightness multiplication circuit 64 multiplies the lightness signal (L) and the lightness gain value, and outputs the result as a lightness signal (L) after color adjustment. Note that initial values are written in the LUTs in the color adjustment circuit 120 when the power of the liquid crystal projector 100 is turned on. The value of the LUT is rewritten by a color adjustment instruction by a user operation described below.

Next, color adjustment processing performed by the liquid crystal projector 100 according to a user instruction will be described. A user who performs color adjustment performs color adjustment while viewing the color adjustment image projected on the screen 200 by the liquid crystal projector 100. The color adjustment image includes a hue adjustment image, a saturation adjustment image, and a brightness adjustment image.
FIG. 9 is an explanatory diagram of a hue adjustment image among the color adjustment images. The hue adjustment image is created by the CPU 130 based on the correspondence relationship between the input signal value and the output signal value stored in the LUT 41. Specifically, the horizontal axis of the hue adjustment image in FIG. 9 corresponds to the input signal value, and the vertical axis corresponds to the output signal value. The CPU 130 projects the created hue adjustment image on the screen 200. These functions are performed by the CPU 130 as functions of the color adjustment instruction unit 132. Then, the user who sees the hue adjustment image projected on the screen 200 uses the operation buttons 192 to perform color adjustment related to the hue.

  The CPU 130 rewrites the output signal value of the hue signal (H) stored in the LUT 41 in accordance with a color adjustment instruction performed by the user via the operation button 192. The LUT 41 that has rewritten the output signal value changes the value of the hue signal (H) input to the hue adjustment circuit 40 in accordance with the rewritten output signal value and outputs it.

  In the hue adjustment image shown in FIG. 9, the horizontal axis corresponds to the input signal value, and the vertical axis corresponds to the output signal value. Both the vertical axis and the horizontal axis are provided with reference axes at locations of hue values corresponding to blue (B), magenta (M), red (R), yellow (Y), green (G), and cyan (C). . The thick line in the hue adjustment image represents the content of the hue signal changing process performed by the hue adjustment circuit 40. The user can select one of blue (B), magenta (M), red (R), yellow (Y), green (G), and cyan (C) by using the cross key button and the determination button provided in the operation button 192. Select and determine the hue axis. Then, the user changes the shape of the thick line by moving the thick line of the selected hue up and down, and performs color adjustment related to the hue of the image projected by the liquid crystal projector 100. As an example, according to the thick line shown in the hue adjustment image in FIG. 9, the hue adjustment circuit 40 brings “red (R) to yellow (Y) and cyan (C) to green (G) of the projected image. The process is performed on the hue signal (H).

Next, a saturation correction process performed by the liquid crystal projector 100 according to a user instruction will be described.
FIG. 10 is an explanatory diagram of a saturation adjustment image among the color adjustment images. Actually, the saturation adjustment image includes an image when the saturation value is Sv = 0 (hereinafter also referred to as a minimum saturation image) and an image when the saturation value is Sv = 1023 (hereinafter, maximum). There are two images, also called chroma images. The minimum saturation image and the maximum saturation image are different in the shape of the thick line indicating the processing contents, but the other portions are the same. Therefore, FIG. 10 shows a saturation adjustment image when Sv = 0, that is, The minimum saturation image is shown.

  The horizontal axis of the minimum saturation image shown in FIG. 10 indicates the value of the hue signal input to the color adjustment circuit 120. The vertical axis represents the value of the output gain of the saturation signal that is output corresponding to the input signal value of the input saturation signal. On the horizontal axis, reference axes are provided at locations of hue values corresponding to blue (B), magenta (M), red (R), yellow (Y), green (G), and cyan (C). The thick line in the minimum saturation image represents the output gain value corresponding to the value of the saturation signal to be output with respect to the input saturation signal of Sv = 0 for each value of the input hue signal. As described above, the maximum saturation image is the same image except for the shape of the thick line of the minimum saturation image shown in FIG.

  In the same manner as the hue adjustment operation described above, the user uses the cross key button and the determination button included in the operation button 192 to select blue (B), magenta (M), red (R), yellow (Y), green ( G) Selects or determines the hue axis of cyan (C). Then, the user changes the shape of the thick line of the minimum saturation image and the maximum saturation image, and adjusts the output gain of the saturation signal of the image projected by the liquid crystal projector 100, thereby adjusting the color adjustment related to saturation. Do.

The processing contents performed by the saturation adjustment circuit 50 will be described with reference to FIG.
FIG. 11 is an explanatory diagram of a concept along the contents of a specific example of processing performed by the saturation adjustment circuit 50. As shown in LUT 51 and LUT 52 in FIG. 11, the output gain of the saturation signal when Sv = 0 and Sv = 1023 is obtained by the user deforming the shape of the thick line of the minimum saturation image and the maximum saturation image in advance. It is assumed that a value has been set. Here, a case where an image signal is input to the color adjustment circuit 120 and a hue signal (H) and a saturation signal (S) included in the image signal are input to the saturation adjustment circuit 50 is considered. For example, the hue value Hv and the saturation value Sv are assumed to be Hv = p and Sv = q, respectively. When a hue signal of Hv = p is input to each of the LUT 51 and the LUT 52, the LUT 51 outputs an output gain value when Sv = 0, and the LUT 52 outputs an output gain value when Sv = 1023. In this specific example, as shown in FIG. 11, the output gain value when Sv = 0 in the LUT 51 is 1.5. The output gain value in the LUT 52 when Sv = 1023 is 0.7. These two output gain values are input to the saturation gain interpolation circuit 53.

  As shown in FIG. 11, the saturation gain interpolation circuit 53 generates an interpolation straight line when Hv = p. The interpolation straight line is a line obtained by connecting a point corresponding to the output gain value 1.5 when Sv = 0 and a point corresponding to the output gain value 0.7 when Sv = 01023 by a straight line. When the saturation gain interpolation circuit 53 generates an interpolation line corresponding to Hv = p, the saturation gain value corresponding to the input signal value (saturation value) Sv = q of the input saturation signal is calculated from the interpolation line. And output to the saturation multiplication circuit 54. In this specific example, as shown in FIG. 11, the saturation gain value corresponding to the input signal value (saturation value) Sv = q is 1.3. The saturation multiplication circuit 54 outputs a saturation signal corresponding to a value obtained by multiplying the input signal value of the saturation signal (S) input to the saturation adjustment circuit 50 by the saturation gain value 1.3, after color adjustment. Output as a saturation signal.

  Next, brightness correction processing performed by the liquid crystal projector 100 in accordance with a user instruction will be described. The user who performs color adjustment performs color adjustment related to lightness while viewing the lightness adjustment image among the color adjustment images projected on the screen 200 by the liquid crystal projector 100. The brightness adjustment image for the user to adjust the brightness of the image is the same image as the saturation adjustment image described above, and the fact that the adjustment target element has become the brightness is the above-mentioned saturation adjustment image. It is different from the image for adjusting the degree. Therefore, description and illustration of the brightness adjustment image are omitted.

  As described above, in the liquid crystal projector 100, according to the color adjustment instruction performed by the user via the operation control unit 190 and the operation button 192, the CPU 130 performs processing of the color adjustment instruction unit 132 for each LUT included in the color adjustment circuit 120. Rewriting is performed. As a result, color adjustment of an image projected by the liquid crystal projector 100 is performed. The liquid crystal projector 100 includes an OSD (On Screen Display) processing unit (not shown). Then, as a function of the OSD processing unit, the CPU 130 projects the hue adjustment image, the saturation adjustment image, and the lightness adjustment image on the screen 200 by superimposing them on the projection image. In addition, the thick line indicating the content of the change / correction process expressed on the color adjustment image is subjected to a curve interpolation process that forms a smooth curve shape when the user moves up and down by a color adjustment operation. 132 is doing.

  As described above, since the hue, saturation, and brightness are adjusted after being converted into the HLS signal by the first color space conversion circuit 110, the user can easily adjust intuitively. On the other hand, since the liquid crystal light valve 160 is controlled by a YUV signal or an RGB signal, in the first embodiment, the second color space conversion circuit 140 converts the HLS signal converted by the first color space conversion circuit 140 into a YUV signal. To do. The second color space conversion circuit 140 performs HLS-YUV conversion on the HLS signal that has been color-adjusted by the user and has been changed and corrected by the color adjustment circuit 120, and the converted YUV signal is liquid crystal. It is a circuit that outputs to the light valve drive circuit 150. However, when simply converting an HLS signal to a YUV signal, the following inconvenience occurs.

  FIG. 12 shows a view of the YUV color space and the HLS color space as viewed from the Y axis and the L axis. Here, the YUV color space is a three-dimensional orthogonal coordinate space, and a YUV signal is defined in the color gamut C1 in FIG. On the other hand, the HLS color space is a three-dimensional polar coordinate space, and an HLS signal is defined in the color gamut C2 in FIG. That is, the conversion process performed by the second color space conversion circuit 140 is a process of converting (S, H) in the color gamut C2 to (U, V) in the color gamut C1. However, when the user increases the saturation by the color adjustment instruction and adjusts the color corresponding to the position P, the HLS signal corresponding to the saturation signal (S) and the hue signal (H) at the position P is converted into the YUV signal. Is converted to the position P1 in the color gamut C1. The HLS signal at the position P1 becomes, for example, a saturation signal (S1) and a hue signal (H1) as shown in FIG. 12, and a difference in hue occurs before and after the conversion, and the color change before and after the conversion becomes more conspicuous. . Therefore, the second color space conversion circuit 140 converts the HLS signal into a YUV signal so that the hue does not change before and after the conversion as follows.

  FIG. 13 shows a block diagram of a configuration example of the second color space conversion circuit 140. The second color space conversion circuit 140 includes a Ph output device 71, LUT 73 and LUT 74, a first color difference output device 75, a second color difference output device 76, and a saturation adjustment circuit (saturation signal adjustment unit) 80. Here, the Ph output device 71, LUT 73, LUT 74, first color difference output device 75, and second color difference output device 76 function as a color difference signal generation circuit (color difference signal generation unit). Similar to the configuration of the first color space conversion circuit 110, a synchronous clock (not shown) is input to each arithmetic unit to synchronize the operation between the circuits, but the synchronous clock signal is not shown. ing. Therefore, the HLS signal input to the second color space conversion circuit 140 is converted as a YUV signal corresponding to the set of signals using this synchronous clock, and is output in synchronization.

  As described above, the lightness signal (L) input to the second color space conversion circuit 140 has a one-to-one correspondence with the luminance signal (Y) in the coordinate space shown in FIG. (L) is output as it is as the luminance signal (Y).

The Ph output device 71 calculates a quadrant value DIV_H (first quadrant) on the U-V graph (FIG. 7) of the hue angle Ph and the hue value Hv corresponding to the hue signal (H) from the input hue signal (H). To a value corresponding to the fourth quadrant).
FIG. 14 is an explanatory diagram showing a calculation method for calculating the hue angle Ph and the quadrant value DIV_H corresponding to the hue value Hv input to the Ph output device 71. The method of calculating the hue angle Ph differs depending on the magnitude of the hue value Hv. As an example, when the hue value Hv = 100 (degrees), the hue value Hv corresponds to the range of 90 to 180 (degrees) in FIG. 14, and thus the calculation method of the hue angle Ph is Ph = 180−Hv. , Ph = 80 (degrees). At this time, the hue value Hv (= 100 (degrees)) exists in the second quadrant in the U-V graph (FIG. 7) and is output as DIV_H = 1. In this way, the hue angle Ph and the quadrant value DIV_H are output from the hue value Hv.

  In FIG. 13, a signal corresponding to the hue angle Ph output from the Ph output unit 71 is input to the LUT 73 and the LUT 74. The LUT 73 is an LUT that outputs cos (Ph) that is a cosine value in response to the input signal of the hue angle Ph. The LUT 74 is a LUT that outputs sin (Ph), which is a sine value, corresponding to the input hue angle Ph signal. A signal corresponding to the hue angle Ph output from the Ph output device is converted into a signal corresponding to cos (Ph) and sin (Ph) via the LUT 73 and the LUT 74, and the first color difference output device 75 and the second color difference are output. It is output toward the output device 76.

  The saturation adjustment circuit 80 includes a comparator (comparison unit) 81 and a saturation maximum value generation circuit (saturation maximum value generation unit) 82. The saturation maximum value generation circuit 82 outputs a saturation maximum value Smax that is the maximum value of the saturation value Sv corresponding to the hue value Hv in the color gamut C1. Since the color gamut C1 can be clearly defined, the saturation maximum value generation circuit 82 outputs the saturation component at the boundary value of the color gamut C1 among the saturation values Sv corresponding to the hue value Hv as the saturation maximum value Smax. do it. Such a saturation maximum value generation circuit 82 can be configured by an LUT.

  FIG. 15 is an explanatory diagram of the maximum saturation value Smax output from the maximum saturation value generation circuit 82 in accordance with the hue value Hv. When the saturation maximum value generation circuit 82 is configured by an LUT, the saturation maximum obtained by calculating in advance corresponding to each hue value using the hue value Hv as an input signal value and the saturation maximum value Smax as an output signal value. The value Smax may be stored. Then, when the hue value Hv is given as the input signal value, the output signal value stored corresponding to the input signal value may be output as the saturation maximum value Smax.

  The comparator 81 compares the saturation value Sv with the maximum saturation value Smax and outputs a value corresponding to the comparison result. Specifically, the comparator 81 selects and outputs the smaller one of the saturation value Sv and the saturation maximum value Smax. That is, when the saturation value Sv from the color adjustment circuit 120 is equal to or less than the maximum saturation value Smax, the comparator 81 selectively outputs the saturation value Sv. When the saturation value Sv from the color adjustment circuit 120 is larger than the maximum saturation value Smax, the comparator 81 selects and outputs the maximum saturation value Smax. The value thus selected and output by the comparator 81 is input to the first color difference output unit 75 and the second color difference output unit 76 as the saturation value Sv.

  FIG. 16 is an operation explanatory diagram of the second color space conversion circuit 140. FIG. 16 is a view of the YUV color space and the HLS color space as viewed from the Y axis and the L axis, and the color gamuts C1 and C2 are the same as those in FIG. Since the second color space conversion circuit 140 performs the color space conversion process as described above, the color at the position P in the color gamut C2 is mapped to the position P2 in the color gamut C1 while keeping the hue value Hv constant. . Although the HLS signal at this position P2 has different saturation values before and after conversion, the hue value does not change before and after conversion. Therefore, it is difficult to see the difference in color before and after the conversion, and as a result, the original color can be maintained even if the color is converted to a YUV signal.

As shown in FIG. 13, the first color difference output unit 75 outputs a signal corresponding to the first color difference value Uv based on a signal corresponding to the saturation value Sv, cos (Ph), and the quadrant value DIV_H. To do.
FIG. 17 is an explanatory diagram illustrating an arithmetic expression performed by the first color difference output unit 75 in correspondence with the value of the quadrant value DIV_H. The first color difference output unit 75 selects an arithmetic expression for outputting the first color difference value Uv based on the value (0 to 3) of the quadrant value DIV_H. Then, a signal corresponding to the first color difference value Uv is output based on the input saturation value Sv and cos (Ph) using the arithmetic expression selected corresponding to the quadrant value DIV_H.

The second color difference output unit 76 outputs a signal corresponding to the second color difference value Vv based on a signal corresponding to the saturation value Sv, sin (Ph), and the quadrant value DIV_H.
FIG. 18 is an explanatory diagram showing an arithmetic expression of the calculation performed by the second color difference output unit 76 in correspondence with the value of the quadrant value DIV_H. The second color difference output unit 76 selects an arithmetic expression for outputting the second color difference value Vv based on the value of the quadrant value DIV_H. Then, a signal corresponding to the second color difference value Vv is output based on the saturation value Sv and sin (Ph) using the arithmetic expression selected corresponding to the quadrant value DIV_H. Thus, the second color space conversion circuit 140 performs HLS-YUV conversion on the input HLS signal and outputs a YUV signal.

  As described above, the liquid crystal projector 100 performs YUV-HLS conversion on the input image signal of the YUV signal by the first color space conversion circuit 110 and outputs an HLS signal. Then, the color adjustment circuit 120 changes / corrects the image signal, which is an HLS signal, according to a color adjustment instruction from the user. Thereafter, the liquid crystal projector 100 performs HLS-YUV conversion while maintaining the hue in the second color space conversion circuit 140, and outputs a YUV signal. At this time, since the color adjustment circuit 120 changes and corrects the image signal in the state of the HLS signal, the liquid crystal projector 100 determines the processing contents as three elements of hue, brightness, and saturation, that is, Munsell color specification. It can be shown to the user as a color adjustment image expressed in a system. Further, the user can change and correct the color adjustment of the image in each element of hue, brightness, and saturation while viewing the color adjustment image. Furthermore, in the first embodiment, the hues in the color adjustment image have six reference axes of blue (B), magenta (M), red (R), yellow (Y), green (G), and cyan (C). It expresses using. Therefore, the user can easily adjust the color of the image with reference to the above six hues, which are the color standards. In addition, since the liquid crystal projector 100 includes the first color space conversion circuit 110 and the color adjustment instruction unit 132 as hardware, the processing is performed at high speed, and the input image signal is converted into an HLS signal, and is changed and corrected. Can be performed in real time. Furthermore, since the conversion is performed so that the hue does not change, it becomes difficult to see the difference in color before and after the conversion, and the original color can be maintained. As a result, the color and the like of the image can be adjusted with high accuracy.

[Second Embodiment]
In the first embodiment, the example in which the saturation adjustment circuit 90 generates the maximum saturation value based on the hue value Hv from the color adjustment circuit 120 in the second color space conversion circuit 140 has been described. However, the present invention is not limited to this. It is not something.

FIG. 19 is a block diagram showing a configuration example of the second color space conversion circuit according to the second embodiment of the present invention. The second color space conversion circuit 140a in the second embodiment can be applied to the liquid crystal projector 100 of FIG. 1 instead of the second color space conversion circuit 140. In FIG. 19, the same parts as those in FIG.
The second color space conversion circuit 140a differs from the second color space conversion circuit 140 in that the saturation maximum value generation circuit 92 outputs the saturation maximum value Smax based on the hue angle Ph and the quadrant value DIV_H, and the comparator. 91 is a point for comparing the saturation value Sv with the maximum saturation value Smax. The hue value Hv from the color adjustment circuit 120 corresponds to a combination of the hue angle Ph and the quadrant value DIV_H. Therefore, the saturation maximum value generation circuit 92 can be configured by an LUT that outputs the saturation maximum value Smax corresponding to the combination of the hue angle Ph and the quadrant value DIV_H as shown in FIG.

[Third Embodiment]
In the first embodiment and the second embodiment, the second color space conversion circuit has been described as outputting the first color difference signal and the second color difference signal using the saturation corresponding to the hue. However, the present invention is not limited to this. It is not a thing. In the third embodiment according to the present invention, the first color difference signal and the second color space conversion circuit maintain a constant ratio between the first color difference signal and the second color difference signal generated based on the hue and saturation. By adjusting the two-color difference signal, the hue before and after conversion is prevented from changing.

FIG. 20 is a block diagram showing a configuration example of the second color space conversion circuit according to the third embodiment of the present invention. The second color space conversion circuit 140b in the third embodiment can be applied to the liquid crystal projector 100 of FIG. 1 instead of the second color space conversion circuit 140. In FIG. 20, the same parts as those in FIG.
The second color space conversion circuit 140b is different from the second color space conversion circuit 140 in that the saturation maximum value generation circuit 82 is omitted and a color difference adjustment circuit (color difference signal adjustment unit) 95 is provided. The color difference adjustment circuit 95 receives a signal u1 corresponding to the first color difference value Uv output from the first color difference output unit 75 and a signal v1 corresponding to the second color difference value Vv output from the second color difference output unit 76. . The color difference adjustment circuit 95 is obtained by clipping the signal u1 or the signal v1 to the boundary value of the color gamut C1 (see FIG. 12) corresponding to the YUV signal while maintaining the ratio of the signal u1 and the signal v1. 1 color difference signal U and 2nd color difference signal V are output.

FIG. 21 is an operation explanatory diagram of the second color space conversion circuit 140b. FIG. 21 is a view of the YUV color space and the HLS color space viewed from the Y axis and the L axis, and the color gamuts C1 and C2 are the same as those in FIG. FIG. 21 also shows the color gamut C3 of the signals u1 and v1.
In FIG. 21, by the processing of the color difference adjustment circuit 95, the color at the position P in the color gamut C2 having the signal u1 and the signal v1 is the position that is the boundary position of the color gamut C1 while maintaining the ratio between the signal u1 and the signal v1. Mapped to P3. In the case of FIG. 22, the signal u1 is clipped to the boundary value of the color gamut C1. Since the ratio of the signal u1 and the signal v1 corresponds to the hue value Hv, the hue value of the HLS signal at this position P3 does not change before and after the conversion, although the saturation value before and after the conversion is different. Therefore, it is difficult to see the difference in color before and after the conversion, and as a result, the original color can be maintained even if the color is converted to a YUV signal.

Such a color difference adjustment circuit 95 can be realized by performing the following operation.
FIG. 22 shows an operation explanatory diagram of the color difference adjustment circuit 95. The color difference adjustment circuit 95 outputs the first color difference signal U and the second color difference signal V obtained by the arithmetic expression shown in FIG. 22 according to the comparison result of the signals u1 and v1. When the color difference adjustment circuit 95 is configured by an LUT, the signal u1 and the signal v1 are input signal values, the first color difference signal U and the second color difference signal V are output signal values, and the first corresponding to the combination of the signal u1 and the signal v1. The one color difference signal U and the second color difference signal V may be stored. Then, when the signal u1 and the signal v1 are given as input signal values, the output signal values stored corresponding to the input signal values may be output as the first color difference signal U and the second color difference signal V.

  The present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

  (1) In the above embodiment, the second color space conversion circuit 140 converts the HLS signal output from the color adjustment circuit 120 into a YUV signal, but the present invention is not limited to this. For example, the signal conversion performed by the second color space conversion circuit 140 is not limited to the signal conversion to the YUV signal, but may be conversion to other signal formats as long as the signal is suitable for image display. Further, if the liquid crystal projector 100 includes a circuit and a processing unit that can display an image in the YUV signal format, the liquid crystal projector 100 is the same as that of the first embodiment even though the second color space conversion circuit 140 is not included. An effect can be obtained.

  (2) In the above-described embodiment, the color adjustment image is shown to the user by the liquid crystal projector 100 projecting onto the screen 200, but the present invention is not limited to this. For example, a color adjustment image may be displayed on a display screen of a computer connected to the liquid crystal projector 100 to be shown to the user.

  (3) In the above embodiment, the processing content performed by the color adjustment circuit 120 is shown as a color adjustment image on the display unit that can be visually recognized by the user, and the user can view the projection image while viewing the color adjustment image. Although the color adjustment is performed, the present invention is not limited to this. For example, the liquid crystal projector 100 does not display a color adjustment image, and the hue, lightness, and saturation, that is, a color adjustment operation panel expressed in the Munsell color system, and each hue such as blue (B) for color adjustment. An adjustment dial may be provided. In this case, color adjustment can be performed by switching hue adjustment, lightness adjustment, and saturation adjustment with a separate switching button. Alternatively, the liquid crystal projector 100 may be provided with an operation function unit for color adjustment, and the user may adjust the color of the projection image by operating the operation function unit while viewing the projection image on the screen 200.

  (4) In the above embodiment, in the color adjustment image, the hue in the color adjustment image is set to blue (B) magenta (M), red (R), yellow (Y), green (G), cyan (C However, the number of reference axes may be any number such as 3, 4, 8, or the like. Further, the user may arbitrarily set the number of hue reference axes in the color adjustment image. In addition, the hue reference axis may not be provided in the color adjustment image, and the hue may be expressed by continuous tone. Also, the color adjustment image is shown to the user as a three-dimensional representation of the Munsell color solid, and the user can directly display the change / representation on the Munsell color solid with a mouse or the like provided in a computer connected to the liquid crystal projector 100. The content of the correction process may be manipulated.

  (5) In the above embodiment, the liquid crystal projector 100 is exemplified as the image display device. However, the light modulation element is not limited to the liquid crystal light valve, and for example, a DMD (Digital Micromirror Device) can be used. The present invention can also be implemented as a direct-view image display device such as a plasma display or an organic EL display.

  (6) In the above embodiment, the first color difference signal U and the second color difference signal V may be directly adjusted based on the input saturation value Sv and hue value Hv.

  (7) The present invention can be realized in various modes. For example, a color space conversion device and method, an image processing device and method, an image display device and method, an integrated circuit for realizing the functions of these devices or methods, a computer program, a recording medium on which the computer program is recorded, and the like Can be realized.

DESCRIPTION OF SYMBOLS 10 ... Lightness calculation part, 20 ... Saturation calculation part, 21 ... 1st multiplier, 22 ... 2nd multiplier,
23 ... Adder, 24 ... Floating point converter, 25, 31, 36, 41, 51, 52, 61, 62, 73, 74 ... LUT, 26 ... Saturation index calculator,
27: Bit shift computing unit, 30 ... Hue calculation unit, 35 ... Selector,
37 ... selector subtractor, 38 ... selector adder, 40 ... hue adjustment circuit,
50 ... saturation adjustment circuit, 53 ... saturation gain interpolation circuit, 54 ... saturation multiplication circuit,
60: Lightness adjustment circuit 63: Lightness gain interpolation circuit 64: Lightness multiplication circuit
75 ... 1st color difference output device, 76 ... 2nd color difference output device,
80, 90 ... saturation adjustment circuit (saturation signal adjustment unit), 81, 91 ... comparator (comparison unit),
82, 92 ... saturation maximum value generation circuit (saturation maximum value generation unit),
95: Color difference adjustment circuit (color difference signal adjustment unit), 100 ... Liquid crystal projector,
102 ... Internal bus 110 ... First color space conversion circuit,
120: Color adjustment circuit (color adjustment unit), 130: CPU, 132 ... Color adjustment instruction unit,
140, 140a, 140b ... second color space conversion circuit,
150 ... Liquid crystal light valve drive circuit, 160 ... Liquid crystal light valve,
170 ... light source unit, 171 ... lamp, 172 ... lens, 180 ... projection lens,
190 ... Operation control unit, 192 ... Operation buttons, 200 ... Screen,
C1 to C3 ... color gamut, D ... selector output value, DIV_H ... quadrant value,
R: Square root result value, H: Hue signal, Hv: Hue value, Ks: First real value,
L: Lightness signal, Ls: First exponent value, Lv: Lightness value, S: Saturation signal,
Sv ... saturation value, U ... first color difference signal, Uv ... first color difference value, Uv ² ... first multiplication value,
V: second color difference signal, Vv: second color difference value, Vv ² : second multiplication value

Claims (8)

A color space conversion device for converting an HLS signal into a YUV signal,
A saturation signal adjustment unit that adjusts a saturation signal included in the HLS signal according to a hue signal included in the HLS signal;
A color space conversion comprising: a color difference signal generation unit that generates a color difference signal included in the YUV signal based on the hue signal and the saturation signal adjusted by the saturation signal adjustment unit apparatus. In claim 1,
The saturation signal adjustment unit
A saturation maximum value generation unit for generating a saturation maximum value corresponding to the hue signal;
A comparison unit that outputs the smaller one of the saturation value corresponding to the saturation signal or the saturation maximum value, and
The color difference signal generation unit
The color space conversion device, wherein the color difference signal is generated based on the hue signal and an output signal from the comparison unit. In claim 2,
The saturation maximum value generation unit
A color space conversion apparatus, wherein a saturation component at a boundary value of a color gamut corresponding to the YUV signal is output as the maximum saturation value. A color space conversion device for converting an HLS signal into a YUV signal,
A color difference signal generation unit that generates a first color difference signal and a second color difference signal included in the YUV signal based on a hue signal and a saturation signal included in the HLS signal;
While maintaining the ratio between the signal value of the first color difference signal and the signal value of the second color difference signal, the signal value of the first color difference signal or the signal value of the second color difference signal corresponds to the YUV signal. A color space conversion apparatus comprising: a color difference signal adjustment unit that outputs the first color difference signal and the second color difference signal obtained by clipping to a boundary value of a region. A first color space converter for converting a YUV signal into an HLS signal;
A color adjustment unit that adjusts at least one of a hue signal, a lightness signal, and a saturation signal that constitute the HLS signal converted by the first color space conversion unit, and outputs an adjusted HLS signal;
An image processing apparatus comprising: the color space conversion apparatus according to claim 1, which converts an HLS signal adjusted by the color adjustment unit into a YUV signal. An image display device that displays an image based on an image signal,
The color space conversion device according to claim 1, which converts an HLS signal corresponding to the image signal into a YUV signal.
An image display device that displays an image using the YUV signal converted by the color space conversion device. A color space conversion method for converting an HLS signal into a YUV signal,
A saturation signal adjustment step of adjusting a saturation signal included in the HLS signal according to a hue signal included in the HLS signal;
A color space conversion method comprising: a color difference signal generation step for generating a color difference signal included in the YUV signal based on the hue signal and the saturation signal adjusted in the saturation signal adjustment step. . A color space conversion method for converting an HLS signal into a YUV signal,
A color difference signal generating step for generating a first color difference signal and a second color difference signal included in the YUV signal based on a hue signal and a saturation signal included in the HLS signal;
While maintaining the ratio between the signal value of the first color difference signal and the signal value of the second color difference signal, the signal value of the first color difference signal or the signal value of the second color difference signal corresponds to the YUV signal. A color space conversion method comprising: a color difference signal adjustment step of outputting the first color difference signal and the second color difference signal obtained by clipping to a boundary value of a region.

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